Borders' Dictionary of Health Physics

A
Weighting factors assigned for partitioning of tissue weighting factors (w_T for lungs and for extrathoracic tissues) among all respiratory tract tissues.
(ICRP 66)

A
The symbol for atomic number.
(USAEC-1974)

A_z
The area under an ROC curve, often used as an index of delectability or "diagnostic accuracy." Strictly, A_z refers only to ROCs with "binormal form," but occasionally it is used more loosely to indicate the area under any ROC curve. Values of A, and the index da are related by the expression A_z = F (da/ Ö2) where F(·) represents the cumulative standard-normal distribution function. Perfect and random decisions in a detection task correspond to A_z = 1.0 and A_z = 0.5, respectively. A_z can be interpreted as the average value of test "sensitivity" for "specificities" ranging from 0 to 1, or equivalently, as the average value of test "specificity" for "sensitivities" ranging from 0 to 1.
(ICRU 54)

A-bomb
An atomic bomb.
(USAEC-1974)

A/D convertor
An electronic device used to change an analog signal to a digital one.
(AM-1993)

A₁
The maximum activity of special form radioactive material permitted in a Type A package.
(10CFR71.4)

A₁
The maximum activity of special form material permitted in a Type A package.
(49CFR173.403)

A₂
The maximum activity of radioactive material, other than special form radioactive material, permitted in a Type A package. These values are either listed in Appendix A of this part, Table A-1, or may be derived in accordance with the procedure prescribed in Appendix A of this part.
(10CFR71.4)

A₂
The maximum activity of radioactivity, other than special form or low specific activity radioactive material, permitted in a Type A package.
(49CFR173.403)

A₂
A quantity of radioactive material, other than special-form radioactive material, as specified in the applicable documents listed in 2.1.1 and 2.1.2 of this standard.
(ANSI N14.5-1987)

ABCC
Atomic Bomb Casualty Commission (See RERF).
(RAH)

ABCC
Atomic Bomb Casualty Commission (See RERF).
(BEIR III)

ABCC
Atomic Bomb Casualty Commission (See RERF).
(BEIR I)

Abiotic substances
Inorganic or organic, nonliving substances in the environment.
(NUREG/CR 3332)

Abnormal condition
A transient-process state, or a state resulting from an unusual incident in which operating parameters affecting control of radioactive materials in the offgas move out of the normal operating range.
(ANSI N303-1978)

Abrasive blasting respirator
A respirator designed to protect the wearer against inhalation of abrasive material and against impact and abrasion from rebounding abrasive material.
(ANSI Z88.2-1980)

Abrasive blasting respirator
See respirator.
(ANSI Z88.2-1969)

Abrupt loss
A loss occurring in the time interval between consecutive sequential performances of a material control test which is designed to detect anomalies potentially indicative of a loss of strategic special nuclear material from a specific unit of SSNM (i.e., a quantity characterized by a unique measurement) introduced into a process.
(10CFR74.4)

Abscopal effect
An effect ascribable to radiation exposure, but observed in a region of the body outside of the irradiation field and believed to have received insignificant dose.
(NCRP 66)

Abscopal effect
An effect ascribable to radiation exposure, but observed in a region of the body outside of the irradiation field and believed to have received insignificant dose.
(ICRU 30)

Absolute filter
Obsolete term for HEPA filter.
(ERDA 76-21)

Absolute humidity
Vapor content of water in air expressed as g m^-3. A key parameter in the calculation of dose from tritium released to the atmosphere.
(NCRP 76)

Absolute humidity
Vapor content of water in air expressed as g m^-3. A key parameter in the calculation of dose from tritium released to the atmosphere.
(NUREG/CR 3332)

Absolute risk
Excess risk that adds to the existing or baseline risk already present by an increment that depends upon the dose, but is independent of the level of existing risk.
(NCRP 121)

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.
(ICRP 59)

Absolute risk
An expression of excess risk based on the assumption that the excess risk from radiation exposure adds to the underlying (baseline) risk by an increment dependent on dose but independent of the natural underlying risk.
(BEIR V)

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. The resultant risk coefficient is normalized to a population base of 1 million people and is expressed as number of excess cases per million persons per rad per year at risk. Absolute risk coefficients project a constant level of excess risk over the period of expression.
(BEIR III)

Absolute risk
Product of assumed relative risk times the total population at risk. The number of cases that will result from exposure of a given population.
(BEIR I)

Absorbed dose, D
The energy absorbed per unit mass at a specific place in a material. The special name for the unit of absorbed dose is the gray (Gy) which has units of joules per kilogram (J/kg). The special unit of absorbed dose is the rad. 1 J/kg = 1 Gy = 100 rad. As used in this standard, "absorbed dose" stands for the absorbed dose in the material of interest, that is, soft tissue or in a phantom approximating soft tissue in composition.
(ANSI/HPS N13.11-1993)

Absorbed dose
The quotient de by dm where de is the mean energy imparted by ionizing radiation to the matter in a volume element and dm is the mass of the matter in that volume element, i.e., the absorbed dose, D = de/dm. The special name for the SI unit of absorbed dose is gray, 1 gray = 1 J kg^-1.
(ICRU 30)

Absorbed dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. The special unit of absorbed dose is the rad. One rad equals 0.01 joule per kilogram. One rad = 100 ergs/gram.
(NCRP 62)

Absorbed dose
The mean energy imparted by ionizing radiation to matter, per unit mass of irradiated material, at the place of interest.
(NCRP 59)

Absorbed dose
The absorbed dose, D, is the quotient of de by dm, where de is the mean energy imparted by ionizing radiation to the matter in a volume element, and dm is the mass of the matter in that volume element.

The special unit of absorbed dose is the rad and the SI unit of absorbed dose is the gray.
(ICRU 26)

Absorbed dose
The energy imparted to matter in a volume element by ionizing radiation divided by the mass of irradiated material in that volume element.
(ANSI N319-1976)

Absorbed dose
The mean energy imparted by ionizing radiation to matter, per unit mass of irradiated material, at the place of interest. The unit of absorbed dose is the rad. See rad.
(NCRP 48)

Absorbed dose
The mean energy imparted to matter by ionizing radiation per unit mass of matter. The special unit of absorbed dose is the rad. One rad equals 10^-2 joule per kilogram (100 ergs per gram).
(NCRP 49)

Absorbed dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. The unit of absorbed dose is the rad. One rad = 100 ergs per gram, or 0.01 J/kg.
(BEIR I)

Absorbed dose
The quotient de by dm where de is the mean energy imparted by ionizing radiation to the matter in a volume element and dm is the mass of the matter in that volume element.

The special unit of absorbed dose is the rad. 1 rad = 10^-2 J kg^-1.
(ICRU 19)

Absorbed dose
The energy absorbed per unit mass at a specific place in a material. The special unit of absorbed dose is the rad, equal to 0.01 joule per kilogram.
(ICRU 20)

Absorbed dose
The absorbed dose of any ionizing radiation is the energy imparted to matter by directly and indirectly ionizing radiation per unit mass of irradiated material. The special unit of absorbed dose is the rad.
(NCRP 38)

Absorbed dose
The energy imparted to matter in a volume element by ionizing radiation divided by the mass irradiated material in that volume element. The special unit of absorbed dose in the rad.
(ANSI N13.3-1969)

Absorbed dose
The quotient DE_D by D_m, where DE_D is the energy imparted by ionizing radiation to the matter in a volume element, and D_m is the mass of the matter in that volume element.

(NBS 92)

Absorbed dose
Energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest. The unit of absorbed dose is the rad. (When the meaning is clear, this term amy be shortened to "dose".)
(NBS 73)

Absorbed dose
The absorbed dose of any ionizing radiation is the amount of energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest. It is expressed in rads. Note: Without the qualifying word "absorbed", dose can have several meanings.
(NBS 66)

Absorbed dose
Absorbed dose of any ionizing radiation is the amount of energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest. The absorbed dose is measured in rads.
(NBS 63)

Absorbed dose
The energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the rad and the Gray (Gy).
(10CFR20.1003)

Absorbed dose
Energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest in that material. The unit of absorbed dose is the gray (Gy) or rad. One rad is equal to 0.01 Gy.
(HPS N13.41-1997)

Absorbed Dose
The quotient of de by dm where de is the mean energy imparted by ionizing radiation to the matter in a volume element and dm is the mass of the matter in that volume element, i.e., the absorbed dose D = de/dm. The unit of absorbed dose is the gray (Gy).
(NCRP 125)

Absorbed dose
The energy absorbed in matter by ionizing radiation per unit mass of irradiated material at the place of interest in that material. The absorbed dose is expressed in units of rad (or gray). (1 rad = 0.01 gray.)
(10CFR834.2-1996)

Absorbed dose
The physical dose quantity given by

where de is the mean energy imparted by ionising radiation to the matter in a volume element and dm is the mass of the matter in this volume element. The SI unit for absorbed dose is joule per kilogram (J kg^-1) and its special name is gray (Gy).
(ICRP 68)

Absorbed dose
The physical dose quantity defined as the quotient of the energy absorbed in an organ or tissue T by its mass (1 J kg^-1 = 1 Gy).
(ICRP 67)

Absorbed dose
The energy from ionizing radiation absorbed per unit mass is called the absorbed dose. The unit of absorbed dose is the gray (1 Joule per kg) or, historically, the rad which is equal numerically to 10^-2 kg^-1 (100 erg g^-1).
(NCRP 118)

Absorbed dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. Absorbed dose is expressed in units of gray (Gy); 1 Gy = 1 J kg^-1.
(NCRP 114)

Absorbed dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the point of interest; The special name for the unit of absorbed dose (J kg^-1) is the gray (Gy).
(NCRP 111)

Absorbed dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. The units of absorbed dose are the rad or the gray. 1 rad = 100 ergs g^-1 or 0.01 J kg^-1; 1 Gy = 100 rad = 1 J kg^-1.
(HPJ 60)

Absorbed dose
The mean energy imparted to the irradiated medium, per unit mass, by ionizing radiation. Units: gray (Gy), rad.
(BEIR V)

Absorbed dose
Absorbed dose, D, is defined by the relationship:

where de is the mean energy imparted by ionising radiation to the matter in a volume element and dm is the mass of the matter in this volume element. The SI unit for absorbed dose is joule per kilogram (J kg^-1) and its special name is gray (Gy).
(ICRP 60)

Absorbed dose
The absorbed dose, D, is the quotient of de by dm, where de is the mean energy imparted by ionizing radiation to matter of mass dm,

Unit: J kg^-1 The special name for the unit of absorbed dose is gray (Gy).
(ICRU 44)

Absorbed dose
The quantity of energy from ionizing radiation that is absorbed per unit mass is the absorbed dose. The special S.I. unit of absorbed dose is the gray (Gy). One gray of absorbed dose is numerically equal to one joule per kilogram.
(NCRP 103)

Absorbed dose
The quotient of dE by dm where dE is the mean energy imparted by ionizing radiation to the matter in a volume element and dm is the mass of the matter in that volume element, i.e., the absorbed dose, D = dE/dm. The special name for the SI unit of absorbed dose (J kg^-1) is the gray (Gy). The earlier unit of absorbed dose was the rad which is equal to 0.01 Gy.
(NCRP 101)

Absorbed dose
The differential de/dm, where de is the mean energy imparted by ionizing radiation to matter of mass dm. The special SI unit of absorbed dose is the gray (Gy); the conventional unit is the rad (1 rad = 0.01 Gy).
(FGR 11)

Absorbed dose
The mean energy imparted to the irradiated medium, per unit mass, by ionizing radiation. Units: gray (Gy), rad.
(BEIR IV)

Absorbed dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. In SI units, the unit of absorbed dose is the gray (Gy), defined as 1 joule per kilogram. Still in use temporarily is the rad; one rad equals 0.01 joules per kilogram.
(NCRP 93)

Absorbed dose
The quotient of d by dm where d is the mean energy imparted by ionizing radiation to the matter in a volume element and dm is the mass of the matter in that volume element, i.e., the absorbed dose, D = d/dm. The special unit of absorbed dose is the rad. In the SI it is the gray (Gy).
(NCRP 84)

Absorbed dose
The radiation energy absorbed per unit mass of the target material. Formally,

where dE is the mean energy imparted by ionizing radiation to matter of mass dm. Like temperature, absorbed dose is a point, or intensive function. The traditional unit of absorbed dose is the rad. The SI unit of absorbed dose is the gray (Gy).
(NCRP 83)

Absorbed dose
The energy from ionizing radiation absorbed per unit mass is called the absorbed dose. The special unit of absorbed dose is the rad and is equal numerically to 100 erg/gram (10^-2 Joule/kg).
(NCRP 78)

Absorbed dose
The energy deposited in matter by ionizing radiation per unit mass of irradiated material. The unit of absorbed dose is the rad [the SI unit is the gray (Gy), where 100 rad = 1 Gy].
(NUREG/CR 3332)

Absorbed dose
The energy imparted by ionizing radiation to unit mass of matter such as tissue. Unit gray, Symbol Gy. 1 Gy = 1 joule per kilogram.
(ICRP 36)

Absorbed dose
The absorbed dose of any ionizing radiation is the energy imparted to matter by the ionizing radiation per unit mass of irradiated material at the point of interest.
(NCRP 69)

Absorbed dose
When ionizing radiation passes through matter, some of its energy is imparted to the matter. The amount absorbed per unit mass of irradiated material is called the absorbed dose. The special unit of the absorbed dose is the RAD.
(NCRP 65)

Absorbed dose
When ionizing radiation passes through matter, some of its energy is imparted to the matter. The amount absorbed per unit mass of irradiated material is called the absorbed dose and is measured in rems and rads. (See threshold dose.)
(USAEC-1974)

Absorbed dose (D)
Energy absorbed per unit mass of irradiated material. The SI unit for the quantity absorbed dose is the gray (Gy): 1 Gy = 1 J kg^-1 = 100 rad = 10⁴ erg g^-1.
(ANSI/HPS N13.22-1995)

Absorbed dose (D)
The energy absorbed by matter from ionizing radiation per unit mass of irradiated material at the place of interest in that material. The absorbed dose is expressed in units of rad (or gray) (1 rad = 0.01 gray).
(10CFR835.2-1993)

Absorbed dose (D)
Quotient of de by dm, where de is the mean energy imparted by ionizing radiation to matter of mass dm.

(IEC 50-393-1993)

Absorbed dose, D
The energy absorbed from ionizing radiation per unit mass of any material. More precisely: D = de/dm where de is the mean energy imparted by ionizing radiation to an element of matter of mass dm.
(MIRD)

Absorbed dose (D)
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the point of interest; unit of absorbed dose has been the rad and now in the System International (SI) is the gray (Gy), 100 rad = 1 Gy.
(NCRP 105)

Absorbed dose (D)
The energy imparted per unit mass by ionizing radiation to matter at a specified point. The SI unit of absorbed dose is joule per kilogram (J/kg). The special name for this unit is gray (Gy). The previously used special unit of absorbed dose, rad, is being replaced by the gray. 1 rad = 0.01 Gy. 1 Gy = 100 rad.
(NCRP 102)

Absorbed dose (D)
The quotient dE by dm, where dE is the mean energy imparted by ionizing radiation to matter of mass dm.

(ICRU 43)

Absorbed dose (D)
The quotient dE by dm, where dE is the mean energy imparted by ionizing radiation to matter of mass dm.

(ICRP 51)

Absorbed dose (D)
The energy absorbed per unit mass at a specific place in a material, such as, soft tissue or in a phantom approximating soft tissue in composition. The special unit of absorbed dose is the rad. 1 rad = 10 millijoule per kilogram (mJ/kg) (100 ergs per gram (erg/g) = 0.01 Gy).
(ANSI N13.15-1985)

Absorbed dose (D)
The energy absorbed per unit mass at a specific place in a material. The special unit of absorbed dose is the rad. The SI unit of absorbed dose is joule per kilogram (J/kg). Its special name is gray (Gy) . 1 J/kg = 1 Gy = 100 rad. As used in ANSI N13.11, "absorbed dose" stands for the absorbed dose in the material of interest, that is, soft tissue or in a phantom approximating soft tissue in composition. Note: Ignoring trace elements. the composition of soft tissue is taken as 76.2% O, 11.1% C, 10.1% H, and 2.6% N.
(ANSI N13.11-1983)

Absorbed dose (D)
The energy imparted to matter by ionizing radiation per unit mass of irradiated material.
(ICRP 33)

Absorbed dose (D)
The quotient dE by dm, where dE is the mean energy imparted by ionizing radiation to matter of mass dm.

(ICRU 33)

Absorbed dose (D)
The quotient dE by dm where dE is the mean energy imparted by ionizing radiation to the matter in a volume element and dm is the mass of the matter in that volume element. The special unit of absorbed dose is the rad.
(NCRP 51)

Absorbed dose (D)
The absorbed dose (D) due to any directly or indirectly ionizing radiation is the energy imparted to matter by ionizing particles per unit mass of irradiated material. The special unit of absorbed dose is the rad and is equal to an energy absorption of 0.01 joule kg^-1 or 100 ergs g^-1.
(ICRP 15)

Absorbed dose distribution (dose distribution)
A representation of the variation of absorbed dose with position in any region of an irradiated object.
(ICRU 24)

Absorbed dose distribution (dose distribution)
A representation of the variation of absorbed dose with position in any region of an irradiated object.
(ICRU 23)

Absorbed dose index (D_I)
The absorbed dose index at a point is the maximum absorbed dose within a 30 cm-diameter sphere centered at this point and consisting of material equivalent to soft tissue with a density of 1 g cm^-3.
(ICRP 51)

Absorbed dose index (D_I)
The maximum absorbed dose within a 30-cm diameter sphere centered at the point of interest and consisting of material equivalent to soft tissue with a density of 1 g cm^-3.
(NCRP 51)

Absorbed dose index rate ()
The quotient of dD_I by dt, where dD_I is the increment of absorbed dose index in the time interval dt.

(ICRU 33)

Absorbed dose rate
The time derivative of absorbed dose is the absorbed dose rate, D, i.e.

where dD is the increment of absorbed dose in the time interval dt.
(ICRP 60)

Absorbed dose rate
Absorbed dose per unit time.
(NCRP 69)

Absorbed dose rate
Absorbed dose per unit time.
(NCRP 48)

Absorbed dose rate
The quotient of DD by Dt, where DD is the increment of absorbed dose in time Dt. The special unit of absorbed dose rate is any quotient of the rad by a suitable unit of time (rad/d, rad/min, rad/h, etc.).

(NBS 92)

Absorbed dose rate
The quotient of DD by Dt, where DD is the increment of absorbed dose in the time Dt.
(ICRU 10f)

Absorbed dose rate
The quotient of DD by Dt, where DD is the increment of absorbed dose in the time Dt.
(ICRU 10b)

Absorbed dose rate ()
The quotient of dD by dt, where dD is the increment of absorbed dose in the time interval dt. A special unit of absorbed dose rate is any quotient of the rad or its multiple or submultiple by a suitable unit of time (rad s^-1, mrad h^-1, etc.).

(ICRU 19)

Absorbed dose rate ()
Quotient of dD by dt, where dD is the increment of absorbed dose in the time interval dt.

(IEC 50-393-1993)

Absorbed dose rate ()
The quotient of dD by dt, where dD is the increment of absorbed dose in the time interval dt.
(ICRU 33)

Absorbed fraction
The fraction of energy emitted as a specified radiation type in a specified source tissue which is absorbed in a specified target tissue.
(NCRP 84)

Absorbed fraction
The ratio of the energy absorbed by a target organ to the energy emitted by a source organ (or region) within the body.
(NUREG/CR 3332)

Absorbed fraction
The fraction of energy emitted as a specified radiation type in a specified source tissue which is absorbed in a specified target tissue.
(ICRP 30)

Absorbed fraction
A term used in internal dosimetry. It is the fraction of the photon energy (emitted within a specified volume of material) which is absorbed by the volume. The absorbed fraction depends on the source distribution, the photon energy, and the size, shape and composition of the volume.
(RHH)

Absorbed fraction (AF(T¬S)_i)
The fraction of energy emitted as a specified radiation type i in a specified source region S which is absorbed in a specified target tissue T.
(ICRP 67)

Absorbed fraction (AF(T¬S)_R)
The fraction of energy emitted as a specified radiation type R in a specified source region S which is absorbed in a specified target tissue T.
(ICRP 68)

Absorbed fraction (AF_j(T¬S))
The fraction of energy emitted as a specified radiation type j in a specified source tissue S which is absorbed in a specified target tissue T.
(ICRP 56)

Absorbed fraction (f)
The ratio of radiation energy absorbed in the target region to that emitted in the source organ. This is a dimensionless number. (See also specific absorbed fraction.)
(NCRP 83)

Absorbed fraction, f_i
The fraction of the energy of type-i radiation emitted from the source organ that is absorbed in the target organ.
(MIRD)

Absorbed-dose index (D_i) or dose-equivalent index (H_i) at a point
The maximum absorbed dose or dose equivalent within a sphere with a 30-cm diameter centered at the point of measurement, consisting of material equivalent to soft tissue with a density of 1 gm/cm³. Note: In the case of radiation of low penetrating power, it is recommended to divide the sphere into a shallow shell (from the surface to a depth of 0.007cm), a deep shell (from 0.007 cm to 1 cm), and a core (from a depth of 1 cm to the center), and to determine the so-called "restricted" index quantities, called the shallow and deep-absorbed-dose or dose-equivalent indexes. For the sake of simplicity, the terms "restricted absorbed-dose index" and "restricted dose-equivalent index" is not used in this standard.
(ANSI N13.15-1985)

Absorbent
A material which takes up a constituent through the action of diffusion, allowing the constituent to penetrate into the structure of the absorbent, if a solid, or dissolve in it, if a liquid. When chemical reaction takes place during absorption, the process is called chemisorption.
(ANSI N13.1-1969)

Absorber
Any material that absorbs or diminishes the intensity of ionizing radiation. Neutron absorbers, like boron, hafnium and cadmium are used in control rods for reactors. Concrete and steel absorbs gamma rays and neutrons in reactor shields. A thin sheet of paper or metal will absorb or attenuate alpha particles and all except the most energetic beta particles.
(USAEC-1974)

Absorber, neutron
An object with which neutrons interact significantly or predominantly by reactions resulting in their disappearance as free particles without the production of other neutrons.
(ANSI N1.1-1976)

Absorber, neutron (material)
A material with which neutrons interact significantly by reactions resulting in their disappearance as free particles.
(ANSI N1.1-1976)

Absorption
Movement of material to blood regardless of mechanism. Generally applies to dissociation of particles and the uptake into blood of soluble substances and material dissociated from particles.
(ICRP 68)

Absorption
A process whereby gas or vapor molecules are transferred to the liquid phase.
(AM-1993)

Absorption
Transfer of energy from ionizing radiation to an absorber (e.g., tissue; see attenuation.)
(NCRP 105)

Absorption
A phenomenon in which some or all of the energy of a beam of radiation is transferred to the matter which it traverses.
(NCRP 51)

Absorption
The process by which the number of particles or photons entering a body of matter is reduced by interaction of the particles of radiation with matter; similarly, the reduction of the energy of a particle while traversing a body of matter. This term is sometimes erroneously used for capture.
(USAEC-1974)

Absorption
The process by which radiation imparts some or all of its energy to any material through which it passes.
(RHH)

Absorption (electromagentic)
A process characterized by the net transfer of energy from an electromagnetic field to matter (e.g., tissue) involving the eventual irreversible conversion of the electromagnetic energy into other energy forms, ultimately to heat. "Net" transfer implies that the portion of electromagnetic energy that enters but again leaves, still in electromagnetic form, is not considered to have been absorbed. See also "specific absorption rate."
(NCRP 67)

Absorption (of material)
Uptake by the blood of a material taken into the body.
(HPJ 60)

Absorption (radiation)
A process in which all or part of the energy of incident radiation is transferred to the matter through which it passes by various interactions with the basic particles (electrons, nuclei, etc.) of which the matter exists.
(HPJ 60)

Absorption band (of a scintillator)
Part of the absorption spectrum corresponding to energies, or wavelengths, for which the probability of absorption of photons is greatest.
(IEC 50-394-1993)

Absorption coefficient
Fractional decrease in the intensity of a beam of x or gamma radiation per unit thickness (linear absorption coefficient), per unit mass (mass absorption coefficient), or per atom (atomic absorption coefficient) of absorber, due to deposition of energy in the absorber. The total absorption coefficient is the sum of individual energy absorption processes (Compton effect, photoelectric effect, and pair production.
(BEIR III)

Absorption coefficient
Of a substance, for a parallel beam of specified radiation: the quantity µ_abs in the expression µ_abs Dx for the fraction absorbed in passing through a thin layer of thickness Dx of that substance. It is a function of the energy of the radiation. Accordingly as Dx is expressed in terms of length, mass per unit area, moles per unit area, or atoms per unit area, µ_abs is called the linear, mass, molar or atomic absorption coefficient. Note: It is the part of the attenuation coefficient resulting from energy absorption only.
(ANSI N1.1-1976)

Absorption coefficient (µ_abs)
Of a substance, for a parallel beam of specified radiation, the quantity µ in the expression µ_abs dx for the fraction of energy absorbed in passing through a thin layer of thickness dx of that substance.
(IEC 50-393-1993)

Absorption control
Control of a reactor by adjustment of the properties, position, or quantity of neutron-absorbing material, other than fuel, moderator and reflector material, in such a way as to change the reactivity.
(IEC 50-393-1993)

Absorption curve
A plot of an absorption radiation quantity (e.g., energy flux density) as a function of the distance traversed in an absorber.
(ANSI N1.1-1976)

Absorption Functions [A(t)]
Dissolution and absorption functions of radionuclides found in the lung after deposition (functions can be exponential, polynomial or constant relationships).
(NCRP 125)

Absorption ratio, differential
Ratio of the concentration of a radionuclide in a given organ or tissue to the concentration that would be obtained if the same administered quantity of this nuclide were uniformly distributed in the body.
(RHH)

Absorption, neutron
A neutron interaction in which the incident neutron disappears as a free particle even when one or more neutrons are subsequently emitted accompanied by other particles, e.g., in fission.
(ANSI N1.1-1976)

Abundance ratio
The ratio of the number of atoms of one isotope to the number of atoms of another isotope of the same element in a given sample.
(ANSI N1.1-1976)

Abundance, isotopic
The relative number of atoms of a particular isotope in a mixture of the isotopes of an element, expressed as a fraction of all the atoms of the element.
(ANSI N1.1-1976)

Abundance, natural
Of a specified isotope of an element, the isotopic abundance in the element as found in nature.
(ANSI N1.1-1976)

Academic training
Academic training is successfully completed job related college-level work.
(ANSI/ANS-15.4-1988)

Accelerated ageing
Acceleration process designed to simulate an advanced life condition in a short period of time.
(IEC 50-393-1993)

Acceleration chamber
The annular vacuum tube, commonly called a "donut", in which the electrons are accelerated in a circular electron accelerator.
(NBS 55)

Accelerator
A device that accelerates charged particles (e.g., protons or electrons) to high speed, often used for the production of certain radionuclides or for treatment of radiation therapy patients.
(NCRP 105)

Accelerator
A machine capable of accelerating charged particles in a vacuum and of discharging the resultant particulate or other radiation into another medium.
(ANSI N43.1-1978)

Accelerator
A device for imparting kinetic energy to charged particles. Usually, the energy added is greater than 0.1 MeV.
(NCRP 51)

Accelerator
A device for imparting kinetic energy to charged particles. Usually, the energy added is greater than 0.1 MeV.
(ANSI N1.1-1976)

Accelerator
A device for increasing the velocity and energy of charged elementary particles, for example, electrons or protons, through application of electrical and/or magnetic forces. Accelerators have made particles move at velocities approaching the speed of light. Types of accelerators include betatrons, Cockcroft-Walton accelerators, cyclotrons, linear accelerators, synchrocyclotrons, synchrotrons, and Van de Graff generators.
(USAEC-1974)

Accelerator
A device for imparting large kinetic energy to charged particles such as electrons, protons, deuterons and helium ions.
(NBS 63)

Accelerator (particle accelerator)
A device for imparting large kinetic energy to electrically charged particles such as electrons, proton, deuterons and helium ions. Common types of particle accelerators are direct voltage accelerators (including Van de Graff, Cockcroft-Walton, Dynamitron, resonant transformer and insulating core transformer), cyclotrons (including synchrocyclotrons and isochronous cyclotrons), betatrons, and linear accelerators.
(BEIR III)

Accelerator operating energy
See continuous spectrum of X-rays.
(NBS 55)

Acceptable degree of accuracy
The amount of error or uncertainty in model predictions tolerated for any given assessment situation. Usually, a degree of accuracy is required for potential outcomes involving high risks and/or economic costs.
(NCRP 76)

Acceptable degree of accuracy
The amount of error or uncertainty in model predictions tolerated for any given assessment situation. Usually, a greater degree of accuracy is required for potential outcomes involving high risks as well as economic costs.
(NUREG/CR 3332)

Acceptable Minimum Detectable Amount (AMDA)
The amount of radioactive material that measurement procedures should be able to measure, assuming they are free of interference from other radionuclides unless specifically addressed. The values listed should not be construed as being the minimum detectable amount, but rather an acceptable minimum detectable amount based on good practice and need.
(ANSI N13.30-1989D)

Acceptable source
Source of radiation listed in the appropriate reference source table in this standard.
(ANSI N42.17B-1989)

Acceptable source
Source of radiation listed in the appropriate reference source table in this standard.
(ANSI N42.17C-1989)

Acceptable source
Source of radiation listed in the appropriate reference source table in this standard.
(ANSI N42.17A-1989)

Acceptance criteria
Specified limits placed on characteristics of an item, process, or service defined in codes, standards, or other requirement documents.
(ANSI N46.2-1978)

Acceptance test
A contractual test to prove to the customer that the device meets certain conditions of its specification.
(IEC 50-394-1993)

Acceptance test
A test made upon completion of fabrication, installation, repair, or modification of a system, unit, component or part to verify to the user or owner that the item meets specified requirements.
(ERDA 76-21)

Acceptance testing
Evaluation or measurement of performance characteristics to verify that certain stated specifications and contractual requirements are met.
(ANSI N42.17C-1989)

Acceptance testing
Evaluation or measurement of performance characteristics to verify that certain stated specifications and contractual requirements are met.
(ANSI N42.17B-1989)

Acceptance testing
Evaluation or measurement of performance characteristics to verify that certain stated specifications and contractual requirements are met.
(ANSI N42.17A-1989)

Access control system
A system to reduce the likelihood of unauthorized or inadvertent access to high levels of radiation or airborne radioactive material, or to the hazard itself.
(NCRP 88)

Access-controlled site
A location where RAM is handled, stored, or utilized, and where security measures have been taken to prevent unauthorized entry.
(ANSI N14.24-1985)

Accessible environment
(1) The atmosphere,
(2) the land surface,
(3) surface water,
(4) oceans, and
(5) the portion of the lithosphere that is outside the controlled area.
(10CFR60.2)

Accessible location
A process location at which SSNM could be acquired without leaving evidence of the acquisition, i.e., without tools or other equipment to obviously violate the integrity of the containment.
(10CFR74.4)

Accessible location
Any region around a source of ionizing radiation that can be reached without rupture of structures or without use of specially designed tools not generally available.
(NCRP 38)

Accessible location
Any region around a source of ionizing radiation that can be reached without rupture of structures or without use of specially designed tools not generally available.
(NBS 63)

Accessory
An optional component part intended for attachment to or use with x-ray equipment, which when attached or used, affects quantity, quality, or direction of x-rays.
(ANSI N537-1976)

Accident
An unintentional or unexpected happening that is undesirable or unfortunate, especially one resulting in injury, damage, harm or loss.
(NCRP 111)

Accident
Any circumstance encountered during transportation that may result in the loss of control of radioactive material as evidenced by the release of radioactive material from any package, even without apparent damage, or by damage to any package, with or without apparent release, or by a movement of shielding material with respect to the radioactive source.
(ANSI N14.27-1986)

Accident
An unplanned event that has the potential for a release of radioactive materials or for an increase in radiation levels in excess of Technical Specifications.
(ANSI N303-1978)

Accident conditions
Substantial deviations from operational states which are expected to be infrequent and which could lead to release of unacceptable quantities of radioactive materials.
(IEC 50-393-1993)

Accident conditions (hypothetical accident conditions)
Those conditions that are specified in 10 CFR 71.73 for type B packages.
(ANSI N14.19-1986)

Accident conditions of transport
The hypothetical accident conditions defined in the applicable documents listed in 2.1.1 and 2.1.2 of this standard.
(ANSI N14.5-1987)

Accident dosimetry
Determination of high levels of deep absorbed dose resulting from uncontrolled conditions.
(ANSI/HPS N13.11-1993)

Accident dosimetry
Determination of high levels of deep absorbed dose resulting from uncontrolled conditions.
(ANSI N13.11-1983)

Accident monitor
Radiation monitor designed for measuring radiation in reactor plants during accident and post accident conditions.
(IEC 50-394-1993)

Accidental coincidence rate (RF)
An alternative name for fortuitous coincidence rate.
(ICRU 52)

Accountability
Quantitative accounting for nuclear material inventories and transfers through a system of measurements, records and reports.
(ANSI N1.1-1976)

Accountable Sealed Radioactive Source
A sealed radioactive source having a half-life equal to or greater than 30 days and an isotopic activity equal to or greater than the corresponding value provided in appendix E of this part.
(10CFR835.2-1998)

Accredited testing laboratory
A testing laboratory that has been accredited by an authoritative body with respect to its qualifications to perform verifications tests on the type of instruments covered by this standard.
(ANSI N42.17A-1989)

Accumulation mode
A mode in the atmospheric particle size distribution, formed primarily by coagulation of smaller particles.
(AM-1993)

Accuracy
The characteristics of an analysis or determination that ensures that both the bias and precision of the resulting quantity will remain within specified limits.
(HPS N13.30-1996)

Accuracy
An indication of the correctness of a measurement.
(AM-1993)

Accuracy
A measure of the extent of agreement between the measured value and the true value.
(NCRP 112)

Accuracy
The degree of agreement of a measured value with the true or expected value of the quantity of concern.
(HPJ 60)

Accuracy
The degree of agreement of the observed value with the conventionally true value of the quantity being measured.
(ANSI N42.17A-1989)

Accuracy
The degree of agreement of the observed value with the conventionally true value of the quantity being measured. Accuracy includes linearity, zerodrift, and hysterisis.
(ANSI N42.17C-1989)

Accuracy
The degree of agreement of the observed value with the conventionally true value of the quantity being measured.
(ANSI N42.17B-1989)

Accuracy
The closeness of agreement between an observed value and an accepted reference value.
(ANSI N15.54-1988)

Accuracy
A measure of the correspondence of the measured result to the "true" or given value.
(ANSI N13.15-1985)

Accuracy
As applied to environmental assessment models, accuracy implies agreement between the model prediction and actual events. An "accurate" model should be precise and unbiased.
(NCRP 76)

Accuracy
As applied to environmental assessment models, accuracy implies agreement between the model prediction and actual events. An 'accurate' model should be precise and unbiased. However, because of the stochastic nature of environmental processes, all deterministic models are inherently inaccurate.
(NUREG/CR 3332)

Accuracy
The degree of agreement with the true value of the quantity being measured.
(ANSI N317-1980)

Accuracy
The accuracy, usually described in terms of overall uncertainty, is the estimate of the overall possible deviation from the "true" value. As used in this standard, the overall uncertainty is a total of the estimated errors plus the random error of the measurement.
(ANSI N42.13-1978)

Accuracy
The degree of agreement of the observed value with the true value of the quantity being measured.
(ANSI N323-1978)

Accuracy
The degree of agreement of the observed value with the true value of the quantity being measured.
(ANSI N42.18-1974)

Accuracy
The degree of agreement of the observed value with the true value of the quantity being measured.
(ANSI N13.10-1974)

Acidic
Substances that are acids or that react with water to produce an acid. In water they produce positively charged hydrogen ions. They taste sour and many are corrosive to tissues (for example, hydrogen chloride, sulfur dioxide, fluorine, nitrogen dioxide, acetic acid, carbon dioxide, hydrogen sulfide, and hydrogen cyanide).
(ANSI Z88.2-1969)

Acinus
Minute sac-like beginnings of the alveolar gland, an air cell of the lung.
(NCRP 125)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR40.4)

Act
The Low-Level Radioactive Waste Policy Amendments Act of 1985 (Pub. L. 99-240).
(10CFR62.2)

Act
The Atomic Energy Act of 1954, including any amendments to the Act.
(10CFR55.4)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR150.2)

Act
The Atomic Energy Act of 1954 (68 Stat. 919) including any amendments thereto;
(10CFR170.3)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR30.4)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR70.4)

Act
The Atomic Energy Act of 1954, (68 Stat. 919) including any amendments thereto.
(10CFR19.3)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR72.3)

Act
The Atomic Energy Act of 1954 (42 U.S.C. 2011 et seq.), as amended.
(10CFR20.1003)

Act
The Atomic Energy Act of 1954 (Pub. L. 83-703, 68 Stat. 919) including any amendments thereto.
(10CFR51.4)

Act
The Atomic Energy Act of 1954 (68 Stat. 919) including any amendments thereto.
(10CFR50.2)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR74.4)

Act
The Clean Air Act (42 U.S.C. 7401 et seq.).
(40CFR61.02)

Act
The Atomic Energy Act of 1954, as amended.
(10CFR834.2-1996)

Act
The Atomic Energy Act of 1954 (68 Stat. 919), including any amendments thereto.
(10CFR20.3)

Actinide series
The series of elements beginning with actinium, Element No. 89, and continuing through lawrencium, Element No. 103, which together occupy one position in the Periodic Table. The series includes uranium and all man-made transuranic elements. This group is referred to as the "Actinides".
(USAEC-1974)

Actinides
The series of elements beginning with actinium, element number 89, and continuing through lawrencium, element number 103, which together occupy one position in the periodic table. The series includes uranium, element number 92, and all man-made transuranic elements.
(HPJ 60)

Actinium series
The naturally radioactive series starting with ²³⁵U.
(ENV RAD)

Actinium series (sequence)
The series of nuclides resulting from the radioactive decay of Uranium-235. Many man-made nuclides decay into this sequence. The end product of this sequence is lead-207.
(USAEC-1974)

Actinomycetes
A group of bacteria with a morphology resembling fungi.
(AM-1993)

Actinon
The isotope of radon in the actinium series (²¹⁹Rn).
(ENV RAD)

Action level
A quantity of radioactivity in excreta or in the body at which certain defined actions are taken to investigate exposure conditions or restrict further exposures.
(ANSI/HPS N13.22-1995)

Action level
The concentration of radon at which intervention is recommended to reduce the exposure in a dwelling or workplace.
(ICRP 65)

Activated carbon
A type of time-integrated sampling method which allows the detection of gamma rays from radon decay products adsorbed on carbon. Also a method for removing radon from drinking water.
(ENV RAD)

Activation
Process of inducing radioactivity by irradiation.
(IEC 50-393-1993)

Activation
The process of making a material radioactive by bombardment with neutrons, protons or other nuclear particles.
(HPJ 60)

Activation
The process of inducing radioactivity by irradiation.
(NCRP 51)

Activation
The process of inducing radioactivity by irradiation.
(ANSI N1.1-1976)

Activation
The process of making a material radioactive by bombardment with neutrons, protons or other nuclear particles.
(USAEC-1974)

Activation
The process of inducing radioactivity by irradiation.
(RHH)

Activation analysis
A method of chemical analysis based on the identification and measurement of characteristic radiations of nuclides formed by irradiation.
(ANSI N1.1-1976)

Activation analysis
A method for identifying and quantitatively measuring chemical elements in a sample. Atoms in the sample are first made radioactive by bombardment with neutrons, charged particles, or other nuclear radiation; they then give off characteristic nuclear radiation by which they can be identified and their relative abundance can be determined.
(ERDA 76-21)

Activation analysis
A method for identifying and measuring chemical elements in a sample of material. The sample is first made radioactive by bombardment with neutrons, charged particles or gamma rays. The newly formed radioactive atoms in the sample give off characteristic nuclear radiations (such as gamma rays) that tell what kind of atoms are present and how many. Activation analysis is usually more sensitive than chemical analysis. It is used in research, industry, archaeology and criminology.
(USAEC-1974)

Activation analysis
A method of chemical analysis, especially for small traces of material, based on the detection of characteristic radiations following a nuclear bombardment.
(RHH)

Activation detector
A radiation detector in which the induced radioactivity produced by exposure in a radiation field is used to determine particle flux density or particle fluence.
(ANSI N1.1-1976)

Activation foil
An activation detector in the form of a foil.
(ANSI N1.1-1976)

Activator
Impurity, or displaced atom, which increases the luminescence efficiency of a material to be used as a scintillating material.
(IEC 50-394-1993)

Active assay
Assay based on the observation of phenomena induced by an external source.
(ANSI N15.37-1981)

Active Inventory
The sum of additions to inventory, beginning inventory, ending inventory, and removals from inventory, after all common terms have been excluded. Common terms are any material values which appear in the active inventory calculation more than once and come from the same measurement.
(10CFR74.4)

Active maintenance
Any significant remedial activity needed during the period of institutional control to maintain a reasonable assurance that the performance objectives in Sections 61.41 and 61.42 are met. Such active maintenance includes ongoing activities such as the pumping and treatment of water from a disposal unit or one-time measures such as replacement of a disposal unit cover. Active maintenance does not include custodial activities such as repair of fencing, repair or replacement of monitoring equipment, revegetation, minor additions to soil cover, minor repair of disposal unit covers, and general disposal site upkeep such as mowing grass.
(10CFR61.2)

Active mine
An underground uranium mine which is being ventilated to allow workers to enter the mine for any purpose.
(40CFR61.21)

Active sampling
Aerosol measurement using an air-moving device to draw the air into the collector or detector; as opposed to passive sampling.
(AM-1993)

Actively performing the functions of an operator or senior operator
That an individual has a position on the shift crew that requires the individual to be licensed as defined in the facility's technical specifications, and that the individual carries out and is responsible for, the duties covered by that position.
(10CFR55.4)

Activity
The rate of disintegration (transformation) or decay of radioactive material. The units of activity are the curie (Ci) and the becquerel (Bq).
(10CFR20.1003)

Activity
The transition rate stated in becquerels, curies, or other acceptable units.
(HPS N13.30-1996)

Activity
A measurable property of a particle population, e.g., number, surface, mass, especially radioactivity.
(AM-1993)

Activity
A synonym for radioactivity. The strength of a radioactive source. In absolute units it relates to the number of radioactive atoms decaying per unit time; in relative terms it is expressed in terms of the number of recorded counts per unit time. The unit is the becquerel, symbol Bq. 1 Bq = 1 transformation per second.
(HPJ 60)

Activity
The mean number of decays per unit time of a radioactive nuclide. Units: becquerel (Bq), curie (Ci).
(BEIR V)

Activity
The activity, A, of an amount of radioactive nuclide in a particular energy state at a given time is the quotient of dN by dt, where dN is the expectation value of the number of spontaneous nuclear transformations from that energy state in the time interval dt.

The unit of activity is the reciprocal second, s^-1, with the special name becquerel (Bq).
(ICRP 60)

Activity
The mean number of decays per unit time of a radioactive nuclide. The special S.I. unit of activity is the becquerel. One becquerel is equal to one reciprocal second.
(NCRP 103)

Activity
The number of nuclear transitions occurring in a given quantity of radioactive material per unit time. The SI unit of activity is s^-1. The special name for the unit of activity is becquerel (Bq). The previously used special unit of activity, curie (Ci), is being replaced by the becquerel. 1 Bq = 2.7 x 10^-11 Ci. 1 Ci = 3.7 x 10¹⁰ Bq.
(NCRP 102)

Activity
Disintegration rate of a specified quantity of radioactive material stated in nuclear transformation rate, becquerels, curies, or other acceptable units.
(ANSI N13.30-1989D)

Activity
The number of nuclear transformations per unit time; units of activity are becquerel or curie.
(NCRP 105)

Activity
The mean number of decays per unit time of a radioactive nuclide. Units: becquerel (Bq), curie (Ci)..
(BEIR IV)

Activity
The expectation value of the number of spontaneous nuclear transitions per unit time of a nuclide in a specified energy state.
(ANSI N15.22-1987)

Activity
The amount of a radioactive nuclide, defined in terms of its transition rate,

where dN is the expectation value of the number of spontaneous nuclear transitions in the time interval dt. Alternatively, the activity of a radioactive nuclide is equal to the product of the decay constant, l, and the number of nuclei, N, in the specified energy state. Note, however, that
.
The traditional unit of activity is the curie (Ci). The SI unit of activity is the becquerel (Bq).
(NCRP 83)

Activity
The rate at which spontaneous transformations occur in an amount of a radionuclide. Unit becquerel, Symbol Bq. 1 Bq = 1 s^-1.
(ICRP 36)

Activity
The number of nuclear transformations occurring in a given quantity of material per unit time. The special unit of activity is the curie.
(NCRP 65)

Activity
The number of spontaneous nuclear transformations which occur in a quantity of a radioactive nuclide per unit time. The special unit of activity is the curie.
(NCRP 51)

Activity
The number of spontaneous nuclear disintegrations occurring in a given quantity of material during a suitably small interval of time divided by that interval of time. The SI derived unit of activity is the becquerel (Bq).
(ANSI N1.1-1976)

Activity
The number of nuclear transformations (a change of nuclide or an isomeric transition) occurring in a given quantity of material per unit time. See curie.
(NCRP 49)

Activity
Radioactivity. (See specific activity.)
(USAEC-1974)

Activity
The number of nuclear transformations occurring per unit time.
(ANSI N44.3-1973)

Activity
The time rate of disintegration of a radionuclide. The special unit of activity is the curie, symbol Ci, equal to 3.7 x 10¹⁰ disintegrations per second.
(ICRU 20)

Activity
The number of nuclear transformations occurring in a given quantity of material per unit time.
(RHH)

Activity
The number of atoms decaying per unit time.
(NBS 73)

Activity
See radioactivity.
(NBS 54)

Activity (A)
Quotient of dN by dt, where dN is the expectation value of the number of spontaneous nuclear transitions from a particular energy state at a given time, in the time interval dt.
(IEC 50-393-1993)

Activity (A)
The number of nuclear transistions occurring in a given quantity of radioactive material per unit time. The SI unit of activity is s^-1. The special name for the unit of activity is becquerel (Bq).
(NCRP 107)

Activity (A)
The activity of an amount of radioactive nuclide in a particular energy state at a given time is the quotient of dN by dt, where dN is the expectation value of the number of spontaneous nuclear transitions from that energy state in the time interval dt.

(ICRU 33)

Activity (A)
The activity (A) of a quantity of radioactive nuclide is the quotient of dN by dt where dN is the number of nuclear transformations which occur in this quantity in time dt.

The special unit of activity is the curie (Ci). 1 Ci = 3.7 x 10¹⁰ s^-1 (exactly).
(ICRU 19)

Activity (A)
The activity (A) of a quantity of radioactive nuclide is the quotient of DN by Dt where DN is the number of nuclear transformations which occur in this quantity in time Dt. The special unit of activity is the curie (c).

(NBS 92)

Activity (radioactive)
The number of radioactive disintegrations occurring per unit time in a given quantity of radionuclide. The unit of activity is the curie. See curie.
(NCRP 48)

Activity (radiological)
The activity, A, of a quantity of N atoms of a nuclide in a specified radioactive energy state is the quotient of dN by dt, A = -dN/dt, where dN is the number of spontaneous transitions from this energy state occurring in the time interval.
(ANSI N15.54-1988)

Activity coefficient
A measure of the deviation from ideal solution behavior.
(AM-1993)

Activity concentration
Amount of radioactive material in a unit of air.
(AM-1993)

Activity concentration
The quantity of radioactivity per unit volume or mass of a substance.
(ANSI N13.14-1983)

Activity concentration
The activity of a material divided by its volume.
(ANSI N1.1-1976)

Activity exposure
The "activity exposure" of an individual to ²²²Rn or ²²⁰Rn is the time-integral over the activity concentration of ²²²Rn or ²²⁰Rn, respectively, to which the individual is exposed during a definite period of time. Its unit is for example Bq-h-m^-3.
(ICRP 47)

Activity fractioning monitor (AFM)
An instrument that separates airborne radioactivity into two or more specific fractions and monitors each fraction.
(ANSI N42.17B-1989)

Activity function, A_h(t)
The activity in source organ h as a function of time.
(MIRD)

Activity intake
"Activity intake" by inhalation is the inhaled activity of a radionuclide during a definite period of time.
(ICRP 47)

Activity intake by inhalation (I_a)
"Activity intake" by inhalation is the inhaled activity of a radionuclide during a definite period of time.
(ICRP 32)

Activity Median Aerodynamic Diameter (AMAD)
The diameter of a unit density sphere with the same terminal settling velocity in air as that of the aerosol particle whose activity is the median for the entire aerosol [ICRP 30, Part 1 (ICRP 1979)].
(HPS N13.42-1997)

Activity Median Aerodynamic Diameter (AMAD)
The diameter in an aerodynamic particle size distribution for which the total activity above and below this size are equal. A log-normal distribution of particle sizes is usually assumed.
(NCRP 125)

Activity median aerodynamic diameter (AMAD)
The diameter of a unit density sphere with the same terminal settling velocity in air as that of the aerosol particle whose activity is the median for the entire aerosol.
(ANSI/HPS N13.22-1995)

Activity median aerodynamic diameter (AMAD)
The diameter of a unit density sphere with the same terminal settling velocity in air as the aerosol particle whose activity is the median for the entire aerosol.
(FGR 11)

Activity median diameter
Particle diameter with 50% of airborne activity above and 50% below this size.
(AM-1993)

Activity median diameter (AMD)
The median diameter of the size distribution of the aerosol with associated radioactivity.
(NCRP 97)

Activity response
The net number of counts registered by the detector system per unit of time divided by the activity of the radionuclide that is being measured during the same unit of time.
(ANSI N42.12-1980)

Activity, A
A measure of radioactivity that is proportional to the number of nuclear transitions per unit time. The activity A of a particular radionuclide at a particular time is A = dN/dt, where dN is the expectation value of the number of spontaneous nuclear transitions in the time interval dt.
(MIRD)

Activity, administered, A₀
The amount of activity administered to the subject. The typical routes are intravenous, oral, inhalation, and subcutaneous.
(MIRD)

Activity, cumulated,
The time integral of the activity [òA(t) dt], which is proportional to the sum of all the nuclear transitions during a given time interval.
(MIRD)

Activity, initial value of the j-th component, A_j
The initial value of the j-th component activity within a particular organ.
(MIRD)

Actual and likely use scenario
A scenario that is consistent with anticipated future uses of land or property considering the history of use; Federal and State use designations; local zoning and future land use plans; and proximity to residences or ecosystems, natural resources, or unique areas of historic or cultural significance.
(10CFR834.2-1996)

Actuated equipment
Equipment of prime movers and driven devices used to accomplish one or more safety tasks.
(IEC 50-394-1993)

Actuating mechanism
An assembly that is used to engage securely or disengage a special lifting device and a container.
(ANSI N14.6-1986)

Acute exposure
Exposure to uranium intake of a short duration.
(ANSI/HPS N13.22-1995)

Acute exposure
Radiation exposure of short duration.
(BEIR I)

Acute radiation exposure
Radiation exposure received during a short time period (eg., 24 hours).
(NCRP 111)

Acute release
A short-period release (period short compared with a year) of radioactive materials into the environment associated either with one event or with a short series of events.
(ICRP 29)

Adapter
A structural member inserted between elements of the hoisting system that are not otherwise compatible.
(ANSI N14.6-1986)

Addition
Any process by which alkaline earths transfer from blood to bone and remain longer than time t.
(ICRP 20)

Addition rate
The rate measured by the parameter At in radioisotope kinetics [called accretion rate]. Its units are (mass of calcium/time) and the time t to which it refers is the same as the period between injection of the radioisotope and the time of calculation. When divided by the total mass of calcium, c, its units are typically %/year, and then addition rate is the sum of the apposition rate and the augmentation rate.
(ICRP 20)

Additions to material in process
(1) Receipts that are opened, except for receipts opened only for sampling and subsequently maintained under tamper-safing;
(2) opened sealed sources; and
(3) material removed from process for nonconformance with chemical or physical specifications that is subsequently reprocessed, measured for contained SSNM, and reintroduced to process.
(10CFR74.4)

Additive action
A dose-effect dependence in which additional effect produced by radiation X adds to that due to radiation Y as though the effect due to Y was produced by a biologically equivalent dose of X.
(ICRU 30)F

Additive interaction model
This model is used to find the combined risk for risk factors which have no interaction with each other. For example the combined mortality risk of cigarette smoking and automobile accidents is the sum of the separate risks.
(BEIR IV)

Additive interaction model (AIM)
The assumption that the total risk from exposures to radiation and to another risk factor is equal to the sum of the excess risks from the two taken separately.
(BEIR V)

Additivity
A quantity is additive when, in a superposition of radiation fields, its value is equal to the sum of its values resulting from the individual fields.
(ICRU 43)

Address of use
The building or buildings that are identified on the license and where byproduct material may be received, used, or stored.
(10CFR35.2)

Adenosarcoma
A mixed tumor which consists of a substance like embryonic connective tissue together with glandular elements.
(BEIR V)

Adenosarcoma
A mixed tumor which consists of a substance like embryonic connective tissue together with glandular elements.
(BEIR IV)

Adjoint flux
Solution to the adjoin diffusion or transport equation. For a critical system, it is proportional to the importance function.
(ANSI N1.1-1976)

Adjust
To alter the response by means of a variable, built-in control such as a potentiometer.
(ANSI N42.17A-1989)

Adjust
To alter the response by means of a variable, built-in control such as a potentiometer.
(ANSI N42.17C-1989)

Adjust
To alter the response by means of a variable, built-in control such as a potentiometer.
(ANSI N42.17B-1989)

Administrative control
The formal procedures or rules established and monitored by plant management to ensure safety and controlled operation of the plant.
(ANSI N303-1978)

Administrator
The Administrator of the Environmental Protection Agency or his authorized representative.
(40CFR61.02)

Admittance
The complex ratio of phasor current to phasor voltage at given terminals of a circuit or at a given reference plane of a transmission line or waveguide. Admittance, Y, is the reciprocal of impedance
(Y = I/V = Z^-1) and is expressed in units of siemens (S) (formerly ohm^-1, W^-1; reciprocal ohm, mho).
(NCRP 67)

Adrenalin
The official British Pharmacopoeia name for epinephrine.
(HPJ 60)

Adsorbent
A solid having the ability to concentrate substances on its surface by means of physical condensation of molecules, chemical reaction, isotopic exchange, or another mechanism.
(ANSI N303-1978)

Adsorbent
A material, generally a solid, which retains a substance contacting it, through the short range molecular forces which bind the adsorbed material at the surface of the adsorbent.
(ANSI N13.1-1969)

Adsorber
A device for removing gases or vapors from air by means of preferential physical condensation and retention of molecules on a solid surface. Adsorbers used in nuclear applications are often impregnated with chemicals to increase their activity for organic radioactive iodine compounds.
(ERDA 76-21)

Adsorber cell
A modular replaceable adsorber element.
(ERDA 76-21)

Adsorption
Transfer of gas or vapor molecules from the surrounding gas to a solid surface.
(AM-1993)

Adsorption
See charcoal absorption method.
(NCRP 97)

Adsorption
The adhesion of one substance to the surface of another.
(RHH)

Adsorption isotherm
A function relating the volume of vapor adsorbed on a surface to the pressure of the vapor in the gas phase at a fixed temperature.
(AM-1993)

Adult
An individual 18 or more years of age.
(10CFR20.1003)

Advanced reactor
Any nuclear reactor concept other than light water reactors and high temperature gas cooled reactors.
(10CFR170.3)

Advantage factor
The ratio of the value of a specified radiation quantity at a position where an enhanced effect is produced to the value of the same radiation quantity at some reference position.
(ANSI N1.1-1976)

Adverse opinion
A statement that the nuclear material balance report is not presented fairly and all substantial reasons for the adverse opinion are stated.
(ANSI N15.11-1983)

Advisory committee
Group of persons with appropriate expertise, including the appointed teacher, set up by a governing body to counsel it on radiation protection.
(ICRP 36)

AEC filter
A HEPA filter with fiberglass medium. Obsolete term for HEPA filter.
(ERDA 76-21)

Aerodynamic (Equivalent) Diameter
Diameter of a unit-density sphere having the same gravitational-settling velocity as the particle in question.
(AM-1993)

Aerodynamic (Equivalent) Diameter (AD)
The diameter of a unit density sphere having the same settling velocity as the particle of interest.
(NCRP 125)

Aerodynamic diameter
The diameter of a unit density particle that has the same settling velocity as the particle described.
(NCRP 103)

Aerodynamic diameter
The diameter of a unit density particle that has the same settling velocity as the particle prescribed.
(NCRP 97)

Aerodynamic diameter
The diameter of a unit density particle that has the same settling velocity as the particle described.
(NCRP 78)

Aerodynamic diameter
The diameter of a unit density sphere having the same settling velocity as the particle in question of whatever shape and density.
(ANSI Z88.2-1980)

Aerodynamic diameter
The diameter of a unit-density sphere that would have the same terminal velocity due to gravity as the particle under consideration.
(TID-26608)

Aerodynamic diameter
Particles of the same diameter but differing densities will have different terminal settling velocities. Two particles of different densities are said to have equivalent aerodynamic diameters if their densities and diameters are such that the terminal settling velocities are equal, or that they are acted upon by air drag to an equal degree. Since comparisons with unit density materials are frequently made, aerodynamic diameter is the diameter of a unit density sphere with the same settling velocity as the particle in question.
(ANSI N13.1-1969)

Aerodynamic diameter
The diameter of a unit density sphere having the same settling velocity as the particle in question of whatever shape and density.
(ANSI Z88.2-1969)

Aerodynamic diameter (d_ae)
Diameter (µm) of unit density sphere that has same terminal settling velocity in air as the particle of interest.
(ICRP 68)

Aerodynamic Downwash
The downward movement of a plume associated with the turbulence created when air passes over a structure
(ANSI/HPS N13.45-1998)

Aerodynamic particle sizer
A particle spectrometer that uses an acceleration system to differentiate particles by aerodynamic diameter and a laser velocimeter to detect particles.
(AM-1993)

Aerosol
A suspension of solid or liquid particles in a gas.
(NCRP 125)

Aerosol
Suspension in a gaseous medium of solid or liquid particles with dimensions generally in the range between 0.01 µm and 10 µm.
(IEC 50-393-1993)

Aerosol
An assembly of liquid or solid particles suspended in a gaseous medium long enough to be observed and measured; generally, about 0.001-100 µm in size.
(AM-1993)

Aerosol
Suspension of solid or liquid particles in a gas.
(ANSI N42.17B-1989)

Aerosol
A suspension of solid or liquid particles in a gas.
(NCRP 97)

Aerosol
A system consisting of particles, solid or liquid, suspended in air.
(ANSI Z88.2-1980)

Aerosol
A dispersion of very small particles and/or droplets in air.
(ERDA 76-21)

Aerosol
A stable suspension of solid or liquid particles in a gas.
(TID-26608)

Aerosol
A dispersion of solid or liquid particles in air or other gases.
(ANSI N13.1-1969)

Aethalometer
An instrument used to measure the optical absorption of collected aerosol samples.
(AM-1993)

AF-absorbed Fraction (AF(T¬S)_R)
The fraction of energy emitted as a specified radiation R in a specified source tissue S which is absorbed in a specified target tissue T.
(ICRP 66)

Affected Indian tribe
(1) Within whose reservation boundaries a repository for high-level radioactive waste or spent fuel is proposed to be located; or
(2) Whose Federally defined possessory or usage rights to other lands outside of the reservation's boundaries arising out of Congressionally ratified treaties or other Federal law may be substantially and adversely affected by the locating of such a facility; Provided, That the Secretary of the Interior finds, upon the petition of the appropriate governmental officials of the Tribe, that such effects are both substantial and adverse to the Tribe.
(10CFR60.2)

Affected Indian tribe
Any Indian tribe
(1) Within whose reservation boundaries a monitored retrievable storage facility is proposed to be located;
(2) Whose federally defined possessory or usage rights to other lands outside of the reservation's boundaries arising out of congressionally ratified treaties may be substantially and adversely affected by the locating of such a facility: Provided, That the Secretary of the Interior finds, upon the petition of the appropriate governmental officials of the tribe, that such effects are both substantial and adverse to the tribe.
(10CFR72.3)

Affected unit of local government
Any unit of local government with jurisdiction over the site where an MRS is proposed to be located.
(10CFR72.3)

After-heat
Heat resulting from residual radioactivity in reactor fuel or components after a reactor has been shut down.
(IEC 50-393-1993)

After-heat
(1) For a shutdown reactor: the heat resulting from residual radioactivity and fission.
(2) For reactor fuel or reactor components after removal from the reactor: the heat resulting from residual radioactivity.
(ANSI N1.1-1976)

After-loading technique
A procedure in which inactive guides are initially placed in the patient and the radioactive sources introduced later under more favorable conditions of protection. The sources may be inserted manually or by means of a remote control device.
(NCRP 48)

After-power
For a shutdown reactor: the power corresponding to the after-heat.
(ANSI N1.1-1976)

Aftercooling
The cooling of a reactor after it has been shut down.
(USAEC-1974)

Afterheat
The heat produced by the continuing decay of radioactive atoms in a reactor after fission has stopped. Most of the afterheat is due to the radioactive decay of fission products.
(USAEC-1974)

Afterloading techniques
In afterloading techniques, unloaded applicators or guides are introduced into the patient cavities, according to a chosen plan and without exposure of the staff. The treatment sources are inserted later, after the position of the applicators has been radiographically checked using dummy sources. The dose distribution can also be computed so that the position of the guides can be corrected if necessary before the sources are inserted.
(ICRU 38)

Age
(1) One-sixth of the normalized second spatial moment of the neutron flux density (flux age) at energy E, or of the neutron slowing down density past energy E (slowing down age), for a point isotropic neutron source, i.e.,

where r is the radial distance from the source and f(E,r) is either the neutron flux density or the neutron slowing-down density as appropriate.
(2) When the fermi age theory of slowing down is applicable, the age is called the Fermi age and its value is given by the following expression (for a monoenergetic source at energy E₀),

where,
E is the neutron energy;
D_f is the diffusion coefficient for the neutron flux density;
x is the average logarithmic energy decrement;
S_s is the macroscopic elastic scattering cross section.
(ANSI N1.1-1976)

Age-related degradation
A change in a system's, structure's, or component's performance or physical or chemical properties resulting in whole or part from one or more aging mechanisms. Examples of this type of change include changes in dimension, ductility, fatigue resistance, fracture toughness, mechanical strength, polymerization, viscosity, and dielectric strength.
(10CFR54.3)

Age-related degradation unique to license renewal
Degradation
(1) That occurs during the term of the current operating license but whose effects are different in character or magnitude after the term of the current operating license (the period of extended operation); or
(2) Whose effects were not explicitly identified and evaluated by the licensee for the period of extended operation and the evaluation found acceptable by the NRC or
(3) That occurs only during the period of extended operation.
(10CFR54.3))

Ageing
Change with passage of time of physical, chemical or electrical properties of a component or module under design range operating conditions, which may result in degradation of significant performance characteristics.
(IEC 50-393-1993)

Agglomerate
A group of particles held together by van der Waals forces or surface tension.
(AM-1993)

Aggregate
A heterogeneous particle in which the various components are not easily broken apart.
(AM-1993)

Aggregate
Aggregate is the granular material which is mixed with water and cement to form concrete. Concrete for radiation shielding is classified as ordinary or high density according to the unit weight of aggregate used. The aggregates are defined in ANSI/ANS-6.4 are those usually used for radiation shielding; other aggregates are sometimes used when it can be objectively shown that they produce concrete of the required strength, durability, and shielding characteristics.
(ANSI/ANS-6.4-1985)

Aging mechanism
The physical or chemical processes that result in degradation. These mechanisms include but are not limited to fatigue, erosion, corrosion, erosion/corrosion, wear, thermal embrittlement, radiation embrittlement, microbiologically induced effects, creep, and shrinkage.
(10CFR54.3))

Agreement
The Agreement between the United States and the International Atomic Energy Agency for the Application of Safeguards in the United States. Unless otherwise specified, the term refers both to the principal text of the Agreement, consisting of 90 articles, and to the Protocol thereto.
(10CFR75.4)

Agreement for cooperation
Any agreement with another nation or group of nations concluded under section 123 of the Atomic Energy Act, as amended.
(10CFR110.2)

Agreement state
Any State with which the Commission has entered into an effective agreement under subsection 274b. of the Act. Non-agreement state means any other state.
(10CFR170.3)

Agreement state
Any State with which the Atomic Energy Commission or the Nuclear Regulatory Commission has entered into an effective agreement under subsection 274b. of the Atomic Energy Act of 1954, as amended.
(10CFR40.4)

Agreement state
Any State with which the Commission has entered into an effective agreement under subsection 274b. of the Act. Non-agreement state means any other state.
(10CFR150.2)

Agreement state
Any State with which the Commission has entered into an effective agreement under subsection 274b. of the Act.
(10CFR75.4))

Agreement state
Any State with which the Commission has entered into an effective agreement under subsection 274b. of the Act. Non-agreement state means any other state.
(10CFR70.4)

Agreement state
Any State with which the Commission or the Atomic Energy Commission has entered into an effective agreement under subsection 274b of the Atomic Energy Act of 1954, as amended.
(10CFR35.2)

Agreement state
(1) Has entered into an agreement with the Nuclear Regulatory Commission under section 274 of the Atomic Energy Act of 1954 (42 U.S.C. 2021); and
(2) Has authority to regulate the disposal of low-level radioactive waste under such agreement.
(10CFR62.2)

Agreement State
Any state with which the U.S. Nuclear Regulatory Commission has entered into an agreement to allow that state to assume regulatory authority over certain radioactive materials.
(ANSI/HPS N13.45-1998)

Agreement state
Any state with which the Atomic Energy Commission or the Nuclear Regulatory Commission has entered into an effective agreement under subsection 274b. of the Act. Non-agreement State means any other state.
(10CFR30.4)

Agreement state
A State with which the Atomic Energy Commission or the Nuclear Regulatory Commission has entered into an effective agreement under subsection 274(b) of the Atomic Energy Act of 1954, as amended.
(40CFR61.101)

Agreement state
A state which has entered into an agreement with the U.S. Nuclear regulatory Commission to conduct licensing and inspection programs.
(NCRP 101)

Agreement states
Any state with which the U.S. Nuclear Regulatory Commission or the U.S. Atomic Energy Commission has entered into an effective agreement under subsection 274b of the Atomic Energy Act of 1954, as amended (73 Stat. 689) concerning licensing of by-product materials.
(NCRP 93)

AI-alveolar-Interstitial Region
Consists of the respiratory bronchioles, alveolar ducts and sacs with their alveoli, and the interstitial connective tissue; airway generations 16 and beyond.
(ICRP 66)

Air changes per hour (ACH)
The number of air changes per hour in a building.
(ENV RAD)

Air cleaning equipment
Air-cleaning equipment is a device or combination of devices for separating contaminants from the air handled by an exhaust system.
(ANSI Z9.2-1971)

Air cleanup system
A system provided to decontaminate the air in, or exhausted from, a contained space following a system upset or prior to personnel access to the contained space.
(ERDA 76-21)

Air dose
The dose is measured by a properly calibrated appropriate instrument in air at or near the body surface in the region of highest dose rate.
(10CFR20.4)

Air dose
Absorbed dose in air is the quotient of the mean energy imparted by ionizing radiation to a volume element of air divided by the mass of air in that volume element. Air dose is expressed in rads. The air doses considered in these reports are essentially constant over distances large compared to the ranges of the charged particles producing the doses. Thus, the air dose is also a measure of the indirectly ionizing radiation field (primarily photon radiation) generating these charged particles.
(NCRP 94)

Air kerma
Kerma value for air.
(IEC 50-393-1993)

Air kerma
The sum of the initial kinetic energies of all the charged ionizing particles liberated by uncharged ionizing particles per unit mass of a specified material. Kerma is measured in the same unit as absorbed dose. The SI unit of kerma is joule per kg and its special name is gray (Gy). Kerma can be quoted for any specific material at a point in free space or in any absorbing medium.
(NCRP 118)

Air kerma
See kerma.
(NCRP 107)

Air kerma
See kerma.
(NCRP 105)

Air kerma
See kerma.
(NCRP 102)

Air kerma rate constant (G_d)
The air kerma rate constant of a radioactive nuclide emitting photons is the quotient of l²K_d by A, where K_d is the air kerma-rate due to photons of energy greater than d, at a distance l from a point source of this nuclide having an activity A.

(ICRU 33)

Air kerma, K_a
The total energy per unit mass transferred from an x-ray or gamma-ray beam to air. More precisely, it is the quotient of dE_tr, by dm, where dE_tr, is the sum of the initial kinetic energies of all electrons liberated by photons in a volume element of air of mass dm:

(ANSI/HPS N13.11-1993)

Air line respirator
See respirator.
(ANSI Z88.2-1980)

Air line respirator
See respirator.
(ANSI Z88.2-1969)

Air monitoring
Sampling and analysis of air to determine the quantity of pollutants present.
(AM-1993)

Air pollution
Condition of materials present in the air at levels detrimental to the health and/or welfare of human beings.
(AM-1993)

Air purifying respirator
See respirator.
(ANSI Z88.2-1980)

Air purifying respirator
See respirator.
(ANSI Z88.2-1969)

Air quality standards
Level beyond which air pollutants can cause damage to humans, animals, plants, or materials.
(AM-1993)

Air regulating valve
An adjustable valve used to regulate, but which cannot completely shut off, the airflow to the facepiece, helmet, hood, or suit of an air-line respirator.
(ANSI Z88.2-1980)

Air regulating valve
An adjustable valve used to regulate airflow to the facepiece, helmet or hood of an air-line respirator.
(ANSI Z88.2-1969)

Air sampler
Device designed to trap on a filter the radioactive contamination contained in a known volume of air passing through the filter in a preset time interval.
(IEC 50-394-1993)

Air sampling
The collection and analysis of samples of air to measure its radioactivity or to detect the presence of radioactive substances.
(USAEC-1974)

Air supply device
A hand- or motor-operated blower for the hose mask, or a compressor or other source of respirable air for the air-line respirator.
(ANSI Z88.2-1980)

Air supply device
A hand- or motor-operated blower for the hose mask, or a compressor or other source of respirable air for air-line and abrasive-blasting respirators.
(ANSI Z88.2-1969)

Air-equivalent
Descriptive of material for walls and electrodes of ionization chambers selected to produce ionization for proton or electron measurement essentially equivalent to that in a free air ionization chamber. This is possible only over limited ranges of photon energies.
(NBS 51)

Air-equivalent ionization chamber
Ionization chamber in which the materials of the walls, the electrodes, and the filling gas, have the same effective atomic number as air, allowing some relaxation of the BraggGray cavity conditions so that the cavity size may be large compared with the range of the secondary particles.
(IEC 50-394-1993)

Air-equivalent scintillation detector
Radiation scintillation detector made from a material whose effective atomic number is equal, or nearly equal to that of air.
(IEC 50-394-1993)

Air-generated DOP
See DOP Aerosol.
(ERDA 76-21)

Airborne dust or particulates monitor
Radiation monitor for the continuous measurement of the radioactive emission rate of airborne dust or particulates.
(IEC 50-394-1993)

Airborne emission
Material released to the atmosphere in the form of dusts, fumes, particulates, mists, vapors, or gases.
(10CFR834.2-1996)

Airborne radioactive material
Radioactive material dispersed in the air in the form of dusts, fumes, particulates, mists, vapors, or gases.
(10CFR20.1003)

Airborne radioactive material
Any radioactive material dispersed in the air in the form of dusts, fumes, mists, vapors or gases.
(10CFR20.3)

Airborne radioactive material or airborne radioactivity
Radioactive material dispersed in the air in the form of dusts, fumes, particulates, mists, vapors, or gases.
(10CFR835.2-1998)

Airborne radioactive material or airborne radioactivity
Radioactive material in any chemical or physical form that is dissolved, mixed, suspended, or otherwise entrained in air.
(10CFR835.2-1993)

Airborne radioactivity
Radioactivity in any chemical or physical form that is dissolved, mixed, suspended, or otherwise entrained in air.
(10CFR835.2-1993)

Airborne radioactivity
Radioactivity in any chemical or physical form that is dissolved, mixed, suspended, or otherwise entrained in air.
(ANSI N42.17B-1989)

Airborne radioactivity area
Any area, accessible to individuals, where:
(1) The concentration of airborne radioactivity, above natural background, exceeds or is likely to exceed the derived air concentration (DAC) values listed in appendix A or appendix C of this part; or
(2) An individual present in the area without respiratory protection could receive an intake exceeding 12 DAC-hours in a week.
(10CFR835.2-1998)

Airborne radioactivity area
A room, enclosure, or area in which airborne radioactive materials, composed wholly or partially of licensed material exist in concentrations -
(1) In excess of the derived air concentrations (DACs) specified in appendix B, to Secs. 20.1001-20.2401 or
(2) To such a degree that an individual present in the area without respiratory equipment could exceed, during the hours an individual is present in a week, an intake of 0.6 percent of the annual limit on intake (ALI) or 12 DAC-hours.
(10CFR20.1003)

Airborne radioactivity area
Any room, enclosure or operating area in which airborne radioactive materials composed wholly or partly of licensed material, exist in concentrations in excess of the amount specified in Appendix B, Table I, Column 1 of this part, or any room, enclosure or operating area in which airborne radioactive materials composed wholly or partly of licensed material, exist in concentrations which, averaged over the number of hours in any week during which individuals are in the area, exceed 25 percent of the amount specified in Appendix B, Table I, Column 1 of this part.
(10CFR20.203)

Airborne radioactivity area
Any area in which airborne radioactive materials exist in concentrations in excess of the recommended concentration guides (MPC) or any area in which airborne radioactive materials exist in concentrations which, when averaged over the number of hours in any week during which individuals are in the area, exceed 25 percent of the exposure guides specified in ANSI N43.1-1978.
(ANSI N43.1-1978)

Airy disk
A disk-like image of a small point produced by an optical system with diffraction-limited resolution.
(AM-1993)

Aitken nuclei
Atmospheric particles in the approximate size range of 0.01-0.1 µm.
(AM-1993)

ALAP
As low as practicable. Obsolete term for ALARA.
(ERDA 76-21)

ALARA
As Low As Reasonably Achievable, economic and social factors being taken into consideration.
(ANSI/HPS N13.22-1995)

ALARA
An acronym for as low as reasonably achievable, a radiation protection philosophy or practice that specifies reduction of radiation exposures to as low as reasonably achievable, with economic and social factors being taken into account.
(NCRP 121)

ALARA
An acronym referring to one element of the system of dose limitation, i.e., the recommendation to keep all radiation exposures as low as reasonably achievable, economic and social factors being taken into account.
(NCRP 118)

ALARA
A principle of radiation protection that encourages the limitation of radiation exposures to values which are "as low as reasonably achievable", economic and social factors being taken into account.
(NCRP 111)

ALARA
A principle of radiation protection that encourages management to limit radiation exposure of exposed persons. As Low As Reasonably Achievable, economic, and soical factors being taken into account.
(NCRP 107)

ALARA
As Low As Reasonably Achievable, economic and social factors taken into account.
(NCRP 101)

ALARA
As Low As Reasonably Achievable, economic and social factors taken into account.
(FGR 11)

ALARA
A system of dose limitation based on keeping exposures "as low as reasonably achievable," economic and social factors being taken into account.
(NCRP 93)

ALARA
As low as reasonably achievable. The design philosophy used to determine the need for, or extent of, air cleaning and off-gas facilities, based on their cost effectiveness in reducing adverse impacts with respect to offsite and onsite dose criteria. Formerly known as ALAP.
(ERDA 76-21)

ALARA (acronym for "As Low As Reasonably Achievable")
Making every reasonable effort to maintain exposures as far below the dose limits in this part as is practical consistent with the purpose for which licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.
(10CFR20.1003)

ALARA (acronym for "As Low As is Reasonably Achievable")
Making every reasonable effort to maintain exposures to radiation as far below the dose limits specified in 10 CFR Part 20 as is practical consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.
(10CFR34.3)

ALARA (As Low As is Reasonably Achievable)
The approach to radiation protection to manage and control exposures (both individual and collective) to the work force and to the general public to as low as is reasonable, taking into account social, technical, economic, practical, and public policy considerations. As used in this part, ALARA is not a dose limit but a process which has the objective of attaining doses as far below the applicable limits of this part as is reasonably achievable.
(10CFR835.2-1993)

ALARA (As Low As Reasonably Achievable)
Making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practical:
(1) Consistent with the purpose for which the licensed activity is undertaken,
(2) Taking into account the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and
(3) In relation to utilization of nuclear energy in the public interest.
(10CFR35.2)

ALARA (As Low As Reasonably Achievable)
The radiation protection principle to maintain doses to people as low as reasonably achievable, economic and social factors being taken into account.
(NCRP 114)

ALARA (As Low As Reasonably Achievable)
The principle of limiting the radiation dose of exposed persons to levels as low as is reasonably achievable, economic and social factors being taken into account.
(NCRP 105)

ALARA process
A logical procedure for evaluating alternative operations, processes, and other measures, designed to reduce exposures to radiation and emissions of radioactive material into the environment, taking into account societal, environmental, technological, economic, practical, and public policy considerations to make a judgment concerning the optimum level of public health protection.
(10CFR834.2-1996)

ALARA program
The set of design specifications, operating procedures, techniques, monitoring and surveillance programs, records, and instructions used to implement the ALARA process.
(10CFR834.2-1996)

Alarm
1 - Audible signal or visual signal given on the alarmfascia and possibly other displays, to provide information to site personnel about equipment or events.
2 - A device that provides audio or visual signals to call attention to events.
(IEC 50-393-1993)

Alarm
An audible or visual signal activated when the instrument reading or response exceeds a preset value of falls outside a preset range.
(ANSI N42.17B-1989)

Alarm
An audible or visual signal activated when the instrument reading or response exceeds a preset value of falls outside a preset range.
(ANSI N42.17C-1989)

Alarm
An audible and/or visual signal activated when the instrument reading or response exceeds a preset value of falls outside a preset range.
(ANSI N42.17A-1989)

Alarm system
A system that provides instructions, alerts individuals to a potential or actual change in safe working environment, and that may initiate mitigating actions.
(NCRP 88)

Alarm Threshold
A predetermined quantity of SSNM calculated from the specified probability of detection for a given loss and the standard deviation associated with a material control test. An alarm threshold serves to trigger a response action.
(10CFR74.4)

Albedo
The probability under specified conditions that a particle entering into a region through a surface will return through that surface.
(ANSI/ANS-6.4-1985)

Albedo
The ratio of the absorbed dose index or particle fluence reflected out of a non-source medium to the absorbed dose index or particle fluence into it. See also reflection coefficient.
(NCRP 51)

Albedo dosimeter
A personnel dosimeter (especially a neutron detection type which enables one to determine the absorbed dose from the component of radiation backscattered (or moderated) by the wearer of the dosimeter.
(NCRP 101)

Albedo neutron dosemeter
Neutron dosemeter which is capable of measuring the fraction reflected by a human body of the energy fluence incident on that body.
(IEC 50-394-1993)

Albedo, neutron
The probability under specified conditions that a neutron entering a region through a surface will return through that surface.
(ANSI N1.1-1976)

Alert
Events may occur, are in progress, or have occurred that could lead to a release of radioactive material but that the release is not expected to require a response by offsite response organizations to protect persons offsite.
(10CFR40.4)

Alert
Events may occur, are in progress, or have occurred that could lead to a release of radioactive material[s] but that the release is not expected to require a response by an offsite response organization to protect persons offsite.
(10CFR70.4)

Alevin
Fish fry on which the yolk is still apparent. Particularly applied to salmonids.
(NCRP 109)

Algae
A microscopic plant.
(AM-1993)

Algorithm
A formula or set of steps for solving a problem.
(NCRP 102)

Algorithm
An explicit step by step procedure for producing a solution to a given problem. In a computer model, an algorithm may be any statement or set of statements expressing the functional operation of a model which enables a set of input data to produce a given output.
(NCRP 76)

ALI-Annual Limit on Intake
The annual limit on intake of any radionuclide is that intake that will result in a committed effective dose equal to the annual limit on effective dose. The ALI for any radionuclide is obtained by dividing the annual effective dose limit by the committed effective dose resulting from the intake of 1 Bq of that radionuclide.
(ICRP 66)

Aliasing
Observation of a low-frequency signal because of inadequate sampling or measurement rate; see Nyquist frequency.
(AM-1993)

Aligned field
See expanded and aligned field.
(ICRU 43)

Alignment
Steps taken to adjust the volume data from two or more, calibration runs for differences in heel volume so that all runs have a common starting point.
(ANSI N15.19-1989)

Alignment point
A point of reference used to align a set of calibration runs.
(ANSI N15.19-1989)

Aliquant
A representative portion of a whole that divides the whole leaving a remainder; for example 5 is an aliquant of 16 (ASTM 1995a).
(HPS N13.30-1996)

Aliquant
A divisor that does not divide a sample into a number of equal parts without leaving a remainder; a sample resulting from such a divisor.
(HPJ 60)

Aliquot
A representative portion of a whole that divides the whole exactly without leaving a remainder; for example 5 is an aliquot of 15 ASTM 1995a).
(HPS N13.30-1996)

Aliquot
A divisor that divides a sample into a number of equal parts, leaving a remainder; a sample resulting from such a divisor.
(HPJ 60)

Alkaline
Substances that are alkalies or that react with water to produce an alkali. When in water solution, they result in the production of negatively charged hydroxyl ions (OH-). They taste bitter and many are corrosive to tissues (for example, ammonia, amines, phosphine, arsine, and stibine).
(ANSI Z88.2-1969)

Alkaline earth
An oxide of any of several bivalent strongly basic metals comprising calcium, strontium, barium, magnesium, radium, and beryllium.
(HPJ 60)

All or nothing radiation relay
Relay activated in response to radiation produced by a radionuclide, thus producing a change-over from a given state to the complementary state in an electrical controlling or signaling circuit, after the appearance of certain variations in the fluence rate.
(IEC 50-394-1993)

Allelic
Relating to one or more of a series of genes that may occupy the same position or locus on a specific chromosome.
(HPJ 60)

Allobar
A form of an element differing in isotopic composition having a different average atomic weight from the usually occurring form.
(USAEC-1974)

Allobars
Forms of an element having different atomic weights due to different isotopic compositions.
(ANSI N1.1-1976)

Allowable test leakage rate
The more restrictive of L_A or L_N, taking into consideration the differences between test and transport conditions.
(ANSI N14.5-1987)

Allowable test release rate
The more restrictive of R_N and R_A, taking into consideration the differences between test and transport conditions.
(ANSI N14.5-1987)

Alpha decay
Radioactive decay in which an alpha particle is emitted. This lowers the atomic number of the nucleus by two and its mass number by four.
(ANSI N1.1-1976)

Alpha emission density
The number of alphas per unit space emerging from a source element. For radon progeny in the lung, the emission source density is the number of alphas per unit surface area in each tube.
(ENV RAD)

Alpha errors
Type I errors of statistical hypothesis testing. The probability that a null or test hypothesis will be incorrectly rejected in an instance of hypothesis testing. The probability that a difference will be found to exist when, in fact, there is no true difference.
(NCRP 80)

Alpha particle
Stable particle having the same bound configuration of 2 protons and 2 neutrons as a helium 4 nucleus and emitted during a nuclear disintegration.
(IEC 50-393-1993)

Alpha particle
A charged particle emitted from the nucleus of an atom having a mass and charge equal in magnitude of a helium nucleus; i.e., two protons and two neutrons.
(HPJ 60)

Alpha particle
The nucleus of a helium atom which is ejected from some radionuclides during radioactive decay.
(NCRP 111)

Alpha particle
Two neutrons and two protons bound as a single particle that is emitted from the nucleus of certain radioactive isotopes in the process of decay or disintegration.
(BEIR V)

Alpha particle
The nucleus of a helium atom which is ejected from some radionuclides during radioactive decay.
(NCRP 103)

Alpha particle
Two neutrons and two protons bound as a single particle that is emitted from the nucleus of certain radioactive isotopes in the process of decay or disintegration.
(BEIR IV)

Alpha particle
The nucleus of a helium atom which is ejected from some radionuclides during radioactive decay.
(NCRP 78)

Alpha particle
A charged particle emitted from the nucleus of an atom having a mass and charge equal in magnitude of a helium nucleus; i.e., two protons and two neutrons.
(BEIR III)

Alpha particle
A positively charged particle emitted by certain radioactive materials. It is made up of two neutrons and two protons bound together, and hence is identical with the nucleus of a helium atom. It is the least penetrating of the three common types of radiation (alpha, beta, gamma) emitted by radioactive materials, and is stopped by a sheet of paper.
(NCRP 65)

Alpha particle
A helium-4 nucleus emitted during a nuclear transformation; by extension, any helium-4 nucleus.
(ANSI N1.1-1976)

Alpha particle
A charged particle emitted from the nucleus of an atom having a mass and charge equal in magnitude of a helium nucleus; i.e., two protons and two neutrons.
(BEIR I)

Alpha particle
A charged particle emitted from the nucleus of an atom having a mass and charge equal in magnitude of a helium nucleus; i.e., two protons and two neutrons.
(RHH)

Alpha particle or ray (a)
The nucleus of a helium atom ejected from a radioactive nucleus when it disintegrates.
(NCRP 48)

Alpha particles
Nuclei of helium atoms consisting of two protons and two neutrons in close association. They have a net positive charge of +2 and can therefore be accelerated in large electrical devices similar to those used for protons, and they are also emitted during the decay of some radioactive isotopes.
(NCRP 98)

Alpha radiation
Ionizing radiation composed of alpha particles.
(IEC 50-393-1993)

Alpha radiation (or particles)
Charged particles consisting of two protons and two neutrons in close, stable association (Helium nucleus), emitted from a radioactive nucleus during decay.
(NCRP 105)

Alpha ratio
Of fissionable nuclei: the ratio of the radiative capture cross section to the fission cross section.
(ANSI N1.1-1976)

Alpha ray
A stream of alpha particles. Loosely, a synonym for alpha particle.
(USAEC-1974)

Alpha rays, or particles
Particles emitted during radioactive disintegration, having a mass number 4 and atomic number 2. They are thus identical with nuclei of ordinary helium atoms.
(NBS 54)

Alpha track detector
A type of detector that records alpha particles from decay products by radiation damage on film. After exposure, these tracks are revealed by etching with NaOH or KOH solution and counted manually or automatically under a microscope.
(ENV RAD)

Alpha-cup
Alpha particle sensitive detector in a gas permeable cup which is buried in the ground to detect the activity from radon and its daughters.
(IEC 50-394-1993)

Alternate ac source
An alternating current (AC) power source that is available to and located at or nearby a nuclear power plant and meets the following requirements:
(1) is connectable to but not normally connected to the offsite or onsite emergency ac power systems;
(2) Has minimum potential for common mode failure with offsite power or the onsite emergency ac power sources;
(3) is available in a timely manner after the onset of station blackout; and
(4) Has sufficient capacity and reliability for operation of all systems required for coping with station blackout and for the time required to bring and maintain the plant in safe shutdown (non-design basis accident).
(10CFR50.2)

Alternative method
Any method of sampling and analyzing for an air pollutant which is not a reference method but which has been demonstrated to the Administrator's satisfaction to produce results adequate for the Administrator's determination of compliance.
(40CFR61.02)

Aluminum equivalent
The thickness of type 1100 aluminum alloy affording the same attenuation, under specified conditions, as the material in question.
(NCRP 102)

Aluminum equivalent
The thickness of aluminum affording the same attenuation, under specified conditions, as the material in question.
(RHH)

Alveolar
Part of the respiratory system in which gas exchange occurs; alveoli are small sacs at the end of the bronchioles.
(AM-1993)

Alveolar Dead Space
Portion of the tidal volume that enters the alveoli but does not take part in gas exchange.
(NCRP 125)

Alveolar epithelial cells (Type I)
Flattened epithelial cells lining alveolar surface through which gaseous exchange normally occurs.
(ICRP 66)

Alveolar epithelial cells (Type II)
Cuboidal epithelial cells that are precursors to alveolar Type I cells.
(ICRP 66)

Alveolar macrophages
Unattached phagocytic cells found in nearly all alveoli.
(ICRP 66)

Alveolar-interstitial region (AI)
Consists of the respiratory bronchioles, alveolar ducts and sacs with their alveoli, and the interstitial connective tissue; airway generations 16 and beyond.
(ICRP 68)

Alveoli
Terminal air sacs of the lung that provide for oygen-carbon dioxide gas exchange and consist of Type I cells, Type II cells, and macrophages.
(NCRP 125)

Alveoli
The terminal air sacs of the lungs.
(RHH)

AMAD
Activity Median Aerodynamic Diameter. Fifty percent of the activity in the aerosol is associated with particles of aerodynamic diameter (d_ae) greater than the AMAD. Used when deposition depends upon inertial impaction and sedimentation, typically when the AMAD is > 0.5 µm.
(ICRP 68)

AMAD
Activity Median Aerodynamic Diameter. Fifty percent of the activity (aerodynamically classified) of aerodynamic diameter (d_ae) greater than the AMAD. A log normal distribution of particle sizes is usually assumed.
(ICRP 66)

Ambient aerosol
The aerosol existing in the environment of interest.
(NCRP 97)

Ambient air
Surrounding air.
(AM-1993)

Ambient air
The general air in the area of interest (e.g., the general room atmosphere) distinct from a specific stream of volume of air that may have different properties.
Editorial Note: This definition was removed from 10CFR835.2 in the 1998 revision.
(10CFR835.2-1993)

Ambient air
The general air in the area of interest (e.g., the general room atmosphere) distinct from a specific stream of volume of air that may have different properties.
(ANSI N42.17B-1989)

Ambient background
Those counts that can be observed, and thereby allowed for, by measuring a source that is identical to the unknown source in all respects except for the absence of radioactivity. These counts are attributable to environmental radioactivity in the detector itself, the detector shielding material, and the sample container; cosmic rays; electronic noise pulses; etc.
(ANSI N42.12-1980)

Ambient dose equivalent
Symbolized H*(d), this quantity repre-sents the dose equivalent at depth d in the ICRU tissue equivalent, 30-cm diameter sphere and along the radius opposed to the direc-tion of the radiation field when the field has been expanded and aligned. An expanded radiation field is one in which the direction-ality and energy fluence distribution at a point of interest are maintained constant and expanded throughout the volume of interest. An aligned radiation field is the same as an expanded field except that the field is made monodirectional throughout the volume.
(NCRP 112)

Ambient dose equivalent
The ambient dose equivalent, H*(d), at a point in a radiation field, is the dose equivalent that would be produced by the corresponding aligned and expanded field, in the ICRU sphere at a depth, d, on the radius opposing the direction of the aligned field.
(ICRP 60)

Ambient dose equivalent: H*(d)
The dose equivalent that would be produced by the corresponding aligned and expanded field, in the ICRU sphere at a depth, d, on the radius opposing the direction of the aligned field.
(ICRU 43)

Amblyopia
A dimness of vision; the partial loss of sight.
(ICRP 49)

American Bureau of Shipping (ABS)
The ABS is a non-profit, nongovernmental, international ship-classification society that establishes standards for the design, construction, and periodic survey of merchant vessels and other marine structures. The regulations promulgated by the USCG appoint the ABS as the prime assigning and issuing authority for load line certificates.
(ANSI N14.24-1985)

Americium
Symbol Am. Element number 95. All isotopes are radioactive. The isotope of most interest is ²⁴¹Am, produced by the decay of ²⁴¹Pu present in fallout.
(HPJ 60)

Amines
Various basic compounds derived from ammonia by replacement of hydrogen by one or more univalent hydrocarbon radicals.
(HPJ 60)

Amino acids
An amphoteric organic acid containing the amino group NH₂, especially any of the alpha-amino acids that are the chief components of proteins and are synthesized by living cells or are obtained as essential components of the diet.
(HPJ 60)

Aminoaciduria
A condition in which one or more amino acids are excreted in excessive amounts in the urine.
(HPJ 60)

Ampere
See unit of electrical current.
(NCRP 82)

Ampere
The unit of current that, when flowing through each of two long parallel wires separated by one meter in free space, results in a force between the two wires (due to their magnetic fields) of 2 x 10^-7 newtons for each meter of length.
(RHH)

Amplification
As related to radiation detection instruments, the process (gas, electronic, or both) by which ionization effects are magnified to a degree suitable for their measurement.
(HPJ 60)

Amplification
As related to radiation detection instruments, the process (gas, electronic, or both) by which ionization effects are magnified to a degree suitable for their measurement.
(RHH)

Amplifier
A device intended to increase the value of an electrical input quantity by means of energy drawn from an additional electrical source.
(IEC 50-394-1993)

Amplifier, linear
A pulse amplifier in which the output pulse height is proportional to an input pulse height for a given pulse shape up to a point at which the amplifier overloads.
(RHH)

Amplifier, pulse
An amplifier, designed specifically to amplify the intermittent signals of a nuclear detector, incorporating appropriate pulse-shaping characteristics.
(RHH)

Amplifying semiconductor detector
Semiconductor detector in which charge multiplication is produced by a secondary process such as an avalanche.
(IEC 50-394-1993)

Amplitude-to-time converter
Assembly or sub-assembly intended to provide either, an output signal the duration of which is proportional to the amplitude of the input signal, or two output signals one delayed with respect to the other by a time interval proportional to the amplitude of the input signal.
(IEC 50-394-1993)

AMTD
Activity Median Thermodynamic Diameter. Fifty percent of the activity in the aerosol is associated with particles of thermodynamic diameter (dth) greater than the AMTD. Used when deposition depends principally on diffusion, typically when AMAD is < 0.5 µm.
(ICRP 68)

AMTD
Activity Median Thermodynamic Diameter. Fifty percent of the activity (thermodynamically classified) in the aerosol is associated with particles of thermodynamic diameter (d_th) greater than the AMTD. A log-normal distribution of particle sizes is usually assumed.
(ICRP 66)

Amylase
Any of the enzymes (as amylopsin) that accelerate the hydrolysis of starch and glycogen or their immediate hydrolysis products.
(HPJ 60)

Analogue offset
Analogue value subtracted from the input signal of an analogue to digital converter in order to change the value of the input signal in such a way that it corresponds to the channel coded zero.
(IEC 50-394-1993)

Analogue signal
Signal in which the characteristic quantity representing information may at any instant assume any value within a continuous interval.
(IEC 50-394-1993)

Analogue-to-digital converter, ADC
Assembly or sub-assembly intended to provide an output signal which is a digital representation of the analogue input signal.
(IEC 50-394-1993)

Analysis
Process of mathematical or other logical reasoning that leads from stated premises to the conclusion concerning specific capabilities of equipment and its adequacy for a particular application.
(IEC 50-393-1993)

Analysis
As used in ANSI/ANS-6.4, the term analysis applies to the analysis of radiation transport in and through shields including predictions of dose rates and neutron and gamma-ray fluxes as modified by the introduction of shields in the systems involved.
(ANSI/ANS-6.4-1985)

Analysis, activation
A method of chemical analysis, especially for small traces of material, based on the detection of characteristic radiations following a nuclear bombardment.
(RHH)

Analysis, feather
A technique for the determination of the range in aluminum of beta particles of a radionuclide by comparison of the absorption curve with the absorption curve of a reference source, usually ²¹⁰Bi (range - 501 mg/cm²).
(RHH)

Analysis, isotope dilution
A method of chemical analysis for a component of a mixture, based on the addition to the mixture of a known amount of labeled component of known specific activity, followed by isolation of a quantity of the component and measurement of the specific activity of that sample.
(RHH)

Analysis, neutron activation
A method of elemental analysis. especially for small traces of material, based on the detection of characteristic emitted radiation following bombardment of the sample with neutrons.
(HPJ 60)

Analyte
The particular radionuclide to be determined in a sample of interest.
(HPS N13.30-1996)

Analyte
The particular radionuclide to be determined in a sample of interest.
(HPJ 60)

Analyte
The particular radionuclide to be determined in a sample of interest.
(ANSI N13.30-1989D)

Analyzer, multichannel
The specific component measured in a chemical analysis; also called "analate".
(HPJ 60)

Analyzer, pulse height
An electronic circuit which sorts and records the pulses according to height.
(RHH)

Anatomic models
Stylized descriptions of the location, size and shape of selected portions of the anatomy of man, woman or child.
(HPJ 60)

Anatomic models
Stylized descriptions of the location, size and shape of selected portions of the anatomy of man, woman or child.
(NCRP 87)

Anatomic models
Stylized descriptions of the location, size and shape of selected portions of the anatomy of man, woman or child.
(NCRP 84)

Anatomical Dead Space
Volume of the airways of the lung in which no gas exchange occurs.
(NCRP 125)

Anatomical dead space
The region of the lung given by the tracheo-bronchial and nasopharyngeal regions, which normally constitute the part of the lung not responsible for gas exchange with blood.
(ENV RAD)

Anemia
Deficiency of blood as a whole, or deficiency in the number of the red corpuscles or of the hemoglobin.
(RHH)

Anemia
Abnormally low red blood corpuscles or low haemoglobin.
(NBS 63)

Anergy
Diminished reactivity to specific antigen(s); it may take the form of diminished immediate hypersensitivity or diminished delayed hypersensitivity or both.
(HPJ 60)

Aneuploid
Having numbers of chromosomes not equal to exact multiples of the haploid number. Down syndrome is an example.
(BEIR V)

Aneuploid
Having numbers of chromosomes not equal to exact multiples of the haploid number. Down syndrome is an example.
(BEIR IV)

Anger camera
A highly collimated gamma detector used for radioactivity scans in nuclear medicine.
(NCRP 65)

Angiography
The radiographic visualization of blood vessels following introduction of contrast material.
Cerebral a., Radiography of the vascular system of the brain after injection of contrast material into the arterial blood stream.
Coronary a., Radiographic visualization of the coronary arteries after the introduction of contrast material.
Digital subtraction a., Radiographic visualization of blood vessels, with images produced by subtracting background structures and enhancing the contrast of those area that change in density between a preliminary "mask" image and subsequent images.
(NCRP 107)

Angiography
Radiography of blood vessels after injection of a radio-opaque material into an artery.
(NCRP 68)

Angiography
Radiography of blood vessels after injection of a radio-opaque material into an artery.
(NCRP 48)

Angioplasty
Reconstruction of blood vessels.
Percutaneous transluminal a., Distilation of a blood vessel by means of a baloon catheter inserted through the skin and into the chosen vessel and then passed through the lumen of the vessel to the site of the lesion, where the ballon is inflated to flatten plaque against the artery wall.
(NCRP 107)

Angle of incidence
The angle between the beam axis and the normal to the irradiated surface.
(ICRU 24)

Angstrom (symbol Å or A)
A unit of length, used in measuring electromagnetic radiation, equal to 10^-8 centimeter. Named for A.J. Angstrom, Swedish spectroscopist.
(USAEC-1974)

Angstrom (symbol Å)
Unit of length = 10^-8 cm.
(BEIR III)

Angstrom (symbol Å)
Unit of length = 10^-8 cm.
(RHH)

Angstrom unit
One angstrom unit equals 10^-8 cm (Symbol: Å).
(BEIR I)

Angular dependence
Response of the detector as a function of the angle of incidence of the radiation being detected and a reference orientation.
(ANSI N42.17A-1989)

Angular dependence
Response of the detector as a function of the angle of incidence of the radiation being detected.
(ANSI N42.17C-1989)

Angular distribution factor: r(d)
The ratio of the maximum directional dose equivalent, H'(d)_max, and the ambient dose equivalent, H*(d):

(ICRU 43)

Angular response
The response of the instrument detector to particles or photons which impinge on the detector at angles deviant from a normal to the facial plane of usual incidence.
(NCRP 112)

Anion
Negatively charged ion.
(BEIR III)

Anion
Negatively charged ion.
(BEIR I)

Anisoaxial sampling
Sampling condition in which the air flowing into an inlet has a different direction from the ambient air flow.
(AM-1993)

Anisokinetic
A condition which prevails when the velocity of air entering a sampling probe or the collector when held in the airstream is different from the velocity of the airstream being sampled at that point.
(ANSI N13.1-1969)

Anisotropic
Having different properties in different directions.
(NCRP 67)

Anisotropic
Not isotropic, having different properties in different directions. See also isotropic.
(NCRP 51)

Anisotropy
Referring to the character of a medium in which, at any point, the properties are different in different directions.
(NCRP 76)

Ankylosing spondylitis
Arthritis of the spine.
(BEIR V)

Annealing
Thermal treatment of the phosphor either prior to exposure to erase the effects of previous exposure, or prior to readout to reduce low-temperature thermoluminescence responses.
(ANSI N545-1975)

Annihilation
Interaction between a particle and its antiparticle with resulting disappearance of them and emission of different particles.
(IEC 50-393-1993)

Annihilation
An interaction between a positive and a negative electron in which they both disappear; their energy, including rest energy, being converted into electromagnetic radiation (called annihilation radiation).
(ANSI N1.1-1976)

Annihilation
(See antimatter.)
(USAEC-1974)

Annihilation radiation
Ionizing radiation that is produced when a particle and its antiparticle interact and cease to exist.
(IEC 50-393-1993)

Annihilation radiation
The electromagnetic radiation emitted as a result of the combination and disappearance of an electron and a positron. Two gamma rays of 0.511 MeV energy are emitted in most cases.
(NCRP 51)

Annual effective dose equivalent
The dose equivalent received during a year. The sum of the annual whole body dose equivalent and the committed effective dose equivalent from all intakes during the year. Annual effective dose equivalent is expressed in units of sievert (Sv).
(NCRP 114)

Annual limit on (formerly "of") intake (ALI)
The activity of a radionuclide which, if inhaled or ingested alone by Reference Man, would result in a committed dose equivalent equal to that of the most limiting primary guide.
(FGR 11)

Annual Limit on Intake
The activity of a radionuclide taken into the body by inhalation or ingestion that commits a worker to receiving the relevant dose equivalent limit.
(ICRP 36)

Annual Limit on Intake (ALI)
The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in a committed effective dose equivalent of 5 rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue. (ALI values for intake by ingestion and by inhalation of selected radionuclides are given in Table 1, Columns 1 and 2, of appendix B to Secs. 20.1001-20.2401).
(10CFR20.1003)

Annual Limit on Intake (ALI)
The activity of a radionuclide which, if taken into the body of Reference Man (ICRP 1975), would result in a committed dose equal to the ICRP (ICRP 1977) limit. The ALI is equivalent to an exposure of 2,000 DAC-hours. When based on limitation of stochastic risk of cancer and genetic effects, it corresponds to a committed effective dose equivalent of 50 mSv (5 rem) and is referred to as a stochastic ALI (SALI). When based on prevention of non-stochastic effects to a single organ or tissue, it corresponds to a committed dose equivalent of 500 mSv (50 rem) and is referred to as a non-stochastic ALI (NALI). NOTE: Whenever ALI is used in this standard, it represents the most limiting of the ALIs (NALI or SALI) for the radionuclide, unless otherwise specified.
(HPS N13.42-1997)

Annual Limit on Intake (ALI)
A recommended limit on the annual intake (in Bq) for an individual radionuclide; it is a secondary limit based on calculations that limit the internal committed effective dose equivalent to the standard recommended by the ICRP (ICRP 30).
(ANSI/HPS N13.22-1995)

Annual Limit on Intake (ALI)
The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide -in a year by the reference man (ICRP Publication 23) that would result in a committed effective dose equivalent of 5 rems (0.05 sievert) or a committed dose equivalent of 50 rems (0.5 sievert) to any individual organ or tissue. ALI values for intake by ingestion and inhalation of selected radionuclides are based on Table 1 of the U.S. Environmental Protection Agency's Federal Guidance Report No. 11, Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion, published September 1988.
(10CFR835.2-1993)

Annual Limit on Intake (ALI)
The activity of a radionuclide that taken alone would irradiate a person, represented by Reference Man, to the limit set for occupational exposure by recommending and regulating bodies.
(NCRP 84)

Annual Limit on Intake (ALI)
The activity of a radionuclide which taken alone would irradiate a person, represented by Reference Man, to the limit set by the ICRP for each year of occupational exposure.
(ICRP 54)

Annual Limit on Intake (ALI)
The activity of a radionuclide that, taken into the body in during a year, would provide a committed effective dose equivalent to a person, represented by Reference Man, equal to the annual occupational effective dose equivalent limit (H_E,L) or in some cases, the organ dose equivalent limit (nonstochastic effect). The ALI is normally expressed in becquerels (Bq) or curies.
(NCRP 91)

Annual Reference Level of Intake (ARLI)
Activity of a radionuclide that, taken into a body during a year, would provide a committed effective dose to a person, represented by Reference Man, equal to 20 mSv (ARLI is expressed in becquerels, Bq).
(NCRP 125)

Annual Reference Levels of Intake (ARLI)
The activity of a radionuclide that, taken into the body during a year, would provide a committed effective dose to a person, represented by Reference Man, equal to 20 mSv. The ARLI is expressed in becquerel (Bq).
(NCRP 118)

Annual refresher safety training
A review conducted or provided by the licensee for its employees on radiation safety aspects of industrial radiography. The review may include, as appropriate, the results of internal inspections, new procedures or equipment, new or revised regulations, accidents or errors that have been observed, and should also provide opportunities for employees to ask safety questions.
(10CFR34.3)

Annual throughput
In a reactor installation, the average yearly amount of fresh fuel introduced as a replacement for spent fuel.
(ANSI N1.1-1976)

Annually
(1) At intervals not to exceed 1 year or
(2) once per year, at about the same time each year (plus or minus 1 month).
(10CFR36.2)

Anode
Positive electrode; electrode to which negative ions are attracted.
(RHH)

Antagonistic effect
A dose effect dependence in which the additional effect produced by radiation X, in combination with a fixed dose of radiation Y, is less effective than X alone when account is taken of a dose of X biologically equivalent to Y.
(ICRU 30)

Antenna
A device for transmitting (or receiving) electromagnetic energy into space (or from) space. Several such devices (antenna elements) may be taken together to form a simple antenna system or array.
(NCRP 67)

Antenna pattern
A graphical representation of a field parameter of radiating electromagnetic waves in a plane that includes the radiation device at the origin of the space coordinates. (See radiation pattern.)
(NCRP 67)

Antenna, dipole
See dipole antenna.
(NCRP 67)

Antenna, field regions of
Classification of the important spatial subdivisions of an antenna's electromagnetic field. The subdivisions, in non-uniquely defined distances from the antenna, include the reactive near field region adjacent to the antenna, the radiating near field region (for large antennas commonly referred to as the Fresnel region), and the furthermost, the far field region, also known as the Fraunhofer region.
(NCRP 67)

Anthropogenic
Caused by or resulting from the acts of man.
(NCRP 109)

Anthropomorphic
Having the configuration of the human body.
(HPJ 60)

Anti-coincidence method
A technique inspired by the coincidence method but which, instead of registering coincident events, is based on the signals which are not coincident with those of the opposite channel.
(ICRU 52)

Antibody
Any of the body globulins that combine specifically with antigens and neutralize toxins, agglutinate bacteria or cells, and precipitate soluble antigens.
(HPJ 60)

Anticipated operational occurrence
All operational processes deviating from normal operation which are expected to occur once or several times during the operating life of the plant and which, in view of appropriate design provisions, do not cause any significant damage to items important to safety nor lead to accident conditions.
(IEC 50-393-1993)

Anticipated processes and events
Those natural processes and events that are reasonably likely to occur during the period the intended performance objective must be achieved. To the extent reasonable in the light of the geologic record, it shall be assumed that those processes operating in the geologic setting during the Quaternary Period continue to operate but with the perturbations caused by the presence of emplaced radioactive waste superimposed thereon.
(10CFR60.2)

Anticoincidence
Generation of an event or a pulse used to prevent a circuit or instrument from providing an output signal corresponding to a signal, or signals, at a specified input or inputs within a specified time interval.
(IEC 50-394-1993)

Antimatter (antiparticles)
Matter in which the ordinary nuclear particles (neutrons, protons, electrons, etc.) are conceived of as being replaced by their corresponding antiparticles (antineutrons, antiprotons, positrons, etc.). An antihydrogen atom, for example, would consist of a negatively charged antiproton with an orbital positron. Normal matter and antimatter would mutually annihilate each other upon contact, being converted totally into energy.
(USAEC-1974)

Antiparticle
Particle having the same mass and spin as the given particle, an opposite quantum number, and an electric charge, if it is charged, that is opposite in sign.
(IEC 50-393-1993)

AP
Proceeding in a direction from the front (anterior) side of a body to the back (posterior) side. Said of a unidirectional radiation field.
(ICRU 43)

Aperture (e.g. for computed tomography)
The opening in the collimation that allows radiation to reach the detector.
(NCRP 102)

Apparatus
General term used for designating instruments, detectors, assemblies, sub-assemblies and components.
(IEC 50-394-1993)

Applicable limit
That level of exposure or concentration of radioactive material which is permitted by pertinent regulations or established as recommended radiation exposure standards by authoritative bodies such as the National Council on Radiation Protection and Measurement and the International Commission on Radiological Protection.
(USAS N13.2-1969)

Application
Any request filed with the Commission for a permit, license, approval, exemption, certificate, other permission, or for any other service.
(10CFR170.3)

Applicator
A type of antenna designed to conduct, transmit, or transfer electromagnetic energy from an electromagnetic source to an object being irradiated. (A common application is diathermy).
(NCRP 67)

Applicator (treatment cone)
A structure which indicates the extent of the radiation field at a given distance from the source, and which may or may not itself incorporate the collimating diaphragm. Applicators may be either closed-ended or open-ended. ICRU 24 adds: Applicators are used frequently for "fixed SSD" techniques, never with "isocentric" techniques.
(ICRU 24)

Appointed teacher
Teacher with sufficient training nominated by the governing body to supervise radiation protection in a teaching establishment.
(ICRP 36)

Apposition
The formation of bone at bone surfces and involves a local increase in bone volume. Bone (as distinct from cartilage) can increase in volume only by means of the apposition of a layer of bone to existing bone surfaces by osteoblasts.
(ICRP 20)

Apposition rate (or rate of bone formation)
The volume of new bone formed per unit time per unit volume of bone formed and its units are typically %/year. Linear apposition rate - The thickness of the layer of new bone formed per unit time and its units are typically micron/day. When necessary for clarity, the former may be called volume apposition rate.
(ICRP 20)

Approach to criticality
A series of small increases in reactivity of a subcritical system by successive small changes in one of its parameters from which a safe prediction of the value of that parameter which makes the system critical may be obtained by extrapolation.
(ANSI N1.1-1976)

Appropriate Blank
A sample, person, or phantom that is, ideally, identical in physiochemically and radiologically significant ways with the sample, person, or phantom to be analyzed. When feasible the appropriate blank should not contain environmental quantities of the analyte.
(HPS N13.30-1996)

Appropriate blank
A sample, person, or phantom, that is, ideally, identical in physiochemically and radiologically significant ways with the sample, person, or phantom being analyzed. For direct bioassay the appropriate blank may also be the subject of analysis, if one analyzes a portion of the count versus energy spectrum that is unaffected by the radionuclide of interest, and if one applies a correction factor appropriate for obtaining a blank count for the spectral region(s) of interest. An appropriate blank provides the necessary signal response in the final measurement process so that signals resulting from ambient amounts of the analyte, interfering nuclides, and extraneous background radiation can be subtracted from signals from routine samples to permit detection and measurement of an additional amount of analyte above the ambient amount of the analyte normally contained in the medium of interest.
(ANSI N13.30-1989D)

Appropriate Nuclear Regulatory Commission regional office
(1) For domestic shipments-the Regional Office within whose region the licensee who is responsible for the physical protection arrangements of the shipment is located.
(2) For export shipments-the Regional Office within whose region the licensee who is responsible for the physical protection arrangements of the shipment is located, and the Regional Office for the region in which the last point of exit of the shipment from the U.S. is located.
(3) For import shipments-the Regional Office within whose region the licensee who is responsible for the physical protection arrangements of the shipment is located, and the Regiorial Office for the region in which the first point of entry of the shipment into the U.S. is located.
(10CFR73.2)

Approved
Tested and listed as satisfactory by the Bureau of Mines (BM) of the U.S. Department of the Interior, or jointly by the Mining Enforcement and Safety Administration (MESA) of the U.S. Department of Interior and the National Institute for Occupational Safety (NIOSH) of the U.S. Department of Health, Education and Welfare, or jointly by the Mines Safety and Health Administration (MSHA) of the U.S. Department of Labor and the National Institute for Occupational Safety (NIOSH) of the U.S. Department of Health, Education and Welfare.
(ANSI Z88.2-1980)

Approved
Tested and listed as satisfactory by an authority having jurisdiction, such as U.S. Department of the Interior, Bureau of Mines, or U.S. Department of Agriculture.
(ANSI Z88.2-1969)

Approved permit program
A state permit program approved by the Administrator as meeting the requirements of part 70 of this chapter or a Federal permit program established in this chapter pursuant to title V of the Act (42 U.S.C. 7661).
(10CFR61.2)

Aqueous tritium
The tritium associated with water molecules.
(NCRP 62)

Aquifer
A formation or group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
(NCRP 123I)

Aquifer
A formation or group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
(NCRP 76)

Aquifer
A formation (or group of formations) of water-bearing stratum that contains sufficient permeable rock, sand, or gravel to yield significant quantities of water to wells and springs.
(NUREG/CR 3332)

Aquitard (confining bed)
A body of impermeable material stratigraphically located adjacent to one or more aquifers, which tends to isolate the water in a permeable portion of the aquifer from another portion.
(NCRP 76)

Archicortex
A ring of gray matter around the choroid fissure on the medial side of the brain. It is the first part of the cerebral cortex to differentiate. Initially it is a region localized in the medial wall between the choroid plexus and the sulcus of the corpus callosum. As the hemisphere grows, it migrates through the medial wall to the inferior horn of the lateral ventricle. Phylogenetically, it is the oldest part of the cortex.
(ICRP 49)

Area
The vertical projection of the pile upon the earth's surface.
(40CFR61.251)

Area
See controlled, exclusion, noncontrolled, occupiable, radiation, radioactivity areas.
(NCRP 51)

Area (or workplace) monitoring
Monitoring intended to provide information about the radiation environment and about radiation conditions associated with the operations that are performed. Area monitoring also includes measurements made in the environment of the installation. The results of workplace monitoring are mainly used for categorizing and predicting radiation exposures. The objective of are monitoring is to establish that operational conditions are satisfactory; it is of only limited value in the estimation of dose equivalent to individuals.
(ICRU 43)

Area monitoring
The positioning of fixed instrumentation in different areas of a facility or a site in order to measure normal radiation levels and any changes thereto.
(NCRP 59)

Area occupancy factor (t)
A factor (< 1) by which the absorbed dose index or neutron fluence rate, used for shielding calculations, should be multiplied to correct for the degree of occupancy of the area in question while the radiation source is "on" and the barrier protecting the point of interest is being irradiated.
(NCRP 51)

Area of use
A portion of an address of use that has been set aside for the purpose of receiving, using, or storing byproduct material.
(10CFR35.2)

Area sample
A sample taken in a fixed location assumed to be representative of the area being investigated.
(AM-1993)

Armed escort
An armed person, not necessarily uniformed, whose primary duty is to accompany shipments of special nuclear material for the protection of such shipments against theft or radiological sabotage.
(10CFR73.2)

Armed response personnel
Persons, not necessarily uniformed, whose primary duty in the event of attempted theft of special nuclear material or radiological sabotage shall be to respond, armed and equipped, to prevent or delay such actions.
(10CFR73.2)

Artificial radioactivity
Manmade radioactivity produced by particle bombardment or electromagnetic irradiation.
(BEIR I)

As low as is reasonably achievable (ALARA)
As low as is reasonably achievable taking into account the state of technology, and the economics of improvement in relation to
(1) Benefits to the public health and safety,
(2) Other societal and socioeconomic considerations, and
(3) The utilization of atomic energy in the public interest.
(10CFR72.3)

As Low As Reasonably Achievable (ALARA)
Making every reasonable effort to keep exposure to ionizing radiation as far below established limits as is practical, economic and social factors being taken into account.
(ANSI/HPS N13.45-1998)

As low as reasonably achievable (ALARA)
A conceptual radiation exposure guideline with the intent to encourage protection practices that are better than any prescribed standard. This is the basic criterion for all cases in which a nonthreshold dose-effect relationship either exists or has to be assumed.
(NUREG/CR 3332)

As low as reasonably achievable (ALARA)
As low as is reasonably achievable, taking into account
(1) the state of technology,
(2) the economic of improvements in relation to
(a) benefits to the public health and safety,
(b) other social and socioeconomic considerations, and
(c) the utilization of atomic energy in the public interest. [Formerly "as low as practicable" (ALAP).]
(ANSI N303-1978)

Ash
Solid residue that results from the incineration process, which includes bottom ash from the primary chamber and any fly ash collected from the emissions stack, scrubber, or filter train.
(ANSI/HPS N13.45-1998)

Aspect ratio
The aspect ratio of slot or rectangular exhaust hoods is the ratio of the width to the length of the hood opening.
(ANSI Z9.2-1971)

Aspiration efficiency
Fraction of particles entering an inlet from the ambient environment.
(AM-1993)

Assay
The determination of the activity of a radionuclide in a sample.
(ANSI N42.12-1980)

Assay
The determination of kind and quantity of radioactive material present by physical or chemical measurements.
(NBS 51)

Assembly (of nuclear instrumentation)
Set of interconnected instruments used to achieve a specific total function.
(IEC 50-394-1993)

Assessment
A continuing evaluation of the adequacy of the established measurement process and its compliance with the established policies, procedures, and practices.
(ANSI N15.54-1988)

Assessment
A continuing evaluation of the adequacy of the established measurement process and its compliance with the established policies, procedures, and practices.
(ANSI N15.41-1984)

Associated equipment
Equipment that is used in conjunction with a radiographic exposure device to make radiographic exposures that drives, guides, or comes in contact with the source, (e.g., guide tube, control tube, control (drive) cable, removable source stop, "J" tube and collimator when it is used as an exposure head.
(10CFR34.3)

Ataxia telangiectasia (AT)
An inherited disorder associated with an increased risk of cancer, lymphoma in particular, and characterized by immunologic, chromosomal, and DNA defects.
(BEIR V)

Atelectasis
Collapse of the alveoli of the lung or portion of the lung due to pressure of a pleural effusion or blockage of the small bronchial tubes.
(NCRP 125)

Athermal effect
See non-thermal effect.
(NCRP 67)

Atom
Particle consisting of an assembly of protons and neutrons surrounded by a number of electrons equal to the number of protons.
(IEC 50-393-1993)

Atom
The smallest particle of an element which is capable of entering into a chemical reaction.
(HPJ 60)

Atom
A unit of matter consisting of a nucleus surrounded by a number or electrons equal to the number of protons in the nucleus.
(ANSI N1.1-1976)

Atom
The smallest particle of an element.
(NCRP 48)

Atom
A particle of matter indivisible by chemical means. It is the fundamental building block of the chemical elements. The elements, such as iron, lead and sulfur, differ from each other because they contain different kinds of atoms. There are about six sextillion (6 followed by 21 zeros, or 6 x 10²¹) atoms in an ordinary drop of water. According to present day theory, an atom contains a dense inner core (the nucleus) and a much less dense outer domain consisting of electrons in motion around the nucleus. Atoms are electrically neutral.
(USAEC-1974)

Atom
The smallest particle of an element which is capable of entering into a chemical reaction.
(RHH)

Atom smasher
An accelerator.
(USAEC-1974)

Atomic battery
A radioisotopic generator.
(USAEC-1974)

Atomic bomb
A bomb whose energy comes from the fission of heavy elements, such as uranium or plutonium.
(USAEC-1974)

Atomic clock
A device that uses the extremely fast vibrations of molecules or atomic nuclei to measure time. These vibrations remain constant with time, consequently short intervals can be measured with much higher precision than by mechanical or electrical clocks.
(USAEC-1974)

Atomic cloud
The cloud of hot gases, smoke, dust and other matter that is carried aloft after the explosion of a nuclear weapon in the air or near the surface. The cloud frequently has a mushroom shape.
(USAEC-1974)

Atomic energy
All forms of energy released in the course of nuclear fission or nuclear transformation.
(10CFR72.3)

Atomic energy
All forms of energy released in the course of nuclear fission or nuclear transformation.
(10CFR70.4)

Atomic energy
All forms of energy released in the course of nuclear fission or nuclear transformation.
(10CFR50.2)

Atomic energy
A term sometimes used to denote nuclear energy.
(ANSI N1.1-1976)

Atomic energy
Nuclear energy.
(USAEC-1974)

Atomic energy act
The Atomic Energy Act of 1954, as amended (42 U.S.C. 2011).
(10CFR110.2)

Atomic energy commission
The independent civilian agency of the federal government with statutory responsibility for atomic energy matters. Also the body of five persons, appointed by the President, to direct the agency.
(USAEC-1974)

Atomic mass
Symbol A. The mass of an atom relative to other atoms. The present-day basis of the scale of atomic weights is carbon; the most common isotope of this element has arbitrarily been assigned an atomic weight of 12. The unit of the scale is 1/12 the weight of the carbon-12 atom, or roughly the mass of one proton or one neutron. The atomic weight of any element is approximately equal to the total number of protons and neutrons in is nucleus.
(HPJ 60)

Atomic mass
(See atomic weight, mass.)
(USAEC-1974)

Atomic mass
The mass of a neutral atom of a nuclide, usually expressed in terms of "atomic mass units." The "atomic mass unit" is one-twelfth the mass of one neutral atom of carbon-12; equivalent to 1.6604 x 10^-21 g. (Symbol: u).
(BEIR I)

Atomic mass (symbol M)
The mass of a neutral atom of a nuclide, usually expressed in atomic mass units; atomic mass unit is one-twelfth the mass of one neutral atom of carbon-12 equal to 1.660565 x 10^-27 kg.
(BEIR III)

Atomic mass unit (symbol amu)
One-twelfth the mass of a neutral atom of the most abundant isotope of carbon, ¹²C.
(USAEC-1974)

Atomic number
Symbol Z. The number of protons in the nucleus of an atom and also its characteristic atomic number. The atomic numbers of the known elements form a complete series from 1 (hydrogen) to 103 (lawrencium).
(HPJ 60)

Atomic number
The number of protons in the nucleus of a neutral atom of a nuclide. The "effective atomic number" is calculated from the composition and atomic numbers of a compound or mixture. An element of this atomic number would interact with photons in the same way as the compound or mixture. (Symbol: Z).
(RHH)

Atomic number (symbol Z)
The number of protons in the nucleus of an atom, and also its positive charge. Each chemical element has its characteristic atomic number, and the atomic numbers of the known elements form a complete series from 1 (hydrogen) to 103 (lawrencium).
(USAEC-1974)

Atomic number (Z)
Number of protons contained in an atomic nucleus.
(IEC 50-393-1993)

Atomic reactor
A nuclear reactor.
(USAEC-1974)

Atomic weapon
Any device utilizing atomic energy, exclusive of the means for transporting or propelling the device (where such means is a separable and divisible part of the device), the principal purpose of which is for use as, or for development of, a weapon, a weapon prototype, or a weapon test device.
(10CFR50.2)

Atomic weapon
An explosive weapon in which the energy is produced by nuclear fission or fusion.
(USAEC-1974)

Atomic weight
The mass of an atom relative to other atoms. The present-day basis of the scale of atomic weights is carbon; the commonest isotope of this element has arbitrarily been assigned an atomic weight of 12. The unit of the scale is 1/12 the weight of the carbon-12 atom, or roughly the mass of one proton or one neutron. The atomic weight of any element is approximately equal to the total number or protons and neutrons in its nucleus.
(USAEC-1974)

Atomic weight
The weighted mean of the masses of the neutral atoms of an element expressed in atomic mass units.
(RHH)

Atomizer
A device used to produce droplets by mechanical disruption of a bulk liquid.
(AM-1993)

Attached daughters
The short-lived daughter products of radon that are attached to the ambient aerosol.
(NCRP 97)

Attached fraction
Fraction of airborne radon progeny attached to aerosol particles.
(ENV RAD)

Attenuation
Reduction of a quantity related to radiation, such as energy, fluence, etc., upon passage of radiation through matter, resulting from all types of interaction with matter.
(IEC 50-393-1993)

Attenuation
The process by which a beam of radiation is reduced in intensity when passing through some material. It is the combination of absorption and scattering processes and leads to a decrease in flux density of the beam when projected through matter.
(HPJ 60)

Attenuation
The reduction of radiation intensity upon passage of radiation in matter.
(NCRP 102)

Attenuation
Loss of energy from ionizing radiation by scatter and absorption.
(NCRP 105)

Attenuation
A general term, expressed as a ratio, used to denote a decrease in magnitude of certain field or circuit quantities associated with the transmission of energy from one point to another, irrespective of the process involved.
(NCRP 67)

Attenuation
Process by which a beam of radiation is reduced in intensity when passing through material - combination of absorption and scattering processes, leading to a decrease in flux density of beam when projected through matter.
Attenuation Coefficient, Compton - The fractional number of photons removed from a beam of radiation per unit thickness of material through which it is passing as a result of Compton effect interactions.
Attenuation Coefficient, Linear - The fractional number of photons removed from a beam of radiation per unit thickness of material through which it is passing due to all absorption and scattering processes.
Attenuation Coefficient, Pair Production - That fractional decrease in the intensity of a beam of ionizing radiation due to pair production in a medium through which it passes.
Attenuation Coefficient, Photoelectric Effect - That fractional decrease in the intensity of a beam of ionizing radiation due to photoelectric effect in a medium through which it passes.
Attenuation Factor - A measure of the opacity of a layer of material for radiation transversing it; the ratio of the incident intensity to the transmitted intensity. It is equal to I_o/I, where I_o and I are the intensities of the incident and emergent radiation, respectively. In the usual sense of exponential absorption (I = I_oe^-µx), the attenuation factor is e^-µx, where x is the thickness of the material and µ is the absorption coefficient.
(BEIR III)

Attenuation
The reduction of dose equivalent index rate upon passage of radiation through matter. NCRP 51 is concerned with broad-beam attenuation, i.e., that occurring when the radiation field is wide at the barrier.
(NCRP 51)

Attenuation
The reduction of a radiation quantity upon passage of radiation through matter resulting from all types of interaction with that matter. Note: Attenuation usually does not include geometric attenuation.
(ANSI N1.1-1976)

Attenuation
The reduction of exposure rate upon passage of radiation through matter. NCRP 49 is concerned with broad beam attenuation, i.e., that occurring when the field area is large at the barrier and the point of measurement is near the exit surface.
(NCRP 49)

Attenuation
Decrease in dose rate caused by the passage of radiation through material.
(NBS 73)

Attenuation
A decrease in dose rate in passing through material.
(NBS 54)

Attenuation block
A block or stack of material with a cross section larger than the beam with a total thickness equivalent to 3.8 cm of type 1100 aluminum.
(NCRP 102)

Attenuation coefficient (µ)
Of a substance, for a parallel beam of specified radiation, the quantity µ in the expression µdx for the fraction of a radiation intensity reduced by attenuation in passing through a thin layer of thickness dx of that substance.
(IEC 50-393-1993)

Attenuation coefficient (attenuation constant)
The real part (a) of the propagation coefficient that results in an exponential decrease in magnitude of a field component with distance in the direction of propagation, The attenuation coefficient is expressed in units of inverse meter (m^-1).
(NCRP 67)

Attenuation factor
For a given attenuating body in a given configuration, the factor by which a radiation intensity at some point of interest is reduced owing to the interposition of the body between the source of radiation and the point of interest.
(IEC 50-393-1993)

Attenuation factor
For a given attenuating body in a given configuration, the factor by which a radiation quantity at some point of interest is reduced owing to the interposition of the body between the source of radiation and the point of interest.
(ANSI N1.1-1976)

Attenuation length
The penetration distance in which a radiation beam is attenuated by a factor of e.
(NCRP 51)

Attenuation, geometric
The reduction of a radiation quantity due to the effect of the distance between the point of interest and the source (e.g., the inverse-square law for a point source), and excluding the effect of any matter present.
(ANSI N1.1-1976)

Attenuation, geometrical
Falloff of a radiation beam because of distance, usually from the source, as opposed to absorption or scattering in a medium.
(ICRU 30)

Audio-radiation prospecting indicator
Portable radiation prospecting indicator that provides an audible indication of ionizing particle fluence rate.
(IEC 50-394-1993)

Audit
A means of assuring that current activities are in compliance with program policies and procedures.
(ANSI N15.54-1988)

Audit
A means of assuring that current activities are in compliance with program policies and procedures.
(ANSI N15.41-1984)

Audit
A documented examination, evaluation, and correction activity, performed in accordance with this standard, to verify that all or a portion of a safeguards system or subsystem has been adequately developed, documented, and implemented as necessary to satisfy applicable requirements.
(ANSI N15.38-1982)

Audit
A planned and documented activity performed to determine by investigation, examination, or evaluation of objective evidence, the adequacy of and compliance with established procedures, instructions, drawings, and other applicable documents, and the effectiveness of implementation. An audit should not be confuse with surveillance or inspection activities performed for the sole purpose of process control or product acceptance.
(ANSI N46.2-1978)

Auditable data
Technical information which is documented and organized in a readily understandable and traceable manner that permits independent auditing of the inferences or conclusions based on the information.
(IEC 50-393-1993)

Auditee
Those organizational components responsible for the management and implementation of those portions of a safeguards system that are included within the scope of the audit.
(ANSI N15.38-1982)

Auditor
Any qualified person or persons who perform all or any portion of an audit.
(ANSI N15.38-1982)

Auger effect
Return to the ground state of an atom, ionized in an inner shell, by the ejection of one or more electrons from surrounding shells.
(IEC 50-393-1993)

Auger effect
The emission of an electron from the extranuclear portion of an excited atom when the atom undergoes a transition to a less excited state.
(RHH)

Auger electron
Electron ejected from the surrounding shells due to the return to the ground state of an atom, ionized in an inner shell.
(IEC 50-393-1993)

Augmentation
Any process by which alkaline earths transfer from blood without apposition and remain longer than time t. Its units are typically %/year. It is calculated by subtracting the apposition rate from the addition rate. It is believed to be primarily due...
(ICRP 20)

Authorities
Any governmental agencies or recognized scientific bodies which by their charter define regulations or standards dealing with radiation protection.
(ANSI N13.10-1974)

Authorities
Any governmental agencies or recognized scientific bodies which by their charter define regulations or standards dealing with radiation protection.
(ANSI N42.18-1974)

Authorized individual
Any individual, including an employee, a student, a consultant, or an agent of a licensee who has been designated in writing by a licensee to have responsibility for surveillance of or control over special nuclear material or to have unescorted access to areas where special nuclear material is used or stored.
(10CFR73.2)

Authorized nuclear pharmacist
A pharmacist who is:
(1) Board certified as a nuclear pharmacist by the Board of Pharmaceutical Specialties;
(2) Identified as an authorized nuclear pharmacist on a Commission or Agreement State license that authorizes the use of byproduct material in the practice of nuclear pharmacy; or
(3) Identified as an authorized nuclear pharmacist on a permit issued by a Commission or Agreement State specific licensee of broad scope that is authorized to permit the use of byproduct material in the practice of nuclear pharmacy.
(10CFR35.2)

Authorized release limits
A release limit established by a competent authority or by the management of an institution that may apply only in limited circumstances.
(ICRP 29)

Authorized user
A physician, dentist, or podiatrist who is:
(1) Board certified by at least one of the boards listed in Paragraph (a) of Secs. 35.910, 35.920, 35.930, 35.940, 35.950, or 35.960;
(2) Identified as an authorized user on a Commission or Agreement State license that authorizes the medical use of byproduct material; or
(3) Identified as an authorized user on a permit issued by a Commission or Agreement State specific licensee of broad scope that is authorized to permit the medical use of byproduct material.
(10CFR35.2)

Autocorrelation
Relationship of the measured values to previously measured ones.
(AM-1993)

Autocorrelation function
The autocorrelation function is the ensemble average of the joint second moment of any image process. The noise autocorrelation function is defined in general as:

where n(i) is the noise at location i. For additive noise, this is equivalent to the autocovariance function, which is the autocorrelation about the mean.
The autocorrelation function is the Fourier transform of the Wiener spectrum.
(ICRU 54)

Autocovariance
See Autocorrelation Function.
(ICRU 54)

Autofluoroscope
A device for visualizing the spatial distribution of a radionuclide within an organ or gland in the body. The autofluoroscope uses a multielement stationary detector compound of individual NaI(Tl) crystals. An image of the radionuclide ...
(RHH)

Automatic exposure control (phototiming)
A method for timing radiographic examinations, the duration of the exposure being controlled by the amount of radiation which reaches a radiation-sensitive detector after it has passed through a patient.
(NCRP 68)

Automatic test
Test in which the operation of all or part of the protection system is checked in a completely automatic sequence, which can be started either manually by the operator or cyclically by a clock.
(IEC 50-394-1993)

Automation
The controlling of a step or steps in a nondestructive assay by means of a mechanical and electronic device, or both, that replaces human observations, efforts, and decisions.
(ANSI N15.37-1981)

Autoradiograph
Record of radiation from radioactive material in an object, made by placing the object in close proximity to a photographic emulsion.
(RHH)

Autoradiograph
A photographic record of radiation from radioactive material in an object, made by placing the object very close to a photographic film or emulsion. The process is called autoradiography. It is used, for instance, to locate radioactive atoms or ...
(USAEC??)

Autoradiography
Radiograph of the distribution of radioactive sources in a material which is made by placing the material close to an image recording system.
(ANSI N1.1-1976)

Auxiliary building(s)
Building(s), near or adjacent to the reactor containment building in which primary system support equipment is housed.
(ANSI N320-1979)

Avalanche
The multiplicative process in which a single charged particle accelerated by a strong electric field produces additional charged particles through collision with neutral gas molecules. This cumulative increase of ions is known as "Townsend ionization" or "Townsend avalanche".
(RHH)

Avalanche breakdown (of a junction)
A breakdown caused by the cumulative multiplication of charge carriers in a semiconductor under the action of a strong electric field which causes some charge carriers to gain enough energy to create new hole-electron pairs, field-induced impact ionization.
(IEC 50-394-1993)

Avalanche voltage
Applied reverse voltage at which avalanche breakdown occurs.
(IEC 50-394-1993)

Average energy (W) expended in a gas per ion pair formed
The quotient E by N_W, where N_W is the average number of ion pairs formed when a charged particle of initial energy E is completely stopped by the gas.
(NBS 92)

Average life (mean life)
Average of lives of individual atoms of a radioactive substance; 1.443 times radioactive half-life.
(BEIR III)

Average life (mean life)
The average of the individual lives of all the atoms of a particular radioactive substance. It is 1.443 times the radioactive half-life.
(BEIR I)

Average logarithmic energy decrement
Average value of the decrease per collision of the logarithm of the neutron energy.
(IEC 50-393-1993)

Averaged scan
An assay performed with scanning that produces a single value representing the gamma ray activity of the entire sample.
(ANSI N15.35-1983)

Avogadro's constant (N_A)
Number of elementary entities in a mole of a substance, approximately equal to 6,022 14 x 10⁺²³ mol^-l.
(IEC 50-393-1993)

Avogadro's number
Number of atoms in a gram atomic weight of any element; also the number of molecules in a gram molecular weight of any substance. It is numerically equal to 6.023 x 10²³ on the unified mass scale. (Symbol: N_A).
(RHH)

Axis
See beam axis.
(ICRU 23)

Axis of rotation
The axis about which a rotational treatment unit may rotate. It is usually horizontal. If the patient rotates instead of the machine, the axis of rotation is that about which the patient rotates.
(ICRU 24)

Note: References shown in ()