Borders' Dictionary of Health Physics

B cells
A subpopulation of lymphocytes that manufacture specific protein molecules or antibodies that bind selectively to particular antigens.
(HPJ 60)

B filter
A lead shield that is placed against the neck of phantom to totally obscure the view of the thyroid gland or reference standard from the detector. The dimensions of the "B" filter are 10.2 x 10.2 x 1.3 cm (4 x 4 x 1/2 in).
(ANSI N44.3-1973)

B filter technique
A technique utilizing a "B" filter for correction of background and extrathyroidal activity.
(ANSI N44.3-1973)

Back-scatter
Scattering of particles by material through angles greater than 90° with respect to their initial direction.
(IEC 50-393-1993)

Back-scatter soil density meter
Portable radiation density meter intended to determine soil density by measurement of the radiation back-scattered by the soil.
(IEC 50-394-1993)

Back-scatter thickness meter
Thickness meter with beta or gamma source intended to determine the material thickness by measurement of the radiation back-scattered by the material.
(IEC 50-394-1993)

Background
Ambient signal response recorded by measurement instruments that is independent of radioactivity contributed by the radionuclides being measured in the person or sample.
(HPS N13.30-1996)

Background
Radiation from:
(i) Naturally occurring radioactive materials which have not been technologically enhanced;
(ii) Cosmic sources;
(iii) Global fallout as it exists in the environment (such as from the testing of nuclear explosive devices);
(iv) Radon and its progeny in concentrations or levels existing in buildings or the environment which have not been elevated as a result of current or prior activities; and
(v) Consumer products containing normal amounts of radioactive material or producing nominal amounts of radiation.
(10CFR835.2-1993)

Background
Ionizing radiation present in the region of interest and coming from sources other than that of primary concern. (See Natural Background Radiation also).
(NCRP 105)

Background
Background radiation.
(USAEC-1974)

Background (radiation)
Ionizing radiation recorded from sources other than that of primary concern.
(ANSI N44.3-1973)

Background area
A location at which the dose rate in tissue from ionizing radiation is less than 0.003 millirad per hour (mrad/hr).
(ANSI N13.15-1985)

Background check source
A sealed vial of liquid-scintillation solution containing no added radioactive material.
(ANSI N42.15-1980)

Background counts (in radioactivity counters)
Counts recorded in the instrument when measuring a background check source.
(ANSI N42.15-1980)

Background level (of a measuring assembly)
For an activity measuring assembly when the assembly is placed under its normal conditions of operation, value indicated in the absence of the source whose radiation is to be measured.
(IEC 50-394-1993)

Background radiation
Ionizing radiation present in the region of interest and coming from sources other than that of primary concern.
(ANSI N1.1-1976)

Background radiation
Radiation arising from sources other than the one directly under consideration. Radiations are always present, due to cosmic rays and natural radioactivity of materials in the earth and building materials.
(NCRP 48)

Background radiation
The radiation in man's natural environment, including cosmic rays and radiation from the naturally radioactive elements, both outside and inside the bodies of men and animals. It is also called natural radiation. The term may also mean radiation that is unrelated to a specific experiment.
(USAEC-1974)

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

Background radiation
Radiation arising from radioactive material other than the one under consideration. Background radiation due to cosmic rays and natural radioactivity is always present. There may also be additional background radiation due to the presence of sources of radiation in other parts of the building.
(NBS 66)

Background radiation
Radiation arising from radioactive material other than the one under consideration. Background radiation due to cosmic rays and natural radioactivity is always present. There may also be background radiation due to the presence of radioactive substance in other parts of the building, in the building material itself, etc.
(NBS 54)

Background radiation
Radiation from cosmic sources; naturally occurring radioactive material, including radon (except as a decay product of source or special nuclear material); and global fallout as it exists in the environment from the testing of nuclear explosive devices or from past nuclear accidents such as Chernobyl that contribute to background radiation and are not under the control of the licensee. "Background radiation" does not include radiation from source, byproduct, or special nuclear materials regulated by the Commission.
(10CFR20.1003)

Background radiation
Radiation from: (i) naturally-occurring radioactive materials as they exist in nature prior to enhancement or processing by man; (ii) cosmic and natural terrestrial radiation; (iii) global fallout as it exists in the environment; (iv) consumer products containing nominal amounts of radioactive material or producing nominal levels of radiation; and (v) radon and its progeny in concentrations or levels existing in buildings or the environment which have not been elevated as a result of current or prior DOE activities. Background radiation does not include radiation from source, byproduct, or special nuclear materials, or naturally-occurring and accelerator-produced radioactive materials (NARM) used in connection with Departmental or DOE contractor activities.
(10CFR834.2)

Background radiation
Ionizing radiation at a point, consisting of radiation from natural and man-made sources, excluding the radiation intended to be measured.
(IEC 50-393-1993)

Background radiation
See radiation.
(HPJ 60)

Background radiation
The amount of radiation to which a member of the population is exposed from natural sources, such as terrestrial radiation due to naturally occurring radionuclides in the soil, cosmic radiation originating in outer space, and naturally occurring radionuclides deposited in the human body.
(BEIR V)

Background radiation
Radiation arising from natural sources; background radiation due to cosmic rays and natural radioactivity, including radon and its decay products, is always present in the human body and the earth.
(NCRP 103)

Background radiation
The amount of radiation to which a member of the population is exposed from natural sources, such as terrestrial radiation from naturally occurring radionuclides in the soil, cosmic radiation originating in outer space, and naturally occurring radionuclides deposited in the human body. The natural background radiation received by an individual depends on geographic location and living habits. In the U.S., the background radiation is on the order of 1 mSv (100 mrem) per year, excluding indoor radon.
(NCRP 98)

Background radiation
Radiation arising from radioactive material other than that under consideration; background radiation due to cosmic rays and natural radioactivity is always present; there may also be background radiation due to the presence of radioactive substances in building material.
(BEIR IV)

Background urinary uranium
An excretion rate in urine equivalent at equilibrium to the average food and water intake of natural uranium. This value varies for different locations and food sources.
(ANSI/HPS N13.22-1995)

Backreflection (scattering)
The reflection of radiation in a direction generally greater than 90o to that of the incident radiation.
(NCRP 51)

Backscatter
When radiation of any kind strikes matter (gas, liquid or solid), some of it may be reflected or scattered back in the general direction of the source. An understanding or exact measurement of the amount of backscatter is important when beta particles are being counted in an ionization chamber, in medical treatment with radiation, or in use of industrial radioisotopic thickness gauges.
(USAEC-1974)

Backscatter factor
See peak scatter factor.
(NCRP 69)

Backscattering
The scattering of radiation in a direction generally opposite to that of the incident radiation.
(ANSI N1.1-1976)

Backscattering
The deflection of radiation by scattering processes through angles greater than 90 degrees, with respect to the original direction of motion.
(RHH)

Bacteria
Single-celled microorganisms; some genera produce endospores.
(AM-1993)

Balance of plant
The remaining systems, components, and structures that comprise a complete nuclear power plant and are not included in the nuclear steam supply system.
(10CFR170.3)

Bare
Not having a reflector.
(ANSI N1.1-1976)

Barge
Any non-self-propelled vessel.
(ANSI N14.24-1985)

Barge motions
Barges may experience any one or combination of six motions in the course of transport, which represent the six degrees of freedom of a rigid body: three rotational and three translational.
Roll: Rotational motion about the longitudinal axis.
Pitch: Rotational motion about the transverse axis.
Yaw: Rotational motion about the vertical axis.
Surge: Translational motion along the longitudinal axis.
Sway: Translational motion along the transverse axis.
Heave: Translational motion along the vertical axis.
(ANSI N14.24-1985)

Barn
A unit of area used in expressing nuclear cross sections. (1 barn = 10^-28 m² = 10^-24 cm².)
(ANSI N1.1-1976)

Barn
A unit area used in expressing a nuclear cross section. 1 barn equals 10^-24 cm².
(NCRP 38)

Barn
Unit of expressing the probability of a specific nuclear reaction in terms of cross-sectional area. Numerically it is 10^-24 cm².
(RHH)

Barn
A unit of area used in expressing a nuclear cross section. 1 barn = 10^-24 cm². Cross sections per atom are customarily measured in barns.
(NBS 63)

Barn (b) (deprecated)
Unit of area used in expressing cross section exactly equal to 10^-28 m².
(IEC 50-393-1993)

Barn (symbol b)
A unit area used in expressing the cross sections of atoms, nuclei electrons, and other particles. One barn is equal to 10^-24 square centimeter.
(USAEC-1974)

Barricade shield
A type of movable shield for protection from radiation.
(USAEC-1974)

Barrier
Any material or structure that prevents or substantially delays movement of water or radionuclides.
(10CFR60.2)

Barrier
See protective barrier.
(NCRP 102)

Barrier
See protective barrier.
(NCRP 49)

Barrier
See protective barrier.
(NBS 73)

Barrier shield
A wall or enclosure shielding the operator from an area where radioactive material is being used or processed by remote control equipment.
(USAEC-1974)

Barriers, protective
Barriers of radiation-absorbing material, such as lead, concrete and plaster, used to reduce radiation exposure.
Barriers, Primary Protective - Barriers sufficient to attenuate the useful beam to the required degree.
Barriers, Secondary Protective - Barriers sufficient to attenuate stray radiation to the required degree.
(RHH)

Baryon
One of a class of heavy elementary particles which includes neutrons, protons and hyperons.
(USAEC-1974)

Baryon
One of a class of heavy elementary particles which includes neutrons, protons and hyperons.
(RHH)

Barytes concrete
A type of heavy concrete containing barytes (a dense barium mineral) added to improve its shielding characteristics.
(ANSI N1.1-1976)

Basal Cell
Cells that form a single row along basement membrane and are responsible for the pseudostratified appearance of the epithelium.
(NCRP 125)

Basal cell
The target cell at risk in lung cancer production whose minimum depth is of the order of 35 µm below the surface of the mucus layer or 22 µm below the surface of the bronchial epithelium. The basal cells are the dividing stem cells which produce replacement cells for those lost normally from the bronchial epithelium.
(NCRP 78)

Basal cell carcinoma
Also known as basal cell epithelioma or basalioma, a slow-growing neoplasm arising from the basal cells of the epidermis or hair follicles that rarely metastasises.
(ICRP 59)

Basal cells
Cuboidal epithelial cells attached to the basement membrane of extrathoracic and bronchial epithelium and not extending to the surface.
(ICRP 68)

Basal cells
Low cuboidal epithelial cells attached to the basement membrane of extrathoracic and bronchial epithelium and not extending to the surface.
(ICRP 66)

Baseline
The average value of the calorimeter out put when the calorimeter is empty and at equilibrium. The baseline is also referred to as the "null" or "zero" of the calorimeter, and is usually expressed in microvolts.
(ANSI N15.54-1988)

Baseline leakage range
The level of source leakage determined for each source as based on the best estimates indicated by a range of continuing periodic leakage measurements, to serve as a reference for evaluating leakage fluctuations.
(ANSI N44.2-1973)

Baseline rate
The cancer experience observed in a population in the absence of the specific agent being studied; the baseline rate might, however, include cancers from a number of other causes, such as smoking, background radiation, etc.
(BEIR V)

Basement Membrane
Very thin membrane beneath the epithelium.
(NCRP 125)

Basic component
(1) When applied to nuclear power reactors, any plant structure, system, component, or part thereof necessary to assure (i) The integrity of the reactor coolant pressure boundary, (ii) The capability to shut down the reactor and maintain it in a safe shutdown condition, or
(iii) The capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to those referred to in Sec. 50.34(a)(1) or Sec. 100.11 of this chapter, as applicable.
(2) When applied to other types of facilities or portions of such facilities for which construction permits are issued under Sec. 50.23, a component, structure, system or part thereof that is directly procured by the construction permit holder for the facility subject to the regulations of this part and in which a defect or failure to comply with any applicable regulation in this chapter, order, or license issued by the Commission could create a substantial safety hazard.
(3) In all cases, basic component includes safety related design, analysis, inspection, testing, fabrication, replacement parts, or consulting services that are associated with the component hardware, whether these services are performed by the component supplier or other supplier.
(10CFR50.2)

Basic limits
The Commission's dose limits and secondary limits such as the annual limit of intake.
(ICRP 29)

BAT selection process
The evaluation of candidate alternative technologies in order to select the BAT after considering: technology; economics; the age of equipment and facilities involved; the process employed; the engineering aspects of the application of various types of control techniques; process changes; other environmental impacts (including energy requirements); safety considerations; and policy considerations.
(10CFR834.2)

Batch
A portion of source material or special nuclear material handled as a unit for accounting purposes at a key measurement point and for which the composition and quantity are defined by a single set of measurements. The source material or special nuclear material may be in bulk form or contained in a number of separate items.
(10CFR74.4)

Batch
A portion of nuclear material handled as a unit for accounting purposes at a key measurement point and for which the composition and quantity are defined by a single set of specifications or measurements. The nuclear material may be in bulk form or contained in a number of separate items.
(10CFR75.4)

Batch Burn
The process of charging an incinerator, completing the incineration cycle for that charge, allowing the combustion chamber to cool down, and removing the ash residue prior to introduction of another charge.
(ANSI/HPS N13.45-1998)

Batch mode
An older, traditional method of processing in which transactions are collected and prepared for computer input to process as a single unit.
(NUREG/CR 3332)

Bayesian analysis
Analysis in which Bayes' theorem is used to derive posterior probabilities from assumed prior knowledge together with observational data. For example, biological information on the relationship between species and hazardous substances can be combined with data on interspecies dose response to calculate the response of human populations.
(BEIR IV)

BB_seq
Compartment representing prolonged retention in airway walls of small fraction of particles deposited in the bronchiolar region.
(ICRP 66)

BB-bronchial region
Consists of the trachea and bronchi from which deposited material is cleared by ciliary action; airway generations 0 through 8.
(ICRP 66)

bb-bronchiolar region
Consists of the bronchioles and terminal bronchioles; airway generations 9 through 15.
(ICRP 66)

BB_bas
Tissue in bronchial region through which basal cell nuclei are distributed.
(ICRP 66)

BB_sec
Tissue in bronchial region through which secretary cell nuclei are distributed.
(ICRP 66)

Beam
Practically unidirectional flow of electromagnetic radiation or of particles with limited cross-sectional area.
(IEC 50-393-1993)

Beam
A bundle or pencil of rays proceeding from a source.
(NCRP 69)

Beam
The beam is the region in space traversed by photons or particles from the source. Its edges frequently are determined by a collimator, its cross section perpendicular to the beam axis is the field and its direction is that of photon or particle travel.
(NCRP 66)

Beam
The x- or gamma-ray beam is the region in space traversed by photons from the source. Its edges frequently are determined by a collimator, its cross section perpendicular to the beam axis (q.v.) is the field and its direction is that of photon travel.
(ICRU 24)

Beam
A stream of particles or electromagnetic radiation, going in a single direction.
(USAEC-1974)

Beam
A bundle or pencil of rays proceeding from a source.
(ICRU 23)

Beam
A unidirectional or approximately unidirectional flow of electromagnetic radiation or of particles.
Useful Beam (Radiology) - Radiation which passes through the aperture, cone or other collimating device of the source housing. Sometimes called the primary beam.
(RHH)

Beam (also charged particle beam, radiation beam)
A flow of electromagnetic or particulate radiation that is either a) collimated and generally unidirectional, or b) divergent from a small source but restricted to a small solid angle.
(NCRP 59)

Beam axis
The straight line passing through the center of the source and the center of symmetry of the plane figure formed by the edge of the diaphragm which defines the beam. If the final diaphragm has no center of symmetry, there is no beam axis. However, in such cases it is usually possible to utilize the isocenter, front or back pointer or other mechanical locating device to define a line of reference which serves as an effective beam axis. (Note: An acceptable alternative expression is central ray, but the term central axis is tautological and should not be used).
(NCRP 69)

Beam axis (central ray)
The beam axis may be defined in three stages:
(a) Mechanical Definition: The collimator axis is normally defined in terms of the rotation of the collimator and is the axis about which it rotates. If the collimator is fixed but symmetrical, its axis can be defined as the line perpendicular to the end plane of the diaphragm and passing through the center point of this plane.
(b) Geometrical Definition: In order to define the beam axis geometrically, the center of the source must be placed on the collimator axis. The beam axis is now coincident with the collimator axis and may be defined as the line passing through the center of the source and the center of the final beam limiting diaphragm.
(c) Dosimetric Definition: If the beam is dosimetrically symmetrical (if necessary, as the result of the insertion of a flattening filter, q.v.) the beam axis is the axis of dosimetric symmetry of the beam.
(ICRU 24)

Beam axis (dosimetric definition)
If the beam is dosimetrically symmetrical (if necessary, as the result of the insertion of a flattening filter) the beam axis is the axis of dosimetric symmetry of the beam.
(ICRU 30)

Beam flattening filter
A beam flattening filter is a filter (q.v.) designed to make the energy fluence rate or absorbed dose rate reasonably constant across the beam. In general, a beam cannot be flattened equally at all depth in a phantom and, therefore, a filter is designed to achieve flatness at a chosen depth.
(ICRU 24)

Beam hole
Hole through a reactor biological shield into the interior of a reactor for the passage of a beam of radiation for experiments outside the reactor.
(IEC 50-393-1993)

Beam hole
A hole through a reactor shield or shields into the interior of the reactor for the passage of a beam of radiation outside the reactor.
(ANSI N1.1-1976)

Beam hole
An opening through a reactor shield and, generally, through the reactor reflector, which permits a beam of radioactive particles or radiation to be used for experiments outside the reactor.
(USAEC-1974)

Beam hole (glory hole)
Hole through the shield, and usually through the reflector, of a reactor to permit the escape of a beam of radiation, in particular a beam of fast neutrons, for experimental purposes.
(RHH)

Beam limiting device (beam ???ing device)
A device which provides a means to restrict the dimensions of the useful beam. In regions outside the beam the device, if an integral part of the radiation-producing equipment, shall provide shielding adequate to meet the leakage requirements of the source assembly to which it is attached.
(NCRP 102)

Beam profile
A graph of absorbed dose versus position in a cross sectional plane. Normally the profile is measured in a water phantom along a principal axis.
(ICRU 24)

Beam quality (see also "radiation quality")
The term "quality" refers in a general way to the penetrating power of an x-ray beam. Soft x rays possess low penetrating ability. Hard x rays possess high penetrating ability.
(NCRP 66)

Beam width (half power)
The angular width of a lobe, usually the major lobe, of the radiation pattern, in the plane containing the lobe maximum, subtended by the two points at which the power density level is one-half maximum.
(NCRP 67)

BEAR committee
Advisory Committee on the Biological Effects of Atomic Radiation (precursor of BEIR Committee).
(BEIR III)

BEAR committee
Advisory Committee on the Biological Effects of Atomic Radiation (precursor of BEIR Committee).
(BEIR I)

Becquerel
SI unit of activity. 1 Bq = 1 s^-1. (Read as 1 nuclear transition per second.)
(NCRP 83)

Becquerel (Bq)
One disintegration per second.
(10CFR34.3)

Becquerel (Bq)
The SI unit of activity; 1 Bq = 1 disintegration s^-1.
(ANSI/HPS N13.22-1995)

Becquerel (Bq)
The name for the SI unit of activity, 1 Bq = 1 s^-1
(ICRP 68)

Becquerel (Bq)
A unit of radioactivity. One becquerel is one nuclear transformation per s.
(NCRP 118)

Becquerel (Bq)
The name for the SI unit of activity, 1 Bq = 1 s^-1
(ICRP 67)

Becquerel (Bq)
SI unit of activity of a radionuclide equal to second to the power minus one.
(IEC 50-393-1993)

Becquerel (Bq)
SI unit of radioactivity. 1 Bq = 1/second (Read as 1 nuclear transition or disintegration per second).
(NCRP 111)

Becquerel (Bq)
A unit of radioactivity equal to one radioactive disintegration per second.
(HPJ 60)

Becquerel (Bq)
The special name for the SI unit of activity. One becquerel is one reciprocal second or 1 s^-1. 3.7 x 10¹⁰ Bq = 1 Ci.
(NCRP 107)

Becquerel (Bq)
SI unit of activity. (See Units).
(BEIR V)

Becquerel (Bq)
The special name for the SI unit of activity. One becquerel is one reciprocal second or 1 s^-1. 3.7 x 10¹⁰ Bq = 1 Ci.
(NCRP 102)

Becquerel (Bq)
The special name for the unit of activity in SI. 1 Bq = 1 s^-1, i.e., one disintegration per second. 1 Bq = 27 x 10^-12 Ci.
(NCRP 105)

Becquerel (Bq)
A special unit of activity in S.I. units. It is numerically equal to one per second. 1 Bq = 27 pCi.
(NCRP 103)

Becquerel (Bq)
The special name for the unit of activity in the SI. 1 Bq = 1 s^-1.
(NCRP 101)

Becquerel (Bq)
SI unit of activity. (See Units).
(BEIR IV)

Becquerel (Bq)
On nuclear disintegration per second; the name for the SI unit of activity. 1 Bq = 2.7 x 10^-11 Ci.
(FGR 11)

Becquerel (Bq)
The special name for the SI unit of activity, 1 Bq = 1 s^-1 (approximately 2.7 x 10^-11 Ci).
(ICRP 30)

BEIR committee
Advisory Committee on the Biological Effects of Ionizing Radiations.
(BEIR III)

BEIR committee
Advisory Committee on the Biological Effects of Ionizing Radiations.
(BEIR I)

BEIR III-1980
Refers to the third National Research Council's Committee of Biological Effects of Ionizing Radiation, as well as to the report published by this committee in 1980.
(BEIR V)

Beneficiation
Preliminary conditioning of an ore for refinement.
(NCRP 118)

Bent beam linear accelerator
A linear accelerator geometry in which the accelerated electron beam must change direction by 270° to strike the target.
(NCRP 102)

Benthic
Relating to or occurring at the bottom of a body of water.
(NUREG/CR 3332)

Benthos
Aquatic bottom-dwelling organisms (benthic organisms).
(NCRP 76)

Beryllium prospecting meter
Radiation prospecting meter for beryllium ores, its operation being usually based on gamma-neutron reaction in beryllium due to a gamma radiation source, the neutrons produced being counted after being moderated.
(IEC 50-394-1993)

Best available technology (BAT)
The preferred technology for a particular activity, selected from among others after taking into account factors related to technology, economics, public policy, and other parameters. As used in this part, the BAT is not a specific level of treatment, but is the conclusion of a selection process in which several alternatives are evaluated.
(10CFR834.2)

BET method
Brunauer-Emmett-Teller method; procedure using the adsorption isotherm of a material to measure its surface area.
(AM-1993)

Beta cutoff energy
The minimum energy required of a beta particle for that particle to travel a specific distance through a known media.
(ANSI N42.17C-1989)

Beta cutoff energy
The minimum energy required of a beta particle for that particle to travel a specific distance through a known media.
(ANSI N42.17A-1989)

Beta decay
Radioactive decay in which a beta particle is emitted or in which orbital electron capture occurs.
(NCRP 118)

Beta decay
Radioactive decay in which a beta particle is emitted or in which orbital electron capture occurs.
(ANSI N1.1-1976)

Beta gauge
A method of mass measurement which relies on the attenuation of a beam of beta particles.
(AM-1993)

Beta particle
A energetic electron emitted in certain nuclear decay processes.
(AM-1993)

Beta particle
Electron or positron, which has been emitted by an atomic nucleus during a nuclear transformation or which results from the disintegration of a neutron or of an unstable particle.
(IEC 50-393-1993)

Beta particle
A charged particle emitted from the nucleus of an atom and having a mass and charge equal in magnitude to those of the electron.
(HPJ 60)

Beta particle
An electron, of either positive or negative charge, emitted by an atomic nucleus during a nuclear transformation.
(NCRP 111)

Beta particle
A charged particle emitted from the nucleus of certain unstable atomic nuclei, having the charge and mass of an electron.
(BEIR V)

Beta particle
Charged particle emitted from the nucleus of an atom, with mass and charge equal to those of an electron.
(BEIR III)

Beta particle
An elementary particle emitted from a nucleus during radioactive decay, having a single electrical charge and a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron.
(NCRP 65)

Beta particle
An electron, of either positive or negative charge, which has been emitted by an atomic nucleus or neutron in a nuclear transformation.
(ANSI N1.1-1976)

Beta particle
Charged particle emitted from the nucleus of an atom, with a mass and charge equal in magnitude to that of the electron.
(BEIR I)

Beta particle or rays (b)
Electrons, positive or negative, emitted by a nucleus of a radioactive atom when it disintegrates.
(NCRP 48)

Beta particles (beta rays)
Electrons, positive or negative, emitted during radioactive disintegration.
(NBS 73)

Beta particles (beta rays)
Electrons, positive or negative, emitted during radioactive disintegration.
(NBS 54)

Beta radiation
Ionizing radiation composed of beta particles.
(IEC 50-393-1993)

Beta radiation (or particles)
Electrons emitted from a radioactive nucleus during decay.
(NCRP 105)

Beta rays (or beta particles)
Electrons (either negative or positive) emitted during radioactive disintegration.
(NBS 66)

Beta treatment
The formation of beta-phase uranium by appropriate heating followed by rapid cooling. This improves dimensional stability, particularly under irradiation, by producing randomly oriented grains.
(ANSI N1.1-1976)

Beta-gamma doorway monitor
Radiation monitor with detectors arranged about a doorway to measure beta or gamma emission rate due to contamination of persons or objects passing through the doorway.
(IEC 50-394-1993)

Betatron
A machine capable of emitting very high energy x rays or electrons.
(NCRP 48)

Betatron
A doughnut-shaped accelerator in which electrons traveling in an orbit of constant radius, are accelerated by a changing magnetic field. Energies as high as 340 MeV have been attained.
(USAEC-1974)

Betatron
A magnetic induction accelerator which makes use of a varying magnetic field to accelerate electrons. Electrons are injected into a toroidal vacuum chamber which is between the poles of an iron-core magnet. The rate of change of the magnetic flux and the magnetic field at the orbit radius are related to maintain a constant radius for the accelerating electrons.
(RHH)

Betatron (induction accelerator)
A device for the acceleration of particles, ordinarily electrons, in a circular orbit in an increasing magnetic field by means of magnetic induction.
(NBS 55)

BeV
Symbol of billion (or 10⁹) electron volts. Also written as BeV.
(USAEC-1974)

Bias
The deviation of the expected value of a random variable from the corresponding correct or assigned value.
(10CFR74.4)

Bias
The deviation of a single measured value of a random variable from a corresponding expected value, or a fixed mean deviation from the expected value that remains constant over replicated measurements within the statistical precision of the measurement. (Synonyms: deterministic error, fixed error, systematic error.)
(HPS N13.30-1996)

Bias
Consistent difference between a measurement and a true or accepted value.
(AM-1993)

Bias
A systematic error inherent in a method of caused by some artifact or idiosyncrasy of the measurement system. Temperature effects and extraction inefficiencies are examples of this first kind. Blanks, contamination, mechanical lossess, and calibration errors are examples of the latter kinds. Bias may be both positive and negative, and several kinds can exist concurrently, so net bias is all that can be evaluated, except under special conditions.
(HPJ 60)

Bias
(a) The deviation of the expected value of a random variable from a corresponding correct value.
(b) A fixed deviation from the true value that remains constant over replicated measurements within the statistical precision of the measurement.
(Synonyms: deterministic error, fixed error, systematic error.)
(ANSI N13.30-1989D)

Bias
The difference between a population mean of measurements or test results and an accepted reference or true value.
(ANSI N15.54-1988)

Bias
The bias of the values of the performance index, P_i, is:

where the sum is extended over all n values of P_i for a particular test in a given radiation category, interval of absorbed dose indexes, and phantom depth.
(ANSI N13.15-1985)

Bias
The tendency for an estimate to deviate from an actual or real event. Bias may be the tendency for a model to over or under-predict.
(NCRP 76)

Bias
A constant error that appears as a persistent positive or negative deviation of the method average from the true or reference value.
(ANSI N15.36-1983)

Bias
The bias of the values of the performance quotient, P_i, is:

where the sum is extended over all n values of P_i for a particular test in a given radiation category, and for a particular phantom depth (shallow or deep).
(ANSI N13.11-1983)

Bias
The tendency for an estimate to deviate from an actual or real event. Bias may be the tendency for a model to over or under-predict.
(NUREG/CR 3332)

Bias Statistic
An estimation of bias calculated from a finite sample of data using a specified formula.
(HPS N13.30-1996)

Bias statistic
An estimation of bias calculated from a finite sample of data using a specified formula.
(ANSI N13.30-1989D)

Bias, B
The bias of the values of the performance quotient, P_i , is set equal to the average of these values:

where the sum is extended over all n values of P_i for a particular test in a given radiation category (or subcategory), and for a particular phantom depth (shallow or deep).
(ANSI/HPS N13.11-1993)

Biennially
Occurring every two years (not to exceed 30 months).
(ANSI/ANS-15.4-1988)

Bifurcation
The point at which a tube in the lung divides to form the next generation.
(ENV RAD)

Bimodal size distribution
Particle size distribution with two distinct maxima.
(AM-1993)

Bin
A crate used primarily in the NIM system.
(IEC 50-394-1993)

Binary signal
Two-state digital signal.
(IEC 50-394-1993)

Binding energy
- For an atomic nucleus: the net energy required to decompose it into its constituent particles. - For a particle in a system : the net energy required to remove it from the system
(IEC 50-393-1993)

Binding energy
(1) For a particle in a system, the net energy required to remove it from the system. (Sometimes called separation energy.)
(2) For a system, the net energy required to decompose it into its constituent particles.
(Also called total binding energy.)
(ANSI N1.1-1976)

Binding energy
The binding energy of a nucleus is the minimum energy required to dissociate it into its component neutrons and protons. Neutron or proton binding energies are those required to remove a neutron or proton, respectively, from a nucleus. Electron binding energy is that required to remove an electron from an atom or a molecule.
(USAEC-1974)

Binormal ROC curve
An ROC curve that can be represented by the mathematical expression TPF = F (a + b · Z_FPF) where F (·) represents the cumulative standard-normal distribution function, Z_FPF indicates the normal deviate which corresponds to FPF, and a and b are adjustable parameters. Most empirical ROCs are well approximated by this form.
(ICRU 54)

Bioaccumulation factor
The ratio of radionuclide concentration in an organism to that in water.
(NUREG/CR 3332)

Bioaccumulation factor (BF)
The ratio of a radionuclide concentration in an organism or tissue to that in water or food products.
(NCRP 123I)

Bioaccumulation factor (BF)
The ratio of a radionuclide concentration in an organism or tissue to that in water or food products.
(NCRP 76)

Bioaerosol
A suspension of particles of biological origin; viable or dead cells; spores or pollen grains; fragments, products, or residues of organisms.
(AM-1993)

Bioassay
Determination of the kind, quantity, concentration, and/or location of radioactive material in the human body (i.e., in vivo bioassay) or in excreta removed from the body (i.e., in vitro bioassay).
(HPS N13.42-1997)

Bioassay
Another word for radiobioassay.
(HPS N13.30-1996)

Bioassay
The determination of the kind, quantity, location, and/or retention of radionuclides in the body by direct (in vivo) measurement or by indirect (in vitro) analysis of material excreted or removed from the body.
(ANSI/HPS N13.22-1995)

Bioassay
The determination of kinds, quantities, or concentrations, and, in some cases, locations of radioactive material in the human body, whether by direct measurement or by analysis, and evaluation of radioactive materials excreted or removed from the human body.
(10CFR835.2-1993)

Bioassay
An analysis of body fluids, tissue, or excreta to determine the absence of degree of presence of radioactive materials. Used as an index of radioactivity in the body.
(HPJ 60)

Bioassay
The determination of the kind, quantity or concentration, and location of radioactive material in the body by direct (in vivo) measurement or by analysis or materials excreted or removed from the body.
(ANSI N13.14-1983)

Bioassay
A determination of the concentration of a substance in a human body by an analysis of urine feces, blood, bone or tissue.
(ANSI Z88.2-1980)

Bioassay
The determination of kinds, amounts, or concentrations and locations of radioactive materials in the human body, whether by direct measurement (in vivo counting) or by analysis and evaluation of materials excreted or removed from the human body.
(ANSI N43.1-1978)

Bioassay
The determination of the kind, quantity or concentration, and location of radioactive material in the human body by direct (in vivo) measurement or by analysis of materials excreted or removed from the body.
(ANSI N343-1978)

Bioassay
Analysis of biological material to determine the presence and quantities of internally deposited radionuclides.
(USAS N13.2-1969)

Bioassay
Analysis of excreta to determine the absence or degree of presence of radioactive material.
(ANSI N13.6-1966)

Bioassay (radiobioassay)
The determination of the kinds, quantities or concentrations, and, in some cases, the locations of radioactive material in the human body, whether by direct measurement (in vivo counting) or by analysis and evaluation of materials excreted or removed from the human body.
(10CFR20.1003)

Bioassay Area
Any work area where unencapsulated radioactive material is present in a form and quantity such that there is significant potential to receive an intake equal to or greater than the investigation level.
(HPS N13.42-1997)

Bioassay area
Any airborne radioactivity area and any other area where unencapsulated radioactive material is present in a form and quantity such that the area has a significant potential of becoming an airborne radioactivity area as defined by the Code of Federal Regulations, Title 10, Part 20, paragraph 20.203(d).
(ANSI N343-1978)

Bioassay Compartment
A physiological entity, such as an organ, tissue, or cells of a particular type. Material entering such compartments is assumed to instantaneously mix uniformly with material already present in the compartment. Excreta compartments (e.g., urine samples) are included in this definition.
(HPS N13.42-1997)

Bioassay procedure
A procedure used to determine the kind, quantity, location and/or retention of radionuclides in the body by direct (in-vivo) measurements or by in-vitro analysis of material excreted or removed from the body.
(NCRP 118)

Biochemical
Characterized, produced by, or involving chemical reactions in living organisms.
(HPJ 60)

Biodistribution kinetics
A mathematical description of the in vivo distribution of a radionuclide as a function of time following its administration. This may be given as a sum of exponential terms, for a given organ.
(MIRD)

Biohazards
Micro-organisms or viruses which cause disease, or substances such as toxins or venoms produced by living organisms.
(NCRP 111)

Biokinetic model
A set of mathematical relationships formulated to relate the intake to the uptake, distribution, and retention of a radionuclide in various organs and tissues of the body. Some models include subsequent excretion from the body by various pathways. Note: A biokinetic model is used in ICRP Publication 30 in conjunction with an intake model to estimate dose per unit intake of particulates containing radionuclides. Sometimes the term "metabolic model" is used to connote "biokinetic model."
(ANSI/HPS N13.22-1995)

Biokinetic model
A series of mathematical relationships formulated to describe the intake, uptake and retention of a radionuclide in various organs of the body and the subsequent excretion from the body by various pathways.
(HPJ 60)

Biologic disappearance constant, l_h (or l_j)
The fraction of the radionuclide that is removed from the source organ h (or the j-th component of the fraction removed) per unit time, by biologic processes.
(MIRD)

Biologic half-time, T_j
The time in which one-half of the j-th exponential component of a particular radionuclide is removed from a specific source organ by biologic processes.
(MIRD)

Biological dose
The radiation dose absorbed in biological material. Measured in rems.
(USAEC-1974)

Biological dosimetry
Measurement of the degree of a biological response to radiation, that is then used indirectly as a measure of the absorbed dose received by a tissue.
(ICRU 30)

Biological half-life (T_b)
The time required for a biological system, such as a person, to eliminate by natural process, other than radioactive decay, one-half of the amount of a substance, such as a radionuclide that has entered it.
(HPJ 60)

Biological half-time
The time required for the body to eliminate one-half of an administered dosage of any substance by regular processes of elimination.
(NCRP 81)

Biological half-time
The time required for the body to eliminate one-half of an administered dosage of any substance by regular processes of elimination.
(NCRP 75)

Biological half-time
The time required for a biological system to eliminate, by natural processes, half the amount of a substance (e.g., radioactive material) that has entered it.
(NCRP 65)

Biological half-time
The time required for the body to eliminate one-half of an administered dosage of any substance by regular processes of elimination.
(NCRP 62)

Biological half-time
The time required for a biological system to eliminate, by natural processes, half the amount of a substance (e.g., radioactive material) that has entered it.
(USAEC-1974)

Biological shield
Shield whose prime purpose is to reduce ionizing radiation to biologically permissible levels.
(IEC 50-393-1993)

Biological shield
A mass of absorbing material placed around a reactor or radioactive source, to reduce the radiation to a level that is safe for human beings.
(USAEC-1974)

Biological/Pathological/infectious Low-Level Radioactive Waste
A waste stream consisting of research animal carcasses, tissues/body fluids, syringes and other materials that have come into contact with tissues/body fluids, and discarded viral/microbiological material that is contaminated with radioactivity.
(ANSI/HPS N13.45-1998)

Biosphere
The life zone of the earth, including the lower part of the atmosphere, the hydrosphere, soil, and the lithosphere to a depth of about two kilometers.
(NCRP 81)

Biosphere
The life zone of the earth, including the lower part of the atmosphere, the hydrosphere, soil, and the lithosphere to a depth of about two kilometers.
(NUREG/CR 3332)

Biosphere
The life zone of the earth, including the lower part of the atmosphere, the hydrosphere, soil, and the lithosphere to a depth of about two kilometers.
(NCRP 75)

Bipolar ion field
Region in which ions of both polarities exist.
(AM-1993)

Bird cage
A container and attached cage-like structure for maintaining a safe distance between a body of fissile material and other objects (including other bodies of fissile material), which if brought to close, might give rise to criticality.
(ANSI N1.1-1976)

Birefringence
The interaction of an electromagnetic wave with an anisotropic medium resulting in a differential propagation velocity for two components of the wave. For some directions of propagation this will result in the splitting of a single incident wave into two refracted waves (in addition to the reflected wave), one for each of two linear polarizations determined by the medium. Each refracted wave is associated with a different index of refraction. The paths and intensities of the refracted waves are functions of the direction and polarization characteristics of the incident wave.
(NCRP 67)

Black
Allowing no transmission or reflection of radiation.
(ANSI N1.1-1976)

Black (reactor technology)
Of a body or medium, effectively absorbing all of the radiation of some specified energy or range of energies incident on it.
(ANSI N1.1-1976)

Black body
An ideal body that is in thermal equilibrium with the electromagnetic energy incident upon it. It behaves as if the incident energy is completely absorbed. The electromagnetic energy radiated by such a body in each spectral region is the maximum obtainable from any body at the same temperature.
(NCRP 67)

Blank
The measured value obtained when a specified component or a sample is not present during the measurement. In such a case, the measured value/signal for the component is believed to be due to artifacts, hence should be deducted from a measured value to give a net value due to the component contained in a sample. The blank measurement must be made so that the correction process is valid.
(HPJ 60)

Blanket
Region of fertile material placed around or within the core of a reactor for the purpose of conversion.
(IEC 50-393-1993)

Blanket
A region of fertile material placed around or within a reactor core for the purpose of conversion. By extension, the term blanket may be used when the purpose is transformation of nonfertile material.
(ANSI N1.1-1976)

Blanket
A layer of fertile material, such as uranium-238 or thorium-232, placed around the fissionable material in a reactor.
(USAEC-1974)

Blast wave
A pulse of air, propagated from an explosion, in which pressure increases sharply at the front of a moving air mass, accompanied by strong, transient winds.
(USAEC-1974)

Blind sample
A sample submitted for analysis whose composition is known to the submitter but unknown to the analyst. A blind sample is one way to test proficiency of a measurement process.
(HPJ 60)

Blind Testing
Testing of capabilities when the service laboratory is not aware that they are being tested for conformance.
(HPS N13.30-1996)

Blood dyscrasia
Any persistent change from normal of one or more of the blood components.
(RHH)

Body burden
The quantity of radioactive material contained in the individual's body at a particular point in time.
(HPJ 60)

Body burden
The quantity of radioactive material contained in the individual's body at a particular point in time.
(NCRP 87)

Body burden
The total quantity of a radionuclide in the whole body.
(ANSI N13.14-1983)

Body burden
The total quantity of radionuclide present in the body.
(ANSI N343-1978)

Body burden
The total quantity of radionuclide present in the body.
(ANSI N1.1-1976)

Body burden
The amount of radioactive material present in the body of a man or an animal.
(USAEC-1974)

Body burden
The total quantity of radionuclide present in the body.
(ANSI N13.6-1966)

Body burden, maximum permissible
The body burden of a radionuclide which, if maintained at a constant level, would produce the maximum permissible dose equivalent in the critical organ.
(ANSI N1.1-1976)

Body phantom
A phantom in the shape of a human body or part of it. A body phantom is generally composed of various tissue substitutes simulating the human body or a part of the body with respect to size, shape, position, mass density, and radiation interactions.
(ICRU 44)

Body section radiography
See tomography.
(NCRP 102)

Body-present
A body-present quantity is one defined in the human body or in a phantom with dimensions comparable with those of the human body.
(ICRU 43)

Boiling water reactor
A reactor in which water, used as both coolant and moderator, is allowed to boil in the core. The resulting steam can be used directly to drive a turbine.
(USAEC-1974)

Boiling water reactor (BWR)
A nuclear reactor in which water used for coolant is allowed to boil.
(NCRP 81)

Boiling water reactor (BWR)
A nuclear reactor in which water used for coolant is allowed to boil.
(NCRP 75)

Boiling water reactor (BWR)
A nuclear reactor in which water used for coolant is allowed to boil.
(NCRP 62)

Boltzmann charge distribution
Residual or minimum charge distribution on particles after exposure to a bipolar ion field.
(AM-1993)

Bolus
A tissue substitute placed next to the irradiated object to provide extra scattering or build-up or attenuation in the beam. Its purpose is usually to even out the irregular contours of a patient in order to present a plane incident surface to the beam.
(ICRU 44)

Bolus
Tissue-equivalent material placed around the irradiated object to provide extra scattering, buildup or attenuation of the beam. Its purpose is often to even out the irregular contours of the object to be irradiated in order to present a plane incident surface normal to the beam.
(ICRU 30)

Bolus
Additional tissue-equivalent material placed around the irradiated object to provide extra scattering or attenuation.
(ICRU 23)

Bond (reactor technology)
1) The intimated contact between fuel and can or cladding. It is called metallurgical when the materials are so close that inter-atomic forces are operative and mechanical if the contact is less intimate.
2) A material effecting the intimate contact between fuel and can or cladding.
(ANSI N1.1-1976)

Bone
Bone is defined as calcified matrix. It is comprised of organic matrix, bone crystals, an amorphous mineral component, and the water within organic matrix and within lacunae and canaliculi. It does not include the spaces within the blood-carrying haversian or Volkmann canals and it does not include marrow. It does not include cartilage. Its density is taken to be 2.0 g/cm³ and its calcium content 0.4-0.5 g Ca/cm³.
(ICRP 20)

Bone marrow
The soft organic material that fills the cavities of the bones.
(HPJ 60)

Bone marrow
Soft material which fills the cavity in most bones; it manufactures most of the formed elements of the blood.
(RHH)

Bone seeker
Any compound or ion that migrates preferentially into bone after reaching the systemic circulation.
(HPJ 60)

Bone seeker
A radioisotope that tends to accumulate in the bones when it is introduced into the body. An example is strontium-90, which behaves chemically like calcium.
(USAEC-1974)

Bone seeker
Any compound or ion which migrates in the body preferentially into bone.
(BEIR I)

Bone surface
Bone surface is the surface of bone as seen in a light microscope. It includes the endosteal and periosteal surfaces of cortical bone, the surfaces of haversian and Volkmann canals, the surfaces of resorption cavities, and the surfaces of trabeculae. It does not include the surfaces of lacunae or canaliculi. It should not be confused with the surfaces of the sub-microscopic bone crystals.
(ICRP 20)

Bone volume
Bone as bounded by bone surface. It includes the volume of lacunae and canaliculi but does not include the marrow or the space within the haversian or Volkmann canals.
(ICRP 20)

Bone-seeker
Any compound or ion that migrated in the body preferentially into bone.
(BEIR III)

Bone-seeker
Any substance which migrates, in-vivo, preferentially into bone.
(ANSI N1.1-1976)

Booster element
A fuel element temporarily inserted in a thermal reactor core to provide xenon override.
(ANSI N1.1-1976)

Boral
A dispersion of boron carbide in aluminum used as a neutron absorber.
(ANSI N1.1-1976)

Boron chamber
An ionization chamber utilizing a nuclear reaction with ¹⁰B for the detection and measurement of slow neutrons.
(ANSI N1.1-1976)

Boron coated semiconductor detector
Semiconductor detector containing boron-10 in the form of a coating on its surface to detect thermal neutrons.
(IEC 50-394-1993)

Boron counter tube
A radiation counter tube, utilizing a nuclear reaction with ¹⁰B for the detection of slow neutrons.
(ANSI N1.1-1976)

Boron trifluoride ionization chamber
Ionization chamber using boron trifluoride to detect thermal neutrons.
(IEC 50-394-1993)

Boron trifluoride proportional counter tube
Proportional counter tube containing boron trifluoride to detect thermal neutrons.
(IEC 50-394-1993)

Boron-lined counter tube
Counter tube containing a boron sensitive lining on its walls on appropriately shaped electrodes to detect thermal neutrons.
(IEC 50-394-1993)

Boron-lined ionization chamber
Ionization chamber using a boron sensitive lining on its walls or on appropriately shaped electrodes to detect thermal neutrons.
(IEC 50-394-1993)

Boundary layer
Region of flow near the bounding surface, where the flow is dominated by friction forces resulting in reduced flow velocity relative to the free stream.
(AM-1993)

Boundary layer
The portion of a moving fluid in which turbulent diffusion is taking place. This turbulence may be due to mechanical effects, thermal effects, or some combination of both.
(NCRP 76)

Bowing
1) Of a fuel element or fuel assembly, bending due to a nonuniform temperature distribution, externally applied loads or inelastic strains resulting from irradiation, or some combination of these three factors.
2) Of a fuel charge, an uneven distribution of fuel used to produce a desired neutron flux density or power distribution.
(ANSI N1.1-1976)

Box model
A pollutant transport model based on mass conservation of the pollutant in a specified volume. Such models are inherently simple but physically sound.
(NCRP 76)

Bq-becquerel
The name for the SI unit of radioactivity, 1 Bq = 1 transformation s^-1.
(ICRP 66)

Brachytherapy
Use of an encapsulated source to deliver gamma or beta radiation at a distance up to a few centimeters by surface, intracavitary or interstitial application.
(NCRP 107)

Brachytherapy
Use of an encapsulated source to deliver gamma or beta radiation at a distance up to a few centimeters by surface, intracavitary or interstitial application.
(NCRP 105)

Brachytherapy
A method of radiation therapy in which an encapsulated source or group of sources is utilized to deliver beta or gamma radiation at a distance of a few centimeters, by surface, intracavitary or interstitial application.
(NCRP 48)

Brachytherapy
A method of radiation therapy in which an encapsulated source is utilized to deliver beta or gamma radiation at a distance of a few centimeters, by surface, intracavitary or interstitial application.
(NCRP 49)

Brachytherapy
Radiation treatment using solid or enclosed radioisotopic source on the surface of a body or at a short distance from the area to be treated.
(USAEC-1974)

Brachytherapy
Therapy at short distances with beta or gamma radiation. Implantation or placement therapy with needles, inserts or other such applications containing radioactive materials. Useful in the treatment of various diseases.
(RHH)

Brachytherapy source
An individual sealed source or a manufacturer-assembled source train that is not designed to be disassembled by the user.
(10CFR35.2)

Bragg-gray cavity
Ideal cavity containing gas within a solid medium, sufficiently small so as not to disturb the distribution of either primary or secondary radiation in the medium.
(IEC 50-394-1993)

Bragg-gray cavity ionization chamber
Ionization chamber intended to determine the exposure or absorbed dose from X or gamma radiation or neutrons in a medium.
(IEC 50-394-1993)

Bragg-gray principle
The relationship between energy absorbed in a small gas-filled cavity in a medium to energy absorbed (in the medium) from ionizing radiation. The relationship is expressed as:

where:
E = energy/cc absorbed in the medium;
W = average energy needed to produce and ion pair in the gas;
J = the number of ion pairs/cc formed in the gas; and
S = ratio of the stopping power for secondary particles in the medium to that in the gas.
(RHH)

Bragg-grey relation
A relationship stating that the ionization produced in a small gas-filled cavity in a homogeneous medium by a uniform field of ionizing radiation is proportional to the absorbed dose in that medium.
(ANSI N1.1-1976)

Branch
A duct or pipe connecting an exhaust hood to a main or submain.
(ANSI Z9.2-1971)

Branching
The occurrence of two or more modes by which a radionuclide can undergo radioactive decay. For example, RaC can undergo alpha or Beta minus decay. An individual atom of a nuclide exhibiting branching disintegrates by one mode only. The fraction disintegrating by a particular mode is the "branching fraction" for that mode. The "branching ratio" is the ratio of two specified branching fractions (also called multiple disintegration).
(RHH)

Branching Angle
Angle of change in direction of the bulk air-flow moving from the parent airway segment into the daughter segment.
(NCRP 125)

Branching fraction
In branching decay: the fraction of nuclei which disintegrate in a specified way. It is usually expressed as a percentage.
(ANSI N1.1-1976)

Branching ratio
Ratio of the branching fractions for two specified modes of disintegration.
(IEC 50-393-1993)

Branching ratio
The ratio of the branching fractions for two specified modes of disintegration.
(ANSI N1.1-1976)

Breakdown (of a reverse biased PN junction)
Transition from a state of high resistance to a state of substantially lower resistance for increasing magnitude of reverse voltage.
(IEC 50-394-1993)

Breathing Frequency
Number of breaths per unit time.
(NCRP 125)

Breathing Mode
Fraction of inhalation and exhalation of air through the nose and mouth (air passing each way, such as 100/0 percent, 50/50 percent, etc).
(NCRP 125)

Breathing tube
A tube through which air or oxygen flows to the facepiece, mouthpiece, helmet, hood, or suit.
(ANSI Z88.2-1980)

Breathing tube
A tube through which air or oxygen flows to the facepiece, helmet, or hood.
(ANSI Z88.2-1969)

Breathing zone
The breathing zone is identified as that region adjacent to a worker's mouth and nostrils from which air is drawing into the lungs while he performs his assigned work. Air taken from this region will truly represent the air the worker is breathing while he works, whether standing, sitting or moving.
(ANSI N13.1-1969)

Breathing Zone Air Sample (BZA)
An air sample considered to be representative of the air inhaled by a worker.
(HPS N13.42-1997)

Breathing zone air sampler (BZA)
This term is used for an air sampling device that collects airborne nuclides in a work place location near the point of a worker's inhalation. This device is designed to quantify a worker's inhalation exposure.
(ANSI/HPS N13.22-1995)

Breathing zone sample
A sample taken as close as possible to the point at which the subject inhales air; represents a subject's inhaled air.
(AM-1993)

Breeder reactor
Reactor which produces more fissile material than it consumes, i.e. has a conversion ratio greater than unity.
(IEC 50-393-1993)

Breeder reactor
A nuclear reactor that produces more fissile material than it consumes.
(NCRP 62)

Breeder reactor
A reactor that produces fissionable fuel as well as consuming it, especially one that creates more than it consumes. The new fissionable material is created by capture in fertile materials of neutrons from fission. The process by which it occurs is known as breeding.
(USAEC-1974)

Breeding
Conversion in a nuclear reactor when the conversion ratio is greater than unity.
(IEC 50-393-1993)

Breeding
Conversion when the conversion ratio is greater than unity.
(ANSI N1.1-1976)

Breeding
(See breeder reactor.)
(USAEC-1974)

Breeding gain
Breeding ratio minus one.
(IEC 50-393-1993)

Breeding gain
Breeding ratio minus one.
(ANSI N1.1-1976)

Breeding gain
See breeding ratio.
(USAEC-1974)

Breeding ratio
A conversion ratio which is greater than unity.
(IEC 50-393-1993)

Breeding ratio
The conversion ratio when it is greater than unity.
(ANSI N1.1-1976)

Breeding ratio
The ratio of the number of fissionable atoms produced in a breeder reactor to the number of fissionable atoms consumed in the reactor. Breeding gain is the breeding ratio minus one.
(USAEC-1974)

Breit-wigner formula
A formula describing the cross section for a nuclear reaction in the vicinity of one or more resonances. For a single resonance, the formula is

where
s (x,y) = cross section for particle x to enter and y to leave a nucleus
G _x = partial width of the energy level for reemission ox x without energy loss
G _y = partial width of the energy level for emission of y
G = total width of the level
* = l /2p , where l is the de Broglie wavelength
l = orbital angular momentum quantum number of the incident particle
E = energy of the reactants
Eo = resonance energy
(ANSI N1.1-1976)

Bremsstrahlung
Ionizing radiation produced by the deceleration or the acceleration of charged particles.
(IEC 50-393-1993)

Bremsstrahlung
Secondary photon radiation produced by deceleration of charged particles passing through matter.
(HPJ 60)

Bremsstrahlung
Secondary photon radiation produced by deceleration of charged particles.
(NCRP 98)

Bremsstrahlung
The production of electromagnetic radiation (photons) by the acceleration (positive or negative) that a fast charged particle (usually an electron) undergoes from the effect of an electric or magnetic field; for instance, from the field of another charged particle (usually a nucleus).
(BEIR IV)

Bremsstrahlung
Secondary photon radiation produced by deceleration of charged particles passing through matter.
(BEIR III)

Bremsstrahlung
The electromagnetic radiation associated with the acceleration or deceleration of charged particles, particularly in the vicinity of the Coulomb fields of nuclei.
(NCRP 51)

Bremsstrahlung
The electromagnetic radiation associated with the deceleration of charged particles. The term is also applied to the radiation associated with acceleration of charged particles.
(ANSI N1.1-1976)

Bremsstrahlung
Electromagnetic radiation emitted (as photons) when a fast-moving charged particle (usually an electron) loses energy upon being accelerated and deflected by an electric field surrounding a positively charged nucleus. X rays produced in ordinary X-ray machines are bremsstrahlung. (in German, the term means "braking radiation".)
(USAEC-1974)

Bremsstrahlung
Secondary photon radiation produced by deceleration of charged particles passing through matter.
(BEIR I)

Bremsstrahlung
Secondary photon radiation produced by deceleration of charged particles passing through matter.
(RHH)

Bremsstrahlung
See X-rays.
(NBS 55)

Bridge potential
The potential difference (voltage) between the two opposing junctions of a resistance bridge calorimeter that are not directly connected to the constant-current source. The bridge potential is directly proportional to the temperature difference between the two sides (reference and sample) of the calorimeter.
(ANSI N15.54-1988)

British Thermal Unit (BTU)
The quantity of thermal energy required to raise the temperature of one pound of water 1 °F at, or near, its point of maximum density (39.1 °F).
(ANSI/HPS N13.45-1998)

British thermal unit (BTU)
The quantity of heat required to increase the temperature of one pound of water one degree Fahrenheit at atmospheric pressure; approximately 252 gram-calories.
(RHH)

Broad beam
In beam attenuation measurements, a beam in which the unscattered and some of the scattered radiation reach the detector.
(ANSI N1.1-1976)

Broad beam conditions
Conditions of a radiation-shielding situation in which the beam impinging on the shield surface includes scattered radiation and is laterally extensive.
(NCRP 51)

Bronchi
The two main branches leading from the trachea to the lungs.
(ENV RAD)

Bronchial Asthma
Allergic reaction characterized by a narrowing of the lumen of the bronchial tubes from spasms of the muscles in the walls or a congestive swelling of the bronchial mucous membrane.
(NCRP 125)

Bronchial epithelium
The surface lining of the conducting airways of the lung. The thickness decreased with bronchial generation from about 80 µm in the trachea to 15 µm in the finest airways.
(NCRP 103)

Bronchial epithelium
The surface layer of cells lining the conducting airways. The thickness decreases with bronchial generation from about 80 µm in the trachea to 15 µm in the finest airways.
(NCRP 78)

Bronchial generation
The branches of airways from the trachea to the gas exchange region of the lung. The branches are numbered sequentially from the trachea (generation 0).
(NCRP 78)

Bronchial region (BB)
Consists of the trachea (generation 0) and bronchi, generations 1 through 8.
(ICRP 68)

Bronchial tree
The branching airways of the respiratory tract from the trachea to the entry to the gas exchange or pulmonary region of the lung.
(ICRP 65)

Bronchiolar region (bb)
Consists of the bronchioles and terminal bronchioles; airway generations 9 through 15.
(ICRP 68)

Bronchioles
The small branches of the tracheobronchial tree of the lung.
(BEIR IV)

Bronchioloalveolar Adenoma
Benign lung neoplasm arising from the epithelium lining bronchioles or alveoli.
(NCRP 125)

Bronchioloalveolar Carcinoma
Malignant lung neoplasm arising from the epithelium lining the bronchioles or alveoli.
(NCRP 125)

Bronchus
One of the two main branches arising from the trachea at its bifurcation, one going to each lung.
(NCRP 125)

Brownian motion
Random motion of particles due to collisions with gas molecules.
(AM-1993)

Brush Cell
Tall cells that rest on the basement membrane and have a prominent tuft on the luminal surface scattered among the epithelium of the trachea, bronchi and bronchioles.
(NCRP 125)

Bubble chamber
Track chamber based on the principle that in a superheated liquid, bubbles are formed due to the boiling of the liquid along paths of ionizing particles.
(IEC 50-394-1993)

Bubble chamber
A device used for detection and study of elementary particles and nuclear reactions. Charged particles from an accelerator are introduced into a superheated liquid, each forming a trail of bubbles along its path. The trails are photographed, and by studying the photograph scientists can identify the particles and analyze the nuclear events in which they originate.
(USAEC-1974)

Bubble meter
A tube with a defined volume into which bubbles are injected to measure flow rate.
(AM-1993)

Bubbler probe
See pneumatic probe.
(ANSI N15.19-1989)

Buckling
Short for material buckling or geometric buckling. These two quantities are equal of a bare critical reactor.
(ANSI N1.1-1976)

Buckling, geometric
A parameter, B2g, depending on the shape and the external dimensions of an assembly, e.g., a reactor core. For a bare reactor B2g is the eigenvalue of the equation.

(where r is the radius vector and Ñ ² the Laplacian) with the condition that the neutron flux density f (r) be zero at the extrapolated boundary of the assembly.
(ANSI N1.1-1976)

Buckling, material
A parameter, Bm2, providing a measurement of the multiplying properties of a medium as a function of its materials and their disposition. In age-diffusion theory Bm2 is the value of B² satisfying the equation

where k_¥ is the infinite multiplication factor, t the age, and L the diffusion length of the neutron.
(ANSI N1.1-1976)

Budget
The funds appropriated by Congress for the NRC for each fiscal year, and if that appropriation is not passed on or before September 1 for that fiscal year, the funds most recently appropriated by Congress for the most recent fiscal year.
(10CFR171.5)

Budget Authority
The authority, in the form of appropriations, provided by law and becoming available during the year, to enter into obligations that will result in immediate or future outlays involving Federal government funds. The appropriation is an authorization by an Act of Congress that permits the NRC to incur obligations and to make payments out of the Treasury for specified purposes. Fees assessed pursuant to Public Law 101-508 are based on NRC budget authority.
(10CFR171.5)

Buffer zone
A portion of the disposal site that is controlled by the licensee and that lies under the disposal units and between the disposal units and the boundary of the site.
(10CFR61.2)

Build-up
The increase in absorbed dose with depth below the surface in a material irradiated by a beam of x-rays or gamma rays. Build-up may be two kinds:
(a) Electron Build-up: This is due to an increasing electron fluence in the material.
(b) Photon Build-up: This is due to scattering in broad beams of radiation.
For high energy beams, process (a) is the more important.
(NCRP 69)

Build-up factor
In the passage of radiation through a medium, the ratio of the total value of a specified radiation quantity at any point to the contribution to that value from radiation reaching the point without having undergone a collision.
(IEC 50-393-1993)

Buildup
The increase in absorbed dose with depth below the surface in a material irradiated by a beam of x-rays or gamma rays. Build-up may be two kinds:
(a) Electron buildup is due to the production by the incident radiation of increasing numbers of forward-moving high-energy electrons increasing with depth until a maximum electron fluence rate has been reached. This effect gives rise to the phenomenon of "skin sparing" and is most marked for photon energies greater than about 400 keV. The effect is not noticeable for x rays generated by potential of less than 400 kV.
(b) Photon Build-up: Multiple photon scattering in the superficial layers of the phantom, which may lead to an increase in the absorbed dose for a short distance. This effect is observed particularly with photons generated by potentials of 50-150 kV and large field sizes.
For high energy beams, process (a) is the more important.
(ICRU 30)

Buildup
In a material irradiated by a beam of x or gamma rays, the increase in absorbed dose with depth below the surface in a material irradiated by a beam of x-rays or gamma rays. Buildup may be two kinds:
(a) Electron buildup (skin sparing): Electron buildup is due to the production by the photons of increasing numbers of forward-moving high-energy electrons. The buildup of moving electrons increases with depth until a maximum electron fluence rate has been reached. This effect gives rise to the phenomenon of "skin sparing" and is most marked for photon energies greater than about 400 keV. Due to the short range and angular distribution of electrons having energies less than 400 keV, the effect is not noticeable for x rays generated by potentials of less than 400 kV.
(b) Photon Build-up: Multiple photon scattering in the superficial layers of the phantom, which may lead to an increase in the absorbed dose for a short distance. This effect is observed particularly with photons generated by potentials of 50-150 kV and large field sizes. The buildup effect tends to be masked by low energy radiation scattered from the inner surface of the collimator or applicator (q.v.) and by the presence of an artificial surface formed by the end-plate of a closed-ended applicator.
(ICRU 24)

Buildup (of radiation in shield)
That part of the total value of a specified radiation quantity at any point due to radiation that has undergone interactions in the shield or that results from such interactions.
(NCRP 51)

Buildup factor
The ratio of the intensity of X or gamma radiation (both primary and scattered) at a point in an absorbing medium to the intensity of only the primary radiation.
(NUREG/CR 3332)

Buildup factor
In a beam of high-energy x or gamma rays, the ratio of peak absorbed dose to surface absorbed dose is sometimes called the buildup factor.
(ICRU 30)

Buildup factor
In a beam of high-energy x or gamma rays, the ratio of peak absorbed dose to surface absorbed dose is sometimes called the buildup factor.
(ICRU 24)

Buildup factor
In the passage of radiation through a medium, the ratio of the total value of a specified radiation quantity at any point to the contribution to that value from radiation reaching the point without having undergone a collision.
(ANSI N1.1-1976)

Buildup factor
The ratio of the intensity of X or gamma radiation (both primary and scattered) at a point in an absorbing medium to the intensity of only the primary radiation. This factor has particular application for "broad beam" attenuation. "Intensity" may refer to energy flux, dose or energy absorption.
(RHH)

Bulk analysis
Analysis of a sample in its entirety versus analysis of individual particles
(AM-1993)

Bullet/resisting
Protection against complete penetration, passage of fragments of projectiles, and spalling (fragmentation) of the protective material that could cause injury to a person standing directly behind the bullet-resisting barrier.
(10CFR73.2)

Burial
The imbedding of a particle into a filter medium.
(ANSI N13.1-1969)

Burial ground
A land area set aside for the disposal of radioactive or contaminated material. A ground cover serves as radiation shielding.
(ANSI N1.1-1976)

Burial ground
A place for burying unwanted radioactive objects to prevent escape of their radiations, the earth or water acting as a shield. Such objects must be place in watertight, noncorrodible containers so the radioactive material cannot leach out and invade underground water supplies.
(RHH)

Burn Parameters
A set of physical properties, e.g., temperature in primary chamber, whose values determine the efficient destruction of low-level radioactive waste by incineration.
(ANSI/HPS N13.45-1998)

Burn-up
Induced nuclear transformation of atoms during reactor operation.
(IEC 50-393-1993)

Burn-up fraction
Fraction, usually expressed as a percentage, of an initial quantity of nuclei of a given type which has undergone burn-up.
(IEC 50-393-1993)

Burn-up life (of a neutron detector)
Estimated fluence of neutrons of a given energy distribution after which the sensitive material will be consumed to such an extent that the detector characteristics exceed the specified tolerances for a specified purpose.
(IEC 50-394-1993)

Burnable poison
Nuclear poison purposely included in a reactor to help control long-term reactivity changes by its progressive burn-up.
(IEC 50-393-1993)

Burnable poison
Boron or other light elements having high neutron capture cross sections that are added in dissolved form to PWR coolant to reduce reactivity early in core life. The amount added is adjusted so that the high cross section nuclides disappear, "burn" as the reactor core ages.
(NCRP 62)

Burnable poison
Nuclear poison purposely included in a reactor to help control long-term reactivity changes by its progressive burnup.
(ANSI N1.1-1976)

Burnable poison
A neutron absorber (or poison), such as boron, which, when purposely incorporated in the fuel or fuel cladding or a nuclear reactor, gradually "burns up" (is changed into nonabsorbing material) under neutron irradiation. This process compensates for the loss of reactivity that occurs as fuel is consumed and fission-product poisons accumulate, and keeps the overall characteristics of the reactor nearly constant during its use.
(USAEC-1974)

Burner reactor
A converter reactor.
(USAEC-1974)

Burnout heat flux
The local heat flux density at which fuel burnout takes place.
(ANSI N1.1-1976)

Burnout point (reactor technology)
For a liquid cooled reactor, any combination of values of heat-transfer parameters which results in fuel burnout.
(ANSI N1.1-1976)

Burnout ratio
The ratio of nuclear power when the burnout point is reached to the design power. It is a computed quantity used to establish safe design limits.
(ANSI N1.1-1976)

Burnout, fuel (reactor technology)
Severe local damage of a fuel element, due to failure of the coolant to dissipate all the heat produced in the element.
(ANSI N1.1-1976)

Burnup
Induced nuclear transformation of atoms during reactor operation. The term may be applied to fuel or other materials.
(ANSI N1.1-1976)

Burnup
A measure of reactor fuel consumption. It can be expressed as (a) the percentage of fuel atoms that have undergone fission, or (b) the amount of energy produced per unit weight of fuel in the reactor.
(USAEC-1974)

Burnup fraction
The fraction of an initial quantity of a given nuclide that has undergone burnup. It is commonly expressed as a percentage.
(ANSI N1.1-1976)

Burnup, specific
The total energy released per unit mass of a nuclear fuel. It is commonly expressed in megawatt-days per tonne. Also called fuel irradiation level.
(ANSI N1.1-1976)

Burst (in an ionization chamber)
Sudden appearance for a short period of time of a large number of ion pairs due to one or more particles of high energy incident on the filling gas or the walls.
(IEC 50-394-1993)

Burst can
Occurrence of leakage in the cladding.
(IEC 50-393-1993)

Burst of x-radiation
The pulse of X-rays emanating from a circular electron accelerator as a result of one electron acceleration cycle. The duration of the burst is generally of the order of a few microseconds.
(NBS 55)

Bus
An electrical connection between the components of a computer, or programmable instrumentation, along which information is transmitted from any of several sources to any of several destinations.
(IEC 50-394-1993)

Byproduct material
Any radioactive material (except special nuclear material) yielded in or made radioactive by exposure to the radiation incident to the process of producing or utilizing special nuclear material.
(10CFR72.3)

Byproduct material
(1) Any radioactive material (except special nuclear material) yielded in, or made radioactive by, exposure to the radiation incident to the process of producing or utilizing special nuclear material; and
(2) The tailings or wastes produced by the extraction or concentration of uranium or thorium from ore processed primarily for its source material content, including discrete surface wastes resulting from uranium solution extraction processes. Underground ore bodies depleted by these solution extraction operations do not constitute "byproduct material" within this definition.
(10CFR20.1003)

Byproduct material
The tailings or wastes produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content, including discrete surface wastes resulting-from uranium solution extraction processes. Underground ore bodies depleted by such solution extraction operations do not constitute "byproduct material" within this definition.
(10CFR40.4)

Byproduct material
Radioactive material (except special nuclear material) produced by exposure to the radiation incident to the process of producing or using special nuclear material.
(10CFR110.2)

Byproduct Material
Any radioactive material (except special nuclear material) yielded in or made radioactive by exposure to the radiation incident to the process of producing or utilizing special nuclear material.
(10CFR171.5)

Byproduct material
Any radioactive material (except source material or fissionable material) obtained during the production or use of source material or fissionable material. It includes fission products, and many other radioisotopes produced in nuclear reactors.
(USAEC-1974)

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