Borders' Dictionary of Health Physics

R_res, residual maximum beta range
The residual maximum beta range, R_res, is the range in an absorbing material of a beta spectrum of residual maximum energy E_res.
(NCRP 112)

Ra a, -b, etc.
Old terminology for members of the radium decay series. Similar designations were used with other series.
(RAH)

Rabbit
A small sample container propelled pneumatically through a tube leading from the laboratory to a location in a nuclear reactor or near an accelerator where irradiation can take place, and designed to provide short transit times back to the laboratory.
(NCRP 51)

Rabbit
A device to move a sample rapidly from one place (such as inside a research reactor) to another place (such as a radiochemistry laboratory). "Rabbits" often consist of small cylinders of aluminum or plastic, moved by air pressure through a long pipe.
(USAEC-1974)

Rabbit
A small container propelled, usually pneumatically or hydraulically, through a tube in a nuclear reactor to expose substances experimentally to the radiation and neutron fluxes of the active section. Used for rapid removal of samples with very short half lives.
(RHH)

Rabbit (reactor technology)
A small container propelled pneumatically or hydraulically through a tube leading from the laboratory to a location in a nuclear reactor or other device where irradiation of a sample can take place. It is designed to provide short transit times to the laboratory. (Sometimes also called shuttle.)
(ANSI N1.1-1976)

Rad
The special unit of absorbed dose. One rad is equal to an absorbed dose of 100 ergs/gram or 0.01 joule/kilogram (0.01 gray).
(10CFR20.1004)

Rad
A unit of absorbed dose in the conventional system. In the SI system of units 1 Gy = 1 J kg^-1 (See absorbed dose).
(NCRP 118)

Rad
A measure of the dose of any ionizing radiation to body tissues in terms of the energy absorbed per unit mass of the tissue. One rad is the dose corresponding to the absorption of 100 ergs per gram of tissue. (One millirad (mrad) = 0.001 rad.)
(10CFR20.4)

Rad
A unit of absorbed dose: One rad is 0.01 Joule absorbed per kilogram of any material. (Also defined as 100 ergs per gram and written "rad"). It is being replaced by the gray (Gy). One rad equals one hundredth of a gray.
(HPJ 60)

Rad
A special unit for absorbed dose, kerma, and specific energy imparted. One rad is 0.01 joules absorbed per kilogram of any material. (Also defined as 100 ergs per gram.) Being replaced by the gray. One rad equals 0.01 gray.
(NCRP 101)

Rad
A unit of absorbed dose, 100 erg g^-1. In SI unit 1 rad = 0.01 Gy.
(NCRP 98)

Rad
The previously used special unit of absorbed dose. It is equal to 100 ergs per gram. 1 rad = 0.01 Gy (10^-2 gray).
(NCRP 102)

Rad
The special unit of radiation absorbed dose in conventional units. One rad equals the absorption of 0.01 joule per kilogram (100 ergs per gram) of absorbing material. 1 rad = 0.01 Gy.
(NCRP 103)

Rad
The conventional unit of absorbed dose equal to the absorbed energy of 0.01 J kg^-1 (100 ergs g^-1) in any medium and is being replaced by the gray. 1 rad = 0.01 Gy (See note under rem.)
(NCRP 105)

Rad
As used in ANSI N42.17A, the word rad (abbreviated rd) refers to dose in air unless otherwise stated.
(ANSI N42.17A-1989)

Rad
The name of the conventional unit for absorbed dose of ionizing radiation; the corresponding SI unit is the gray (Gy); 1 rad = 0.01 Gy = 0.01 Joule/kg.
(FGR 11)

Rad
A unit of absorbed dose. One rad is 0.01 joules absorbed per kilogram of any material. (Also defined as 100 ergs per gram.) Being replaced by the gray.
(NCRP 87)

Rad
A unit of absorbed dose. One rad is 0.01 joules absorbed per kilogram of any material. (Also defined as 100 ergs per gram.) Being replaced by the gray.
(NCRP 84)

Rad
Traditional unit of absorbed dose. 1 rad = 100 erg g^-1 = 10^-2 J kg^-1.
(NCRP 83)

Rad
The unit of absorbed dose involving the energy absorbed from ionizing radiation per unit mass of any material. One rad equals 100 ergs per gram.
(NCRP 80)

Rad
The special unit of radiation absorbed dose. One rad equals the absorption of 100 ergs/gram of absorbing material (10^-2 Joule/kg).
(NCRP 78)

Rad
The special unit of absorbed dose. 1 rad = 10^-2 J/kg.
(NCRP 69)

Rad
The unit of absorbed dose. One rad is 0.01 joules absorbed per kilogram of any material. (Also defined as 100 ergs per gram.)
(NCRP 68)

Rad
The special unit of absorbed dose. A dose of one RAD means the absorption of 100 ergs of radiation energy per gram of absorbing material or 10^-2 joules per kilogram of absorbing material.
(NCRP 65)

Rad
Special unit of absorbed dose. 1 rad is equal to 10^-2 joule kg^-1 or 100 erg g^-1.
(NCRP 51)

Rad
The unit of absorbed dose. One rad is 0.01 joules absorbed per kilogram of any material. (Also defined as 100 ergs per gram.)
(NCRP 48)

Rad
The special unit of absorbed dose equal to 10^-2 joule kg^-1 (100 erg g^-1).
(NCRP 49)

Rad
The special unit of absorbed dose. One rad equals 100 ergs per gram.
(ANSI N319-1976)

Rad
A unit of absorbed dose. (1 rad = 10^-2 G = 10^-2 J/kg)
(ANSI N1.1-1976)

Rad
Radiation absorbed dose, the basic unit of ionizing radiation. One rad is equal to the absorption of 100 ergs of radiation energy per gram of matter.
(ERDA 76-21)

Rad
(Acronym for radiation absorbed dose.) The basic unit of absorbed dose of ionizing radiation. A dose of one rad means the absorption of 100 ergs of radiation energy per gram of absorbing material. (See absorbed dose.)
(USAEC-1974)

Rad
The unit of absorbed dose equal to 0.01 J/kg in any medium.
(BEIR I)

Rad
Special unit of absorbed dose. 1 rad is equal to 10^-2 joule kg^-1 or 100 erg g^-1.
(NCRP 38)

Rad
Unit of absorbed dose. 1 rad is 100 erg/g.
(NBS 73)

Rad
The rad is a unit of absorbed radiation dose and is equal to 100 ergs per gram.
(NBS 66)

Rad
Unit of absorbed dose. 1 rad is equal to 100 ergs/g.
(NBS 63)

Rad
The rad is a unit of absorbed dose, which is equal to 100 ergs/g. The rad is a measure of the energy imparted to matter by ionizing particle per unit mass of irradiated material at the place of interest. It was recommended and adopted by the International Commission of Radiological Units at the Seventh International Congress of Radiology, Copenhagen, July 1953.
(NBS 55)

Rad
The unit of absorbed dose, which is 100 ergs/g. The rad is a measure of the energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest. It is a unit that was recommended and adopted by the International Commission on Radiological Units at the Seventh International Congress of Radiology, Copenhagen, July 1953.
(NBS 54)

Rad (rad) (deprecated)
Unit of absorbed dose, kerma and specific energy imparted equal to 0.01 Gy.
(IEC 50-393-1993)

Radiant density
Instantaneous amount of radiant energy contained in a unit volume of propagation medium.
(IEC 50-393-1993)

Radiant energy (R)
Energy of particles, excluding their rest energy, emitted, transferred, or received.
(IEC 50-393-1993)

Radiant energy (R)
The energy of particles (excluding rest energy) emitted, transferred or received.
(ICRU 33)

Radiant exposure
Total radiant energy incident on a surface per unit area.
(IEC 50-393-1993)

Radiating near field region
The region in the field of an antenna where the radiation field predominates over the reactive field but lacks substantial plane-wave character and is complicated in structure. The term "radiating near field region" generally is associated with large antennas where the largest dimension of the antenna is very much greater than the free space wavelength. The radiating near field region lies between the reactive near field region and the far-field region. (See "antenna, field regions of", "near-field region", and "radiation field".)
(NCRP 67)

Radiation
Ionizing radiation, e.g., alpha particles, beta particles, gamma rays, x-rays, neutrons, protons, and other particles having sufficient energy to produce ion pairs in matter. As used in this part, radiation does not include non-ionizing radiation.
(10CFR834.2)

Radiation
The emission and propagation of energy through matter or space.
(NCRP 118)

Radiation
Any or all of the following: alpha rays, beta rays, gamma rays, X-rays, neutrons, high speed electrons, high-speed protons, and other atomic particles; but not sound or radio waves, or visible, infra-red, or ultraviolet light.
(10CFR20.3)

Radiation
Emission and propagation of energy through space or through a material medium in the form of waves or particles.
(IEC 50-393-1993)

Radiation
1. The emission and propagation of energy through space of through a material medium in the form of waves, for instance the emission and propagation of electromagnetic waves, or of sound and elastic waves.
2. The energy propagated through space or through a material medium as waves; for example, energy in the form of electromagnetic waves or of elastic waves. The terms "radiation" or "radiant energy", when unqualified, usually refer to electromagnetic radiation; such radiation commonly is classified, according to frequency, as Hertzian, infrared, visible (light), ultraviolet, x-ray, and g-ray.
3. By extension, corpuscular emissions, such as a and b radiation, or rays of mixed or unknown type, as cosmic radiation.
(HPJ 60)

Radiation
Propagation of energy through space. In the context of this report, it is electromagnetic radiation (x rays or gamma rays), or corpuscular radiation (alpha particles, electrons, protons, neutrons) capable of producing ionization.
(NCRP 111)

Radiation
As used in this standard, radiation means ionizing radiation.
(ANSI N2.1-1989)

Radiation
As used in this standard, radiation means ionizing radiation.
(ANSI N12.1-1989)

Radiation
1. The emission and propagation of energy through space or through matter in the form of waves, such as electromagnetic waves, sound waves, or elastic waves.
2. The energy propagated through space or through matter as waves; "radiation" or "radiant energy," when unqualified, usually refers to electromagnetic radiation; commonly classified by frequency - Hertzian, infrared, visible, ultraviolet, x, and gamma ray.
3. Corpuscular emission, such as alpha and beta radiation, or rays of mixed or unknown type, such as cosmic radiation.
(NCRP 98)

Radiation
As used in NCRP 83-1985, the term radiation always implies ionizing radiation, which may be high energy particles or electromagnetic radiation. For electromagnetic radiation, the minimum energy that produces ionization lies in the ultraviolet region of the spectrum.
(NCRP 83)

Radiation
1. Emission and propagation of energy through space or through matter in the forms of waves, such as electromagnetic waves, sound waves, or elastic waves.
2. The energy propagated through space or through matter as waves; "radiation" or "radiant energy" when unqualified, usually refers to electromagnetic radiation; commonly classified by frequency - Hertzian, infrared, visible, ultraviolet, x, and gamma ray.
3. Corpuscular emission, such as alpha and beta radiation, or rays of mixed or unknown type, such a cosmic radiation.
Specifically:

Annihilation radiation:: Photons produced when an electron and a positron unite and cease to exist. The annihilation of a positron-electron pair results in the production of two photons, each of 0.51 MeV energy.
Background radiation:: Radiation arising from radioactive material other than the one directly under consideration. Background radiation due to cosmic rays and natural radioactivity is always present. There may also be background radiation due to the presence of radioactive substances in other parts of the building, in the building material itself, etc.
Characteristic (discrete) radiation:: Radiation originating from an atom after removal of an electron or excitation nucleus. The wavelength of the emitted radiation is specific, depending on the nuclide and particular energy levels involved.
Direct radiation:: Obsolete term for "leakage radiation."
External radiation:: Radiation from a source outside the body - the radiation must penetrate the skin.
Infrared radiation:: Invisible thermal radiation whose wavelength is longer than the red segment of the visible spectrum.
Internal radiation:: Radiation from a source within the body (as a result of deposition of radionuclides in body tissues).
Ionizing radiation:: Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, in its passage through matter.
Leakage (direct) radiation:: All radiation coming from the source housing except the useful beam.
Monochromatic radiation:: Electromagnetic radiation of a single wavelength, or radiation in which all the photons have the same energy.
Monoenergetic radiation:: Radiation of a given type (alpha, beta, neutron, gamma, etc.) in which all particles or photons originate with and have the same energy.
Primary radiation:: The useful beam of an x-ray tube.
Scattered radiation:: Radiation which during its passage through a substance, has been deviated in direction. It may also have been modified by a decease in energy.
Secondary radiation:: Radiation resulting from absorption of other radiation in matter. It may be either electromagnetic or particulate.
Stem radiation:: X rays given off from parts of the anode other than the target, particularly from the target support.
Stray radiation:: The sum of leakage and scattered radiation.
(BEIR III)

Radiation
Propagation of energy through space. In the context of this report, electromagnetic radiation (x rays or gamma rays), or corpuscular radiation (electrons, protons, atomic ions, neutrons, heavy particles), capable of producing ionization.
(NCRP 51)

Radiation
The propagation of energy through matter or space in the form of electromagnetic waves or fast-moving particles (alpha and beta particles, neutrons, etc.). Gamma rays are electromagnetic radiation in which the energy is propagated in "packets" called photons.
(ERDA 76-21)

Radiation
The emission and propagation of energy through matter or space by means of electromagnetic disturbances which display both wave-like and particle like behavior; in this context the "particles" are known as photons. Also, the energy so propagated. The term has been extended to include streams of fast moving particles (alpha and beta particles, free neutrons, cosmic radiation, etc.). Nuclear radiation is that emitted from atomic nuclei in various nuclear reactions, including alpha, beta and gamma radiation and neutrons. (See electromagnetic radiation, ionizing radiation, quantum.)
(USAEC-1974)

Radiation
1) The emission and propagation of energy through space or through a material medium in the form of waves; e.g., the emission and propagation of electromagnetic waves, or of sound and elastic waves.
2) The energy propagated through space or through a material medium as waves. The term radiation or radiant energy, when unqualified, usually refers to electromagnetic radiation. Such radiation is commonly classified by frequency: Hertzian, infrared, visible, ultraviolet, x ray, and gamma ray.
3) Corpuscular emissions, such as alpha and beta radiation, or rays of mixed or unknown type, as cosmic radiation.
(BEIR I)

Annihilation radiation:: Photons produced when an electron and a positron unite and cease to exist. The annihilation of a positron-electron pair results in the production of two photons, each of 0.51 MeV energy.
Background radiation:: Radiation arising from radioactive material other than the one directly under consideration. Background radiation due to cosmic rays and natural radioactivity is always present. There may also be background radiation due to the presence of radioactive substances in other parts of the building, in the building material itself, etc.
Characteristic (discrete) radiation:: Radiation originating from an atom after removal of an electron or excitation nucleus. The wavelength of the emitted radiation is specific, depending on the nuclide and particular energy levels involved.
Direct radiation:: Obsolete term for "leakage radiation."
External radiation:: Radiation from a source outside the body - the radiation must penetrate the skin.
Infrared radiation:: Invisible thermal radiation whose wavelength is longer than the red segment of the visible spectrum.
Internal radiation:: Radiation from a source within the body (as a result of deposition of radionuclides in body tissues).
Ionizing radiation:: Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, in its passage through matter.
Leakage (direct) radiation:: All radiation coming from the source housing except the useful beam.
Monochromatic radiation:: Electromagnetic radiation of a single wavelength, or radiation in which all the photons have the same energy.
Monoenergetic radiation:: Radiation of a given type (alpha, beta, neutron, gamma, etc.) in which all particles or photons originate with and have the same energy.
Primary radiation:: The useful beam of an x-ray tube.
Scattered radiation:: Radiation which during its passage through a substance, has been deviated in direction. It may also have been modified by a decease in energy.
Secondary radiation:: Radiation resulting from absorption of other radiation in matter. It may be either electromagnetic or particulate.
Stem radiation:: X rays given off from parts of the anode other than the target, particularly from the target support.
Stray radiation:: The sum of leakage and scattered radiation.
(RHH)

Radiation
As used in this standard, radiation means ionizing radiation.
(ANSI N2.1-1969)

Radiation
Energy propagated through space. As commonly used in radiology, the term refers to two kinds of ionizing radiation: (1) Electromagnetic waves (X-rays, gamma-rays), and (2) corpuscular emissions from radioactive substances or other sources (alpha and beta particles, etc.).
(NBS 73)

Radiation
Gamma rays and X-rays, alpha and beta particles, high-speed electrons, neutrons, protons, and other nuclear particles; but not sound or radio waves, or visible, infrared, or ultraviolet light.
(NBS 61)

Radiation
In general, radiation is energy that is propagated through space; in particular, for the purposes of this Handbook, it consists of the energy that is propagated in the form of X-rays, gamma rays, electrons, and neutrons.
(NBS 55)

Radiation
Energy propagated through space.
(NBS 51)

Radiation (ionizing radiation)
Alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions. Radiation, as used in this part, does not include non-ionizing radiation, such as radio- or microwaves, or visible, infrared, or ultraviolet light.
(10CFR20.1003)

Radiation (ionizing)
Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, by interaction with matter. Examples are x-ray photons, charged atomic particles and other ions, and neutrons.
Leakage radiation: All radiation coming from within the source assembly except for the useful beam. (Note: Leakage radiation includes the portion of the radiation coming directly from the source and not absorbed iby the source assembly, as well as the scattered radiation produced within the source assembly).
Scattered radiation: Radiation that, during passage through matter is changed in direction. (The change is usually accompanied by a decrease in energy).
(NCRP 107)

Radiation (ionizing)
Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, by interaction with material. Examples are x-ray photons, charged atomic particles and other ions, and neutrons.
Leakage radiation: All radiation coming from within the source assembly except for the useful beam. (Note: Leakage radiation includes the portion of the radiation coming directly from the source and not absorbed by the source assembly, as well as the scattered radiation produced within the source assembly).
Scattered radiation: Radiation that, during passage through matter is changed in direction. (It is usually accompanied by a decrease in energy).
Stray radiation: The sum of the leakage and scattered radiation.
Useful beam: The radiation which passes through the opening in the beam limiting device and which is used for imaging or treatment.
(NCRP 102)

Radiation (protection) survey
An evaluation of the radiation safety in and around an installation.
(NCRP 51)

Radiation (protection) survey
An evaluation of the radiation safety in and around an installation.
(NCRP 49)

Radiation accidents
Accidents resulting in the spread of radioactive material or in the exposure of individuals to radiation.
(USAEC-1974)

Radiation area
An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.
(10CFR20.1003)

Radiation area
Any area accessible to individuals in which radiation levels could result in an individual receiving a deep dose equivalent in excess of 0.005 rem (0.05 millisievert) in 1 hour at 30 centimeters from the source or from any surface that the radiation penetrates.
(10CFR835.2-1993)

Radiation area
Any area, accessible to personnel, in which there exists radiation, originating in whole or in part within licensed material, at such levels that a major portion of the whole body could receive in any one hour a dose in excess of 5 millirem, or in any 5 consecutive days a dose in excess of 100 millirems.
(10CFR20.202)

Radiation area
Any area accessible to personnel, in which there exists radiation at such levels that a major portion of the body (whole body, head and trunk, active blood-forming organs, gonads, or eye lenses) could receive in any one hour a dose equivalent, H, in excess of 5 mrem or in any 5 consecutive days a dose equivalent, H, in excess of 100 mrem.
(ANSI N43.1-1978)

Radiation area
Any area accessible to personnel, in which there may exist radiation at such levels that a major portion of the body could receive in any one hour a dose equivalent, H, in excess of 2.5 mrem or in any 5 consecutive days a dose equivalent in excess of 100 mrem.
(NCRP 51)

Radiation area
Any accessible area in which the level of radiation is such that a major portion of an individual's body could receive in any one hour a dose in excess of 5 millirem, or in any 5 consecutive days a dose in excess of 150 millirem. (See absorbed dose, rem.)
(USAEC-1974)

Radiation biology
(See radiobiology.)
(USAEC-1974)

Radiation bore-hole logging meter
Radiation prospecting meter, including a probe, a counting assembly and the necessary mechanical devices, designed to measure the radiation in a bore-hole as a function of the depth.
(IEC 50-394-1993)

Radiation burn
Radiation damage to the skin. Beta burns result from skin contact with or exposure to emitters of beta particles. Flash burns result from sudden thermal radiation. (See beta particles, flash burn, ionizing radiation, thermal burn.)
(USAEC-1974)

Radiation chemical yield, G(x)
The quotient of n(x) by e, where n(x) is the mean amount of a specified entity, x, produced, destroyed, or changed by the mean energy imparted, e, to the matter.

(ICRU 33)

Radiation chemistry
The branch of chemistry that is concerned with the chemical effects, including decomposition, of energetic radiation or particles on matter.
(USAEC-1974)

Radiation compensated semiconductor detector
Compensated semiconductor detector whose structure is formed by radiation defect doping by preliminary irradiation of the semiconductor material.
(IEC 50-394-1993)

Radiation control officer
That individual who is responsible for those activities which will assure adequate radiation protection.
(USAS N13.2-1969)

Radiation damage
Deterioration of the physical or chemical properties of a material as a result of its irradiation.
(IEC 50-393-1993)

Radiation damage
Deleterious changes in the physical or chemical properties of a material resulting from exposure to ionizing radiation. This term does not apply to biological systems.
(ANSI N1.1-1976)

Radiation damage
A general term for the harmful effects of radiation on matter.
(USAEC-1974)

Radiation detection assembly
An assembly or a combination of sub-assemblies with all necessary technical means of providing measurement conditions and operations.
(IEC 50-394-1993)

Radiation detection instruments
Devices that detect and record the characteristics of ionizing radiation. (See counter, dosimeter, monitor.)
(USAEC-1974)

Radiation detection sub-assembly
A sub-assembly intended for converting ionizing radiation energy into a normalized signal, carrying information about ionizing radiation physical quantities, and which provides the signal for transmission to measuring systems, assemblies and instruments.
(IEC 50-394-1993)

Radiation detector
An element of equipment or a substance which, in the presence of radiation, provides a signal for use in measuring one or more quantities of the incident radiation.
(IEC 50-394-1993)

Radiation detector
An instrument or a material which measures or indicates the presents of ionizing radiation.
(ANSI N1.1-1976)

Radiation dosimetry
The measurement of the amount of radiation delivered to a specific place or the amount of radiation that was absorbed there. (See dosimeter.)
(USAEC-1974)

Radiation emitter
Radionuclide in which radioactive disintegrations result in the emission of ionizing radiation.
(IEC 50-393-1993)

Radiation exposure
In the context of this ANSI N13.6-1966, "exposure" refers very broadly to the act or state of being irradiated by ionizing radiation.
(ANSI N13.6-1966)

Radiation exposure
The time integral of the radiation intensity incident at a given position. Radiation exposures as used in this Handbook are expressed in watt-seconds per square centimeter. (1 watt-sec/cm² is equal to 10⁷ ergs/cm².)
(NBS 55)

Radiation field
Region through which radiation is being propagated.
(IEC 50-393-1993)

Radiation field
Collectively, the components of the total electromagnetic field produced by an antenna that include, only and all, the energy propagated away from the antenna. The radiation field is not understood to exclude the fields that contain reactive energy (energy that enters the space but returns to the antenna), although such reactive fields coexist with radiation fields at the same locations. In most of the radiation field both E and H vary inversely with distance from the antenna. (See "antenna, field regions of" and "radiating near field region".)
(NCRP 67)

Radiation field
The space irradiated by the accelerator.
(NBS 55)

Radiation field
Region in which radiation is propagated.
(NBS 51)

Radiation field map
A drawing of a region traversed by radiation of any kind, showing contours of iso-absorbed dose index rate, isodose-equivalent rate, or iso-fluence rate; sometimes referred to as "radiation profile".
(NCRP 51)

Radiation gauge
Measuring assembly, including an ionizing radiation source, a radiation meter and the necessary mechanical devices, intended for industrial non-destructive measurement of a non-electrical quantity.
(IEC 50-394-1993)

Radiation hazard
Risk of damage produced by the action of radiation in tissue.
(NCRP 48)

Radiation hazard
A condition under which persons might receive radiation in excess of the applicable maximum permissible dose, or where radiation damage might be caused to materials.
(NBS 73)

Radiation hazard
A hazard resulting from the presence of radiation in amounts capable of producing dose rates greater that the maximum permissible dose rates.
(NBS 55)

Radiation hazard
Any possible condition that might result in exposure of persons to radiation in excess of the maximum permissible doses.
(NBS 54)

Radiation illness
An acute organic disorder that follows exposure to relatively severe doses of ionizing radiation. It is characterized by nausea, vomiting, diarrhea, blood cell changes, and in later stages by hemorrhage and loss of hair. (See ionizing radiation.)
(USAEC-1974)

Radiation intensity (radiation energy flux density)
The radiation energy flowing through unit area perpendicular to the beam per unit time. When separate beams of the same or different radiation are considered, the intensity and direction of each individual beam should be specified. Radiation intensities in this Handbook are expressed in watts per square centimeter. This quantity is of particular interest in the specification of accelerator performance, and must not be confused with dose rate, which measures the rate of energy absorption per unit mass of an irradiated medium. (See dose).
(NBS 55)

Radiation length
The mean path length required to reduce the energy of a relativistic charged particle by a factor of e.
(NCRP 51)

Radiation length
The average path length that an electron must travel in matter for its energy to be decreased by a factor of e (2.718...).
(ANSI N1.1-1976)

Radiation level
Means the radiation dose-equivalent rate expressed in millirem per hour (mrem/h). Neutron flux densities may be converted into radiation levels according to Table 1:

Table 1 - Neutron Flux Densities to be Regarded as Equivalent to a Radiation Level of 1 millirem per hour (mrem/h)
Energy of the Neutron Flux density equivalent to 1 mrem/h (Neutrons per square centimeter per second) (n/cm²/s)

Thermal 268.0

5 keV 228.0

20 keV 112.0

100 keV 32.0

500 keV 12.0

1 MeV 7.2

5 MeV 7.2

10 MeV 6.8

Table 1 - Neutron Flux Densities to be Regarded as Equivalent to a Radiation Level of 1 millirem per hour (mrem/h)
Energy of the Neutron	Flux density equivalent to 1 mrem/h (Neutrons per square centimeter per second) (n/cm²/s)
Thermal	268.0
5 keV	228.0
20 keV	112.0
100 keV	32.0
500 keV	12.0
1 MeV	7.2
5 MeV	7.2
10 MeV	6.8

(49CFR173.403)

Radiation level
The dose-equivalent rate of the radiation field at the point in question.
(NCRP 51)

Radiation machine
Any device that produces radiations when the associated control devices are operated.
(NBS 61)

Radiation meter
Instrument intended to measure quantities related to ionizing radiation.
(IEC 50-394-1993)

Radiation monitoring
The continuing collection and assessment of the pertinent information to determine the adequacy of radiation protection practices and to alert to potentially significant changes in conditions or protection performance.
(ANSI N43.1-1978)

Radiation monitoring
Continuous or periodic determination of the amount of radiation present in a given area. (See monitor.)
(USAEC-1974)

Radiation oncologist
A medical practitioner who specializes in the use of radiation for therapy, particularly that of malignant disease. The synonym "radiation therapist" or "radiotherapist" is used in some countries.
(ICRP 44)

Radiation pattern
The angular distribution of the radiating portion of the electromagnetic fields in the vicinity of an antenna. The radiation pattern may refer to such quantities as power per unit solid angle, electric or magnetic field strengths, polarization or phase.
(NCRP 67)

Radiation physics
Study of ionizing radiation and its effects on matter.
(IEC 50-393-1993)

Radiation preservation
Irradiation of food products to ionizing radiation in order to aid their preservation.
(IEC 50-393-1993)

Radiation prospecting meter
Radiation meter designed for radiometric prospecting, based on the detection of ionizing radiation.
(IEC 50-394-1993)

Radiation protection
Legislation and regulations to protect the public and laboratory Or industrial workers against radiation. Also measures to reduce exposure to radiation. (See radiation standards.)
(USAEC-1974)

Radiation protection (safety) officer
The person directly responsible for radiation protection.
(NCRP 51)

Radiation protection (safety) officer
The person directly responsible for radiation protection.
(NCRP 38)

Radiation protection (safety) officer
Person directly responsible for radiation protection. It is his duty to insure that all procedures are carried out in compliance with pertinent established rules, including recommendations in this Handbook.
(NBS 73)

Radiation protection guide
The officially determined radiation doses which should not be exceeded without careful consideration of the reasons for doing so. These standards, established by the Federal Radiation Council, are equivalent to what was formerly called the maximum permissible dose or maximum permissible exposure. (See radioactivity concentration guide.)
(USAEC-1974)

Radiation protection guide (RPG)
This formally used term referred to a radiation dose limit which should normally not be exceeded.
(FGR 11)

Radiation protection instrumentation
Electrical and electronic systems and equipment for the detection and measurement of ionizing radiation and radioactivity and radiation monitoring for radiation protection purposes.
(IEC 50-394-1993)

Radiation protection officer
That individual who is responsible for the radiation protection program.
(ANSI N43.1-1978)

Radiation protection officer
One who has the knowledge and responsibility to apply appropriate radiation protection regulations. He may be the owner of the person in charge of the controlled area or he may be a technically competent person appointed by the above.
(ANSI N43.2-1977)

Radiation protection supervisor
The person directly responsible for radiation protection.
(NCRP 49)

Radiation protection supervisor (RPS)
The person directly responsible for radiation protection. It is his duty to ensure that all procedures are carried out in compliance with established rules.
(NCRP 48)

Radiation protection survey
An evaluation of the radiation safety in and around an installation, that includes radiation measurements, inspections, evaluations and recommendations.
(NCRP 107)

Radiation protection survey
An evaluation of the radiation safety in and around an installation, that includes radiation measurements, inspections, evaluations and recommendations.
(NCRP 102)

Radiation protection survey
An evaluation of the radiation safety status of an installation.
(NCRP 59)

Radiation protection survey
Evaluation of the radiation hazards in and around an installation. It customarily includes a physical survey of the arrangement and use of the equipment and measurements of the exposure rates under expected operating conditions.
(NBS 73)

Radiation quality
The energy imparted to matter divided by the length of the track of the charged particle over which the energy is lost.
(NCRP 104)

Radiation quality
A general term referring to the spatial distribution of absorbed dose in extremely small volumes of target tissue. For example, an exposure to neutron radiation may be quantitatively the same as an exposure to gamma rays, in the sense that, for volumes of tissue on the order of one cubic centimeter, the absorbed energy is the same. Yet at resolutions of a few micrometers the ionizing events will be more uniformly dispersed for the gamma ray radiation that for the neutron radiation, producing quantitatively different biological effects. (See RBE).
(NCRP 98)

Radiation quality
(a) A term referring to the ability of a radiation beam to penetrate into the medium or object being irradiated. It is often expressed in terms of half value layer.
(b) Those characteristics of the radiation that describe the spatial distribution of energy transfers by charged particles, and which influence the effectiveness of any radiation when other physical factors such as absorbed dose, absorbed dose rate and fractionation are kept constant. Linear energy transfer is one method of describing quality.
(NCRP 66)

Radiation quantity
A quantity characteristic of a particular radiation and capable of being measured. Thus particle flux density is a radiation quantity, but hardness is not.
(ANSI N1.1-1976)

Radiation receptor
Any device that absorbs a portion of the incident radiation energy and converts this portion into another form of energy which can be more easily used to produce desired results (e.g., reproduction of an image). (See image receptor.)
(NCRP 107)

Radiation room
A shielded room in which irradiations take place. Underwater irradiators do not have radiation rooms.
(10CFR36.2)

Radiation room
The room to which the bulk of the radiation produced by the accelerator is confined. For the purposes of this Handbook, this room is also assumed to be the room in which the radiation is utilized.
(NBS 55)

Radiation safety (protection) officer
An individual in charge of radiation protection.
(NBS 63)

Radiation safety (radiation protection)
Concerned with recognition, evaluation and control of risks due to radiation exposure.
(NCRP 118)

Radiation safety interlock
A device for precluding access to an area of radiation hazard by automatically removing the hazard.
(ANSI N537-1976)

Radiation safety officer
An individual with responsibility for the overall radiation safety program at the facility.
(10CFR36.2)

Radiation safety officer
The individual identified as the Radiation Safety Officer on a Commission license.
(10CFR35.2)

Radiation safety officer
A technically competent person designated by management to evaluate safety programs and supervise the application of radiation protection regulations (for example, persons having relevant certification from the American Board of Radiology, the American Board of Health Physics or equivalent qualifications).
(NCRP 114)

Radiation Safety Officer for industrial radiography
An individual with the responsibility for the overall radiation safety program on behalf of the licensee and who meets the requirements of Sec. 34.42.
(10CFR34.3)

Radiation sensor
The component of a radiation detector which responds directly to ionizing radiation. It may indicate this response itself or may induce a response in other components.
(ANSI N1.1-1976)

Radiation shielding
Reduction of radiation by interposing a shield of absorbing material between any radioactive source and a person, laboratory area, or radiation-sensitive device. (See absorber, shield.)
(USAEC-1974)

Radiation sickness
A self-limited syndrome characterized by nausea, vomiting, diarrhea, and psychic depression; follows exposure to appreciable doses of ionizing radiation, particularly to the abdominal region; its mechanism is unknown, and there is no satisfactory remedy; usually appears a few hours after irradiation and may subside within a day; may be sufficiently severe to necessitate interrupting a treatment series or to incapacitate the patient.
(BEIR III)

Radiation source
Equipment, or part thereof, or matter emitting or capable of emitting ionizing radiation.
(IEC 50-393-1993)

Radiation source
The region and/or material from which the radiation emanates.
(NCRP 102)

Radiation source
An x-ray tube or radioactive isotope.
(ANSI N43.2-1977)

Radiation source
An apparatus or a material emitting or capable of emitting ionizing radiation.
(ANSI N1.1-1976)

Radiation source
Usually a man-made, sealed source of radioactivity used in teletherapy, radiography, as a power source for batteries, or in various types of industrial gauges. Machines such as accelerators, and radioisotopic generators and natural radionuclides may also be considered as sources.
(USAEC-1974)

Radiation source housing
That portion of an x-ray system which contains the x-ray tube or radioactive isotope.
(ANSI N43.2-1977)

Radiation standards
Exposure standards, permissible concentrations, rules for safe handling, regulations for transportation, regulations for industrial control of radiation, and control of radiation exposure by legislative means. (See radiation protection, radiation protection guide.)
(USAEC-1974)

Radiation sterilization
Irradiation of a material, object, or species to ionizing radiation in order to destroy microorganism.
(IEC 50-393-1993)

Radiation sterilization
Use of radiation to cause a plant or animal to become sterile, that is, incapable of reproduction. Also the use of radiation to kill all forms of life (especially bacteria) in food, surgical sutures, etc.
(USAEC-1974)

Radiation survey
An evaluation of the radiation hazard potential associated with a specified set of conditions incident to the production, use, release, storage, or presence of radiation sources.
(ANSI N43.1-1978)

Radiation survey
See protection survey.
(NBS 54)

Radiation therapy
Treatment of disease with any type of radiation. Often called radiotherapy. (See brachytherapy, teletherapy.)
(USAEC-1974)

Radiation transition
Transition of an atomic nucleus from an excited state into a lower energy state accompanied by gamma radiation emission.
(IEC 50-393-1993)

Radiation warning symbol
An officially prescribed symbol (a magenta trefoil on a yellow background) which should always be displayed when a radiation hazard exists.
(USAEC-1974)

Radiation weighting factor (w_R)
A factor selected to account for the biological effectiveness of the radiation incident on the body or, in the case of sources within the body, emitted by the source. It ranges from 1 to 20 depending on the radiation type and energy of the radiations.
(NCRP 121)

Radiation weighting factor (w_R)
The radiation weighting factor is a dimensionless factor to derive the equivalent dose from the absorbed dose averaged over a tissue or organ and is based on the quality of radiation.
(ICRP 68)

Radiation weighting factor (w_R)
Modifying factors which apply to the tissue or organ absorbed dose and are based on the type and quality of the radiation emitted by an internally deposited radionuclide. The specified values of w_R are given below:

Type of Radiation Energy Range Radiation Weighting Factor, w_R

Photons All energies 1

Electrons and muons All energies 1

Neutrons < 10 keV 5

10 keV to 100 keV 10

> 100 keV to 2 MeV 20

> 2 MeV to 20 MeV 10

> 20 MeV 5

Protons, other than recoil protons > 2 MeV 5

Alpha particles, fission fragments, heavy nuclei 20

Type of Radiation	Energy Range	Radiation Weighting Factor, w_R
Photons	All energies	1
Electrons and muons	All energies	1
Neutrons	< 10 keV	5
	10 keV to 100 keV	10
	> 100 keV to 2 MeV	20
	> 2 MeV to 20 MeV	10
	> 20 MeV	5
Protons, other than recoil protons	> 2 MeV	5
Alpha particles, fission fragments, heavy nuclei		20

(ICRP 60)

Radiation work permit (RWP)
An authorization to perform a specific procedure involving radiation exposure of personnel in a particular area. It contains detailed procedures for every aspect of the work to be done.
(NCRP 114)

Radiation worker
One who works with or around radiation, or who, in the course of completing a task, may be exposed to radiation (e.g., an x-ray technician).
(NCRP 51)

Radiation worker
Any individual engaged in work with radiation who incurs a certain likelihood of radiation exposure during his or her work, as an occupational risk. Radiation protection for such workers is under the direct supervision of the RPS.
(NCRP 48)

Radiation, annihilation
Electromagnetic radiation resulting from the mutual annihilation of matter and antimatter. The energy is determined by the rest mass of the particles. For example, a positron and electron annihilate to produce two 511-keV photons.
(HPJ 60)

Radiation, background
Radiation arising from radioactive material other than the one directly under consideration. Background radiation due to cosmic rays and natural radioactivity is always present. The maybe also be background radiation due to the presence of radioactive substances in other parts of the building, in the building material itself, etc.
(HPJ 60)

Radiation, characteristic (discrete)
Radiation originating from an atom following removal or an electron or excitation of the nucleus. The wavelength of the emitted radiation is specific depending only on the element concerned and the particular energy levels involved.
(HPJ 60)

Radiation, directly ionizing
Radiation consisting of directly ionizing particles.
(ANSI N1.1-1976)

Radiation, external
Exposure to ionizing radiation when the radiation source is located outside the body and the radiation must then penetrate into the deeper tissue.
(HPJ 60)

Radiation, external (radiation protection)
Ionizing radiation reaching the body from sources outside the body.
(ANSI N1.1-1976)

Radiation, indirectly ionizing
Radiation consisting of directly ionizing particles.
(ANSI N1.1-1976)

Radiation, internal
Exposure to ionizing radiation when the radiation source is within the body as a result of deposition of radioelements in body tissues.
(HPJ 60)

Radiation, internal (radiation protection)
Radiation originating within the body from radionuclides in body tissues.
(ANSI N1.1-1976)

Radiation, ionizing
Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, in its passage through matter.
(HPJ 60)

Radiation, ionizing
Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, by interaction with matter. Note: In the fields of regulation and radiation protection (and in this standard), visible and ultraviolet light are excluded.
(ANSI N2.1-1969)

Radiation, ionizing
Any electromagnetic or particulate radiation capable of producing ions, directly or indirectly, by interaction with matter. (In this report ionizing radiation refers to x rays and gamma rays from radioactive substances.)
(NCRP 49)

Radiation, scattered
Radiation which, during its passage through a substance, has been deviated in direction. It may also have been modified by an increase in wavelength. It is one form of secondary radiation.
(HPJ 60)

Radiations
Specific units or types of radiation.
(USAEC-1974)

Radiative capture
Capture of a particle by a nucleus followed by the immediate emission of gamma radiation.
(IEC 50-393-1993)

Radiative capture
A nuclear capture process whose prompt result is emission of electromagnetic radiation only, as when a nucleus captures a neutron and emits gamma rays. (See capture.)
(USAEC-1974)

Radiative inelastic scattering
Inelastic scattering in which some of the kinetic energy of an incident particle goes into excitation of the target nucleus followed by subsequent emission of one or more photons.
(IEC 50-393-1993)

Radio frequency protection guides (RFPG)
The radio frequency field strengths or equivalent plane wave power densities which should not be exceeded without
(1) careful consideration of the reasons for doing so,
(2) careful estimation of the increased energy deposition in the human body, and
(3) careful consideration of the increased risk of unwanted biological effects.
(ANSI C95.1-1982)

Radio-
A general prefix relating to radiation (e.g., radiosensitive) or state of being radioactive (e.g., radioiodine).
(NCRP 105)

Radio-
A prefix denoting radioactivity or a relationship to it, or a relationship to radiation.
(USAEC-1974)

Radio-bioassay meter
Assembly for measurement of the amount of radioactive material inhaled or ingested in a human body by measuring the radioactive emission in a given time interval of exhalation, blood, urine and excrements.
(IEC 50-394-1993)

Radioactivation
Activation.
(USAEC-1974)

Radioactive
Exhibiting radioactivity or pertaining to radioactivity.
(NCRP 118)

Radioactive
Exhibiting radioactivity.
(ANSI N1.1-1976)

Radioactive
Exhibiting radioactivity or pertaining to radioactivity.
(USAEC-1974)

Radioactive aerosol meter
Radioactive air contamination meter which is used for the continuous measurement of the radioactive emission from aerosols in the environmental air.
(IEC 50-394-1993)

Radioactive air contamination indicator
Radiation indicator designed to detect the presence of contamination by radioactive vapors, aerosols, gases, dusts or particulates, in air.
(IEC 50-394-1993)

Radioactive air contamination meter
Radiation meter used to measure the volume radioactive emission in a given time interval of dusts, particulates, aerosols, vapors or gases in air.
(IEC 50-394-1993)

Radioactive air contamination monitor
Radiation monitor designed to measure and check the volume radioactive emission in a given time interval of dusts, particulates, aerosols, vapors or gases in air.
(IEC 50-394-1993)

Radioactive article
Any manufactured instruments and articles such as an instrument, clock, electronic tube or apparatus, or similar instruments and articles having radioactive material as a component part.
(49CFR173.403)

Radioactive capsule
Small container, usually sealed, containing radioactive material.
(NCRP 48)

Radioactive cemetery, burial ground
Site reserved for dumping undesirable radioactive objects, with the appropriate protection.
(IEC 50-393-1993)

Radioactive chain
A radioactive series.
(USAEC-1974)

Radioactive chain; decay chain
A succession of nuclides, each of which transforms by radioactive decay into the next nuclide until a stable nuclide results.
(ANSI N1.1-1976)

Radioactive cloud
A mass of air and vapor in the atmosphere carrying radioactive debris from a nuclear explosion. (See atomic cloud.)
(USAEC-1974)

Radioactive concentration
See activity concentration.
(ANSI N1.1-1976)

Radioactive contamination
Radioactive substance dispersed in materials or places where it is undesirable, e.g. in or on the body of a person, internal or external contamination or on clothing or parts of a laboratory.
(IEC 50-393-1993)

Radioactive contamination
See contamination.
(HPJ 60)

Radioactive contamination
Radioactive substance dispersed in material or places where it is undesirable.
(NCRP 51)

Radioactive contamination
Deposition of radioactive material in any place where it may harm persons, spoil experiments, or make products or equipment unsuitable or unsafe for some specific use. The presence of unwanted radioactive matter. Also radioactive material found on the walls of vessels in used-fuel processing plants, or radioactive material that has leaked into a reactor coolant. Often referred to only as contamination. (See decontamination.)
(USAEC-1974)

Radioactive contents
The radioactive material, together with any contaminated liquids or gases, within the package.
(49CFR173.403)

Radioactive dating
A technique for measuring the age of an object or sample of material by determining the ratios of various radioisotopes or products of radioactive decay it contains. For example, the ratio of carbon-14 to carbon-12 reveals the approximate age of bones, pieces of wood, or other archeological specimens that contain carbon extracted from the air at the time of their origin. (See decay, radioactive.)
(USAEC-1974)

Radioactive decay
The spontaneous transformation of one nuclide into a different nuclide or into a different energy state of the same nuclide. The process results in a decrease, with time, of the number of the radioactive atoms in a sample. Decay generally involves the emission from the nucleus of alpha particles, beta particles or gamma rays.
(NCRP 118)

Radioactive decay
Decrease with time, by spontaneous nuclear transformation, of the activity of a radioactive substance or a mixture of such substances.
(IEC 50-393-1993)

Radioactive decay
See decay.
(HPJ 60)

Radioactive decay
The process by which a spontaneous change in nuclear state takes place. This process is accompanied by the emission of energy in various specific combinations of electromagnetic and corpuscular radiation, and neutrinos.
(ANSI N15.54-1988)

Radioactive decay
See decay, radioactive.
(ANSI N1.1-1976)

Radioactive decay
See decay, radioactive.
(USAEC-1974)

Radioactive decay chain
A series of nuclides in which each member transforms into the next through radioactive decay (not including spontaneous fission) until a stable nuclide has been formed.
(ANSI N1.1-1976)

Radioactive decay constant
See decay constant.
(ANSI N1.1-1976)

Radioactive decay constant (l)
The constant in the radioactive decay law, dN/dt = -lN. It is equal to (ln 2)/T_½, where T_½ is the half-life of the radionuclide in question.
(ANSI N15.22-1987)

Radioactive disintegration
Spontaneous nuclear transformation in which corpuscles or gamma radiation are emitted, or X radiation is emitted following electron capture, or the nucleus undergoes spontaneous nuclear fission.
(IEC 50-393-1993)

Radioactive effluent
Gaseous or liquid release of radioactive materials from a facility to a uncontrolled area.
(NCRP 59)

Radioactive equilibrium
State which prevails when the ratios between the activities of successive members of the series remain constant, in a radioactive series for which the radioactive half-life of the precursor is longer than that of any other member of the series.
(IEC 50-393-1993)

Radioactive equilibrium
That condition in which the activities of the members of a radioactive chain decrease exponentially in time with the half-life of the chain precursor. Such radioactive equilibrium is only possible when the half-life of the precursor is longer than that of any other chain member. If the precursor half-life is so long that the change in the precursor population during the period of interest can be ignored, all the activities become sensibly equal, and the equilibrium is said to be secular; otherwise it is said to be transient.
(ANSI N1.1-1976)

Radioactive fallout
(See fallout.)
(USAEC-1974)

Radioactive half-life
See half-life.
(HPJ 60)

Radioactive half-life
Time required for a radioactive nuclide to decrease to one-half its initial activity by radioactive decay.
(NCRP 81)

Radioactive half-life
Time required for a radioactive nuclide to decrease to one-half its initial activity by radioactive decay.
(NCRP 75)

Radioactive half-life
Time required for a radioactive nuclide to lose 50 percent of its activity by decay.
(NCRP 62)

Radioactive half-life
See half-life.
(USAEC-1974)

Radioactive half-life (T_1/2)
Time required for the activity to decrease to half of its initial value, for a single radioactive decay process.

(IEC 50-393-1993)

Radioactive half-life (T_1/2)
The time required for a given activity of a radioactive nuclide to decay to half that activity. The half-life is equal to (ln 2)/l, where l is the decay constant.
(ANSI N15.54-1988)

Radioactive isotope
Any isotope whose atoms are radioactive.
(NCRP 48)

Radioactive isotope
A radioisotope.
(USAEC-1974)

Radioactive marker
Licensed material used for depth determination or direction orientation. For purposes of this part, this term includes radioactive collar markers and radioactive iron nails.
(10CFR39.4)

Radioactive Material
Source, byproduct, or special nuclear material.
(10CFR110.2)

Radioactive material
Any material having a specific activity greater than 0.002 microcuries per gram (µCi/g). (See definition of specific activity).
(49CFR173.403)

Radioactive material
Material containing one or more constituents exhibiting radioactivity.
(IEC 50-393-1993)

Radioactive material
Any such material whether or not subject to licensing control by the Commission.
(10CFR20.201)

Radioactive material
A material of which one or more constituents exhibit radioactivity. Note: For special purposes such as regulation, this term may be restricted to radioactive material with an activity or a specific activity greater than a specified value.
(ANSI N1.1-1976)

Radioactive material
Material which is undergoing spontaneous nuclear disintegrations, resulting in the emission of corpuscular or electromagnetic radiation, such as alpha, beta, gamma, and X-rays.
(NBS 66)

Radioactive material
Any material, solid, liquid, or gas, that emits radiation spontaneously.
(NBS 61)

Radioactive material (ram)
Any material having a specific activity greater than 0.002 microcurie per gram. (See also Highway route controlled quantities.)
(ANSI N14.24-1985)

Radioactive material area
Any area within a controlled area, accessible to individuals, in which items or containers of radioactive material exist and the total activity of radioactive material exceeds the applicable values provided in appendix E of this part.
(10CFR835.2-1998)

Radioactive material transportation
The movement of radioactive material by aircraft, rail, vessel, or highway vehicle when such movement is subject to Department of Transportation regulations or DOE Orders that govern such movements. Radioactive material transportation does not include preparation of material or packagings for transportation, monitoring required by this part, storage of material awaiting transportation, or application of markings and labels required for transportation.
(10CFR835.2-1998)

Radioactive materials
Substances that spontaneously emit ionizing radiation. (Refer to the current revision of 49 CFR for minimum activity levels deemed significant for transport considerations.)
(ANSI N14.27-1986)

Radioactive neutron source
A neutron source consisting of a combination radioactive material and suitable target material. Neutron production occurs as a result of (a, n) or (g, n) reactions.
(NCRP 38)

Radioactive precautions sign
A sign, tag, or label required in all areas and on all containers where significant amounts of radioactive materials may be found. These must bear the three-bladed radiation caution sign in purple or magenta on a yellow background. The specific sign to be used depends on the type and degree of hazard present.
(NCRP 48)

Radioactive recoil
The acceleration of the residual nucleus upon emission of particular radiation from the parent radionuclide.
(NCRP 94)

Radioactive recoil
The acceleration of the residual nucleus upon emission of particular radiation from the parent radionuclide.
(NCRP 62)

Radioactive recoil
The acceleration of the residual nucleus upon emission of particular radiation from the parent radionuclide.
(NCRP 45)

Radioactive series
Succession of nuclides, each of which transforms by radioactive disintegration into the next until a stable nucleus results.
(IEC 50-393-1993)

Radioactive series
A succession of nuclides, each of which transforms by radioactive decay into the next until a stable nuclide results. The first member is called the parent and the subsequent members are called progeny, daughters or decay products.
(NCRP 118)

Radioactive series
A succession of nuclides, each of which transforms by radioactive disintegration into the next until a stable nuclide results. The first member is called the parent, the intermediate members are called daughters, and the final stable member is called the end product. (See decay, radioactive.)
(USAEC-1974)

Radioactive source
Any quantity of radioactive material which is intended for use as a source or ionizing radiation. (See also radiation source.)
(ANSI N1.1-1976)

Radioactive source
A radiation source.
(USAEC-1974)

Radioactive source backing
Component on which a radioactive material is applied to provide a radioactive source.
(IEC 50-393-1993)

Radioactive source, radionuclide source
Quantity of radioactive material having both an activity and a specific activity above specified levels.
(IEC 50-393-1993)

Radioactive standard
Radioactive source with a known nature and activity at a definite time and which can be used as a reference radiation source.
(IEC 50-393-1993)

Radioactive standard
See standard.
(HPJ 60)

Radioactive standard
A sample of radioactive material, usually with a long half-life, in which the number and type of radioactive atoms at a definite reference time is known. These are used in calibrating radiation measuring equipment or for comparing measurements in different laboratories.
(USAEC-1974)

Radioactive surface contamination indicator
Radiation indicator used to estimate the surface radioactive emission rate, due to contamination of the examined object.
(IEC 50-394-1993)

Radioactive surface contamination meter
Radiation meter used to measure radioactive contamination of an object by measuring its surface radioactive emission rate.
(IEC 50-394-1993)

Radioactive surface contamination monitor
Radiation monitor used to determine the radioactive contamination of an object by measuring and checking its surface radioactive emission rate.
(IEC 50-394-1993)

Radioactive tracer
A small quantity of radioactive isotope (either with carrier or carrier-free) used to follow biological, chemical or other processes, by detection, determination or localization of the radioactivity. (See carrier; tracer, isotopic.)
(USAEC-1974)

Radioactive tracer, radioactive indicator
Radioactive nuclide which, when attached to a chemically similar substance or injected into a biological or physical system can be traced by radiation detection devices, permitting determination of the distribution or location of the substance to which it is attached.
(IEC 50-393-1993)

Radioactive Waste
Solid, liquid, and gaseous materials that are radioactive or become contaminated with radioactivity and for which there is no further use.
(ANSI/HPS N13.45-1998)

Radioactive Waste
Any waste that contains or is contaminated with source, byproduct, or special nuclear material, including any such waste that contains or is contaminated with "hazardous waste" as defined in section 1004(5) of the Solid Waste Disposal Act, 42 U.S.C. 6903(5), but such term does not include radioactive material that is--
(1) Contained in a sealed source, or device containing a sealed source, that is being returned to any manufacturer qualified to receive and possess the sealed source or the device containing a sealed source;
(2) A contaminant on service equipment (including service tools) used in nuclear facilities, if the service equipment is being shipped for use in another nuclear facility and not for waste management purposes or disposal; or
(3) Generated or used in a United States Government waste research and development testing program under international arrangements.
(10CFR110.2)

Radioactive waste
Waste with levels or radioactivity sufficient to exceed background levels, and to be of potential concern to health, thereby requiring special storage, transportation, and disposal methods.
(NCRP 105)

Radioactive waste
Unwanted radioactive materials obtained in the processing or handling of radioactive materials.
(ANSI N1.1-1976)

Radioactive waste
(See waste, radioactive.)
(USAEC-1974)

Radioactive waste or waste
HLW and other radioactive materials other than HLW that are received for emplacement in a geologic repository.
(10CFR60.2)

Radioactive waste, radioactive burial ground
Useless radioactive materials obtained in the processing or handling of radioactive materials.
(IEC 50-393-1993)

Radioactive well logging
Downhole measurement of natural or induced radioactivity emitted by various rock formations penetrated by the drillhole.
(IEC 50-394-1993)

Radioactivity
The property or characteristic of radioactive material to undergo spontaneous transformations ("disintegrations" or "decay") with the emission of energy in the form of radiation. The rate of disintegration or transformation is termed the activity of the radionuclide. The units of activity are the curie (Ci) and the becquerel (Bq). (1 Ci = 3.7 x 10¹⁰ Bq).
(10CFR834.2)

Radioactivity
Property of certain nuclides of spontaneously emitting corpuscles, gamma radiation, or X radiation following electron capture.
(IEC 50-393-1993)

Radioactivity
The spontaneous decay or disintegration of an unstable nucleus, usually accompanied by the emission of alpha particles, beta particles or gamma rays.
(NCRP 118)

Radioactivity
The spontaneous decay or disintegration of an unstable atomic nucleus, usually accompanied by the emission of ionizing radiation.
(NCRP 111)

Radioactivity
The process whereby certain nuclides undergo spontaneous disintegration in which energy is liberated, generally resulting in the formation of new nuclides. The process is accompanied by the emission of one or more types of radiation, such as a particles and g photons.
(HPJ 60)

Radioactivity
The property of some nuclides of spontaneously emitting particles or gamma radiation, emitting x radiation after orbital electron capture, or undergoing spontaneous fission.
Artificial radioactivity - Man-made radioactivity produced by fission, fusion, particle bombardment, or electromagnetic irradiation.
Induced radioactivity - Radioactivity produced in a substance after bombardment with neutrons or other particles. The resulting activity is "natural radioactivity" if formed by nuclear reactions occurring in nature, and "artificial radioactivity" if the reactions are caused by man.
Natural radioactivity - The property of radioactivity exhibited by more than 50 naturally occurring radionuclides.
(BEIR IV)

Radioactivity
The spontaneous decay or disintegration of an unstable atomic nucleus, usually accompanied by the emission of ionizing radiation.
(NCRP 65)

Radioactivity
The spontaneous decay or disintegration of an unstable atomic nucleus accompanied by the emission of radiation.
(ERDA 76-21)

Radioactivity
The property of certain nuclides of spontaneously disintegrating, with emission of alpha or beta particles or gamma radiation, or particulate and gamma radiation simultaneously.
(NCRP 48)

Radioactivity
The property of certain nuclides of spontaneously emitting particle or gamma radiation or of emitting x radiation following orbital electron capture or undergoing spontaneous fission.
(ANSI N1.1-1976)

Radioactivity
The spontaneous decay or disintegration of an unstable atomic nucleus, usually accompanied by the emission of ionizing radiation. (Often shortened to "activity".) (See decay, radioactive.)
(USAEC-1974)

Radioactivity
Spontaneous nuclear disintegration with emission of corpuscular or electromagnetic radiations.
(NBS 66)

Radioactivity
Disintegration of unstable atomic nuclei by the emission of radiation, with a definite half-life.
(NBS 54)

Radioactivity area
An area in which radioactive materials are present.
(NCRP 51)

Radioactivity concentration guide
The concentration of radioactive material in an environment which would result in doses equal, over a period of time, to those in the Radiation Protection Guide. This Federal Radiation Council term replaces the former maximum permissible concentration.
(USAEC-1974)

Radioactivity standard
A radioactivity standard, as used in this standard, shall be either a radioactivity standard that has been certified by a laboratory recognized as a country's National Standardizing Laboratory for radioactivity measurements or a radioactivity standard that has been obtained from a supplier who participates in measurement assurance activities with the National Standardizing Laboratory when such standards are available. In such measurement assurance activities, the supplier's calibration value should agree with the National Standardizing Laboratory value with the overall uncertainty stated by the supplier in its certification of the same batch of sources or in its certification of similar sources.
(ANSI N42.12-1980)

Radioactivity, induced
Radioactivity produced in a substance after bombardment with neutrons or other particles. The resulting activity is natural radioactivity if formed by nuclear reaction occurring in nature and artificial radioactivity if the reactions are caused by humans.
(HPJ 60)

Radioactivity, induced
Radioactivity in nuclides produced by nuclear reactions.
(NCRP 51)

Radioactivity, induced
The radioactivity in nuclides which have been produced by man-made nuclear reactions.
(ANSI N1.1-1976)

Radioactivity, natural
The property of radioactivity exhibited by more than 50 naturally occurring radionuclides.
(HPJ 60)

Radioactivity, natural
Radioactivity of naturally occurring nuclides.
(ANSI N1.1-1976)

Radiobioassay
Measurement of amount or concentration of radionuclide material in the body or in biological material excreted or removed from the body and analyzed for purposes of estimating the quantity of radioactive material in the body.
(HPS N13.30-1996)

Radiobioassay
Measurement of amount or concentration of radioactive material in the body or in biological material excreted or removed from the body and analyzed for purposes of estimating the quantity of radioactive material in the body.
(ANSI N13.30-1989D)

Radiobiology
The body of knowledge and the study of the principles, mechanisms, and effects of ionizing radiation on living matter.
(USAEC-1974)

Radiobiology
The branch of biology which deals with the effects of radiation on biological systems.
(RHH)

Radiochemistry
That part of chemistry which deals with radioactive materials. (It includes the production of radionuclides and their compounds by processing irradiated or naturally occurring radioactive materials, the application of chemical techniques to nuclear studies, and the application of radioactivity to the investigation of chemical problems.)
(ANSI N1.1-1976)

Radiochemistry
The body of knowledge and the study of the chemical properties and reactions of radioactive materials.
(USAEC-1974)

Radiochemistry
The aspects of chemistry connected with radionuclides and their properties, with the behavior of minute quantities of radioactive materials by means of their radioactivity, and the use of radionuclides in the study of chemical problems.
(RHH)

Radiochromatograph
Apparatus intended to draw a representative curve of the activity of different components of a mixture, labeled with radionuclides and deposited separately in a gaseous or liquid carrier or on a solid substrate.
(IEC 50-394-1993)

Radiodefect detector
Radiation detector which operates by utilizing defects produced by ionizing radiation in the material constituting the sensitive volume of the detector.
(IEC 50-394-1993)

Radioecology
The body of knowledge and the study of the effects of radiation on species of plants and animals in natural communities.
(USAEC-1974)

Radioelement
Chemical element having one or more naturally occurring radioisotopes.
(IEC 50-393-1993)

Radioelement
An element containing one or more radioactive isotopes; a radioactive element.
(USAEC-1974)

Radiogalaxies
Any galaxy emitting more than the normal energy within the radiofrequency band from 10 MHz to 10 GHz.
(NCRP 94)

Radiogalaxies
Any galaxy emitting more than the normal energy within the radiofrequency band from 10 MHz to 10 GHz.
(NCRP 45)

Radiogenic
Of radioactive origin; produced by radioactive transformation. (See decay, radioactive; transmutation.)
(USAEC-1974)

Radiograph
A film or other record produced by the action of x rays on a sensitized surface.
(NCRP 107)

Radiograph
A film or other record produced by the action of x rays on a sensitized film.
(NCRP 102)

Radiographer
Any individual who performs or who, in attendance at the site where the sealed source or sources are being used, personally supervises industrial radiographic operations and who is responsible to the licensee for assuring compliance with the requirements of the Commission's regulations and the conditions of the license.
(10CFR34.3)

Radiographer
Any individual who performs or who, in attendance at the site where the sealed source or sources are being used, personally supervises radiographic operations and who is responsible to the licensee for assuring compliance with the requirements of the Commission's regulations and the conditions of the license.
(10CFR30.4)

Radiographer
A member of a profession supplementary to medicine qualified to operate equipment used for radiation therapy. Synonyms in some countries include "radiotherapy technician" or "radiotherapy technologist".
(ICRP 44)

Radiographer certification
Written approval received from a certifying entity stating that an individual has satisfactorily met certain established radiation safety, testing, and experience criteria.
(10CFR34.3)

Radiographer's assistant
Any individual who under the direct supervision of a radiographer, uses radiographic exposure devices, sealed sources or related handling tools, or radiation survey instruments in industrial radiography.
(10CFR34.3)

Radiographer's assistant
Any individual who under the personal supervision of a radiographer, uses radiographic exposure devices, sealed sources or related handling tools, or radiation survey instruments in radiography.
(10CFR30.4)

Radiographic exposure device
Any instrument containing a sealed source fastened or contained therein, in which the sealed source or shielding thereof may be moved, or otherwise changed, from a shielded to unshielded position for purposes of making a radiographic exposure.
(10CFR34.2)

Radiographic exposure device (also called a camera, or a projector)
Any instrument containing a sealed source fastened or contained therein, in which the sealed source or shielding thereof may be moved, or otherwise changed, from a shielded to unshielded position for purposes of making a radiographic exposure.
(10CFR34.3)

Radiographic operations
All activities associated with the presence of radioactive sources in a radiographic exposure device during use of the device or transport (except when being transported by a common or contract transport), to include surveys to confirm the adequacy of boundaries, setting up equipment and any activity inside restricted area boundaries.
(10CFR34.3)

Radiography
The examination of the structure of materials by nondestructive methods, utilizing sealed sources of byproduct materials.
(10CFR30.4)

Radiography
The examination of the structure of materials by nondestructive methods, utilizing sealed sources of byproduct materials.
(10CFR34.2)

Radiography
The production of images on film or other record by the action of x rays transmitted through the patient.
(NCRP 107)

Radiography
The production of images on film by the action of x rays on a sensitized surface.
(NCRP 102)

Radiography
The observation of internal features of an object by means of an image produced on photographic film by radiation transmitted through the object.
(NCRP 68)

Radiography
The observation of internal features of an object by means of an image produced on photographic film by radiation transmitted through the object.
(NCRP 48)

Radiography
The use of ionizing radiation for the production of shadow images on a photographic emulsion. Some of the rays (gamma rays or X rays) pass through the subject, while others are partially or completely absorbed by the more opaque parts of the subject and thus cast a shadow on the photographic film.
(USAEC-1974)

Radiography
The making of shadow images on photographic emulsion by the action of ionizing radiation. The image is the result of the differential attenuation of the radiation in its passage through the object being radiographed.
(RHH)

Radiography source
A sealed source of small dimensions designed for use in industrial or medical radiography.
(ICRU 18)

Radioisotope
Radioactive isotope of a given element.
(IEC 50-393-1993)

Radioisotope
An unstable atom having the same atomic number but a different number of neutrons in the nucleus than the comparable stable atom. (See isotope).
(NCRP 105)

Radioisotope
The radioactive isotopes of a given element, usually referred to as radioisotopes of that element. The term radioisotope is loosely, but commonly, used for radionuclide. (See radionuclide.)
(ANSI N15.22-1987)

Radioisotope
A radioactive isotope of a specified element. Note: The term should not be used with the meaning radionuclide.
(ANSI N1.1-1976)

Radioisotope
A radioactive isotope. An unstable isotope of an element that decays or disintegrates spontaneously, emitting radiation. More than 1300 natural and artificial radioisotopes have been identified. (See decay, radioactive; isotope.)
(USAEC-1974)

Radioisotope
An isotope that exhibits radioactivity, which is the process of nuclear disintegration with emission of corpuscular or electromagnetic radiation.
(ANSI N7.2-1963)

Radioisotope
A radioactive nuclide.
(NBS 73)

Radioisotope
A radioactive isotope of an element.
(NBS 66)

Radioisotope
A radioactive isotope.
(NBS 54)

Radioisotope, radionuclide
A radioactive species of atom characterized by the number of protons and neutrons in its nucleus.
(FGR 11)

Radioisotopes
A radioactive atomic species of an element with the same atomic number and usually identical chemical properties.
(BEIR IV)

Radioisotopes
A radioactive atomic species of an element with the same atomic number and usually identical chemical properties.
(BEIR III)

Radioisotopic generator
A small power generator that converts the heat released during radioactive decay directly into electricity. These generators generally produce only a few watts of electricity and use thermoelectric or thermionic converters. Some also function as electrostatic converters to produce a small voltage. Sometimes called an "atomic battery". (See decay, radioactive; SNAP.)
(USAEC-1974)

Radiological area
Any area within a controlled area defined in this section as a "radiation area," "high radiation area," "very high radiation area," "contamination area," "high contamination area," or "airborne radioactivity area."
(10CFR835.2-1998)

Radiological area
Any area within a controlled area which must be posted as a "radiation area," "high radiation area," "very high radiation area," "contamination area," "high contamination area," or "airborne radioactive area" in accordance with §835.603.
(10CFR835.2-1993)

Radiological health company
The radiological health company is a private organization that may be hired by the shipper, carrier, or any other interested party to perform radiation surveys and conduct personnel dosimetry programs as part of the shipping or transfer operations.
(ANSI N14.24-1985)

Radiological sabotage
Any deliberate act directed against a plant or transport in which an activity licensed pursuant to the regulations in this chapter is conducted, or against a component of such a plant or transport which could directly or indirectly endanger the public health and safety by exposure to radiation.
(10CFR73.2)

Radiological safety officer
Person responsible for radiological safety in connection with use, handling, and storage of radioactive materials. It is his duty to make certain that all procedures are carried out in compliance with established rules, including regulations contained in this Handbook.
(NBS 54)

Radiological worker
A general employee whose job assignment involves operation of radiation producing devices or working with radioactive materials, or who is likely to be routinely occupationally exposed above 0.1 rem (0.001 sievert) per year total effective dose equivalent.
(10CFR835.2-1993)

Radiology
The science which deals with the use of all forms of ionizing radiation in the diagnosis and the treatment of disease.
(USAEC-1974)

Radiology
That branch of medicine which deals with the diagnostic and therapeutic applications of radiant energy including x rays and radionuclides.
(RHH)

Radioluminescence
Visible light caused by radiations from radioactive substances; an example is the glow from luminous paint containing radium and crystals of zinc sulfide, which give off light when struck by alpha particles from the radium. (See luminescence.)
(USAEC-1974)

Radioluminescent detector
Radiation detector which operates by utilizing luminescence in the material constituting the sensitive volume of the detector.
(IEC 50-394-1993)

Radiolysis
The decomposition of a material by ionizing radiation.
(ANSI N1.1-1976)

Radiolysis
The dissociation (or decomposition) of molecules by radiation. Example: A small proportion of water in a reactor core dissociates into hydrogen and oxygen during operation of the reactor.
(USAEC-1974)

Radiometric
Pertaining to measurements made on radioactive nuclides.
(ANSI N15.54-1988)

Radiometric analysis
An analytical technique that includes procedures for measuring by radioactive tracer methods elements which themselves are not radioactive.
(ANSI N1.1-1976)

Radiometric force
Force produced by light pressure
(AM-1993)

Radiomimetic substances
Chemical substances which cause biological effects similar to those caused by ionizing radiation.
(USAEC-1974)

Radiomutation
A permanent, transmissible change in form, quality, or other characteristic of a cell or offspring from the characteristics of its parent, due to radiation exposure. (See genetic effects of radiation, mutation.)
(USAEC-1974)

Radionuclide
A type of atom which spontaneously undergoes radioactive decay.
(40CFR61.101)

Radionuclide
A type of atom which spontaneously undergoes radioactive decay.
(40CFR61.91)

Radionuclide
A nuclide that is radioactive.
(NCRP 118)

Radionuclide
Radioactive nuclide.
(IEC 50-393-1993)

Radionuclide
A radioactive species of atom characterized by its mass num-ber, atomic number and nuclear energy state, provided that the mean life in that state is long enough to be observable.
(NCRP 114)

Radionuclide
A radioactive (unstable) nuclide. Technically enhanced radioactivity.
(HPJ 60)

Radionuclide
Any nuclide whose atoms are radioactive.
(NCRP 111)

Radionuclide
A radioactive nuclide. (See nuclide).
(NCRP 105)

Radionuclide
A radioactive species of an atom characterized by the constitution of its nucleus.
(BEIR IV)

Radionuclide
A radioactive nuclide. (See nuclide).
(ANSI N15.22-1987)

Radionuclide
A radioactive nuclide. A nuclide that is radioactive.
(NCRP 87)

Radionuclide
A nuclide that is radioactive.
(NCRP 84)

Radionuclide
A radioactive nuclide. A nuclide that is radioactive.
(NCRP 65)

Radionuclide
A radioactive nuclide. A nuclide that is radioactive.
(ANSI N1.1-1976)

Radionuclide
A radioactive nuclide. (See nuclide).
(USAEC-1974)

Radionuclide (radioactive nuclide)
Any radioactive form of an element.
(NCRP 48)

Radionuclide exposure
The situation leading to intake of a radionuclide and/or the situation after a radionuclide has been deposited in an organ or tissue.
(NCRP 87)

Radionuclide exposure
The situation leading to intake of a radionuclide and/or the situation after a radionuclide has been deposited in an organ or tissue.
(NCRP 84)

Radiopharmaceutical
A radioactive pharmaceutical or chemical used for diagnostic or therapeutic purposes.
(NCRP 107)

Radiopharmaceutical
A radioactive drug product administered to a patient for diagnostic or therapeutic nuclear medicine procedures.
(NCRP 105)

Radiopharmaceutical
A pharmaceutical compound which has been tagged with a radionuclide.
(RHH)

Radiopharmacy
The preparation of radioactive pharmaceuticals and radionuclides. Also, the place at which radiopharmaceuticals are prepared.
(NCRP 107)

Radioresistance
A relative resistance of cells, tissues, organs, or organisms to the injurious action of radiation.
(USAEC-1974)

Radioresistance
Relative resistance of cells, tissues, organs, or organisms to the injurious action of radiation. The term may also be applied to chemical compounds or to any substances.
(RHH)

Radioresistance (radiation protection)
The relative resistance of cells, tissues, organs or organisms to the injurious action of ionizing radiation. The term may also be applied to chemical compounds.
(ANSI N1.1-1976)

Radiosensitivity
The relative susceptibility of cells, tissues, organs, organisms, and any substances to the injurious action of ionizing radiation. Radio-resistance and the radiosensitivity are usually employed in a comparative sense, rather than in an absolute one.
(ANSI N1.1-1976)

Radiosensitivity
A relative susceptibility of cells, tissues, organs or organisms to the injurious action of radiation.
(USAEC-1974)

Radiosensitivity
Relative susceptibility of cells, tissues, organs, organisms, or any living substance to the injurious action of radiation. Radiosensitivity and its antonym radioresistance, are currently used in a comparative sense, rather than in an absolute one.
(BEIR I)

Radiosensitivity (radiation protection)
Relative susceptibility of cells, tissue, organs and organisms to the injurious action of radiation; "radiosensitivity" and its antonym, radioresistance, are used in a comparative sense rather than an absolute one.
(BEIR IV)

Radiotherapy
Radiation therapy.
(USAEC-1974)

Radiotoxicity
The toxicity attributable to the radiation emitted by a radioactive substance within the body.
(ANSI N542-1977)

Radium
[Symbol Ra] A radioactive metallic element with atomic number 88. As found in nature, the most common isotope has an atomic weight of 226. It occurs in minute quantities associated with uranium in pitchblende, carnotite and other minerals; the uranium decays to radium in a series of alpha and beta emissions. By virtue of being an alpha- and gamma emitter, radium is used as a source of luminescence and as a radiation source in medicine and radiography.
(USAEC-1974)

Radon
A radioactive noble gas; in this Report, either ²²²Rn or ²²⁰Rn.
(NCRP 118)

Radon
In this report refers to the radioactive inert gas, ²²²Rn.
(NCRP 103)

Radon
As used in this report, refers to the radioactive noble gas ²²²Rn.
(NCRP 78)

Radon
[Symbol Rn] A radioactive element, one of the heaviest gases known. Its atomic number is 86, and its atomic weight is 222. It is a daughter of radium in the uranium radioactive series.
(USAEC-1974)

Radon breath analysis
Examination of exhaled air for the presence of radon to determine the presence and quantity of radium in the human body. (See personnel monitoring.)
(USAEC-1974)

Radon content meter
Radiation meter used to measure the content per unit volume of radon and its daughters in the atmosphere.
(IEC 50-394-1993)

Radon daughter products
In this report, refers to the short-lived daughter products of radon.
(NCRP 97)

Radon daughters
The short-lived radionuclides formed as a result of decay of ²²²Rn. They consist of ²¹⁸Po (RaA), ²¹⁴Pb (RaB), ²¹⁴Bi (RaC), and ²¹⁴Po (RaC'). Their effective combined halflife is about 30 minutes.
(NCRP 78)

Radon decay products
In this report, the short-lived radionuclides formed as a result of ²²²Rn. They consist of ²¹⁸Po (RaA), ²¹⁴Pb (RaB), ²¹⁴Bi (RaC), and ²¹⁴Po (RaC'). Their respective half-lives are 3.05 minutes, 26.8 miFnutes, 19.7 minutes, and 164 microseconds, Their effective combined half life is approximately 30 minutes.
(NCRP 103)

Radon decay products
Radon daughter products.
(NCRP 97)

Radon flux
The number of radon atoms passing through a unit cross-sectional area per unit time.
(NCRP 118)

Radon progeny
The decay products of radon-222, used herein in the more limited sense of the short-lived decay products from polonium-218 through polonium-214.
(ICRP 65)

Radon progeny
Radon daughter products.
(NCRP 97)

Radon progeny (radon daughters)
The short-lived radionuclides formed as a result of decay of radon. For ²²²Rn, they consist of ²¹⁸Po (RaA), ²¹⁴Pb (RaB), ²¹⁴Bi (RaC) and ²¹⁴Po (RaC'). Combined numbers of these radionuclides are reduced by one-half approximately every 30 min.
(NCRP 118)

Radon prone
An area in which the characteristics of the ground cause more buildings than usual to have elevated radon levels.
(ICRP 65)

Radon source strength
The intensity, power, or concentration of radon action from its point of origin. Refers to the general intensity of radon evolution from a specific soil or rock type beneath a house.
(RRM)

Radon-222 generating waste
Any waste or residue in areas used for storage or disposal that contains radium-226 in concentrations that are sufficient to emit radon-222 in excess of 20 pCi/m²-sec, if not otherwise controlled.
(10CFR834.2)

Raffinate
Fluid from the purification step in a mill, depleted in the mineral of interest relative to the fluid entering the purification process. The raffinate may be reused in the process stream or discarded.
(NCRP 118)

Ramp insertion of reactivity
A linear increase of reactivity with time.
(ANSI N1.1-1976)

Random coincidence
False coincidence due to pulses from unrelated events, where the pulses happen to arrive at the input of a coincidence circuit, within the coincidence resolving time.
(IEC 50-394-1993)

Random error
The deviation of a random variable from its expected value.
(10CFR74.4)

Random error
An error associated with random (statistical) fluctuations inherent to or associated with the determination of a particular quantity. Such errors may be evaluated using standard statistical techniques.
(NCRP 112)

Random error
The deviation of a measured value from the reference value as a result of statistical fluctuations.
(ANSI N15.54-1988)

Random photon summing
The simultaneous detection of two or more photons originating from the disintegrations of more than one atom.
(ANSI N42.12-1980)

Random summing
The simultaneous detection of two or more photons originating from the disintegrations of more than one atom.
(ANSI N42.14-1978)

Range
All values lying between the upper and lower detection limits.
(ANSI N42.17C-1989)

Range
All values lying between the upper and lower indicated limits.
(ANSI N42.17A-1989)

Range
All values lying between the upper and lower indicated limits.
(ANSI N42.17B-1989)

Range
The set of values lying between the upper and lower detection limits.
(ANSI N320-1979)

Range
The set of values lying between the upper and lower detection limits.
(ANSI N323-1978)

Range
The distance that a charged particle penetrates a material before it ceases to ionize. In the case of electrons, the range is not well defined.
(ANSI N1.1-1976)

Range, counter
The range of reactor power within which a particle counter is required for adequate measurement of the neutron flux density.
(ANSI N1.1-1976)

Range, extrapolated
See extrapolated range.
(ANSI N1.1-1976)

Range, ion or electron
The distance into a material that a charged particle penetrates before it ceases to ionize. "Projected extrapolated range" is the distance into a material that is determined by extrapolating the straight-line portion of the curve of absorbed dose vs. distance, to zero dose. "Maximum range" is the distance into a material that is determined by the interception of the curve of absorbed dose vs. distance with the radiation background; used particularly to determine the maximum range of electrons.
(NCRP 51)

Range, operating
The range of reactor power within which a reactor is designed to operate in a steady-state condition.
(ANSI N1.1-1976)

Range, period
See range, time constant.
(ANSI N1.1-1976)

Range, power
The range of power within which reactor control is primarily based upon measurement of temperature or neutron flux density rather than time constant (period).
(ANSI N1.1-1976)

Range, source
The range of reactor power within which a supplementary neutron source is required to facilitate the measurement of neutron flux density.
(ANSI N1.1-1976)

Range, time constant
The range of power within which reactor control is primarily based upon measurement of reactor time constant (reactor period) rather than reactor power. (Also called range, period.)
(ANSI N1.1-1976)

Range-energy relation
An expression giving the range of an energetic particle in matter as a function of the energy of the particle.
(ANSI N1.1-1976)

Rare earth
Any of a series of very similar metals ranging in atomic number from 57 through 71.
(RHH)

Rare earths
A group of 15 chemically similar metallic elements, including Elements 57 through 71 on the Periodic Table of the Elements, also known as the Lanthanide Series. (See lanthanide series.)
(USAEC-1974)

Rate, recovery
The rate at which recovery takes place after radiation injury. It may proceed at different rates for different tissues.
(BEIR I)

Ratemeter
Apparatus which gives a continuous indication of the average counting rate.
(IEC 50-394-1993)

Raw (calibration) data
The calibration increment measurements and corresponding measurement system responses as obtained during calibration and before they have been standardized.
(ANSI N15.19-1989)

Rayleigh scattering
Scattering of radiation occurring when the size of the scattering object is much smaller than the radiation wavelength
(AM-1993)

Rays
Alpha: Beams of helium nuclei (2 protons and 2 neutrons)
Beta: Beams of electrons or positrons.
Gamma: Beams of high-energy photons from radioactively decaying elements.
X: Beams of mixed lower energy photons.
Neutron: Beams of neutrons.
Proton: Beams of protons.
(BEIR I)

RBE
The RBE is defined, for a specific radiation (A), as:
RBE(A) =Dose of reference radiation required to produce a specific level response/Dose of radiation A required to produce an equal response.
(NCRP 104)

RBE
See relative biological effectiveness.
(ANSI N1.1-1976)

RBE
The abbreviation of the term "relative biological effectiveness," which is evaluated numerically as the inverse ratio of the doses of two different radiation necessary to produce the same bilogical effect. Values of RBE with reference to gamma rays of radium as a standard are listed below as they are used in this Handbook. They are of an interim nature and are intended only for use in calculating the maximum permissible dose levels.

Radiation RBE

Gamma rays from radium (filtered by 0.5mm of Pt) 1.0 (Standard)

X-rays of energy 0.1 to 100 Mev 1.0

Electrons of energy 0.1 to 100 Mev 1.0

Protons 10.0

Fast Neutrons 10.0

Alpha Rays 20.0

Radiation	RBE
Gamma rays from radium (filtered by 0.5mm of Pt)	1.0 (Standard)
X-rays of energy 0.1 to 100 Mev	1.0
Electrons of energy 0.1 to 100 Mev	1.0
Protons	10.0
Fast Neutrons	10.0
Alpha Rays	20.0

(NBS 55)

RBE (relative biological effectiveness)
RBE is used to compare the effectiveness of absorbed doses of radiation of different types. For protection purposes certain values of RBE have been agreed upon.
(NBS 73)

RBE dose
An old term with the same meaning as dose equivalent now.
(NCRP 84)

RBE dose
RBE dose for protection purposes is the product of absorbed dose in rads and the RBE. The unit of RBE dose is the rem.
(NBS 73)

RBE dose
Product of absorbed dose (as measured in rads) and RBE. The RBE dose is measured in rems.
(NBS 63)

RBE dose
RBE stands for relative biological effectiveness. An RBE dose is the dose measured in rems.
(NBS 59)

Re-entrainment
Return of particles to an air stream after deposition on a collecting surface
(AM-1993)

Reaction (nuclear)
An induced nuclear disintegration; i.e., a process occurring when a nucleus comes in contact with a photon, an elementary particle, or another nucleus. In many cases the reaction can be represented by the symbolic equation: X + a ® Y + b or, in abbreviated form X (a,b) Y.
X is the target nucleus, a is the incident particle or photon, b is an emitted particle or photon, and Y is the product nucleus.
Chain Reaction: Any chemical or nuclear process in which some products or energy released by the process are instrumental in the continuation or magnification of the process.
Endoergic Reaction: Reaction which absorbs energy.
Endothermic Reaction: Reaction which absorbs energy, specifically in the form of heat.
Exothermic Reaction: Reaction which liberates energy, specifically as heat.
Thermonuclear Reaction: A nuclear reaction in which the energy necessary for the reaction is provided by colliding particles possessing kinetic energy by virtue of their thermal agitation. Such reactions occur at appreciable rates only for temperatures of millions of degrees and higher. Their rate increases with temperature. The energy of most stars is believed to be derived from exothermic thermonuclear reactions.
(RHH)

Reaction energy, nuclear
The kinetic energy of the resultant particles and photons less the kinetic energy of the primary particles and photons for a nuclear reaction.
(ANSI N1.1-1976)

Reaction rate
The number of neutrons (or nuclei) undergoing a reaction per unit time.
(ANSI N1.1-1976)

Reaction, induced nuclear
An event in which, because of interaction with a particle or photon, a nucleus is changed in mass, charge, or energy state.
(ANSI N1.1-1976)

Reaction, nuclear
An event in which a nucleus is changed in mass, charge or energy state.
(ANSI N1.1-1976)

Reaction, spontaneous nuclear
A nuclear reaction in which a nucleus spontaneously changes in mass, charge, or energy state.
(ANSI N1.1-1976)

Reaction, thermonuclear
A nuclear reaction in which the energy necessary for the reaction is provided by colliding particles that have kinetic energy by virtue of their thermal agitation. Such reactions occur at applicable rates only for temperatures of millions of degrees and higher, the rate increasing enormously with temperature.
(HPJ 60)

Reactive near-field region
The region in a field of an antenna in which reactive fields are significant, i.e., in which most of the stored electromagnetic energy associated with the antenna is located. In the reactive near-field region, E and H may vary rapidly from point to point. This region starts immediately at the antenna and extends from it for only a short distance, less than or equal to the free space wavelength. The fields can be inductive or capacitive in nature and relate to the inductance or capacitance of the antenna itself. Inductive and capactive fields can coexist near one antenna; in some instances one of them can predominate strongly over the other. In the course of a cycle, a portion of this energy is not propagated beyond the near field and hence, is considered to be stored energy. (See "antenna, field regions of", "near-field region", "Fresnel region", and "radiating near field region".)
(NCRP 67)

Reactivity
A parameter, r, giving the deviation from criticality of a nuclear chain-reaction medium such that positive values correspond to a supercritical state and negative values to a subcritical state. Quantitatively,

where k_eff is the effective multiplication factor. The reactivity is expressed in terms of many different units, such as dollar, cent, and inhour.
(ANSI N1.1-1976)

Reactivity
A measure of the departure of a nuclear reactor from criticality. It is about equal to the effective multiplication factor minus one and is thus precisely zero at criticality. If there is excess reactivity (positive reactivity), the reactor is supercritical and its power will rise. Negative reactivity (subcriticality) will result in a decreasing power level. (See criticality, dollar, excess reactivity, multiplication factor, subcritical assembly, supercritical reactor.)
(USAEC-1974)

Reactivity (r)
Quantity equal to:

where k_eff is the effective multiplication factor.
(IEC 50-393-1993)

Reactivity coefficient
The change in reactivity caused by inserting a small amount of a substance in a reactor. The reactivity coefficient of a substance may depend upon the amount and distribution of the substance inserted, but is usually quoted as the reactivity change per unit mass of the substance at specific positions in the reactor or s a uniform distribution. Void coefficients are special cases of the reactivity coefficients of substances.
(ANSI N1.1-1976)

Reactivity meter
Electronic assembly which, in association with one or more detectors, gives an indication of the reactivity of a nuclear reactor.
(IEC 50-394-1993)

Reactivity oscillator
Any device used to cause the reactivity of a system to vary periodically. The magnitude and phase of the resulting fluctuations in neutron flux density may be used to gain information either about the reactor as a whole or about the absorbing sample. (Also called pile oscillator.)
(ANSI N1.1-1976)

Reactivity temperature coefficient
Partial derivative of reactivity with respect to temperature.
(IEC 50-393-1993)

Reactivity, excess
The maximum reactivity attainable at any time by adjustment of the control members.
(ANSI N1.1-1976)

Reactor
As used in ANSI N320-1979, reactor means a nuclear reactor designed for and capable of operation at a steady state reactor power level of > 1 MWth.
(ANSI N320-1979)

Reactor
See nuclear reactor.
(USAEC-1974)

Reactor control
Intentional variation of the reaction rate in a reactor or the adjustment of reactivity to maintain a desired state of operation.
(IEC 50-393-1993)

Reactor coolant pressure boundary
All those pressure-containing components of boiling and pressurized water-cooled nuclear power reactors, such as pressure vessels, piping, pumps, and valves, which are:
(1) Part of the reactor coolant system, or
(2) Connected to the reactor coolant system, up to and including any and all of the following: (i) The outermost containment isolation valve in system piping which penetrates primary reactor containment, (ii) The second of two valves normally closed during normal reactor operation in system piping which does not penetrate primary reactor containment, (iii) The reactor coolant system safety and relief valves. For nuclear power reactors of the direct cycle boiling water type, the reactor coolant system extends to and includes the outermost containment isolation valve in the main steam and feedwater piping.
(10CFR50.2)

Reactor facility
The structures, systems and components used for the operation of a nuclear reactor. If a site contains more than one nuclear reactor, reactor facility means all structures, systems, and components used for operation of the nuclear reactors at the site.
(ANSI N320-1979)

Reactor lattice
Array of fuel and other materials arranged according to a regular pattern.
(IEC 50-393-1993)

Reactor noise
In a nuclear reactor: the fluctuations in neutron flux density, and hence power, caused by the stochastic nature of the nuclear processes or by random fluctuations in mechanical or hydrodynamic processes having a bearing on reactivity.
(ANSI N1.1-1976)

Reactor oscillator
A device which produces periodic variations of reactivity by the oscillatory movement of an inserted material. (Also called pile oscillator.)
(ANSI N1.1-1976)

Reactor safety fuse
Self-contained device designed to respond to excessive temperature or flux in a reactor and to act to reduce the reaction rate to a safe level.
(IEC 50-394-1993)

Reactor time constant, reactor period
Time required for the neutron fluence rate in a reactor to change by a factor e equal to 2.718..., when the fluence rate is rising or falling exponentially.
(IEC 50-393-1993)

Reactor vessel
Principal vessel surrounding the reactor core.
(IEC 50-393-1993)

Reactor vessel
The principal vessel surrounding at least the reactor core.
(ANSI N1.1-1976)

Reactor, beam
A reactor specially designed to produce beams of neutrons used for research outside the reactor.
(ANSI N1.1-1976)

Reactor, biomedical irradiation
A reactor employed for the primary purpose of affecting biological processes by utilization of the reactor-generated ionizing radiation. Examples of such utilization are cancer research, and determining the effects of varying radiation levels on living matter. (See reactor, irradiation.)
(ANSI N1.1-1976)

Reactor, boiling
A reactor whose primary coolant is allowed to boil.
(ANSI N1.1-1976)

Reactor, breeder
A reactor which produces more fissile material than it consumes, i.e., has a conversion ratio greater than unity.
(BEIR III)

Reactor, breeder
A reactor which produces more fissile material than it consumes, i.e., has a conversion ratio greater than unity.
(ANSI N1.1-1976)

Reactor, breeder
A reactor which produces more fissile material than it consumes, i.e., has a conversion ratio greater than unity.
(BEIR I)

Reactor, breeder
A reactor which produces more fissile material than it consumes, i.e., has a conversion ratio greater than unity.
(RHH)

Reactor, burner
A reactor in which no significant conversion takes place.
(ANSI N1.1-1976)

Reactor, chemonuclear
A reactor designed as a radiation source for making chemical transformations on an industrial scale. (Also called reactor, chemical processing.)
(ANSI N1.1-1976)

Reactor, circulating fuel
A reactor whose fuel (fluid or fluidized) circulates through the core.
(ANSI N1.1-1976)

Reactor, converter
A reactor which produces fissile atoms from fertile atoms, but has a conversion ratio of less than one.
(BEIR III)

Reactor, converter
A reactor in which significant conversion takes place.
(ANSI N1.1-1976)

Reactor, converter
A reactor which produces fissile atoms from fertile atoms, but has a conversion ratio of less than one.
(BEIR I)

Reactor, converter
A reactor which produces fissile atoms from fertile atoms, but has a conversion ratio of less than one.
(RHH)

Reactor, demonstration
A reactor designed to demonstrate the technical feasibility and explore the economic potential of a given type of reactor. It may, in some cases, also serve as a prototype reactor.
(ANSI N1.1-1976)

Reactor, direct-cycle
A reactor in which the primary coolant is used directly to produce useful power.
(ANSI N1.1-1976)

Reactor, dual-cycle
A reactor from which useful power is produced by utilization of heat from both the primary and secondary coolant circuits.
(ANSI N1.1-1976)

Reactor, epithermal
A reactor in which fission is induced predominantly by epithermal neutrons.
(ANSI N1.1-1976)

Reactor, experimental
A reactor operated primarily to obtain reactor physics or engineering data for the design or development of a reactor or type of reactor. Reactors in this class include; zero-power reactor (may also be a research reactor); reactor experiment; and prototype reactor.
(ANSI N1.1-1976)

Reactor, fast
A reactor in which fission is induced predominantly by fast neutrons. (Also called reactor, fast neutron.)
(ANSI N1.1-1976)

Reactor, fluidized bed
A reactor in which the fuel is in the form of a bed of particles which are maintained in a state of noncirculating suspension during reactor operation by the flow of the fluid coolant.
(ANSI N1.1-1976)

Reactor, heterogeneous
A reactor in which the core materials are segregated to such an extent that its neutron characteristics cannot be accurately described by the assumption of homogeneous distribution of the materials throughout the core.
(ANSI N1.1-1976)

Reactor, high-flux
A reactor capable of providing neutron flux densities greater than approximately 10¹⁴ neutrons per cm² per second.
(ANSI N1.1-1976)

Reactor, homogeneous
A reactor in which the core materials are distributed in such a manner that its neutron characteristics can be accurately described by the assumption of homogeneous distribution of the materials throughout the core.
(ANSI N1.1-1976)

Reactor, indirect cycle
A reactor in which the primary coolant transfers its heat to a secondary coolant for useful power.
(ANSI N1.1-1976)

Reactor, integral
A reactor in which the reactor vessel contains the heat exchanger between the primary and secondary coolant circuits.
(ANSI N1.1-1976)

Reactor, intermediate
A reactor in which the fission is induced predominantly by intermediate neutrons. (Also called reactor, intermediate spectrum.)
(ANSI N1.1-1976)

Reactor, irradiation
A reactor used primarily as a source of nuclear radiation for irradiation of materials or for medical purposes. Reactor types in this class include: isotope-production reactor; food-irradiation reactor; chemonuclear reactor; materials processing reactor; biomedical irradiation reactor; and materials testing reactor (may also be a research reactor).
(ANSI N1.1-1976)

Reactor, materials processing
A reactor employed for the purpose of changing the physical characteristics of materials by utilizing the reactor-generated ionizing radiation. Such characteristics may be color, strength, elasticity, dielectric qualities, etc. (See reactor, irradiation.)
(ANSI N1.1-1976)

Reactor, materials testing
A reactor employed for testing materials and reactor components in intense radiation fields.
(ANSI N1.1-1976)

Reactor, mixed-spectrum
A reactor having a widely different neutron spectra in different parts of the core.
(ANSI N1.1-1976)

Reactor, mobile
A reactor that is mounted on a vehicle and is capable of operation which the vehicle is in motion.
(ANSI N1.1-1976)

Reactor, nuclear
An apparatus in which nuclear fission may be sustained in a self-supporting chain reaction.
(BEIR III)

Reactor, nuclear
A device in which a self-sustaining nuclear fission chain reaction can be maintained and controlled (fission reactor). The term is sometime applied to a device in which a nuclear fusion reaction can be produced and controlled (fusion reactor.) (Also called reactor or pile.)
(ANSI N1.1-1976)

Reactor, nuclear
An apparatus in which nuclear fission may be sustained in a self-supporting chain reaction.
(BEIR I)

Reactor, nuclear
An apparatus in which nuclear fission may be sustained in a self-supporting chain reaction. A reactor includes fissionable material (fuel) such as uranium or plutonium, and moderating material (except fast reactors), and usually includes a reflector to conserve escaping neutrons, provision for heat removal, and measuring and control elements. The terms "pile" and "reactor" have been used interchangeably, with reactor now becoming more common. These terms usually are applied only to systems in which the reaction proceeds at a controlled rate, but they also have been applied to bombs. Reactors may be classified on various bases:
By Fuel Arrangement: Heterogeneous, Homogeneous
By Neutron Energy: Epithermal, Fast, Intermediate, Thermal
By Use: Power, Power Breeder, Production, Research
Special: High flux, High Temperature
(RHH)

Reactor, package
A compact, transportable power reactor.
(ANSI N1.1-1976)

Reactor, pebble bed
A reactor in which some or all of the materials (e.g., fuel, fertile material, moderator) are in the form of a stationary bed of small balls (i.e., pebbles) in contact with each other.
(ANSI N1.1-1976)

Reactor, pool
A reactor whose fuel elements are immersed in a pool of water which serves as moderator, coolant, and biological shield. (Also called swimming pool reactor).
(ANSI N1.1-1976)

Reactor, power
A reactor whose primary purpose is to produce power. Reactors in this class include: electric-power reactor; propulsion reactor; and process-heat reactor.
(ANSI N1.1-1976)

Reactor, pressure tube
A reactor whose fuel assemblies and coolant are confined in tubes that withstand the pressure of the coolant.
(ANSI N1.1-1976)

Reactor, pressurized
A reactor whose primary liquid coolant is maintained under such a pressure that no bulk boiling occurs.
(ANSI N1.1-1976)

Reactor, pressurized-water
A reactor whose primary coolant, water, is maintained under such a pressure that bulk boiling does not occur.
(ANSI N1.1-1976)

Reactor, production
A reactor whose primary purpose is to produce fissile or other materials or to perform irradiations on an industrial scale. Unless otherwise specified the term usually refers to a plutonium-production reactor. Reactors in this class include: fissile-material production reactor; isotope-production reactor; and irradiation reactor.
(ANSI N1.1-1976)

Reactor, prototype
A reactor that is the first of a series of the same basic design. Sometimes used to denote a reactor having the same essential features but of a smaller scale than the final series.
(ANSI N1.1-1976)

Reactor, pulsed
A reactor designed to produce intense bursts of neutrons for short intervals of time.
(ANSI N1.1-1976)

Reactor, research
A reactor of any power level used primarily as a research tool for basic or applied research. Reactors in this class include: low-flux research reactor; high-flux research reactor; pulsed reactor; materials testing reactor; and zero-power reactor (may also be an experimental reactor.)
(ANSI N1.1-1976)

Reactor, slurry
A reactor in which the fuel is a circulating suspension of fine particle in a liquid.
(ANSI N1.1-1976)

Reactor, source
A reactor specially designed to supply a stable flux of neutrons having a well-determined energy spectrum, principally for conducting shielding or exponential experiments or for calibrating detectors.
(ANSI N1.1-1976)

Reactor, spectral shift
A reactor in which the neutron spectrum may be adjusted for control or other purposes by varying the properties or amount of moderator.
(ANSI N1.1-1976)

Reactor, tank
A reactor having a primary vessel which contains only the reactor core, control members and a limited quantity of reflector. It is usually applied to a research or training reactor to differentiate it from a pool reactor.
(ANSI N1.1-1976)

Reactor, thermal
A reactor in which fission is induced predominantly by thermal neutrons.
(ANSI N1.1-1976)

Reactor, training
A reactor primarily for training in reactor operation and instruction in reactor behavior.
(ANSI N1.1-1976)

Reactor, transportable
A reactor that is capable of being moved but only when not critical and possibly partly dismantled.
(ANSI N1.1-1976)

Reactor, zero-power
An experimental reactor operated at a power level so low that no provision for cooling is required and the fission product activity is such that the fuel may be handled without serious hazard.
(ANSI N1.1-1976)

Reader for photoluminescence dosemeter
Instrument for reading a photoluminescence dosemeter by measuring the light emitted by the dosemeter when receiving radiation of certain wavelength.
(IEC 50-394-1993)

Reader for thermoluminescence dosemeter
Instrument for reading a thermoluminescence dosemeter by measuring the light emitted by the thermoluminescent detectors, in the dosemeter during heating over a selected temperature interval.
(IEC 50-394-1993)

Reading
The indicated value of the readout.
(ANSI N42.17C-1989)

Reading
The indicated value of the readout.
(ANSI N42.17B-1989)

Reading
The indicated value of the readout.
(ANSI N42.17A-1989)

Readout
The device which conveys information regarding the measurement to the user.
(ANSI N42.17B-1989)

Readout
The device that conveys visual information regarding the measurement to the user.
(ANSI N42.17A-1989)

Readout
The device which conveys information regarding the measurement to the user.
(ANSI N42.17C-1989)

Readout
The measurement of TL output.
(ANSI N13.15-1985)

Readout
The device which conveys information regarding the measurement to the user.
(ANSI N317-1980)

Readout
The device which conveys information regarding the measurement to the user.
(ANSI N320-1979)

Readout
The device which conveys information regarding the measurement to the user.
(ANSI N323-1978)

Reagent or Method Blank
The contribution of the reagents to the measurement process determined by carrying the reagents through all the operations that are used for the sample.
(HPS N13.30-1996)

Real time
True operational time of measurement of a multichannel pulse height analyzer.
(IEC 50-394-1993)

Real time air monitoring
Measurement of the concentrations or quantities of airborne radioactive materials on a continuous basis.
(10CFR835.2-1998)

Rebar
The reinforcing steel bars placed in concrete to increase its structural strength. Owing to the fact that it is not homogeneously spaced throughout the shield, it would require complicated shielding analysis and hence not usually considered as part of the attenuating property of the shield. Rebar is, however, considered as a potential source of secondary gamma radiation when the shield is a combined neutron and gamma-ray shield.
(ANSI/ANS-6.4-1985)

Receipt
Special nuclear material received by a licensee from an offsite source.
(10CFR74.4)

Receiver
The receiver is the organization to which tile radioactive material shipment is being made. The shipper and receiver could be the same organization.
(ANSI N14.24-1985)

Receiver (or relative) operating characteristic (ROC) curve
In signal detection theory, a plot of the conditional probability of deciding that an observed data set (e.g., image) was generated by a specified state (e.g., that a specified disease was present) when that state was in fact present (TPF) vs. the conditional probability of deciding that the data were generated by the specified state when, in fact, it was absent (FPF). This is equivalent to a plot of the "sensitivity" of a diagnostic test versus one minus the "specificity" of the test. Different points on the ROC curve (i.e., different compromises between TPF and FPF or between "sensitivity" and "specificity") are achieved by adopting different settings of the critical value of the decision variable that distinguishes "negative" decisions from "positive" ones, i.e., the decision criterion.
(ICRU 54)

Receiver operating characteristic curves (ROC)
The ROC curve for a diagnostic test is a curve of true-positive fraction versus false-positive fraction obtained by repeatedly changing the decision threshold.
(NCRP 66)

Receiving
Taking delivery of an item at a designated location.
(ANSI N46.2-1978)

Receptor
A location where the concentration of radioactive material from an airborne release is calculated or a hypothetical person to whom a radiation exposure from specified exposure pathways is calculated.
(ANSI/HPS N13.45-1998)

Receptor
See radiation receptor.
(NCRP 102)

Receptor assembly
A radiation receptor in the specialized container necessary for the proper operation of the receptor.
(NCRP 102)

Receptor conditions
Conditions in which the receptor is present.
(ICRU 30)

Receptor free conditions
Conditions for determining exposure or kerma, in which the specimen to be irradiated is deliberately omitted and in which all exposure apparatus and scatter material is kept to a minimum. Also referred to as "free in air" conditions.
(ICRU 30)

Recessive gene disorder
This requires that a pair of genes, one from each parent, be present in order for the disease to manifest. An example is cystic fibrosis.
(BEIR IV)

Reciprocity law
The reciprocity law states that the response of a film (density) to a given exposure is independent of the exposure time, as long as the total exposure is constant.
(NCRP 66)

Reciprocity relationship
A property of the uniform isotropic model in which the specific absorbed fraction is independent of which organ is designated source and which is designated target.
(MIRD)

Recoil
The disattachment of radon decay products from solid surfaces as a result of alpha decay, causing the atom to re-enter the air.
(RRM)

Recoil
The motion imparted to a particle as a result of interaction with radiation or as a result of a nuclear transformation.
(ANSI N1.1-1976)

Recoil nuclei counter tube
Counter tube intended to detect fast neutrons by means of the ionization produced by the recoil nuclei resulting from the collisions of fast neutrons with nuclei of low atomic number.
(IEC 50-394-1993)

Recoil nuclei ionization chamber
Ionization chamber intended to detect fast neutrons by means of the ionization produced by the recoil nuclei resulting from collisions of fast neutrons with nuclei of low atomic number.
(IEC 50-394-1993)

Recoil proton counter tube
Recoil nuclei counter tube containing hydrogen or a hydrogenous material in which the ionization is caused by recoil protons resulting from the collisions of fast neutrons with hydrogen nuclei.
(IEC 50-394-1993)

Recoil proton ionization chamber
Ionization chamber containing hydrogen or a hydrogenous material in which the ionization is caused by recoil protons resulting from the collisions of fast neutrons with hydrogen nuclei.
(IEC 50-394-1993)

Recoil, aggregate
The ejection, from the surface of a sample, of a cluster of atoms attached to one atom is recoiled as the result of alpha particle emission. Although the phenomenon may be quite common, the amount of matter thus carried away is so small as to be undetectable unless it is strongly radioactive. It is observed with strong preparations of alpha-active materials of high specific activity - such as nearly pure polonium compounds - as a migration of a small fraction of the radioactivity onto clean surfaces in the vicinity.
(RHH)

Recombination
Interaction between a negative and a positive charge carrier with resulting neutralization of their charges.
(IEC 50-393-1993)

Recombination
The return of an ionized atom or molecule to the neutral state.
(RHH)

Record
A record consists of several fields, each containing information related to a single identifying characteristic, sometimes called the key field. For example, in a Radiation Work Permit file, each particular Radiation Work Permit is a single record that may be called a Radiation Work Permit. The plural term "records" is used in the broad generic sense of a collection of recorded information.
(NCRP 114)

Record system
A collection of files linked into a coherent whole.
(NCRP 114)

Recordable event
The administration of:
(1) A radiopharmaceutical or radiation without a written directive where a written directive is required;
(2) A radiopharmaceutical or radiation where a written directive is required without daily recording of each administered radiopharmaceutical dosage or radiation dose in the appropriate record;
(3) A radiopharmaceutical dosage greater than 30 microcuries of either sodium iodide I-125 or I-131 when both:
(i) The administered dosage differs from the prescribed dosage by more than 10 percent of the prescribed dosage, and
(ii) The difference between the administered dosage and prescribed dosage exceeds 15 microcuries;
(4) A therapeutic radiopharmaceutical dosage, other than sodium iodide I-125 or I-131, when the administered dosage differs from the prescribed dosage by more than 10 percent of the prescribed dosage;
(5) A teletherapy radiation dose when the calculated weekly administered dose exceeds the weekly prescribed dose by 15 percent or more of the weekly prescribed dose; or
(6) A brachytherapy radiation dose when the calculated administered dose differs from the prescribed dose by more than 10 percent of the prescribed dose.
(10CFR35.2)

Recording level
A level of dose equivalent or intake above which the results of monitoring programs are of sufficient interest to be worth recording and keeping.
(ICRP 35)

Recording level (for intake of radionuclides)
Level of committed dose equivalent or intake above which the result is of sufficient interest to be worth keeping and interpreting. Recording levels are defined for routine monitoring RLR, and for special or operational monitoring, RLS. Derived recording levels, DRLR and DRLS, are values of body or organ content or elimination rate that correspond to recording levels RLR and RLS. The values are calculated by means of defined models of intake, deposition, uptake, retention and elimination.
(ICRP 54)

Records
A collection of recorded information.
(NCRP 114)

Records custodian
A person (individual, enterprise, institution or other body) who has custody of some or all of the records retained by the responsi-ble organization.
(NCRP 114)

Recovery
Actions taken after the plant has been brought to a stable or shutdown condition, including those taken to mitigate the emergency and ultimately return the plant to normal operation.
(ANSI/ANS-3.8.1-1987)

Recovery
The change(s) in response in a cell, an organ or an organism after irradiation that tend to restore functional integrity. This term includes not only repair of target cells, and/or repopulation in the irradiated field, but also abscopal interactions that influence the magnitude of the effect observed. Completed or full recovery means that a cell, organ or organism responds to further exposure as if it had never been irradiated.
(ICRU 30)

Recovery (radiobiology)
The return toward normal of a particular cell, tissue, or organism after radiation injury.
(RHH)

Recovery rate
The rate at which recovery take place after radiation injury; recovery may proceed at different rates for different tissues. Differential Recovery Rate: Among tissues recovering at different rates, those having lower rates will ultimately suffer greater damage from a series of successive irradiations, and this differential effect is considered in fractionated radiation therapy if neoplastic tissues have a lower recovery rate than surrounding normal structures.
(BEIR III)

Recovery time
Minimum time interval from the start of a counted pulse to the instant a succeeding pulse can attain a specified percentage of the amplitude of the counted pulse.
(IEC 50-394-1993)

Recycling
The reuse of fissionable material, after it has been recovered by chemical processing from spent or depleted reactor fuel, reenriched, and then refabricated into new fuel elements. (See fuel cycle, fuel reprocessing, spent fuel.)
(USAEC-1974)

Recycling
The redeposition in bone of activity that has transferred from bone to blood and back to bone again.
(ICRP 20)

Red bone marrow
The component of marrow which contains the bulk of the hematopoietic stem cells.
(ICRP 56)

Red bone marrow
The component of marrow (assumed in ICRP 30-1978 to have a mass of 1500 g) which contains the bulk of the hematopoietic stem cells.
(ICRP 30)

Red bone marrow (active)
The component of marrow which contains the bulk of the haematopoietic stem cells.
(ICRP 68)

Red bone marrow (active)
The component of marrow which contains the bulk of the haematopoietic stem cells.
(ICRP 67)

Redox
Oxidation-reduction, usually referring to the oxidation-reduction potential of a chemical system.
(NCRP 94)

Redox
Oxidation-reduction, usually referring to the oxidation-reduction potential of a chemical system.
(NCRP 45)

Redundancy (in interlock systems)
Repetition; a situation in which two or more systems are designed to perform the same or approximately the same function, thus providing a safety factor in the instance of the failure of one of the systems.
(NCRP 51)

Redundancy (of means)
In an item, the existence of more than one means for performing a required function.
(IEC 50-394-1993)

Redundancy group
Group that duplicates the essential function of other groups to the extent that it can perform the required function independently of the state of the other groups of the same function.
(IEC 50-393-1993)

Redundant equipment or system
A piece of equipment or a system that duplicates the essential function of another piece of equipment of system to the extent that either may perform the required function regardless of the state of operation or failure of the other.
(NCRP 59)

Redundant system
A system in addition to and independent of the primary system which is capable of achieving the objectives of the primary system.
(ANSI N303-1978)

Redundant unit or system
An additional and independent unit or system which is capable of achieving the objectives of the basic system and is brought on-line in the event of failure of the basic system.
(ERDA 76-21)

Reference activity
The activity used in the neck phantom to simulate total uptake by the thyroid gland of the activity administered to the patient. NOTE: It can be in liquid or capsule form.
(ANSI N44.3-1973)

Reference air kerma rate
The reference air kerma rate of a source is the kerma rate to air, in air, at a reference distance of 1 meter, corrected for air attenuation and scattering. For this purpose this quantity is expressed in mGy h^-1 at one meter.
(ICRU 38)

Reference air leakage rates
The maximum permissible leakage rates converted to std cm³/s.
(ANSI N14.5-1987)

Reference base
A procedure, a process, a material, or an object used to determine and correct for the difference between measurements and an accepted norm.
(ANSI N15.54-1988)

Reference base
A procedure, a process, a material, or an object used to determine and correct for the difference between measurements and an accepted norm.
(ANSI N15.41-1984)

Reference conditions
A preestablished set of standard conditions to which both calibration and process meas-urement data are adjusted.
(ANSI N15.19-1989)

Reference dosimeter
The reference monitoring method used for routine measurement and recording of effective dose equivalent for the monitoring period of interest (i.e., annual, quarterly, monthly, etc.) At most facilities, a single dosimeter worn at one location on the body is called the "reference dosimeter." At other facilities, where more than one dosimeter may be routinely worn at specified locations (e.g., torso and extremities), all of the dosimeters are called the "reference dosimeter."
(HPS N13.41-1997)

Reference dosimeter location
The location on the body where the reference dosimeter is worn. For facilities that routinely use a single reference dosimeter, the front surface of the torso between the shoulders and the waist is the typical reference dosimeter location.
(HPS N13.41-1997)

Reference level
Used to establish values of measured quantities such as recording level or investigation level, above which some specified action or decision should be taken.
(ICRP 65)

Reference level
The predetermined value of a quantity, below a limit, which triggers a specified course of action when the value, usually a dose level, is exceeded or is expected to be exceeded.
(NCRP 107)

Reference level
A predetermined value of a quantity (e.g., a dose level), below a primary or derived limit, that triggers a specified course of action when the value is exceeded or expected to be exceeded.
(FGR 11)

Reference man
A hypothetical aggregation of human physical and physiological characteristics arrived at by international consensus. These characteristics may be used by researchers and public health workers to standardize results of experiments and to relate biological insult to a common base.
(10CFR20.1003)

Reference man
A hypothetical aggregation of human (male and female) physical and physiological characteristics arrived at by international consensus for the purpose of standardizing radiation dose calculations.
(10CFR834.2)

Reference man
A hypothetical person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(ANSI/HPS N13.22-1995)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(ICRP 68)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(NCRP 118)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(ICRP 67)

Reference man
A hypothetical person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP 1974).
(NCRP 111)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(HPJ 60)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(ICRP 56)

Reference man
A hypothetical 'average' adult person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(FGR 11)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(NCRP 87)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(ICRP 54)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(NCRP 84)

Reference man
A hypothetical individual whose characteristics are often used to estimate radiation dose. Reference Man is assumed to be 20-30 years of age, 170 cm in height, weighing 70 kg, and living in a climate with an average temperature of from 10o to 20oC. Reference man is a Caucasian and is Western European or North American in habitat and custom.
(NUREG/CR 3332)

Reference man
A person with the anatomical and physiological characteristics defined in the report of the ICRP Task Group on Reference Man (ICRP Publication 23).
(ICRP 30)

Reference method
Any method of sampling and analyzing for an air pollutant, as described in Appendix B to this part.
(40CFR61.02)

Reference orientation
The orientation in which the instrument is normally intended to be operated as stated by the manufacturer.
(ANSI N42.17B-1989)

Reference orientation
The orientation in which the instrument is normally intended to be operated as stated by the manufacturer.
(ANSI N42.17A-1989)

Reference phantom
A reference phantom is a homogeneous phantom with clearly defined geometry, dimensions, elemental composition, and mass density.
(ICRU 44)

Reference plant
The specific nuclear power plant from which a simulation facility's control room configuration, system control arrangement, and design data are derived.
(10CFR55.4)

Reference point
See liquid height.
(ANSI N15.19-1989)

Reference point
The location on the depth dose curve which has an ordinate location value of 100%. For x rays generated by potentials below 400 kV, the reference point is at the surface of the phantom. For higher energies it is frequently taken at the position of the peak absorbed dose. ICRU 24 adds: It may also be at the position of the isocenter (q.v) if one exists. In this latter case, it will be located at some chosen depth below the surface of the phantom.
(ICRU 24)

Reference point of an assembly
Physical mark of a piece of equipment or assembly to be used in order to position it at a point where the conventionally true value of the quantity to be measured is known.
(IEC 50-394-1993)

Reference source
Radioactive secondary standard source for use in the calibration of the measuring instruments.
(IEC 50-394-1993)

Reference standard
A material, device, or instrument whose assigned value is known relative to national standards or nationally accepted measurement systems. This is also commonly referred to as a traceable standard.
(10CFR74.4)

Reference systems concept
A concept that involves the review of an entire facility design or major fraction of a facility design outside of the context of a license application. The standard design would be referenced in subsequent license applications.
(10CFR170.3)

Reference volume
The reference volume is defined as the volume enclosed by the reference isodose surface.
(ICRU 38)

Reflected (scattered) radiation
Radiation that, during passage through matter, has been deviated in direction. It may have been modified also by a change, usually a decrease, in energy.
(NCRP 51)

Reflected wave
See wave, reflected.
(NCRP 67)

Reflection
A process in which radiation enters a region through a surface and partially returns through the same surface.
(ANSI/ANS-6.4-1985)

Reflection coefficient
The ratio of the electric or magnetic field strength phasors associated with the reflected wave to that associated with the incident wave.
(NCRP 67)

Reflection coefficient
The ratio of the absorbed dose index rate (dose equivalent index rate) of reflected radiation at 1 meter from the scatterer divided by the product of the absorbed dose index rate (dose-equivalent index rate) incident on the scatterer and the area of the scatterer that is irradiated.
(NCRP 51)

Reflector
Material or body of material which reflects incident radiation.
(IEC 50-393-1993)

Reflector
A material or a body of material which reflects incident radiation. In nuclear reactor technology, this term is usually restricted to designate part of a reactor placed adjacent to the core to scatter some of the escaping neutrons back into the core.
(ANSI N1.1-1976)

Reflector
A layer of material immediately surrounding a reactor core which scatters back or reflects into the core many neutrons that would otherwise escape. The returned neutrons can then cause more fissions and improve the neutron economy of the reactor. Common reflector materials are graphite, beryllium and natural uranium.
(USAEC-1974)

Reflector
A layer or structure of material between the shield and core of a reactor, designed to reduce the escape of neutrons and return them to the core. Neutrons entering the reflector are scattered randomly, some of them many time. A large fraction may ultimately return to the core. It is possible to design a reflector which will return more than 90% of the neutrons that would otherwise be lost. Requirements for a good reflector are similar to those of a good moderator: Its atoms should have a low neutron-absorption cross section and high scattering cross section. Low atomic mass is not important. A reflector's effectiveness increases with its thickness, approaching a limiting factor when the thickness is several times the transport mean free path. Reflector savings is a measure of the decrease in critical core size obtained by the use of the reflector.
(RHH)

Reflector control
Control of a reactor by adjustment of the properties, position or quantity of the reflector in such a way as to change the reactivity.
(IEC 50-393-1993)

Reflector saving
The reduction which can be made, without change in reactivity, in a specified dimension of the core of a bare reactor when a given reflector is added. The term may also be applied to reduction of critical mass.
(ANSI N1.1-1976)

Refracted wave
See wave, transmitted.
(NCRP 67)

Refraction
Change in speed and direction of radiation passing from one medium into another
(AM-1993)

Refractive index
Ratio of the speed of light in a vacuum to that in a material in question
(AM-1993)

Refractory
The innermost lining of an incinerator that is usually constructed of a castable material or fire brick.
(ANSI/HPS N13.45-1998)

Region
The geographical area surrounding and including the site, which is large enough to contain all the features related to a phenomenon or to a particular event that could potentially impact the safe or environmentally sound construction, operation, or decommissioning of an independent spent fuel storage or monitored retrievable storage installation.
(10CFR72.3)

Region of limited proportionality
Range of applied voltage of a counter tube, between the Geiger-Muller region and the proportional region, in which the gas multiplication factor is dependent on the total number of ion pairs initially produced in the sensitive volume as a result of an ionizing event, and on the applied voltage.
(IEC 50-394-1993)

Regional disposal facility
A non-Federal low-level radioactive waste disposal facility in operation on January 1, 1985, or subsequently established and operated under a compact.
(10CFR62.2)

Registration Holder
Any manufacturer or initial distributor of a sealed source or device containing a sealed source that holds a certificate of registration issued by the NRC or a holder of a registration for a sealed source or device manufactured in accordance with the unique specifications of, and for use by, a single applicant.
(10CFR171.5)

Regulating rod
A reactor control rod used for making frequent fine adjustments in reactivity.
(USAEC-1974)

Regulations
The rules and regulations of the United States Nuclear Regulatory Commission (NRC) and the United States Department of Transportation (DOT).
(ANSI N14.19-1986)

Relative Bias
The quotient of the bias divided by the expected value.
(HPS N13.30-1996)

Relative bias
The quotient of the bias divided by the "true" value.
(ANSI N13.30-1989D)

Relative biological effectiveness
The RBE of a given type of ionizing radiation is a factor used to compare the biological effectiveness of absorbed radiation doses (i.e., rads) due to one type of ionizing radiation with that of other types of ionizing radiation; more specifically, it is the experimentally determined ration of an absorbed dose of a radiation in question to the absorbed dose of a reference radiation required to produce an identical biological effect in a particular experimental organism or tissue.
(HPJ 60)

Relative biological effectiveness
The relative biological effectiveness of radiation A with respect to the reference radiation R is defined as the ratio of an absorbed dose DR in a tissue to the dose DA that causes a quantitatively and qualitatively equal effect. Each RBE value derived from a set of observations for tissue cultures or for responses of tissues, in animals or in man, refers to a defined end-point, produced under a specified set of exposure conditions.
(ICRP 58)

Relative biological effectiveness
Biological potency of one radiation as compared to another to produce the same biological endpoint. It is numerically equal to the inverse of the ratio of absorbed doses of the two radiations required to produce equal biological effect. The reference radiation is often 200-kV X-rays.
(BEIR IV)

Relative biological effectiveness
A ratio of the absorbed dose of a reference radiation to the absorbed dose of a test radiation to produce the same level of biological effect, other conditions being equal.
(NCRP 93)

Relative biological effectiveness
A factor used to compare the biological effectiveness of different types of ionizing radiation. It is the inverse ratio of the amount of absorbed radiation, required to produce a given effect, to a standard or reference radiation required to produce the same effect. (NCRP 65)

Relative biological effectiveness
The RBE is a factor used to compare the biological effectiveness of absorbed radiation doses (i.e. rads) due to different types of ionizing radiation, more specifically, it is the experimentally determined ratio of an absorbed dose of a radiation in question to the absorbed dose of a reference radiation required to produce an identical biological effect in a particular experimental organism or tissue. NOTE: This term should not be used in radiation protection. (See Quality Factor.)
(RHH)

Relative biological effectiveness (RBE)
A factor used to compare the biological effectiveness of absorbed radiation doses from different types or ionizing radiation; more specifically, the experimentally determined ratio of an absorbed dose of radiation in question to the absorbed dose of a reference radiation required to produce an identical biological effect in a particular experimental organism or tissue; if 10 mGy of fast neutrons equaled in lethality 20 mGy 250 kVp x rays, the RBE of the fast neutrons would be 2.
(NCRP 98)

Relative biological effectiveness (RBE)
Biological potency of one radiation as compared with another. The RBE of radiation A with respect to radiation, B, is defined in terms of the absorbed doses, DA, and, DB, which produce equal biological effect. It is equal, therefore, to DB/DA. The standard of reference used in this report is moderately filtered 250 kVp x radiation which thus has an RBE of 1. The use of this term is to be restricted to radiobiology and it should be distinguished from the term quality factor which is employed in radiation protection.
(NCRP 62)

Relative biological effectiveness (RBE)
Relative biological effectiveness is the ratio of the absorbed dose of a reference radiation, to the absorbed dose of a given test radiation, required to produce the same level of response, all other conditions kept constant. RBE depends upon radiation quality as well as upon level and kind of effect, and hence the test conditions as well as the reference radiation must be completely specified.
(ICRU 30)

Relative biological effectiveness (RBE)
Biological potency of one radiation as compared with another, in terms of the inverse ratio of the respective absorbed doses that produce the same biological effect. The use of this term is to be restricted to radiobiology and it should be distinguished from the term quality factor, Q, which is employed in radiation protection.
(NCRP 51)

Relative biological effectiveness (RBE)
For a particular living organism, the ratio of the absorbed dose of a reference radiation that produces a specified biological effect to the absorbed dose of the radiation of interest that produces the same biological effect. Note: This term should only be used in radiobiology.
(ANSI N1.1-1976)

Relative biological effectiveness (RBE)
The RBE is a factor used to compare the biological effectiveness of absorbed radiation doses (i.e., rads) due to different types of ionizing radiation; more specifically, it is the experimentally determined ratio of an absorbed dose of a radiation in question to the absorbed dose of a reference radiation required to produce an identical biological effect in a particular experimental organism or tissues. The RBE is the ratio of rem to rad. (If 1 rad of fast neutrons equalled in lethality 3.2 rads of 250 KVP x rays, the RBE of the fast neutrons would be 3.2).
(BEIR I)

Relative biological effectiveness (RBE)
Biological potency of one radiation as compared with another. The RBE of radiation A with respect to radiation, B, is defined in terms of the absorbed doses, DA, and, DB, which produce equal biological effect. It is equal, therefore, to DB/DA. The standard of reference used in this report is moderately filtered 200 kVp x radiation which thus has an RBE of 1. The use of this term is to be restricted to radiobiology and it should be distinguished from the term quality factor which is employed in radiation protection.
(NCRP 38)

Relative biological effectiveness (RBE)
Biological potency of one radiation as compared with another. It is numerically equal to the inverse of the ratio of absorbed doses of the two radiation required to produce equal biological effect. The standard of reference used in the Handbook is 200 kv X-radiation, which thus has an RBE of 1.
(NBS 63)

Relative error (e_r)
Relative error of indication of a piece of equipment or an assembly, given by the relation

where v is the indicated value of a quantity and v_c is the conventionally true value of this quantity.
(IEC 50-394-1993)

Relative importance
For neutrons of type "A" relative to neutrons of type "B", the average number of neutrons with velocity and position "B" which must be added to a critical system to keep the chain reaction rate constant after removal of a neutron with velocity and position "A".
(IEC 50-393-1993)

Relative intrinsic error (e_i)
Relative error of indication of a piece of equipment or an assembly with respect to a quantity when subjected to a specified reference quantity under specified reference conditions, expressed as:

where v is the indicated value of a quantity and v_c is the conventionally true value of the quantity at the point of measurement.
(IEC 50-394-1993)

Relative mutation risk
Biological potency of one radiation as compared to another to produce the same biological endpoint. It is numerically equal to the inverse of the ratio of absorbed doses of the two radiations required to produce equal biological effect. The reference radiation is often 200-kV X-rays.
(BEIR IV)

Relative permeability
See permeability, relative.
(NCRP 67)

Relative permittivity
See permittivity, relative.
(NCRP 67)

Relative Precision
The quotient of the dispersion of the measurement divided by either the expected value or by the mean of the measurement (see Section 3.4.3 and 4.3.3).
(HPS N13.30-1996)

Relative precision
The quotient of the dispersion of the measurement divided by either the true value or by the mean value of the measurement.
(ANSI N13.30-1989D)

Relative risk
Risk relative to the existing or baseline risk typically expressed as a multiple of the existing or baseline risk.
(NCRP 121)

Relative risk
An expression of risk relative to the underlying baseline risk. If the total risk is twice the underlying baseline risk then the relative risk is 2.
(ICRP 59)

Relative risk
Expression of risk due to exposure as the ratio of the risk among those exposed to that obtaining in the absence of exposure. Relative risk coefficients distribute the radiogenic excess in the pattern of the natural incidence or mortality over the interval of expression.
(NCRP 80)

Relative risk
The ratio of risk from radiation in an irradiated population to the risk in a comparable nonirradiated population.
(NUREG/CR 3332)

Relative risk
The ratio of the risk in those exposed to the risk to those not exposed (incidence in exposed population to incidence in control population).
(BEIR I)

Relative risk projection model
A model which estimates the risk of exposure beyond the years of observation of a studied population by projecting the currently observed percentage increase in cancer risk per unit dose into future years.
(RRM)

Relative settling velocity
Ratio of the terminal gravitational-settling velocity to sampling air velocity in an inlet
(AM-1993)

Relative Standard Deviation
Synonymous with coefficient of variation.
(HPS N13.30-1996)

Relative standard deviation
Synonymous with coefficient of variation.
(ANSI N13.30-1989D)

Relative standard deviation
The estimated standard deviation of an individual measurement divided by the average of the distribution, sometimes expressed in percent. This term is also referred to as "coefficient of variation".
(ANSI N15.22-1987)

Relativistic neutrons
Neutrons of energies above 10 Mev.
(NBS 63)

Relaxation length
The depth of soil which delivers a surface flux of radon that is 1/e of that delivered by soil at the surface.
(NCRP 78)

Relaxation length
The distance in a material through which nuclear radiation must pass in order to reduce (or relax) by nuclear interaction the intensity of 1/e of its original value not including geometric effects (e.g., 1/r²).
(ANSI N1.1-1976)

Relaxation length, effective
The distance within a material in which radiation intensity is reduced to 1/e of its initial value. This term includes geometric effects.
(ANSI N1.1-1976)

Relaxation length, total
The relaxation length at a particular location when the radiation is polyenergetic and the relaxation length is therefore not constant throughout the material.
(ANSI N1.1-1976)

Relaxation spectrum
The variation of relative permittivity with angular frequency, uniquely described by a monotonic decrease of the real component with increasing angular frequency, the maximum slope occurring when the product of angular frequency and the relaxation time is unity, and characterized by a maximum in the imaginary component at the same angular frequency where the slope of the real component is maximum.
(NCRP 67)

Relaxation time
Time for a particle to reach 1/e of its final velocity from an initial velocity or from rest when subjected to an external force; an indicator of a particle's ability to adjust to changes in flow velocity
(AM-1993)

Relaxation time
The time, after a static field has been applied to a dielectric, required for the electric polarization to reach (e - 1)/e of the steady state value. For a dielectric that exhibits a relaxation spectrum, the average relaxation time is equal to the reciprocal of the angular frequency for which the imaginary part of the relative permittivity is a maximum. The relaxation time is expressed in units of second (s).
(NCRP 67)

Relaxation time
A time characteristic of particle motion, the ratio of particle terminal settling velocity to the acceleration of gravity.
(TID-26608)

Release of property
Permission to transfer property from DOE control.
(10CFR834.2)

Release rate
The quantity of radioactive contents per unit time that escapes through a leak.
(ANSI N14.5-1987)

Rem
The special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor (1 rem = 0.01 sievert).
(10CFR20.1004)

Rem
A measure of the dose of any ionizing radiation to body tissues in terms of its estimated biological effect relative to a dose of one roentgen (r) of X-rays. (One millirem (mrem) - 0.001 rem.) The relation of the rem to other dose units depends upon the biological effect under consideration and upon the conditions of irradiation. For the purpose of the regulations in this part, any of the following is considered to be equivalent to a dose of one rem:
(1) A dose of 1 r due to X- or gamma radiation;
(2) A dose of 1 rad due to X-, gamma or beta radiation;
(3) A dose of 0.1 rad due to neutrons or high energy protons;
(4) A dose of 0.05 rad due to particles heavier than protons and with sufficient energy to reach the lens of the eye.
(10CFR20.4)

Rem
A special unit of absorbed dose equivalent. The dose equivalent in rems is numerically equal to the absorbed dose in rads multiplied by the quality factor, the distribution factor, and any other necessary modifying factors. 1 rem = 100 Sv.
(HPJ 60)

Rem
A special unit for dose equivalent. Being replaced by the sievert, 1 rem = 0.01 Sv.
(NCRP 101)

Rem
The previously used special unit of dose equivalent. One rem equals 10^-2 sievert (Sv).
(NCRP 102)

Rem
The conventional unit of dose equivalent. The dose equivalent in rem is numerically equal to the absorbed dose, D, in rad multiplied by the quality factor Q. 1 rem = 0.01 sievert. (See sievert, rad). Note: for most medical applications involving x ray or gamma emitters, the numerical values of the absorbed dose in rad, dose equivalent in rem, and exposure in R are roughly equivalent numerically.
(NCRP 105)

Rem
The conventional unit of radiation dose equivalent. One Sv equals 100 rem.
(NCRP 103)

Rem
A unit of dose equivalent = absorbed dose in rads time quality factor.
(NCRP 98)

Rem
An acronym of radiation equivalent man, the name for the conventional unit of dose equivalent; the corresponding SI unit is the Sievert; 1 Sv = 100 rem.
(FGR 11)

Rem
A unit of dose equivalent. The product of the absorbed dose in rad and modifying factors. Being replaced by the sievert.
(NCRP 87)

Rem
A unit of dose equivalent. The product of the absorbed dose in rad and modifying factors. Being replaced by the sievert.
(NCRP 84)

Rem
The unit of dose equivalent. For radiation protection purposes of this report, covering x and gamma radiation, the number of rems may be considered equivalent to the number of rads or roentgens.
(NCRP 68)

Rem
The special unit of dose equivalent. The dose equivalent in REMS is numerically equal to the absorbed dose in RADS multiplied by the quality factor and any other necessary modifying factors.
(NCRP 65)

Rem
Special unit of dose equivalent.
(NCRP 51)

Rem
A unit of dose equivalent. The dose equivalent in rems is numerically equally to the absorbed dose in rads multiplied by the quality factor, the distribution factor, and any other necessary modifying factors. (Originally derived from roentgen equivalent man.)
(ANSI N1.1-1976)

Rem
The unit of dose equivalent. For radiation protection purposes in this report, covering x, beta, and gamma radiation, the number of rems may be considered equal to the number of rads or roentgens.
(NCRP 48)

Rem
Roentgen equivalent man. The unit of absorbed radiation dose in rads multiplied by the relative biological effectiveness of the radiation.
(ERDA 76-21)

Rem
The unit of dose equivalent. For radiation protection purposes of this report, which covers only x, and gamma radiation, the number of rems may be considered equivalent to the number of rads of absorbed dose or roentgens of exposure.
(NCRP 49)

Rem
(Acronym for roentgen equivalent man.) The unit of dose of any ionizing radiation which produces the same biological effect as a unit of absorbed dose of ordinary X rays. The RBE dose (in rems) = RBE x absorbed dose (in rads).
(USAEC-1974)

Rem
A special unit of dose equivalent. The dose equivalent in rems is numerically equal to the absorbed dose in rads multiplied by the quality factor, the distribution factor, and any other necessary modifying factors. The rem represents that quantity of radiation that is equivalent in biological damage of a specified sort to 1 rad of 250 KVP x rays.
(BEIR I)

Rem
Special unit of dose equivalent.
(NCRP 38)

Rem
Unit of RBE dose.
(NBS 73)

Rem
The quantity of any ionizing radiation such that the energy imparted to a biological system (cell, tissue, organ, or organism) per gram of living matter by the ionizing radiation present in the region of interest has the same biological effectiveness as an absorbed dose of 1 rad from lightly filtered X-rays generated at potentials of 200 to 300 kilovolts. For radiation protection purposes, 1 rem may be taken as equivalent to 1 rad for beta rays and gamma rays.
(NBS 66)

Rem
Unit used in the description of radiobiological effects on man. The dose in rems is numerically equal to the product of the absorbed dose in rads and the value of RBE applicable for the radiation in question.
(NBS 63)

Rem (rem) (deprecated)
Unit of dose equivalent equal to 0.01 Sv.
(IEC 50-393-1993)

Rem meter/rem counter
An instrument whose response simu-lates the dose equivalent response of the human body.
(NCRP 112)

Remedial action
An action consistent with a permanent remedy, taken to control or remove contaminants in order to prevent or minimize radiation doses caused by the interaction of members of the public with the released property.
(10CFR834.2)

Remote engagement
Provision for the engagement of two elements of the hoisting system, such as the lifting yoke(s) and a container, under circumstances that prevent the connection from being made by control directly applied at the point of engagement.
(ANSI N14.6-1986)

Remote site
A location where a DOE activity is carried out that is outside the boundaries of a national laboratory or other major DOE site.
(10CFR834.2)

Remotely controlled afterloading technique
In remotely controlled afterloading techniques, source insertion and removal are operated from a control panel distant from the patient, thus eliminating exposure of the clinical staff. With some of the more advanced devices, the sources are automatically retracted into the storage container when the door of the patient's room is opened. While either manual or mechanical afterloading techniques may be used for low dose-rate applications, remote afterloading techniques are mandatory for medium and high dose-rate applications in order to ensure good radiation protection of the staff.
(ICRU 38)

Removals
Measured quantities of special nuclear material disposed of as discards, encapsulated as a sealed source, or in ultimate product placed under tamper-safing or shipped offsite.
(10CFR74.4)

Renewal term
The period of time that is the sum of the additional amount of time beyond the expiration of the operating license that is requested in the renewal application plus the remaining number of years on the operating license currently in effect.
(10CFR54.3)

Rep
An obsolete unit of absorbed dose in tissue. (Originally derived from roentgen equivalent physical.)
(ANSI N1.1-1976)

Rep
(Acronym for roentgen equivalent physical.) An obsolete unit of absorbed dose of any ionizing radiation, with a magnitude of 93 ergs per gram. It has been superseded by the rad.
(USAEC-1974)

Rep
An obsolete special unit of absorbed dose.
(RHH)

Rep
An obsolete unit of absorbed dose, equal to 93 ergs per gram. Replaced by the rad.
(NBS 66)

Rep (roentgen equivalent physical)
The quantity of any ionizing radiation such that the energy imparted to soft tissue by the ionizing particles is 93 erg/g. (Superseded by rad.)
(NBS 54)

Repair
The partial or complete restoration of functional integrity in cells following damage caused by radiation. Operationally, repair means that after irradiation a cell responds as though it had received a smaller dose than under conditions in which damage is more fully expressed. The ability to observe repair implies, therefore, that a comparison is made with a treatment of reference. Full repair indicates that cells respond as though they had not been previously irradiated. (Repair embraces processes sometimes referred to as: bypassing of damage; shedding of damage; compensating for damage; elimination of damage; and/or the specific biochemical reversal of damage.)
(ICRU 30)

Repair
A disposition involving the process or restoring a nonconforming characteristic to a condition such that the capability of an item to function reliably and safely is unimpaired even though that item still does not conform to the original requirement.
(ANSI N46.2-1978)

Replica mass standard (RMS)
A mass standard that is a physical replica (artifact) of a production object that is routinely weighed. Use of replica or artifact standards minimizes errors associated with buoyancy and loading procedures; for example, this standard establishes the RMS for UF₆ cylinders.
(ANSI N15.18-1988)

Repopulation
The replacement of functional cells (usually by proliferation) following or during an irradiation. Repopulation refers to those cells upon which the biological endpoint depends and usually reflects increases in the numbers of differentiated cells as well as their progenitors. Repopulation may result from cells that were unaltered by the radiation (e.g., due to migration into the irradiated field after exposure) but may also reflect a contribution from surviving cells. In a given case, repopulation could be influenced by systematic responses induced by the radiation (e.g. homeostatic responses).
(ICRU 30)

Representative
As applied to the sampling of radioactive material, means sampling in such a manner that the sample closely approximates both the amount of activity and the physical and chemical properties of the material (eg., particle size and solubility in the case of air sampling of the aerosol to which workers may be exposed).
Editorial Note: This definition was removed from 10CFR835.2 in the 1998 revision.
(10CFR835.2-1993)

Representative
Faithfully showing the quality and characteristics of the entire volume from which the sample is drawn.
(ANSI N13.1-1969)

Reprocessing
Fuel reprocessing.
(USAEC-1974)

Reprocessing (of an irradiated fuel)
Processing of nuclear fuel, after its use in a reactor, to remove fission products and recover fissile and fertile material.
(IEC 50-393-1993)

Reprocessing, fuel
The processing if nuclear fuel, after its use in a reactor, to remove fission products and recover fissile, fertile, and other valuable material.
(ANSI N1.1-1976)

Reproducibility
The degree of conformity among repeated measurements of the same quantity obtained with a single TLD.
(ANSI N545-1975)

Reproducibility (precision)
The degree of agreement of repeated measurements of the same property expressed quantitatively as the standard deviation computed from the results of the series of measurements.
(ANSI N323-1978)

Requirements
Any or all of those regulations, license conditions, policies, procedures, instructions, contracts, guides, codes, standards, manuals, or other similar documents that are applicable wholly or in part to the safeguards system to be audited.
(ANSI N15.38-1982)

RERF
Radiation Effects Research Foundation. Japanese foundation chartered by the Japanese Welfare Ministry under an agreement between the United States and Japan. It is a successor to the ABCC.
(BEIR III)

Rescue respirator use
Wearing a respirator for entry into a hazardous atmosphere to rescue a person(s) in the hazardous atmosphere.
(ANSI Z88.2-1980)

Research and development
(1) theoretical analysis, exploration, or experimentation; or
(2) the extension of investigative findings and theories of a scientific or technical nature into practical application for experimental and demonstration purposes, including the experimental production and testing of models, devices, equipment, materials and processes. "Research and development" as used in this part and Parts 31 through 35 does not include the internal or external administration of byproduct material, or the radiation therefrom, to human beings.
(10CFR30.4)

Research irradiator
A single sealed source or an array of sealed sources designed to irradiated various materials at specified exposure rates within specified limits of uniformity.
(ICRU 18)

Research model
Any model developed to fulfill research objectives. Usually research models are developed to provide insight into explicit processes and mechanisms and thus are mathematically more complex than assessment models.
(NCRP 123I)

Research reactor
A nuclear reactor licensed by the Commission under the authority of subsection 104c of the Act and pursuant to the provisions of §50.21(c) of this chapter for operation at a thermal power level of 10 megawatts or less, and which is not a testing facility as defined by paragraph (m) of this section.
(10CFR170.3)

Research Reactor
A nuclear reactor licensed by the Commission under the authority of subsection 104c of the Act and pursuant to the provisions of Sec. 50.21(c) of this chapter for operation at a thermal power level of 10 megawatts or less, and which is not a testing facility as defined in this section.
(10CFR171.5)

Research reactor
Reactor of any power level used primarily as a research tool for basic or applied research.
(IEC 50-393-1993)

Research reactor
A research reactor is defined as a device designed to support a self-sustaining neutron chain reaction for research, developmental, educational, training or experimental purposes, and which may have provisions for the production of radioisotopes.
(ANSI/ANS-15.4-1988)

Research reactor
A reactor primarily designed to supply neutrons or other ionizing radiation for experimental purposes. It may also be used for training, materials testing, and production of radioisotopes.
(USAEC-1974)

Reservation
(1) Any Indian reservation or dependent Indian community referred to in clause (a) or (b) of section 1151 of title 18, United States Code; or
(2) Any land selected by an Alaska Native village or regional corporation under the provisions of the Alaska Native Claims Settlement Act (43 U.S.C. 1601 et seq.).
(10CFR72.3)

Reset
Switching of a bistable device from present to its initial state.
(IEC 50-393-1993)

Residence
Any home, house, apartment building, or other place of dwelling which is occupied during any portion of the relevant year.
(40CFR61.02)

Residence time
The time during which radioactive material remains in the atmosphere following the detonation of a nuclear explosive. It is usually expressed as a half-time, since the time for all material to leave the atmosphere is not well known. (See fallout.)
(USAEC-1974)

Residence time, t
An average time that the administered activity spends in the source organ. The quotient of the cumulated activity in the source organ divided by the administered activity,
.
(MIRD)

Residual current
Current which continues to be produced by a detector after it is no longer exposed to external radiation, and which is due to activation of the component materials of the detector, to their contamination and to the poor quality of its insulation.
(IEC 50-394-1993)

Residual heat
The total heat source remaining in a shutdown reactor, including after-heat.
(ANSI N1.1-1976)

Residual nuclear radiation
Lingering radiation, or radiation emitted by radioactive material remaining after a nuclear explosion. Residual radiation is arbitrarily designated as that emitted more than one minute after the explosion.
(USAEC-1974)

Residual radioactive material
(1) Waste (which the Secretary of Energy determines to be radioactive) in the form of tailings resulting from the processing of ores for the extraction of uranium and other valuable constituents of the ores; and
(2) other waste (which the Secretary of Energy determines to be radioactive) at a processing site which relates to such processing, including any residual stock or unprocessed ores or low-grade materials. This term is used only with respect to materials at sites subject to remediation under title I of the Uranium Mill Tailings Radiation Control Act of 1978, as amended.
(10CFR40.4)

Residual radioactive material
Any radioactive material that is in or on soil, air, water, equipment, or structures as a consequence of past operations or activities.
(10CFR834.2)

Residual radioactive materials
Residual radioactive materials shall have the same meaning as in secion 101(7) of the Uranium Mill Tailing Radiation Control Act of 1978, 42 U.S.C. 7911(7).
(40CFR61.221)

Residual radioactivity
Radioactivity in structures, materials, soils, groundwater, and other media at a site resulting from activities under the licensee's control. This includes radioactivity from all licensed and unlicensed sources used by the licensee, but excludes background radiation. It also includes radioactive materials remaining at the site as a result of routine or accidental releases of radioactive material at the site and previous burials at the site, even if those burials were made in accordance with the provisions of 10 CFR part 20.
(10CFR20.1003)

Residual Volume
Air that remains in the lung following maximum exhalation.
(NCRP 125)

Resistance
Opposition to the flow of air, as through a canister, cartridge, particulate filter, or orifice.
(ANSI Z88.2-1980)

Resistance
Opposition to the flow of air, as through a canister, cartridge, particulate filter, or orifice.
(ANSI Z88.2-1969)

Resolution
The ability of a detector system to separate or identify two g rays of nearly identical energies.
(HPJ 60)

Resolution
In the context of an image system, the output of which is finally viewed by the eye, it refers to the smallest size or highest spatial frequency of an object of given contrast that is just perceptible. The intrinsic resolution, or resolving power, of an imaging system is measured in line pairs per millimeter (lp/mm), ordinarily using a resolving power target. The resolution actually achieved when imaging lower contrast objects is normally much less, and depends upon many variables such as subject contrast levels and, noise of the overall imaging system.
(NCRP 102)

Resolution
In the context of an image system, the output of which is finally viewed by the eye, it refers to the smallest size or highest spatial frequency of an object of given contrast that is just perceptible. The limiting resolution is the resolution for an object consisting of black and white area, viz., of unit contrast or depth of modulation.
(NCRP 68)

Resolution
In the context of an image system, the output of which is finally viewed by the eye, it refers to the smallest size or highest spatial frequency of an object of given contrast that is just perceptible. The limiting resolution is the resolution for an object consisting of black and white area, viz., of unit contrast or depth of modulation.
(NCRP 66)

Resolution
The minimum detectable change in instrument response.
(ANSI N317-1980)

Resolution (of a radiation measuring assembly)
For a given value of the measured quantity, the smallest difference, determined by statistical fluctuations and drift of the radiation meter, between two adjacent values of the input signal, required to obtain distinct indications of the output.
(IEC 50-394-1993)

Resolution, gamma ray
The measured FWHM, after background subtraction, of a gamma-ray peak distribution, expressed as a percentage of the energy corresponding to the centroid of the distribution.
(ANSI N42.12-1980)

Resolution, gamma ray
The measured FWHM, after background subtraction, of a gamma-ray peak distribution, expressed in units of energy.
(ANSI N42.14-1978)

Resolving time
Smallest time interval which must elapse between the occurrence of two consecutive pulses or ionizing events and still be recognized as separate pulses or events.
(IEC 50-394-1993)

Resolving time
The minimum time that shall exist between successive events if they are to be counted as separate events.
(ANSI N42.15-1980)

Resolving time
The minimum time interval between two distinct events which will permit both to be counted. It may refer to an electronic circuit, to a mechanical indicating device, or to a counter tube.
(RHH)

Resolving time (r_b, r_g)
A coincidence circuit between b and g pulses is usually formed by a logic AND gate, with inputs in the form of square logic pulses of width r_b and r_g for the two channels.
(ICRU 52)

Resolving time correction, dead time correction
Correction to be applied to the observed number of pulses in order to take into account the number of pulses lost due to the resolving time.
(IEC 50-394-1993)

Resonance
The phenomenon whereby particles such as neutrons exhibit a very high interaction probability with nuclei at specific kinetic energies of the particles. Cross sections for neutron capture and scattering, for example, exhibit peaks at these so-called resonance energies and have relatively low values between the peaks. (This term is also applied to several other phenomena in physics.) (See capture, cross section, nuclear reaction, scattering.)
(USAEC-1974)

Resonance absorption
Absorption (including fission and 1/v absorption) of neutrons in the resonance energy region.
(ANSI N1.1-1976)

Resonance capture
Radiation capture of neutrons in the resonance energy range.
(ANSI N1.1-1976)

Resonance energy
The kinetic energy of an incident particle (expressed in the laboratory system) that excites an energy level in a compound nucleus.
(ANSI N1.1-1976)

Resonance energy
The kinetic energy of an incident particle (expressed in the laboratory system) that makes the total energy of the system composed of the incident particle and the target nucleus close to the energy of a nuclear level of the compound nucleus.
(RHH)

Resonance escape probability
In an infinite medium, the probability that a neutron slowing down will traverse all or some specified portion of the range of resonance energies without being absorbed.
(ANSI N1.1-1976)

Resonance integral
The integral over all or some specified portion of the resonance energy range of the product of the absorption cross section of a nuclide and the reciprocal of the neutron energy. It is given by

where s_a is the microscopic absorption cross section and E₁ and E₂ are respectively, the lower and upper energy limits. If the neutron flux density is assumed to vary inversely as the energy, the resonance integral gives a measure of the probability of the neutrons of resonance energy undergoing an absorption reaction. If the neutron flux density does not vary inversely as the energy, the effective resonance integral is used. The term may also be specified for particular reactions such as capture, fission, or activation. Note: This term should not be confused with the excess resonance integral.
(ANSI N1.1-1976)

Resonance integral, effective
The resonance integral in which the cross section is replaced by an effective cross section and which give the true reaction rate when the flux density does not vary inversely as the neutron energy.
(ANSI N1.1-1976)

Resonance integral, epicadmium
That resonance integral which has the effective cadmium cutoff as the lower energy limit.
(ANSI N1.1-1976)

Resonance integral, excess
The resonance integral in which the cross section excludes that part which varies inversely with neutron speed.
(ANSI N1.1-1976)

Resonance level
An energy level in a compound nucleus which is excited in a nuclear reaction. (The interaction cross section exhibits a marked anomaly usually characterized by a high, narrow peak in the curve of cross section as a function of energy.)
(ANSI N1.1-1976)

Resonance neutron
Neutron the kinetic energy of which corresponds to the resonance energy of a specified nuclide.
(IEC 50-393-1993)

Resonance scattering
The reemission of a neutron after it has formed a compound nucleus at a resonance level. If, following reemission, the residual nucleus is not in an excited state, the process is energetically identical to elastic scattering.
(ANSI N1.1-1976)

Resonance spectrum
The variation of relative permittivity with angular frequency uniquely described by a dispersion of the real part around a resonant angular frequency characteristic of the system and a maximum in the imaginary component in the same frequency region. The dispersion of the real part exhibits a maximum below the resonant angular frequency and a minimum above it. In the limit of maximal damping, a resonance spectrum approaches a relaxation spectrum and the frequency dependence of the real part becomes monotonic.
(NCRP 67)

Resonant transformer
A transformer so designed that the inductance and distributed capacitance of its windings comprise a circuit which is in resonance at the frequency of the supplied transformer. As it does not require an iron core, insulation problems and weight are minimized. This principle is the basis of certain 1 and 2 million volt generators used to produce x rays and electron beams.
(RHH)

Resorption
The local reduction of bone volume due to removal of both mineral and organic matrix due to removal of both mineral and organic matrix from bone surface.
(ICRP 20)

Resorption rate
The volume of bone resorbed per unit time per unit volume of bone and its units are typically %/year. Dosimetrically, resorption reduces the volume of bone at risk without changing the activity per gram of remaining bone.
(ICRP 20)

Respirable
Suitable for breathing.
(ANSI Z88.2-1980)

Respirable
Fit to be breathed.
(ANSI Z88.2-1969)

Respirable fraction
Fraction of aerosol that can reach the gas exchange region of the human respiratory system
(AM-1993)

Respirable fraction
The fraction of airborne material that can be inhaled and possibly deposited in the lung.
(NCRP 97)

Respirable fraction
The fraction of airborne material that can be inhaled and possibly deposited in the lung.
(NCRP 94)

Respirable fraction
The fraction of airborne material that can be inhaled and possibly deposited in the lung.
(NCRP 45)

Respirator
A device designed to protect the wearer from inhalation of harmful atmospheres. ANSI Z88.2 lists classification, description and limitations of respirators.
(ANSI Z88.2-1980)

Respirator
A protective device worn on the face or head of an individual to prevent the inhalation of toxic or radioactive materials.
(NCRP 59)

Respirator
A device designed to protect the wearer from inhalation of harmful atmospheres. ANSI Z88.2 lists classification, description and limitations of respirators.
(ANSI Z88.2-1969)

Respiratory protective device
An apparatus, such as a respirator, worn by an individual for the purpose of reducing the individual's intake of airborne radioactive materials.
(10CFR835.2-1998)

Respiratory protective device
An apparatus, such as a respirator, used to reduce the individual's intake of airborne radioactive materials.
(10CFR20.1003)

Respiratory system
The organ system concerned with the exchange of oxygen and carbon dioxide. The respiratory system consists of the air passages through the nose, mouth pharynx, the conducting airways (trachea, bronchia, bronchioles) and the gas exchange surfaces (alveoli) in the pulmonary parenchyma.
(NCRP 78)

Respiratory Tract
Consists of the naso-oro-pharyngo-laryngeal region, tracheobronchial region and pulmonary region, common to humans and animals.
(NCRP 125)

Respiratory tract (lung) model
The model of behavior of particles in the respiratory tract of man; the model of relevance here was developed by the Task Group on Lung Dynamics of the ICRP.
(FGR 11)

Respiratory tract model
A general term for models of the behavior of particles and gases in the human respiratory tract. (See also Task Group Lung Model.)
(NCRP 84)

Respiratory-inlet covering
That portion of a respirator which connects the wearer's respiratory tract to an air-purifying device or respirable gas source, or both. It may be a facepiece, helmet, hood, suit or mouth piece/nose clamp.
(ANSI Z88.2-1980)

Response
For purposes of calibration, response is the quotient of the instrument reading by the true value of the quantity being measured.
(NCRP 112)

Response
The instrument indication produced as a result of some influence quantity.
(ANSI N42.17B-1989)

Response
The instrument indication produced as a result of some influence quantity.
(ANSI N42.17A-1989)

Response
The instrument indication produced as a result of some influence quantity.
(ANSI N42.17C-1989)

Response
The instrument reading.
(ANSI N323-1978)

Response
The response (R) of a dosimeter will here be considered to be the quantity observed as the reaction of the dosimeter to a given magnitude and type of radiation; e.g., electric charge, meter deflection, or scaler count. Dosimeter response is taken here to be proportional to the absorbed dose of radiation received by the sensitive material of the instrument.
(ICRU 26)

Response (of a radiation measuring assembly)
Ratio, under specified conditions, given by the relation : where v is the value of quantity measured by the equipment or assembly under test and vc is the conventionally true value of this quantity.

(IEC 50-394-1993)

Response function
The response function, alpha, of a dosimeter for a given type of radiation is the quotient of absorbed dose in the material of interest by the resultant dosimeter response. The reciprocal of a is the sensitivity of the instrument.
(ICRU 26)

Response modification
The responses of cells, tissues, and organisms to a given dose can be altered in different ways. This is possible because response depends on physical factors (e.g., the quality of the radiation and the dose rate); on chemical factors (e.g., the presence or absence of electron affinic substances or hydrogen donors), and on biological or physiological factors (e.g., changes in the composition or the amount of DNA in a cell, or changes in homeostatic control in an organism).
(ICRU 30)

Response pulse duration (of a photomultiplier tube)
Time duration corresponding to the full width at half maximum in the curve representative of the output current pulse when the photocathode receives a light pulse having a finite flux and infinitesimal duration giving rise to a large number of photoelectrons.
(IEC 50-394-1993)

Response Spectrum
A plot of the maximum responses (acceleration, velocity, or displacement) of idealized single-degree-of-freedom oscillators as a function of the natural frequencies of the oscillators for a given damping value. The response spectrum is calculated for a specified vibratory motion input at the oscillators' supports.
(10CFR100.3)

Response time
The time interval required for the instrument reading to change form 10% to 90% of the final reading following a step change in the radiation field (i.e., signal) at the detector, or, for integrating monitors, 90% of the final value of the first derivative of the indication with respect to time (i.e., rate of change).
(ANSI N42.17B-1989)

Response time
The time interval required for the instrument reading to change form 10% to 90% of the final reading (or vice versa) following a step change in the radiation field (i.e., signal) at the detector.
(ANSI N42.17C-1989)

Response time
The time interval from a step change in the input concentration at the instrument inlet to a reading of 90 percent (nominally equivalent to 2.2 time constants) of the ultimate recorded output.
(ANSI N13.10-1974)

Response time (of a measuring assembly)
Time required after a step variation in the measured quantity for the output signal variation to reach for the first-time a given percentage, usually 90%, of its final value.
(IEC 50-394-1993)

Response variable
The dependent (response) variable in a functional relationship, usually used in a statistical context.
(ANSI N15.19-1989)

Responsible officer
The president, vice-president, or other individual in the organization of a corporation, partnership, or other entity who is vested with executive authority over activities subject to this part.
(10CFR50.2)

Responsible organization
The person (individual, enterprise, institution or other body) responsible for the generation and retention or non-reten-tion of records. The responsible organization need not be the direct custo-dian of the records.
(NCRP 114)

Rest mass (m_o)
Intrinsic mass of a particle excluding the increase of mass acquired by the particle, due its motion, according to the theory of relativity.
(IEC 50-393-1993)

Restricted Area
An area, access to which is limited by the licensee for the purpose of protecting individuals against undue risks from exposure to radiation and radioactive materials. Restricted area does not include areas used as residential quarters, but separate rooms in a residential building may be set apart as a restricted area.
(10CFR19.3)

Restricted area
An area, access to which is limited by the licensee for the purpose of protecting individuals against undue risks from exposure to radiation and radioactive materials. Restricted areas does not include areas used as residential quarters, but separate rooms in a residential building may be set apart as a restricted area.
(10CFR20.1003)

Restricted area
Any area access to which is controlled by the licensee for purposes of protection of individuals from exposure to radiation and radioactive materials. "Restricted area" shall not include any areas used as residential quarters, although a separate room or rooms in a residential building may be set apart as a restricted area.
(10CFR60.2)

Restricted area
Any area to which access is controlled by the licensee for the purpose of protecting individuals from exposure to radiation and radioactive materials.
(ANSI N303-1978)

Restricted data
All data concerning
(1) design, manufacture, or utilization of atomic weapons;
(2) the production of special nuclear material; or
(3) the use of special nuclear material in the production of energy, but shall not include data declassified or removed from the Restricted Data category pursuant to section 142 of the Act.
(10CFR50.2)

Restricted linear energy transfer or restricted linear collision stopping power (L_D)
The restricted linear energy transfer or restricted linear collision stopping power, L_D, of charged particles in a medium is the quotient of dE by dl, where dl is the distanced transversed by the particle and dE is the energy loss due to electronic collisions with energy transfers less than some specified value D:

(ICRU 26)

Restricted release
Removing an item, personal property, or real property from DOE control for a limited, specifically-stated application.
(10CFR834.2)

Resuspension
Wind blown reintroduction to the atmosphere of material originally deposited onto surfaces from a particular source.
(NUREG/CR 3332)

Retained quantity
The quantity of a deposited material in a compartment, in an organ or in the whole body at a given time after intake, deposition or uptake.
(ICRP 54)

Retardation coefficient
The measure of the capability of the porous medium to impede by sorption the movement of a particular radionuclide being carried by the flow.
(NCRP 123I)

Retardation coefficient
The measure of the capability of the porous medium to impede by sorption the movement of a particular radionuclide being carried by the flow.
(NCRP 76)

Retardation coefficient
A measure of the capability of porous media to impede the movement of a particular radionuclide being carried by the fluid.
(NUREG/CR 3332)

Retention function
A mathematical expression for the fractional retention of a nuclide in an organ, tissue, body, or excretion compartment at any time. It can be a fraction of the intake, or a fraction of the uptake in body fluids or in the compartment of interest, i.e., either an intake retention function (IRF) or an uptake retention function (URF).
(ANSI/HPS N13.22-1995)

Retention function
A mathematical expression for the fractional retention of a nuclide in an organ or body at any time following intake.
(NCRP 87)

Retention function
A function describing the time dependence of the retained quantity.
(ICRP 54)

Retention function
A mathematical expression (ignoring radioactive decay) for the fractional retention of a radionuclide in the organ of reference at time t following a single uptake in the organ.
(ANSI N343-1978)

Retention function (R or R_subscript)
The fractional biological retention as a function of time in the body or in tissue indicated by the subscript of an isotope (stable or radioactive) introduced into the blood at time zero. Therefore, when a radioisotope is injected intravenously, R is the total activity in the body at any time corrected for radioactive decay and divided by the activity injected; and R_subscript is the activity in a particular tissue at any time corrected for radioactive decay and divided by the injected activity. The time of injection is time zero, so R at time zero must be unity. All R_subscript at time zero must be zero except R_blood. All the retention functions are dimensionless.
(ICRP 20)

Retention Times
Specific times of retention of a substance that has been inhaled or injected in an organ or organs of the body.
(NCRP 125)

Reticle
A transparent disk with lines or other marks placed in the focal plane of optical systems for calibration or alignment
(AM-1993)

Retinitis pigmentosa
A disease that is frequently hereditary, marked by progressive retinal sclerosis, pigmentation and atrophy.
(NCRP 98)

Retransfer
The transport from one foreign country to another of nuclear equipment or nuclear material previously exported from the United States, or of special nuclear material produced through the use of source material or special nuclear material previously exported from the United States.
(10CFR110.2)

Retrieval
The act of intentionally removing radioactive waste from the underground location at which the waste had been previously emplaced for disposal.
(10CFR60.2)

Reverse current (of a junction)
Current which flows in the reverse direction.
(IEC 50-394-1993)

Reverse direction (of a PN junction)
The direction of current that results when the N-type semiconductor region is at a positive voltage relative to the P-type region.
(IEC 50-394-1993)

Reverse voltage (of a junction)
Applied voltage such that the current flows in the reverse direction.
(IEC 50-394-1993)

Review
A means of assuring that current policies, procedures, and practices are adequate, appropriate, and effective in meeting the goals of the measurement program.
(ANSI N15.54-1988)

Review
A means of assuring that current policies, procedures, and practices are adequate, appropriate, and effective in meeting the goals of the measurement program.
(ANSI N15.41-1984)

Review is completed
That the review has been brought to an end, whether by reason of issuance of a permit, license, approval, certificate, exemption, or other form of permission, or whether the application is denied, withdrawn, suspended, or action on the application is postponed by the applicant.
(10CFR170.3)

Rework
A disposition involving the process by which a non-conforming item is made to conform to original requirements by completion or correction.
(ANSI N46.2-1978)

Reynolds number
Flow similitude parameter, expressed as the ratio of the inertial force of the gas to the friction force of the gas moving over the surface of an object; flow Reynolds number the gas flow in a tube and particle Reynolds number describes the gas flow around a particle
(AM-1993)

Reynolds number
The ratio of inertial to viscous forces in a flow.
(TID-26608)

Rheology
Study of the flow of matter embracing elasticity, viscosity, and plasticity.
(NCRP 125)

Rhinencephalon
The olfactory bulb and all other areas of the brain where efferent fibers from the bulb synapse; commonly taken to include the bulb, the anterior olfactory nucleus, the olfactory trigone, the anterior perforated substance, the olfactory tubercle, the lateral olfactory stria, Broca's diagonal band, and the cortical areas of the temporal lobe of the cerebrum.
(ICRP 49)

Rhm
Roentgens per hour at one meter from the effective center of the source. (In teletherapy this distance is usually measured to the nearest surface of the source as its effective center is generally not known.)
(NBS 73)

Rhm
Roentgens per hour at one meter.
(NBS 54)

Rhm (deprecated)
Roentgens per hour at one meter from the effective center of the source (target). In gamma-ray beam therapy, this distance is measured to the nearest surface of the source as its effective center generally is not known.
(NCRP 49)

Rhombencephalon
The hindbrain, i.e., the part of the brain that develops caudal to cephalic flexure. It includes the pons and medulla oblongata; it gives rise to the cerebellum, and is continuous with the spinal cord.
(ICRP 49)

Rigging company (rigger)
The loading and unloading of the transport vessel, including the securing and unsecuring of the cargo, is generally carried out by a rigging company. There may be more than one organization, depending on the locations of the loading and unloading operations. Usually the tiedown arrangement, design, fabrication, and installation will be performed by the initial-loading rigger, and the remaining unloading or loading operations will follow established procedures. The rigger may also be a specialized heavy hauler and provide transport vehicles to move heavy packages for short distances, in addition to the loading and unloading functions.
(ANSI N14.24-1985)

Rigidity
The momentum of a charged particle per unit charge. Determines the curvature of the particle's trajectory in a magnetic field. Two particles with different charge but the same rigidity will travel along a path having the same curvature in a given magnetic field.
(NCRP 98)

Rise time (of a measuring assembly)
Time for the output quantity to rise from 10% to 90% of its amplitude, for a step function input.
(IEC 50-394-1993)

Risk
Terms relating to risk are grouped together here.

Risk.: In this report, the probability that a fatal lung cancer will occur.
Relative risk.: The ratio of the risk in an exposed population to that in a similar unexposed population.
Excess relative risk.: Relative risk - 1.
Absolute risk.: The probability that a fatal lung cancer will occur.
Excess or attributable risk.: The absolute excess or attributable risk due to an exposure.
Risk coefficient.: The risk per unit exposure.
Risk projection model.: A model describing the variation of risk as a function of the time since exposure. It may be related by a factor to the age specific baseline risk (multiplicative) or added to the baseline risk (additive).
(ICRP 65)

Risk
The product of probability of occurrence and severity of injury, damage or loss.
(NCRP 118)

Risk
The probability of a specified effect or response occurring.

Absolute risk:: Expression of excess risk due to exposure as the arithmetic difference between the risk among those exposed and that obtaining in the absence of exposure.
Annual risk:: The risk in a given year from an earlier exposure(s). The annual risk (average) from an exposure is the lifetime risk divided by the years of expression.
Lifetime risk:: The total risk in a lifetime resulting from an exposure(s). It is equal to the average annual risk times the period of expression.
Relative risk:: An expression of excess risk relative to the underlying (baseline) risk; if the excess equals the baseline risk the relative risk is 2.
(NCRP 98)

Risk coefficient
The probability or chance that a particular stochastic effect will occur per unit dose.
(NCRP 121)

Risk coefficient
The increase in the annual incidence or mortality rate per unit dose: (1) absolute risk coefficient is the observed minus the expected number of cases per person year at risk for a unit dose; (2) the relative-risk coefficient is the fractional increase in the baseline incidence or mortality rate for a unit dose.
(NCRP 98)

Risk coefficient
As used in NCRP 78-1984, the attributable mortality rate of lung cancer per unit exposure following a suitable latent interval. It is expressed in lung cancer deaths per year per WLM.
(NCRP 78)

Risk estimate
The number of cases (or deaths) that are projected to occur in a specified exposed population per unit dose for a defined exposure regime and expression period: number of cases per person-Gray or for radon, the number of cases per person cumulative working-level month.
(NCRP 98)

RNA (ribonucleic acid)
Any of various nucleic acids that contain ribose and uracil as structural components and are associated with the control of cellular chemical activities.
(HPJ 60)

Robustness
The degree to which predicted individual or collective doses, or dose commitments, are jointly affected by imprecision in all parameters of the ecological or biological system model.
(ICRP 29)

Rod
A relatively long, slender body of material used in or in conjunction with a nuclear reactor. It may contain fuel, absorber, or material in which activation or transmutation is desired. (See control rod.)
(USAEC-1974)

Rod
A relatively long and slender body of material used in or with a nuclear reactor. It may contain fuel, absorber, fertile materials, or other material in which activation or transmutation is desired.

Control rod:: Any rod used to control the reaction rate in a nuclear reactor by changing the effective multiplication constant and hence the reaction rate's time derivative. It may be a fuel rod or a part of the moderator; in thermal reactors it commonly is a neutron absorber. Cadmium and boron (as boron steel) are suitable absorbing materials. Sometimes absorbing control rods are made of fertile material to utilize the neutrons absorbed in control. The term includes power control rod, regulating rod, safety rod, and shim rod.
Fuel rod:: A rod-shaped body of nuclear fuel or a long, slender fuel assembly prepared for use in a reactor. A short fuel rod is called a "slug".
Regulating rod:: A control rod intended to accomplish rapid, fine adjustment of the reactivity of a nuclear reactor. It can usually move much more rapidly than a shim rod, but makes a smaller change in the reactor's reactivity. Its rapid and sometimes continuous readjustment may be accomplished by a servo system.
Safety rod:: An emergency control rod capable of shutting down a reactor very quickly, should the ordinary control system (e.g., regulating and shim rods) fail. Since it must be able to reduce the reactor's effective multiplication constant to much less than unity when inserted, it is withdrawn almost completely during normal operation. A safety rod may be suspended above the core by a magnetic coupling and allowed to fall in if power reaches a predetermined level.
Scram rod:: A safety rod.
Shim rod:: A control rod used for making occasional coarse adjustments in the reactivity of a nuclear reactor. It usually moves more slowly than a regulating rod and singly or as one of a group, can make a greater total change in the reactivity. Its name is derived from analogy to a mechanical shim. A shim rod commonly is positioned so that the reactor will be just critical (reactivity = 0, effective multiplication constant = 1) when the regulating rod is near the middle of its range of travel.
(RHH)

Roentgen
The special unit of x- or g-radiation exposure. One roentgen equals 2.58 x 10^-4 coulombs per kilogram of air (abbreviated R).
(HPJ 60)

Roentgen
The traditional unit of exposure. 1 R = 2.58 x 10^-4 C kg^-1 of air.
(NCRP 83)

Roentgen
[Abbreviation R] A unit of exposure to ionizing radiation. It is that amount of gamma or X rays required to produce ions carrying 1 electrostatic unit of electrical charge (either positive or negative) in 1 cubic centimeter of dry air under standard conditions. Named after Wilhelm Roentgen, German scientist who discovered X rays in 1895.
(USAEC-1974)

Roentgen
The quantity of X- or gamma radiation such that the associated corpuscular emission per 00.001293 gram of air produces, in air, ions carrying one electrostatic unit of quantity of electricity of either sign. (A unit of exposure dose.)
(NBS 66)

Roentgen
In the energy range up to 3 Mev, the International Commission of Radiological Units has continued the recognition of the roentgen as a unit of X- and gamma-ray quantity with the following definition: "The roentgen shall be the quantity of X- or gamma radiation such that the associated corpuscular emission per 00.001293 gram of air produces, in air, ions carrying one electrostatic unit of quantity of electricity of either sign."
(NBS 55)

Roentgen (R)
The previously used special unit of exposure. An exposure of one roentgen will produce 2.58 x 10^-4 coulomb of ions of wither sign per kilogram in air. In this report,the previously used physical quantity exposure has been replaced by kerma in air. See kerma. One R does not equal 1 cGy as the units C/kg and J/kg are different. The numerical value of kerma in cGy may be substituted for the numerical value of exposure in R.
(NCRP 102)

Roentgen (R)
A unit of exposure. Exposure in SI units is expressed in Coulombs per kilogram (C kg^-1) of air.
(NCRP 98)

Roentgen (R)
The special unit of exposure, based on a quantity of ionization (charge) produced by the absorption of x or gamma radiation energy in a specified mass of air under standard conditions. 1R = 2.58 x 10^-4 C kg^-1 or air. For radiation protection purposes, an exposure to 1 roentgen of x or gamma rays (air kerma of ~10^-2 J kg^-1) is generally assumed to produce an absorbed dose of 1 rad in water or soft tissue. (See exposure, gray, kerma).
(NCRP 105)

Roentgen (R)
The unit of radiation exposure representing the charge liberated by the radiation per unit mass of air. One Roentgen equals 2.58 x 10^-4 Coulomb per kilogram of air.
(NCRP 80)

Roentgen (R)
The special unit of exposure. One Roentgen equals 2.58 x 10^-4 C/kg.
(NCRP 69)

Roentgen (R)
The special unit of exposure for x and gamma rays. One roentgen produces 2.58 x 10^-4 coulombs per kilogram of air.
(NCRP 68)

Roentgen (R)
The special unit of exposure. One Roentgen equals 2.58 x 10^-4 Coulomb per kilogram of air.
(NCRP 65)

Roentgen (R)
The special unit of exposure equal to 2.58 x 10^-4 coulombs per kilogram. (plural: roentgens).
(NCRP 51)

Roentgen (R)
The special unit of exposure equal to 2.58 x 10^-4 coulombs per kilogram. (plural: roentgens).
(NCRP 49)

Roentgen (R)
A unit of exposure. (1 R = 2.58 x 10^-4 C/kg.)
(ANSI N1.1-1976)

Roentgen (R)
The special unit of exposure for x and gamma rays. One roentgen produces 2.58 x 10^-4 coulombs per kilogram of air.
(NCRP 48)

Roentgen (R)
The special unit of exposure. One Roentgen equals 2.58 x 10^-4 Coulomb per kilogram of air.
(BEIR I)

Roentgen (R)
The special unit of exposure. One Roentgen equals 2.58 x 10^-4 Coulomb per kilogram of air.
(RHH)

Roentgen (R)
Unit of exposure dose of X- or gamma radiation. One roentgen is an exposure dose of X- or gamma radiation such that the associated corpuscular emission per 0.001293 g of air produces, in air, ions carrying 1 esu of quantity of electricity of either sign.
(NBS 73)

Roentgen (R)
The quantity of X- or gamma-radiation such that the associated corpuscular emission per 0.001293 g of air produces, in air, ions carrying 1 esu of quantity of electricity of either sign.
(NBS 54)

Roentgen (R)
The international unit of quantity for both X-rays and gamma rays adopted by the Fifth International Congress of Radiology at Chicago in 1937. It was defined by the International Commission on Radiological Units in the following words: "The International Unit of quantity or dose of X-rays or gamma rays shall be called the roentgen and shall be designated by the symbol r. The roentgen shall be the quantity of X- or gamma-radiation such that the associated corpuscular emission per 0.001293 g of air produces, in air, ions carrying 1 esu of quantity of electricity of either sign."
(NBS 51)

Roentgen (R) (deprecated)
Unit of exposure exactly equal to 2.58 x 10^-4 C kg^-1.
(IEC 50-393-1993)

Roentgen equivalent man
See rem.
(USAEC-1974)

Roentgen equivalent physical (rep)
Although not an internationally accepted unit, the rep is often a convenient shorthand notation for statements of dose of ionizing radiation not covered by the definition of the roentgen. It represents that dose which produces energy absorption of 93 ergs/g of tissue. The actual energy absorption in tissue per roentgen is a function of the tissue composition and of the wavelength of the radiation. It ranges between 60 and 100 ergs/g. For calculations of permissible exposure this variation is ignored, and a beta-ray dose of one rep is said to be physically equivalent to an X-ray dose of 1 r at a given point in the body. The numerical coefficient of the rep has been deliberately changed to 93, instead of the earlier 83, to agree with L.H. Gray's "energy-unit".
(NBS 51)

Roentgen rays
X rays.
(USAEC-1974)

Roentgen rays
X rays.
(RHH)

Roentgen therapy
Radiation therapy with X rays.
(USAEC-1974)

Roentgenography
Radiography by means of x rays.
(USAEC-1974)

Roentgenography
Radiography by means of x rays.
(RHH)

Roentgenology
That part of radiology which pertains to x rays.
(RHH)

Rolle method
A modification of the Kusnetz method for estimating working level by making a single measurement of alpha activity on a filtered air sample.
(NCRP 97)

Rostral
Relating to any anatomical structure resembling a beak.
(ICRP 49)

Rotameter
A device used to measure the flow rate, as indicated by the height of a float centered in a vertical tapered tube
(AM-1993)

Roughing filter
A prefilter with high efficiency for large particles and fibers but low efficiency for small particles; usually of the panel type.
(ERDA 76-21)

Routine Measurements
Radiobioassays conducted on a planned schedule to determine if any intake might have occurred.
(HPS N13.30-1996)

Routine measurements
Radiobioassays conducted on a planned schedule to determine if any intake may have occurred.
(ANSI N13.30-1989D)

Routine Monitoring
The regular bioassay sampling of personnel at predetermined times not related to known intakes.
(HPS N13.42-1997)

Routine respirator use
Wearing a respirator as a normal procedure when carrying out a regular and frequently repeated task.
(ANSI Z88.2-1980)

Routine test
A test to which an individual device is subjected during or after manufacture to ascertain whether it complies with certain criteria.
(IEC 50-394-1993)

Routine uranium bioassay program
A regular program of collecting and measuring bioassay samples in order to monitor and estimate exposures to workers who are exposed, or potentially exposed, to uranium during their routine work activities, and to help ensure that limits of intake are not exceeded. A routine bioassay program should also include pre-placement or pre-work bioassay measurements to establish "baseline" levels not related to the new work environment, as well as termination bioassay measurements to establish exposure status at the termination of employment, or at the end of work at a specific work station or area.
(ANSI/HPS N13.22-1995)

Rover
A nuclear rocket propulsion project.
(RAH)

Rover
A joint program of the Atomic Energy Commission and the National Aeronautics and Space Administration to develop a nuclear rocket for space flight. (See nuclear rocket.)
(USAEC-1974)

RSO
Acronym for Radiation Safety Officer. A person qualified by training and experience to be designated as the individual responsible for the safe use of radiation at a facility.
(NCRP 111)

Run
The net period of time during which an emission sample is collected. Unless otherwise specified, a run may be either intermittent or continuous within the limits of good engineering practice.
(40CFR61.02)

Runaway (reactor)
An increase in power or reactivity that cannot be controlled by the normal reactor control system. It might possibly be terminated safely by the emergency shutdown system or a negative reactivity coefficient.
(ANSI N1.1-1976)

Rutherford
An obsolete unit of radioactivity equivalent to 106 disintegrations per second.
(RHH)

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