Borders' Dictionary of Health Physics

De_i
Deposition in region, i, expressed as a fraction of the number or activity of particles of a given size that are present in a volume of ambient air before inspiration.
(ICRP 66)

D₀
The dose on the straight line part of a plot of the logarithm of the fraction of cells surviving versus radiation dose to reduce the fraction of surviving cells to 1/e or 37%.
(ICRP 59)

D₀
The dose on the straight line part of a plot of the logarithm of the fraction of cells surviving versus radiation dose to the fraction of surviving cells to 1/e or 37 percent.
(NCRP 98)

D_a
An effective SNR, more general than d', that applies to situations in which the decision variable (or some monotonic transformation thereof) arises from one of two normal distributions having different means and, generally, different variances. In such situations, the ROC curve depends on two parameters, a and b, and is given by the mathematical expression TPF = F(a + b-ZFPF) where F(·) represents the cumulative standard-normal distribution function and ZFPF represents the normal deviate that corresponds to false positive fraction. The index d,, is then given by the expression da = a Ö[2/(1 + b²)] and is equal to Ö2 times the normal deviate that corresponds to the area under the ROC curve.
(ICRU 54)

d_ae
Aerodynamic particle diameter (µm). Diameter of unit density sphere that has same terminal settling velocity in air as the particle of interest.
(ICRP 66)

d_e
Equivalent volume diameter (µm). Diameter of a sphere that has the same volume as the particle of interest.
(ICRP 66)

D_q
The "quasithreshold dose" is the dose at which the extrapolated straight portion of the dose-response curve cuts the dose axis at unity survival fraction.
(NCRP 98)

d_th
Thermodynamic particle diameter (µm). Diameter of a spherical particle that has the same diffusion coefficient in air as the particle of interest.
(ICRP 66)

D'
In signal detection theory, an effective SNR that applies only to situations in which the decision variable (or some monotonic transformation thereof) arises from one of two normal distributions having equal variances but different means. In such situations, the ROC curve is symmetric about the - 45o diagonal of the unit square in which it is plotted and is given by the mathematical expression TPF = F (d' + ZFPF) where F (·) represents the cumulative standard-normal distribution function and zFPF represents the normal deviate that corresponds to false positive fraction.
(ICRU 54)

Daily
During each 24 hour period.
(NBS 54)

Dancroff correction
In the calculation of the neutron balance in a reactor cell, a correction applied to the resonance integral of an isolated fuel element or fuel assembly in order to obtain the resonance integral of the same element or assembly when near other elements or assemblies.
(ANSI N1.1-1976)

Danger range
Distance from a source of radioactive material at which the gamma radiation is 6.25 mr/hr (0.00625 r/hr).

See definition for Ig. (6.25 mr/hr corresponds to 300 mr for a 48-hr week.)
(NBS 54)

Danger range, specific
Danger range in centimeters for an unshielded point source of 1 mc of a given radioactive substance.
(NBS 54)

Dark current
A current, usually of electrons, that may flow through an acceleration tube or waveguide from sources other than the cathode of the accelerator. This is an abnormal phenomenon, often associated with poor vacuum conditions or contaminated surfaces in the acceleration region.
(NCRP 51)

Dark current (of a photomultiplier tube)
Current flowing in the anode circuit of a photomultiplier tube in the absence of light.
(IEC 50-394-1993)

Data
Information contained in a field of a record.
(NCRP 114)

Data processing
A series of actions or operations to assemble, analyze, or report data.
(ANSI N15.37-1981)

Data standardization model
The steps taken to adjust raw calibration data to a set of standard reference conditions, resulting in a set of "standardized (calibration) data."
(ANSI N15.19-1989)

Data transfer
The moving of data from a device, person, or set of records to some other device, person, or set of records.
(ANSI N15.37-1981)

Daughter
A synonym for decay product.
(HPJ 60)

Daughter
A nuclide formed by the radioactive decay of another nuclide, which in this context is called the parent. (See radioactive series.)
(USAEC-1974)

Daughter
A synonym for decay product.
(BEIR I)

Daughter
A nuclide formed by the decay of a radioactive nuclide. The daughter may be either radioactive or stable.
(NBS 66)

Daughter product
Nuclide formed from a given radionuclide on decaying.
(IEC 50-393-1993)

Daughter product
An isotope formed as a result of radioactive decay. One daughter atom is formed for each particle emitted.
(BEIR IV)

Daughter product
Any nuclide which follows a specified radionuclide in a decay chain.
(ANSI N1.1-1976)

Daughter products
Isotopes that are formed by the radioactive decay of some other isotope. In the case of ²²⁶Ra, for example, there are 10 successive daughter products, ending in the stable isotope ²⁰⁶Pb.
(HPJ 60)

Daughter, daughter product
A nuclide, stable or radioactive, formed by radioactive decay of another nuclide, which in this context is called the parent.
(NCRP 65)

Daughter, daughter product
A nuclide, stable or radioactive, formed by radioactive decay of another nuclide, which in this context is called the parent.
(ANSI N1.1-1976)

Dead layer (of a semiconductor detector)
Layer of a semiconductor detector in which no significant part of the energy lost by particles can contribute to the resulting signal.
(IEC 50-394-1993)

Dead man switch
A switch so constructed that a circuit-closing contact can be maintained only by continuous pressure on the switch.
(NCRP 102)

Dead time (for analyzer)
Sum of time intervals which follow the acceptance of successive input signals, during which the analyzer is not sensitive to other signals.
(IEC 50-394-1993)

Dead time (of a geiger-muller counter tube)
Time interval after the initiation of a pulse caused by an ionizing event, during which a Geiger-Muller counter tube cannot respond to a further ionizing event.
(IEC 50-394-1993)

Dead time (t_b, t_g)
A fixed time interval, following a registered (or a detected) event, during which the counting system is insensitive to other pulses. It is said to be of the non-extendable type if the dead-time interval follows a registered count, but of the extendable type if all detected events initiate a dead-time period. So-called generalized dead times correspond to a model with intermediate behavior.
(ICRU 52)

Dead time (T_d)
The time after triggering a pulse during which the system is unable to retrigger.
(ANSI N42.12-1980)

Dead-man switch
A switch so constructed that it remains activated only by continuous pressure on the switch.
(NCRP 51)

Deadman switch
A device so designed that a closed circuit can be maintained only by continuous operator pressure.
(ANSI N537-1976)

Decade
A range of values for which the upper limit is a power of ten above the lower limit.
(ANSI N42.17C-1989)

Decade
A range of values for which the upper limit is a power of ten above the lower limit.
(ANSI N42.17A-1989)

Decade
A range of values for which the upper limit is a power of ten above the lower limit.
(ANSI N42.17B-1989)

Decade
Synonymous with power of ten.
(ANSI N323-1978)

Decay (radioactive)
Reduction in activity of a quantity of radioactive material by disintegration of its atoms.
(NCRP 48)

Decay chain
A radioactive series
(USAEC-1974)

Decay chain or decay series
A sequence of radioactive decays. An initial nucleus decays into a product nucleus, or progeny, that differs from the parent nucleus by whatever particles were emitted during the decay. If further decays take place, the subsequent nuclei are also usually called decay products or progeny.
(NCRP 103)

Decay chain or decay series
A sequence of radioactive decays of the same nucleus. An initial nucleus, the parent, decays into a daughter nucleus that differs from the first by whatever particles were emitted during the decay. If further decays take place, the subsequent nuclei are also called daughters. Sometimes to distinguish the sequence, the daughter of the first daughter is called the granddaughter, etc.; ordinarily, however, this quickly becomes too complicated.
(BEIR IV)

Decay constant
Symbol l. The fraction of the number of atoms of a radioactive nuclide that decays in unit time.
(HPJ 60)

Decay constant
For a radionuclide: the probability per unit time for the spontaneous decay of one of its nuclei. It is given by

in which N is the number of nuclei of concern existing at time t. (Also called disintegration constant.)
(ANSI N1.1-1976)

Decay constant (l)
For a radionuclide in a particular energy state, quotient of dP by dt, where dP is the probability of a given nucleus undergoing a spontaneous nuclear transition from that energy state in the time interval dt.

(IEC 50-393-1993)

Decay constant (l)
The fraction of the amount of a radionuclide that undergoes transition per unit time. Formally,

where dP is the probability of a given nucleus undergoing a spontaneous nuclear transition in the time interval dt.
(NCRP 83)

Decay constant (l)
The decay constant of a radionuclide in a particular energy state is the quotient dP by dt, where dP is the probability of a given nucleus undergoing a spontaneous nuclear transition from that energy state in the time interval dt.

(ICRU 33)

Decay constant, partial
For a radionuclide: the probability per unit time for spontaneous decay of one of its nuclei by one of several possible decay modes.
(ANSI N1.1-1976)

Decay curve
Curve representing as a function of time the activity of a radioactive substance.
(IEC 50-393-1993)

Decay curve
A curve showing the relative amount of radioactive substance remaining after any time interval.
(HPJ 60)

Decay curve
A plot of activity of a sample, or a selected constituent of a sample, as a function of time.
(ANSI N1.1-1976)

Decay curve
A curve showing the relative amount of radioactive substance remaining after any time interval.
(RHH)

Decay energy
The energy difference between the ground states of parent and daughter; in the case of alpha decay, some of this appears as recoil energy.
(ANSI N15.22-1987)

Decay heat
The heat produced by radioactive materials as nuclides spontaneously transform into other nuclides or into different energy states. Each decay process has a definite half-life.
(ERDA 76-21)

Decay heat
The heat produced by the decay of radioactive nuclides. (See afterheat; decay, radioactive; SNAP.)
(USAEC-1974)

Decay product
A nuclide resulting from the radioactive disintegration of a radionuclide, being formed either directly or as a result of successive transformations in a radioactive series. A decay product may be either radioactive or stable.
(HPJ 60)

Decay product
A nuclide that is formed as a result of radioactive decay.
(NCRP 103)

Decay product
A nuclide, stable or radioactive, formed by radioactive decay.
(ANSI N1.1-1976)

Decay product
A nuclide resulting from the radioactive disintegration of a radionuclide, formed either directly or as the result of successive transformations in a radioactive series. A decay product may be either radioactive or stable.
(BEIR I)

Decay product (synonym, daughter)
A nuclide resulting from radioactive disintegration of a radionuclide, formed either directly or as a result of successive transformations in a radioactive series; may be either radioactive or stable.
(BEIR III)

Decay product(s)
A radionuclide or a series of radionuclides formed by the nuclear transformation of another which, in this context, is referred to as the parent.
(FGR 11)

Decay series
The consecutive members of a radioactive family of elements. A complete series commences with a long-lived parent such as ²³⁸U and ends with a stable element such as ²⁰⁶Pb.
(ENV RAD)

Decay, branching
Radioactive decay of a nuclide which can proceed in two or more different ways.
(ANSI N1.1-1976)

Decay, radioactive
Disintegration of the nucleus of an unstable nuclide by the spontaneous emission of charged particles and/or photons.
(HPJ 60)

Decay, radioactive
Disintegration of the nucleus of an unstable nuclide by spontaneous emission of charged particles, photons, or both.
(BEIR III)

Decay, radioactive
A spontaneous nuclear transformation in which particles or gamma radiation are emitted of x radiation is emitted following orbital electron capture or the nucleus undergoes spontaneous fission.
(ANSI N1.1-1976)

Decay, radioactive
The spontaneous transformation of one nuclide into a different nuclide or into a different energy state of the same nuclide. The process results in a decrease, with time, of the number of the original radioactive atoms in a sample. It involves the emission from the nucleus of alpha particles, beta particles (or electrons), or gamma rays; or the nuclear capture or ejection of orbital electrons; or fission. Also called radioactive disintegration. (See half-life, nuclear reaction, radioactive series.)
(USAEC-1974)

Decay, radioactive
Disintegration of the nucleus of an unstable nuclide by the spontaneous emission of charged particles and/or photons.
(BEIR I)

Decay, radioactive
Disintegration of the nucleus of an unstable nuclide by spontaneous emission of charged particles, photons, or both.
(RHH)

Decay, radioactive
Spontaneous change of a nucleus with emission of a particle or photon; rate of decay is usually expressed in terms of half life.
(NBS 73)

Decay, radioactive
Spontaneous change of a nucleus with emission of a particle or photon; rate of decay is usually expressed in terms of half life.
(NBS 54)

Deceit
Methods used to attempt to gain unauthorized access, introduce unauthorized materials, or remove strategic special nuclear materials, where the attempt involves falsification to present the appearance of authorized access.
(10CFR73.2)

Decibel (db)
Ten times the logarithm to the base ten of the ratio of two power levels. One-tenth of a bel. The quantities dbm and dbW refer to decibels relative to one milliwatt and one watt respectively.
(NCRP 67)

Decision criterion
In signal detection theory, the critical value that separates the range of decision variable outcomes associated with "negative" decisions from the range associated with "positive" decisions.
(ICRU 54)

Decision Level
The amount of a count (L_c or L_c') or final instrument measurement of a quantity of analyte (D_c or D_c') at or above which a decision is made that the analyte is definitely present.
(HPS N13.30-1996)

Decision level
A net count of activity at which it is decided that a positive detection of activity above an appropriate blank has been obtained, with a specified probability.
(ANSI/HPS N13.22-1995)

Decision level (L_c)
The amount of a count or final instrument measurement of a quantity of analyte at or above which a decision is made that a positive quantity of the analyte is present.
(ANSI N13.30-1989D)

Decision variable
In signal detection theory, a statistical quantity that is assumed to underlie decisions made under uncertainty. For "detection" tasks that involve two mutually exclusive ("positive" and "negative") alternatives, the decision is assumed to be made by comparing the value of the decision variable to a critical value (i.e., decision criterion).
(ICRU 54)

Decladding, chemical
Removal of cladding by chemical means.
(ANSI N1.1-1976)

Declared pregnant woman
A woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception.
(10CFR20.1003)

Declared pregnant worker
A woman who has voluntarily declared to her employer, in writing, her pregnancy for the purpose of being subject to the occupational dose limits to the embryo/fetus as provided at Sec. 835.206. This declaration may be revoked, in writing, at any time by the declared pregnant worker.
(10CFR835.2-1998)

Declared pregnant worker
A woman who has voluntarily declared to her employer, in writing, her pregnancy for the purpose of being subject to the occupational exposure limits to the embryo/fetus as provided in §835.206. This declaration may be revoked, in writing, at any time by the declared pregnant worker.
(10CFR835.2-1993)

Decommission
To remove a facility or site safely from service and reduce residual radioactivity to a level that permits--
(1) Release of the property for unrestricted use and termination of the license; or
(2) Release of the property under restricted conditions and termination of the license.
(10CFR30.4)

Decommission
To remove (as a facility) safely from service and reduce residual radioactivity to a level that permits release of the property for unrestricted use and termination of license.
(10CFR70.4)

Decommissioning
The removal of an incinerator unit from operation.
(ANSI/HPS N13.45-1998)

Decontamination
The removal of radioactive contaminants on surfaces.
(ANSI/HPS N13.45-1998)

Decontamination
Removal of unwanted radioactive material.
(IEC 50-393-1993)

Decontamination
The removal or reduction of radioactive, chemical or biohazard contamination from surfaces by cleaning and washing. Biohazard decontamination may also be accomplished by chemical or thermal (e.g., autoclaving) treatment to destroy the biological activity.
(NCRP 111)

Decontamination
The removal (cleaning) of radioactive material from the cask surfaces.
(ANSI N14.19-1986)

Decontamination
The removal of radioactive contaminants from surfaces (e.g., skin) by cleaning and washing.
(NCRP 65)

Decontamination
Removal or reduction of radioactive contamination.
(ANSI N1.1-1976)

Decontamination
The removal of unwanted substances from personnel, rooms, building surfaces, equipment, etc.
(ERDA 76-21)

Decontamination
The removal of radioactive contaminants from surfaces or equipment, as by cleaning and washing with chemicals. (See radioactive contamination.)
(USAEC-1974)

Decontamination factor
Ratio of the initial concentration of contaminating radioactive material to the final concentration resulting from a process of decontamination.
(IEC 50-393-1993)

Decontamination factor
A measure of air cleaning effectiveness; the ratio of the concentration of a contaminant in the untreated air or gas to the concentration in the treated air or gas.
(ERDA 76-21)

Decontamination factor
The ratio of the initial concentration of contaminating radioactive material to the final concentration resulting from a decontamination process. (The term may refer to a specified nuclide of to gross measurable radioactivity.)
(ANSI N1.1-1976)

Decontamination factor
The ratio of the amount of undesired radioactive material present to the amount remaining after a suitable processing step has been completed. Decontamination factors may refer to the reduction of some particular type of radiation, or to the gross measurable radioactivity.
(RHH)

Decontamination factor (DF)
The ratio of the mass input rate of a contaminant in the untreated stream to the mass discharge rate in the treated stream.
(ANSI N303-1978)

Dedicated check source
A radioactive source that is used to assure the constant operation of a radiation detection or measurement device over several months or years.
(10CFR35.2)

Deep dose equivalent index (H_i,d)
Maximum dose equivalent in the ICRU sphere within a core radius of 14 cm. The sphere is centered at the point in space to which the quantity is assigned. This quantity is one of two restricted dose indices.
(ICRU 43)

Deep-dose equivalent
Which applies to external whole-body exposure, is the dose equivalent at a tissue depth of 1 cm (1000mg/cm²).
(10CFR50.2)

Deep-dose equivalent
Which applies to external whole-body exposure, is the dose equivalent at a tissue depth of 1 cm (1000 mg/cm²).
(10CFR10.1003)

Default value
A value prescribed for a model parameter in the absence of data directly relevant to the assessment situation.
(NCRP 123I)

Default value
A value prescribed for a model parameter in the absence of data directly relevant to the assessment situation.
(NCRP 76)

Default values
Parameter values that are used in radiological assessment models when site-specific values cannot be obtained.
(NUREG/CR 3332)

Defect
(1) A deviation in a basic component delivered to a purchaser for use in a facility or activity subject to a construction permit under this part, if on the basis of an evaluation, the deviation could create a substantial safety hazard; or
(2) The installation, use, or operation of a basic component containing, a defect as defined in paragraph (1) of this definition; or
(3) A deviation in a portion of a facility subject to the construction permit of this part provided the deviation could, on the basis of an evaluation, create a substantial safety hazard.
(10CFR50.2)

Degree of enrichment
Enrichment factor minus one.
(IEC 50-393-1993)

Delay tank
A tank or reservoir for the temporary holdup of radioactive fluids to permit their activity to decay. (Also called decay tank.)
(ANSI N1.1-1976)

Delayed critical
Qualifies the condition that a nuclear chain reacting medium has an effective multiplication factor equal to unity.
(IEC 50-393-1993)

Delayed critical
Identical with critical; the term is used to emphasize that the delayed neutrons are necessary to achieve the critical state.
(ANSI N1.1-1976)

Delayed neutron
Neutron emitted by excited fission products formed by beta decay.
(IEC 50-393-1993)

Delayed neutron
Neutrons emitted by excited nuclei formed in a radioactive process: so-called because they are emitted an appreciable time after fission. They are important in the control of nuclear reactors.
(RHH)

Delayed neutron failed element monitor
Failed element monitor based on detection of delayed neutrons emitted by certain fission products in the coolant.
(IEC 50-394-1993)

Delayed neutron fraction
Identical with critical; the term is used to emphasize that the delayed neutrons are necessary to achieve the critical state.
(ANSI N1.1-1976)

Delayed neutron fraction, effective
The ratio of the mean number of fissions caused by delayed neutrons to the total number of fissions caused by delayed plus prompt neutrons. NOTE: The effective delayed neutron fraction is generally larger than the actual delayed neutron fraction.
(ANSI N1.1-1976)

Delayed neutrons
Neutrons emitted by radioactive fission products in a reactor over a period of seconds or minutes after a fission takes place. Fewer than 1% of the neutrons are delayed, the majority being prompt neutrons. Delayed neutrons are important considerations in reactor design and control. (See dollar.)
(USAEC-1974)

Delivered absorbed dose index (D_I)
The absorbed-dose index value assigned to a dosimeter irradiated in known radiation fields under the specified conditions. The average absorbed-dose index D_I is:

where n is the number of dosimeters in the set.
(ANSI N13.15-1985)

Delta 28
For a given uranium fuel in a given neutron spectrum, the ratio of the total number of ²³⁸U fissions to the number of fissions caused by thermal neutrons. In practice, Delta 28 is often set equal to the ratio of the total number of ²³⁸U fissions to the total number of ²³⁵U fissions.
(ANSI N1.1-1976)

Delta radiation
Electrons, ejected from atoms by ionizing radiation, and having sufficient energy to produce excitation or ionization.
(IEC 50-393-1993)

Delta ray
Any secondary ionizing particle ejected by recoil when a primary ionizing particle passes through matter.
(RHH)

Demand
See demand-type self-contained breathing apparatus and demand-type air-line respirator in ANSI Z88.2-1980.
(ANSI Z88.2-1980)

Demineralizer bed
A mechanical component in a reactor system that selectively removes fission and activation products and other unwanted contaminants from the primary coolant. Demineralizers generally work on the principle of ion exchange, using a chemical resin bed to accumulate materials as they pass through.
(NUREG/CR 3332)

Demister
The preferred generic term for devices used to remove entrained moisture from air.
(ERDA 76-21)

Demonstration
Course of reasoning showing that a certain result is a consequence of assumed premises, explanation or illustration as in teaching by use of examples.
(IEC 50-393-1993)

Densitometer
Instrument utilizing a photocell to determine the degree of darkening of developed photographic film.
(RHH)

Densitometer
Instrument for measuring the degree of darkening (optical density) of photographic film.
(ANSI N13.6-1966)

Density (photographic)
Used to denote the degree of darkening of photographic film. Logarithm of opacity of exposed and processed film. Opacity is the reciprocal of transmission; transmission is the ratio of transmitted to incident intensity.
(RHH)

Density meter
Measuring assembly, including an ionizing radiation source and a radiation meter, intended to measure either the density of a material or the average specific gravity of a heterogeneous mixture, using the variation, within a defined geometry, of the absorption or scattering of the radiation.
(IEC 50-394-1993)

Dental use
The intentional external administration of the radiation from byproduct material to human beings in the practice of dentistry in accordance with a license issued by a State or Territory of the United States, the District of Columbia, or the Commonwealth of Puerto Rico.
(10CFR35.2)

Dentist
An individual licensed by a State or Territory of the United States, the District of Columbia, or the Commonwealth of Puerto Rico to practice dentistry.
(10CFR35.2)

Dentist
An individual licensed by a State or Territory of the United States, the District of Columbia, or the Commonwealth of Puerto Rico to practice dentistry.
(10CFR30.4)

Deoxycytidine
A structural subunit of deoxyribonucleic acid that regulates hereditary characteristics in all living cells.
(HPJ 60)

Deoxyribonucleic Acid (DNA)
The genetic material of cells; a complex molecule of high molecular weight consisting of deoxyribose, phosphoric acid, and four bases which are arranged as two long chains that twist around each other to Form a double helix joined by bonds between the complementary components.
(NCRP 125)

Deoxyribonucleic acid (DNA)
A double helical macromolecule present in chromosomes that contains genetic information coded in specific sequences of its constituent nucleotides.
(HPJ 60)

Deoxyribonucleic acid (DNA)
The basic instruction code which a living cell uses to direct its life processes.
(ENV RAD)

Department
The Department of Energy established by the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565, 42 U.S.C. 7101 et seq.) to the extent that the Department, or its duly authorized representatives, exercises functions formerly vested in the U.S. Atomic Energy Commission, its Chairman, members, officers, and components and transferred to the U.S. Energy Research and Development Administration and to the Administrator thereof pursuant to sections 104 (b), (c), and (d) of the Energy Reorganization Act of 1974 (Pub. L. 93-438, 88 Stat. 1233 at 1237, 42 U.S.C. 5814) and retransferred to the Secretary of Energy pursuant to section 301(a) of the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat 565 at 577-578, 42 U.S.C. 7151).
(10CFR20.1003)

Department and Department of Energy
The Department of Energy established by the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565, 42 U.S.C. 7101 et seq.), to the extent that the department, or its duly authorized representatives, exercises functions formerly vested in the Atomic Energy Commission, its Chairman, members, officers and components and transferred to the U.S. Energy Research and Development Administration and to the Administrator thereof pursuant to sections 104 (b), (c) and (d) of the Energy Reorganization Act of 1974 (Pub. L. 93-438, 88 Stat. 1233 at 1237, 42 U.S.C. 5814) and retransferred to the Secretary of Energy pursuant to section 301(a) of the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565 at 577-578, 42 U.S.C. 7151).
(10CFR50.2)

Department and Department of Energy
The Department of Energy established by the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565, 42 U.S.C. 7101 et seq.) to the extent that the Department, or its duly authorized representatives, exercises functions formerly vested in the U.S. Atomic Energy Commission, its Chairman, members, officers and components and transferred to the U.S. Energy Research and Development Administration and to the Administrator thereof pursuant to sections 104 (b), (c) and (d) of the Energy Reorganization Act of 1974 (Pub. L. 93-438, 88 Stat. 1233 at 1237, 42 U.S.C. 5814) and retransferred to the Secretary of Energy pursuant to section 301(a) of the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565 at 577-578, 42 U.S.C. 7151).
(10CFR40.4)

Department and Department of Energy
The Department of Energy established by the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565, 42 U.S.C. 7101 et seq.) to the extent that the Department, or its duly authorized representatives, exercises functions formerly vested in the U.S. Atomic Energy Commission, its Chairman, members, officers and components and transferred to the U.S. Energy Research and Development Administration and to the Administrator thereof pursuant to sections 104 (b), (c) and (d) of the Energy Reorganization Act of 1974 (Pub. L. 93-438, 88 Stat. 1233 at 1237, 42 U.S.C. 5814) and retransferred to the Secretary of Energy pursuant to section 301(a) of the Department of Energy Organization Act (Pub. L. 9591, 91 Stat. 565 at 577-578, 42 U.S.C. 7151).
(10CFR30.4)

Department and Department of Energy
The Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565, 42 U.S.C. 7101 et seq.), to the extent that the Department, or its duly authorized representatives, exercises functions formerly vested in the U.S. Atomic Energy Commission, its Chairman, members, officers and components and transferred to the U.S. Energy Research and Development Administration and to the Administrator thereof pursuant to sections 104(b), (c) and (d) of the Energy Reorganization Act of 1974 (Pub. L. 93-438, 88 Stat. 1233 at 1237, 42 U.S.C. 5814) and retransferred to the Secretary of Energy pursuant to section 301(a) of the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565 at 577-578, 42 U.S.C. 7151).
(10CFR70.4)

Departure from nucleate boiling (DNB)
The change from nucleate to film boiling. The vapor film formed between the heated surface and the cooling liquid decreases the heat transfer from surface to liquid so that a maximum occurs in the curve of heat flux density versus temperature difference. (See critical heat flux.)
(ANSI N1.1-1976)

Depleted fuel
(See depleted uranium, spent fuel.)
(USAEC-1974)

Depleted material
Material which has undergone depletion.
(ANSI N1.1-1976)

Depleted uranium
The source material uranium in which the isotope uranium-235 is less than 0.711 weight percent of the total uranium present. Depleted uranium does not include special nuclear material.
(10CFR40.4)

Depleted uranium
Uranium containing less uranium-235 than the naturally occurring distribution of uranium isotopes.
(10CFR71.4)

Depleted uranium
Uranium containing less uranium-235 than the naturally occurring distribution of uranium isotopes.
(49CFR173.403)

Depleted uranium
Uranium having a smaller percentage of uranium-235 than the 0.770 found in natural uranium. It is obtained from the spent (used) fuel elements or as by-product tails, or residues, of uranium isotope separation. (Compare natural uranium, spent fuel.)
(USAEC-1974)

Depleted uranium
Depleted uranium is a mixture of the isotopes U-234, U-235, and U-238 in which the abundance of U-235 isotope is decreased below 0.71 percent. The specific activities of depleted uranium are less than that of natural uranium. The chemical toxicity of uranium is the limiting criterion from maximum permissible concentration in air (in terms of mass per unit volume).
(ANSI N7.2-1963)

Depleted uranium (DU)
Depleted uranium is a byproduct of the enrichment process. Depleted uranium has a reduced abundance of ²³⁵U relative to the abundance of 0.7 % in natural uranium. The typical ²³⁵U contents for depleted uranium and natural uranium are 0.2 % and 0.7 %, respectively. Depleted uranium also has a reduced abundance of ²³⁴U.
(ANSI/HPS N13.22-1995)

Depletion
Reduction of the isotope concentration related of one or more specified isotopes in a material or in one of its constituents.
(IEC 50-393-1993)

Depletion
Reduction of the concentration of one or more specified isotopes in a material or in one of its constituents.
(ANSI N1.1-1976)

Depletion
Reduction of the concentration of one or more specified isotopes in a material or in one of its constituents.
(RHH)

Depletion charge (economics)
See fuel consumption charge.
(ANSI N1.1-1976)

Depletion layer (in a semiconductor detector)
Layer of a semiconductor detector which constitutes its sensitive volume ; most of the energy lost by the particles in this region can contribute to the resulting signal.
(IEC 50-394-1993)

Depolymerization
The breaking down of an organic compound into two or more molecules of less complex structure.
(RHH)

Deposition
Refers to the initial processes determining how much of the material in the inspired air remains behind after expiration. Deposition of material may occur during both inspiration and expiration.
(ICRP 68)

Deposition
Material which, after being taken into the body by inhalation, ingestion, injection or absorption through the skin, exists in an organ or tissue at a specified time.
(NCRP 114)

Deposition probability (in lung region)
The fraction of the activity or mass of an inhaled aerosol which is deposited in a particular region of the lung.
(ICRP 54)

Deposition probability (in lung region)
The fraction of the activity or mass of an inhaled aerosol which is deposited in a particular region of the lung.
(ICRP 30)

Deposition velocity
An empirical rate constant that relates the concentration of a radionuclide in air to that on ground or plant surfaces.
(NUREG/CR 3332)

Depth dose
The radiation dose delivered at a particular depth beneath the surface of the body. It is usually expressed as a percentage of surface dose.
(RHH)

Depth of penetration
For a plane electromagnetic wave incident on the boundary of a medium, the distance, from the boundary into the medium along the direction of propagation in the medium , at which the field strengths of the wave have been reduced to 1/e of their boundary values. For complex boundaries (i.e., non-planar), the distance at which the field strengths reduce to 1/e of their boundary values may be very complicated functions of geometry, medium properties, etc., but generally will not deviate considerably from the above definition. Depth of penetration is expressed in units of meter (m).
(NCRP 67)

Depth-dose curve
A curve describing the absorbed dose at points located at varying depths into a material such as the walls of a passageway in the human body.
(ENV RAD)

Derived air concentration (DAC)
The concentration of a given radionuclide in air which, if breathed by reference man for a working year of 2,000 hours under conditions of light work (inhalation rate of 1.2 cubic meters of air per hour), results in an intake of one ALI. DAC values are given in Table 1, Column 3, of appendix B to Secs. 20.1001-20.2401.
(10CFR20.1003)

Derived Air Concentration (DAC)
The quantity obtained by dividing the ALI for any given radionuclide by the volume of air breathed by an average worker during the working year (2,400 m³).
(HPS N13.42-1997)

Derived air concentration (DAC)
The concentration in air (Bq m^-3) that if inhaled by reference man for 2000 h (50 wk, 40 h wk^-1, 0.02 m³ min^-1; or 2400 m³ y^-1 inhalation rate) during employment with average effort, would result in the ALI by inhalation:
DAC = ALI/2.4 x 10³ Bq m^-3
(ANSI/HPS N13.22-1995)

Derived air concentration (DAC)
For the radionuclides listed in appendix A of this part the airborne concentration that equals the ALI divided by the volume of air breathed by an average worker for a working year of 2000 hours (assuming a breathing volume of 2400 m³). For the radionuclides listed in appendix C of this part, the air immersion DACs were calculated for a continuous, non-shielded exposure via immersion in a semi-infinite atmospheric cloud. The value is based upon the derived airborne concentration found in Table I 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)

Derived air concentration (DAC)
Equals the ALI of a radionuclide divided by the volume of air inhaled by Reference Man in a working year (i.e., 2.4 x 10³ m³). The unit of DAC is Bq m^-3.
(HPJ 60)

Derived air concentration (DAC)
The concentration of a radionuclide in air which, if breathed alone for one work year, would irradiated Reference Man to the limits for occupational exposure. The DAC equals the ALI of a radionuclide divided by the volume of air inhaled by Reference Man in a working year (i.e., 2.4 x 10³ m³).
(FGR 11)

Derived air concentration (DAC)
The equivalent of the maximum air concentration as defined in Appendix B, 10 CFR 20.
(ANSI N343-1978)

Derived air concentration - time product (DAC-hr)
The product of the average fractional concentration of airborne radioactivity during a time t, and that time t expressed in hours. The average fractional concentration is the average airborne concentration of a radionuclide divided by the corresponding DAC.
(ANSI N343-1978)

Derived air concentration for submersion
One two-thousandth of the time integral of the concentration of a radionuclide in air which over a working year would alone irradiate a person to the limit specified by the ICRP.
(ICRP 30)

Derived air concentration-hour (DAC-hour)
The product of the concentration of radioactive material in air (expressed as a fraction or multiple of the derived air concentration for each radionuclide) and the time of exposure to that radionuclide, in hours. A licensee may take 2,000 DAC-hours to represent on ALI, equivalent to a committed effective dose equivalent 5 rems. (0.05 Sv).
(10CFR20.1003)

Derived air concentration-hour (DAC-hour)
The product of the concentration of radioactive material in air (expressed as a fraction or multiple of the DAC for each radionuclide) and the time of exposure to that radionuclide, in hours.
(10CFR835.2-1998)

Derived concentration guide (DCG)
The concentration of a radionuclide in air or water that, under conditions of continuous exposure for one year by one exposure mode (e.g., ingestion of water, submersion in air, or inhalation of air), would result in an effective dose equivalent (EDE) equal to the annual dose limit applicable to the group exposed. For exposure of the public, the DCG is the radionuclide concentration in air or water that would result in a EDE of 100 mrem (1 mSv) to a person having the characteristics of the reference man.
(10CFR834.2)

Derived investigation level
A level associated with quantities other than dose equivalent, committed dose equivalent or intake which, by use of a define model, is intended to reflect the investigation level in a particular situation in the work place (see investigation level).
(HPJ 60)

Derived Investigation Level (DIL)
The activity present in a bioassay compartment at the time of a bioassay measurement, resulting from an intake of one (1) investigation level (IL = 0.02 ALI).
(HPS N13.42-1997)

Derived investigation level (DIL)
A measured quantity, derived by calculations from a basic dose level, at which additional monitoring, investigation, or exposure controls are to be carried out (as defined in ICRP 54).
(ANSI/HPS N13.22-1995)

Derived level (DL)
A quantity derived from appropriate dose-equivalent limits or annual limits of intake by a defined biokinetic model in such a way that compliance with the DL implies virtual certainty of compliance with relevant basic internal dose limits.
(ANSI/HPS N13.22-1995)

Derived limit (DL)
A limit derived from the appropriate dose equivalent limits or annual limits of intake by a defined model in such a way that compliance with the DL implied virtual certainty of compliance with the relevant basic limits. A DL may be associated with quantities other than dose equivalent, committed dose equivalent, or intake of a radionuclide.
(ICRP 35)

Derived limits
Any of a number of limits such as "Derived Air Concentration" (DAC) calculated from the basic radiation protection limits by application of standard parameters for the pertinent biological system.
(HPJ 60)

Derived limits
Limits, such as the ALI and DAC, that are derived from primary limits through use of standard assumptions about radionuclide intake and metabolism by Standard Man.
(FGR 11)

Derived limits
Practical limits associated with quantities other than those for which there are basic limits and related to the basic limits by a defined model of the situation. Derived limits may be set for quantities such as rate of release to the environment or contamination of an environmental material or food stuff. The accuracy of the link between derived limits and basic limits depends on the realism of the model used in the derivation.
(ICRP 29)

Derived reference air concentration (DRAC)
The ARLI of a radionuclide divided by the volume of air inhaled by Reference Man in a working year (i.e., 2.4 x 10³ m³). The unit of DRAC is Bq per m³. The DRAC corresponds to the formerly used term maximum permissible concentration (MPC).
(NCRP 118)

Derived Reference Air Concentrations (DRAC)
The ARLI of a radionuclide divided by the volume of air inhaled by Reference Man in a working year (i.e., 2.4 x 10³ m³) (the DRAC is given in Bq m^-3)
(NCRP 125)

Design
The description of a special form material, a package, or a packaging, that enables those items to be fully identified. The description may include specifications, engineering drawings, reports showing compliance with regulatory requirements, and other relevant documentation.
(49CFR173.403)

Design
Technical and management processes which lead to and include the issuance of design output documents such as drawings, specifications and other documents defining technical requirements and performance of radiation shields.
(ANSI/ANS-6.4-1985)

Design
Technical and management processes which commence with identification of design input and which lead to and include the issuance of design output documents.
(ANSI N46.2-1978)

Design Bases
That information that identifies the specific functions to be performed by a structure, system, or component of a facility and the specific values or ranges of values chosen for controlling parameters as reference bounds for design. These values may be restraints derived from generally accepted "state-of-the-art" practices for achieving functional goals or requirements derived from analysis (based on calculation or experiments) of the effects of a postulated event under which a structure, system, or component must meet its functional goals. The values for controlling parameters for external events include:
(1) Estimates of severe natural events to be used for deriving design bases that will be based on consideration of historical data on the associated parameters, physical data, or analysis of upper limits of the physical processes involved; and
(2) Estimates of severe external man-induced events, to be used for deriving design bases, that will be based on analysis of human activity in the region, taking into account the site characteristics and the risks associated with the event.
(10CFR60.2)

Design bases
That information which identifies the specific functions to be performed by a structure, system, or component of a facility, and the specific values or ranges of values chosen for controlling parameters as reference bounds for design. These values may be (1) restraints derived from generally accepted "state of the art" practices for achieving functional goals, or (2) requirements derived from analysis (based on calculation and/or experiments) of the effects of a postulated accident for which a structure, system, or component must meet its functional goals.
(10CFR50.2)

Design bases
That information that identifies the specific functions to be performed by a structure, system, or component of a facility and the specific values or ranges of values chosen for controlling parameters as reference bounds for design. These values may be restraints derived from generally accepted "state-of-the-art" practices for achieving functional goals or requirements derived from analysis (based on calculation or experiments) of the effects of a postulated event under which a structure, system, or component must meet its functional goals. The values for controlling parameters for external events include: (1) Estimates of severe natural events to be used for deriving design bases that will be based on consideration of historical data on the associated parameters, physical data, or analysis of upper limits of the physical processes involved and (2) estimates of severe external man-induced events to be used for deriving design bases that will be based on analysis of human activity in the region taking into account the site characteristics and the risks associated with the event.
(10CFR72.3)

Design basis accident (DBA)
The most serious accident that can be hypothesized from an adverse combination of equipment malfunction, operating errors, and other unforeseen causes.
(ERDA 76-21)

Design Basis Events
(1)(i) Those natural and human-induced events that are reasonably likely to occur regularly, moderately frequently, or one or more times before permanent closure of the geologic repository operations area; and
(ii) Other natural and man-induced events that are considered unlikely, but sufficiently credible to warrant consideration, taking into account the potential for significant radiological impacts on public health and safety.
(2) The events described in paragraph (1)(i) of this definition are referred to as "Category 1" design basis events. The events described in paragraph (1)(ii) of this definition are referred to as "Category 2" design basis events.
(10CFR60.2)

Design capacity
The quantity of spent fuel or high-level radioactive waste, the maximum burnup of the spent fuel in MWD/MTU, the curie content of the waste, and the total heat generation in BTU per hour that the storage installation is designed to accommodate.
(10CFR72.3)

Design input
Those criteria, parameters, bases or other design requirements upon which detailed final design is based.
(ANSI N46.2-1978)

Design life (of equipment)
Time for which satisfactory performance of equipment can be demonstrated for a specific set of operating conditions.
(IEC 50-393-1993)

Design output
Documents such as drawings, specifications and other documents defining technical requirements of structures, systems and components.
(ANSI N46.2-1978)

Design pressure
The pressure that is used for the structural design of a unit, component, or system, and which includes allowance for forces encountered under system upset conditions.
(ERDA 76-21)

Design rated load
The maximum load, as specified in the related purchase documents, that the special lifting device shall be designed to support.
(ANSI N14.6-1986)

Designated medical examiner
A licensed medical practitioner.
(ANSI/ANS-15.4-1988)

Designer
The qualified individual responsible for establishing a concept for the special lifting device and developing the concept into a set of drawings, specifications, and procedures that will control its manufacture.
(ANSI N14.6-1986)

Detachable coupling
A device by means of which the respirator wearer, without using hand tools, may detach the air-supply line from that part of the respirator worn on the person.
(ANSI Z88.2-1980)

Detail transfer function
This function describes the way in which the imaging system averages, displaces or blurs the input signals before they are detected in the output signal. For linear, shift invariant systems the detail transfer function is the PSF or, in frequency space, the optical transfer function.
(ICRU 54)

Detection
Discrimination between the presence and absence of a specified physical state (e.g., sensory stimulus or disease).
(ICRU 54)

Detection axis
A specified imaginary line through the effective center of the detector to which the radiation field direction can be referenced.
(ANSI N42.17A-1989)

Detection axis
A specified imaginary line through the effective center of the detector to which the radiation field direction can be referenced.
(ANSI N42.17C-1989)

Detection efficiency
Under stated conditions of detection, ratio of the number of detected particles to the number of particles of the same type emitted by the radiation source in the same time interval.
(IEC 50-394-1993)

Detection limit
The extreme of quantification for the radiation of interest by the instrument as a whole or an individual readout scale or decade. The lower detection limit is the minimum quantifiable instrument response or reading. The upper detection limit is the maximum quantifiable instrument response or reading. Quantifiable, in this case, means with the specified accuracy.
(ANSI N42.17C-1989)

Detection limit
The extreme of detection or quantification for the radiation of interest by the instrument as a whole or an individual readout scale. The lower detection limit is the minimum quantifiable instrument response or reading. The upper detection limit is the maximum quantifiable instrument response or reading.
(ANSI N323-1978)

Detection threshold
The minimum amplitude for a pulse to be detected.
(ICRU 52)

Detection threshold, detection limit
Value of the indication of the measurement for which the relative random uncertainty equals (100% at the probability level of 95%.
(IEC 50-394-1993)

Detective quantum efficiency (DQE)
The ratio of the noise equivalent quanta to the actual number of exposure quanta from which the image was made.
(ICRU 54)

Detector
That portion of an instrument system sensitive to and used for the quantification of ionizing radiation.
(ANSI N42.17A-1989)

Detector
That portion of an instrument system sensitive to and used for the quantification of ionizing radiation.
(ANSI N42.17B-1989)

Detector
A device or component which produces an electronically measurable quantity in response to ionizing radiation.
(ANSI N323-1978)

Detector
Material or a device that is sensitive to radiation and can produce a response signal suitable for measurement or analysis. A radiation detection instrument.
(USAEC-1974)

Detector
Any device for converting radiation flux to a signal suitable for observation and measurement.
(ANSI N42.18-1974)

Detector
Any device for converting radiation flux to a signal suitable for observation and measurement.
(ANSI N13.10-1974)

Detector efficiency
Ratio of the number of detected particles to the number of particles of the same type which are incident on the detector in the same time interval.
(IEC 50-394-1993)

Detector, 1/v
A neutron detector for which the cross section of the neutron reaction varies inversely with neutron speed.
(ANSI N1.1-1976)

Detector, radiation
Any device for converting radiant energy to a form more suitable for observation. An instrument used to determine the presence and sometimes the amount of radiation or neutron flux.
(HPJ 60)

Detector, radiation
Any device for converting radiant energy to a form more suitable for observation. An instrument used to determine the presence, and sometimes the amount, of radiation.
(RHH)

Detector, resonance
An activation detector whose neutron cross section is characterized by large resonances. It thus gives information about the neutron flux density at the detector resonance energies.
(ANSI N1.1-1976)

Deterministic effect
An effect that has a clinical threshold, i.e., exposures below the threshold do not result in the clinical effect of concern, whereas at exposures above the threshold the effect will occur in a greater number of persons so exposed and the severity increases with dose. Formerly, deterministic effects were termed "nonstochastic" effects.
(NCRP 121)

Deterministic effects
Effects for which the severity of the effect in affected individuals varies with the dose, and for which a threshold usually exists. (Formerly described as nonstochastic effects.)
(NCRP 114)

Deterministic model
A model whose output is predetermined by the mathematical form of its equations and the selection of a single value for each input parameter.
(NCRP 123I)

Deterministic model
A model whose output is predetermined by the mathematical form of its equations and the selection of a single value for each input parameter.
(NCRP 76)

Deterministic model
A model whose output is fixed by the mathematical form of its equations and the selection of a single value for each input parameter; nonstochastic model.
(NUREG/CR 3332)

Deterministic or non-stochastic
Describes effects whose severity is a function of dose; and for those, that a threshold usually exists such as non-malignant damage to skin.
(ICRP 59)

Deuterium
Deuterium and any deuterium compound, including heavy water, in which the ratio of deuterium atoms to hydrogen atoms exceeds 1:5000.
(10CFR110.2)

Deuterium
[Symbol ²H or D] An isotope of hydrogen whose nucleus contains one neutron and one proton and is therefore about twice as heavy as the nucleus of normal hydrogen, which is only a single proton. Deuterium is often referred to as heavy hydrogen; it occurs in nature as 1 atom to 6500 atoms of normal hydrogen. It is nonradioactive. (See heavy water, hydrogen.)
(USAEC-1974)

Deuterium
A heavy isotope of hydrogen with one proton and one neutron in the nucleus. (Symbol: ₁²H or D).
(RHH)

Deuteron
Nucleus of the isotope of mass number 2 of hydrogen, called deuterium.
(IEC 50-393-1993)

Deuteron
The nucleus of the hydrogen isotope with a mass number 2: deuterium.
(ANSI N1.1-1976)

Deuteron
The nucleus of deuterium. It contains one proton and one neutron.
(USAEC-1974)

Deuteron
Nucleus of a deuterium atom.
(RHH)

Deviation
A departure from the technical or quality assurance requirements defined in procurement documents, safety analysis report, construction permit, or other documents provided for basic components installed in a facility subject to the regulations of this part.
(10CFR50.2)

Deviation
A departure from specified requirements.
(ANSI N46.2-1978)

Device
A pocket-sized chirper, pocket-sized alarm rate meter, or pocket-sized alarm dosimeter.
(ANSI N13.27-1981)

Device
Any piece of equipment designated to utilize a sealed source(s).
(ANSI N542-1977)

Device, nuclear
A nuclear explosive used for peaceful purposes, tests or experiments. The term is used to distinguish these explosives from nuclear weapons, which are packaged units ready for transportation or use by military forces. (Compare nuclear weapons.)
(USAEC-1974)

Dewatered
To remove the water from recently produced tailings by mechanical or evaporative methods such that the water content of the tailings does not exceed 30 percent by weight.
(40CFR61.251)

Diagnostic accuracy
In applied signal detection theory, an overall measure of delectability derived from the ROC curve without reference to particular points on the curve (i.e., compromises between TPF and FPF) that may be adopted in particular practical settings. In this sense, diagnostic accuracy is usually quantified by the ROC index, Az. The term "diagnostic accuracy" has also been used in the medical literature in a fundamentally different way to indicate the proportion of medical diagnoses that prove to be correct, thereby depending not only upon the delectability of the disease, but also upon its prevalence and the particular decision criterion that is adopted.
(ICRU 54)

Diagnostic clinical procedures manual
A collection of written procedures that describes each method (and other instructions and precautions) by which the licensee performs diagnostic clinical procedures; where each diagnostic clinical procedure has been approved by the authorized user and includes the radiopharmaceutical, dosage, and route of administration.
(10CFR35.2)

Diagnostic examination
Measurements performed to estimate the amount of radionuclide deposited in a person when an intake is known or is suspected to have occurred.
(ANSI N13.30-1989D)

Diagnostic Measurements
Measurements performed to estimate the amount of radionuclide deposited in a person when an intake is known or is suspected to have occurred.
(HPS N13.30-1996)

Diagnostic source assembly
A diagnostic source housing (x-ray tube housing) assembly with a beam limiting device attached. This assembly shall be so constructed that the leakage radiation air kerma measured at a distance of one meter from the source does not exceed 1 mGy (0.1 rad) in one hour when the source is operated at its leakage technique factor.
(NCRP 102)

Diagnostic-type protective tube housing
An x-ray tube housing so constructed that the leakage radiation measured at a distance of 1 meter from the source cannot exceed 100 mR in 1 hour when the tube is operated at its maximum continuous rated current for the maximum rated tube potential.
(NCRP 49)

Diaphragm
A device with a central aperture so designed as to restrict the beam to an appropriate area at the point of interest.
(NCRP 51)

Diaphragm
The diaphragm is part of the collimator that controls the beam size. In a high energy treatment machine it is the part of the collimator most distant from the source.
(ICRU 24)

Dichotomous impactor
A virtual impactor with two emerging aerosol flows.
(AM-1993)

Dielectric constant
See permittivity, relative.
(NCRP 67)

Dielectric saturation
Response of a medium that leads to a decrease of the real part of the permittivity with increasing field strength.
(NCRP 67)

Dielectric, ideal
A medium in which all of the energy required to establish an electric field in the medium is recoverable a electromagnetic energy when the field is removed. All absorption phenomena are absent in an ideal dielectric. A perfect vacuum is the only known ideal dielectric.
(NCRP 67)

Dielectric, imperfect
A medium in which a part of the energy required to establish an electric field in the medium is not recoverable as electromagnetic energy. The energy that is not returned is usually converted into heat in the dielectric, i.e., has been absorbed. An imperfect dielectric is often referred to as a "lossy" dielectric.
(NCRP 67)

Difference ionization chamber
Ionization chamber composed of two sections arranged in such manner that the resulting output current corresponds to the difference between the ionization currents of the two sections.
(IEC 50-394-1993)

Differential
The power of an unknown item placed in the sample chamber of the calorimeter is balanced against a known amount of electrical or radioactive power generated in the reference chamber of the calorimeter. This method of operation is applicable only to full twin-bridge calorimeters.
(ANSI N15.54-1988)

Differential dE/dx semiconductor detector
Semiconductor transmission detector whose thickness is very small compared to the range of the incident particle and whose entrance and exit dead layers are small compared to the thickness of the detector.
(IEC 50-394-1993)

Differential non-linearity (of a measuring assembly)
1 - Percentage maximum departure of the slope of the plot of output versus input from the slope of a reference line.
2 - Percentage fluctuation of the uniformity of an individual channel width in a multichannel analyzer.
(IEC 50-394-1993)

Differential pressure
The difference between the pressures in two pneumatic probes.
(ANSI N15.19-1989)

Differential recovery rate
Among tissues recovering at different rates, those having slower rates will ultimately suffer greater damage from a series of successive irradiations. This differential effect is considered in fractionated radiation therapy if the neoplastic tissues have a slower recovery rate than surrounding normal structures.
(BEIR I)

Differential-mobility classifier
A device that removes all particles except those within a narrow range of electrical mobility.
(AM-1993)

Diffraction
Change in direction and amplitude of radiation after passing near an object or through an orifice.
(AM-1993)

Diffraction field
The non-uniform instantaneous electromagnetic fields in a region resulting from the vector sum wave components arising from waves having different directions, frequencies, and phases.
(NCRP 67)

Diffused junction detector
Semiconductor detector in which the junction is produced by diffusion of donor (N) or acceptor (P) impurities.
(IEC 50-394-1993)

Diffuser; converter (isotope separation)
The assembly containing separative elements of one stage of a gaseous diffusion cascade. NOTE: Use of the term "converter" in this sense is misleading and should be avoided.
(ANSI N1.1-1976)

Diffusion
Brownian or random motion of particles due to collisions with surrounding molecules resulting in movement from a region of higher to one of lower concentration
(NCRP 125)

Diffusion
Net movement of particles or gas from a higher to a lower concentration.
(AM-1993)

Diffusion
Movement by Brownian or random motion.
(NCRP 103)

Diffusion
The random path followed by very small particles due to the impact of surrounding molecules. This Brownian motion governs the transport of submicrometer-size particles in air.
(BEIR IV)

Diffusion
Brownian movement with a net transport of particles or gas molecules through a gas under a concentration gradient.
(NCRP 97)

Diffusion
Movement by Brownian or random motion.
(NCRP 78)

Diffusion
The spreading out of a material in a fluid due to thermal or mechanical agitation.
(NCRP 76)

Diffusion
Motion (Brownian) caused by random molecular collision.
(TID-26608)

Diffusion (equivalent) diameter
Diameter of a unit-density sphere with the same rate of diffusion as the particle in question.
(AM-1993)

Diffusion area
One-sixth of the mean square distance traveled by a particle of a given type and class from appearance to disappearance, in an infinite homogeneous medium.
(IEC 50-393-1993)

Diffusion area
One sixth of the mean square displacement of particles of a given type and class from appearance to disappearance (within the type and class) in an infinite homogeneous medium.
(ANSI N1.1-1976)

Diffusion barrier
Any material placed over a detector which delays, through increased diffusion time, the rate at which radon or progeny in air reach the detector.
(ENV RAD)

Diffusion barrier (isotope separation)
A porous structure, which because of its small pore size, restricts ordinary gas flow, but permits diffuse flow, thereby exploiting mass differences for isotope separation.
(ANSI N1.1-1976)

Diffusion battery
An aerosol spectrometer used for submicrometer-sized aerosols, in which size is measured by the diffusive loss of particles in an arrangement of ducts (e.g., tubes, filters, screens).
(AM-1993)

Diffusion battery
An instrument designed to separate particles by size according to their diffusion coefficients, based on measurement of particle losses during laminar flow through the battery.
(NCRP 97)

Diffusion category (stability classes)
A category which describes an atmospheric turbulence condition in terms of boundary layer atmospheric stability. Diffusion categories are generally grouped into six classes, ranging from class A, very unstable, through class F, very stable.
(NUREG/CR 3332)

Diffusion chamber
Cloud chamber in which supersaturation of the vapor is produced by continuous diffusion of saturated vapor, this diffusion being due to a temperature difference between the chamber walls.
(IEC 50-394-1993)

Diffusion charging
A process by which airborne particles acquire charge from ions undergoing Brownian motion.
(AM-1993)

Diffusion coefficient
The constant of proportionality that relates the flux of aerosol particles or gas molecules through a gas and the concentration gradient.
(NCRP 97)

Diffusion coefficient (for neutron fluence rate)
Quotient of the neutron current density at a particular energy to the negative gradient of the neutron fluence rate at the same energy in the direction of that current.
(IEC 50-393-1993)

Diffusion coefficient for neutron flux density
The ratio of the neutron current density at a particular energy to the negative gradient of the neutron flux density at the same energy in the direction of that current.
(ANSI N1.1-1976)

Diffusion cooling
The decrease of the average energy of neutrons in a finite assembly due to the preferential leakage of neutrons with higher energies.
(ANSI N1.1-1976)

Diffusion denuder
A device that passes particles (low diffusivity) and removes gases (high diffusivity).
(AM-1993)

Diffusion equation
A partial differential equation describing the diffusion of monoenergetic particles according to diffusion theory.
(ANSI N1.1-1976)

Diffusion Equivalent Diameter
Diameter of a sphere having the same rate of diffusion (or diffusion coefficient) as the particle in question.
(NCRP 125)

Diffusion heating
The increase in the average energy of neutrons in an assembly due to either spectral hardening of the preferential diffusion of higher energy neutrons from an external neutron source.
(ANSI N1.1-1976)

Diffusion length
Square root of the diffusion area.
(IEC 50-393-1993)

Diffusion length
The square root of the diffusion area.
(ANSI N1.1-1976)

Diffusion plant
(See gaseous diffusion.)
(USAEC-1974)

Diffusion theory
An approximate theory for the diffusion of particles, especially neutrons, based on the assumption that in a homogenous medium the current density is proportional to the gradient of the particle flux density.
(ANSI N1.1-1976)

Diffusion tube
An instrument designed to estimate either the particle size or fraction of an aerosol with a given particle size in an air sample. The sample is passed through a tube and the particle concentration is measured before and after passage. A knowledge of the amount deposited in the tube for different flow rates allows estimation of particle size. If the material deposited is known or assumed to be a particular size, the fraction of the total aerosol with this size is estimated.
(NCRP 97)

Diffusion, gaseous (isotope separation)
Isotope separation by means of gas flow through porous membranes.
(ANSI N1.1-1976)

Diffusiophoresis
Particle motion under the influence of a concentration gradient.
(AM-1993)

Digital offset
A number digitally subtracted from the input signal of an operating digital to analogue converter to remove the analogue offset when recovering the transmitted analogue signals for analysis.
(IEC 50-394-1993)

Digital radiography
A diagnositic procedure using an appropriate radiation source and imaging system which collects, processes, stores, recalls and presents image information in a digital rather than analog fashion.
(NCRP 107)

Digital signal
Discretely timed signal in which information is represented by a number of well defined discrete values that one of its characteristic quantities may assume in time.
(IEC 50-394-1993)

Digital subtraction
An image processing procedure used to improve image contrast by subtracting one digitized image from another.
(NCRP 107)

Digital subtraction
An image processing procedure used to improve image contrast by subtracting one digitized image from another.
(NCRP 102)

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

Digitized signal
Digital signal, usually in binary form, with essentially the same information as a given analogue signal.
(IEC 50-394-1993)

Dilution ratio
Factor by which measured concentration is multiplied to obtain mainstream concentration.
(AM-1993)

Dilution system
A system wherein aerosol is mixed with particle-free dilution gas in a known volumetric ratio to reduce concentration.
(AM-1993)

Diminution
Any process in bone volume by which alkaline earths transfer from bone to blood without resorption. It is believed to be primarily due to slow diffusion of ions from calcified matrix to canaliculi followed by a rapid transfer down canaliculi to blood vessels. Dosimetrically, diminution reduces the activity per gram of bone at risk without decreasing bone volume. (Diminution includes osteocytic osteolysis when present.)
(ICRP 20)

Dip counter tube
Counter tube intended to be dipped or immersed into the liquid whose activity is to be measured.
(IEC 50-394-1993)

Dip detector
Radiation detector intended to be dipped or immersed in the liquid whose activity is to be measured.
(IEC 50-394-1993)

Dipole antenna
An antenna that produces a radiation pattern approximating that of an elementary radiating electric dipole. See "electric dipole". Note: A familiar example of a dipole antenna is a metal radiating structure that supports a line current distribution similar to that of a thin straight wire one-half wavelength long so energized that the current has two nodes, on at each of the far ends. However, other configurations are in common use, e.g., biconical and spherical antennas.
(NCRP 67)

Dipole moment (electric)
See electric dipole moment.
(NCRP 67)

Dipole moment (magnetic)
See magnetic dipole.
(NCRP 67)

Dipole, electric
See electric dipole.
(NCRP 67)

Dipole, magnetic
See magnetic dipole.
(NCRP 67)

Direct beam (from an x ray tube)
The beam of x rays coming directly from the x-ray tube and directed toward the particular region to be irradiated.
(NCRP 48)

Direct Bioassay
The in vivo measurement of radioactive material in the human body utilizing radiation detection instrumentation designed for such purposes.
(HPS N13.42-1997)

Direct bioassay
The assessment of radioactive material deposited in the body by detection of radiations emitted by the material (see in-vivo methods).
(HPJ 60)

Direct bioassay
The measurements of radioactive material in the human body utilizing instrumentation that detects radiation emitted from the radioactive material in the body. (Synonymous with in-vivo measurement.)
(ANSI N13.30-1989D)

Direct bioassay
The assessment of radioactive material deposited in the body by detection of radiations emitted by the material (see in-vivo methods).
(NCRP 87)

Direct bioassay
The measurement of radioactivity in the human body utilizing instrumentation which detects radiation emitted from the radionuclides in the body; identical to in vivo measurement.
(ANSI N343-1978)

Direct bioassay (in vivo)
The assessment of radioactive material deposited in the body by detection of radiations emitted by the material, usually by whole body counting.
(NCRP 114)

Direct maintenance
Maintenance by manual means as opposed to the use of remote handling equipment.
(ANSI N1.1-1976)

Direct radiation
Radiation emitted rectilinearly from the target or source. See also primary radiation.
(NCRP 51)

Direct radiation monitors
Those monitors that provide monitoring of ambient airborne radioactivity by measurement of the external radiation field associated with the airborne radioactivity.
(ANSI N42.17B-1989)

Direct Radiobioassay
The measurements of radioactive material in the human body utilizing instrumentation that detects radiation emitted from the radioactive material in the body. (Synonymous with in vivo measurement.)
(HPS N13.30-1996)

Direct reading pocket dosimeter
A direct reading pocket ionization dosimeter is basically a capacitor with a single movable electrode. The capacitor is charged to a predetermined voltage which results in a given separation of the two electrodes. When exposed to X- or gamma radiation, or both, ionization occurs in the chamber surrounding the electrodes and causes a decrease in the charge on the electrodes. This results in a change in position or deflection of the movable electrode. The magnitude of the deflection is a function of the radiation exposure and is observable through a self-contained optical system.
(ANSI N13.5-1972)

Direct recoil fraction
Those atoms which terminate their recoil path in a pore space.
(ENV RAD)

Direct voltage accelerator (potential drop)
An accelerator which uses a constant voltage to accelerate particles and is typically constructed with an ion or electron source inside a "terminal," which operates at a very high voltage with respect to the target area, which is at ground potential. Usually named according to the type of power supply used.
(RHH)

Direct-cycle reactor system
A nuclear power plant system in which the coolant or heat transfer fluid circulates first through the reactor and then directly to a turbine. (Compare indirect-cycle reactor system.)
(USAEC-1974)

Directional dose equivalent
Symbolized H'(d) this quantity represents the dose equivalent at depth d along any selected radius of the ICRU tissue-equivalent, 30-cm diameter sphere when the sphere is placed in an expanded radiation field. (See definition of ambient dose equivalent.)
(NCRP 112)

Directional dose equivalent: H'(d)
The directional dose equivalent, at a point in a radiation field, is the dose equivalent that would be produced by the corresponding expanded field in the ICRU sphere at a depth, d, on a radius in a specified direction.
(ICRP 60)

Directly ionizing particle
Charged particle such as electron, proton, alpha particle, having sufficient kinetic energy to produce ionization by collision.
(IEC 50-393-1993)

Directly ionizing particles
Charged particles (electrons, protons, alpha particles, etc.) having sufficient kinetic energy to produce ionization by collision.
(ICRU 19)

Directly ionizing particles
Charged particles (electrons, protons, alpha particles, etc.) having sufficient kinetic energy to produce ionization by collision.
(NBS 92)

Directly ionizing particles
Charged particles (electrons, protons, alpha particles, etc.) having sufficient kinetic energy to produce ionization by collision.
(ICRU 10b)

Directly ionizing particles
Charged particles (electrons, protons, alpha particles, etc.) having sufficient kinetic energy to produce ionization by collision.
(ICRU 10f)

Directly ionizing radiation
Charged particles (electrons, protons, alpha particles, etc.) having sufficient kinetic energy to produce ionization by collision.
(NCRP 51)

Directly ionizing radiation
Radiation composed of electrically charged particles that are capable of ionizing by collision.
(NCRP 38)

Director
The Director, Office of Nuclear Material Safety and Safeguards, U. S. Nuclear Regulatory Commission.
(10CFR61.2)

Director
The Director of the Nuclear Regulatory Commission's Office of Nuclear Material Safety and Safeguards.
(10CFR60.2)

Director
An individual, appointed or elected according to law, who is authorized to manage and direct the affairs of a corporation, partnership or other entity.
(10CFR50.2)

Dirty bomb
A fission bomb or any other weapon which would distribute relatively large amounts of radioactivity upon explosion, as distinguished from a fusion weapon. (Compare clean bomb.)
(USAEC-1974)

Disadvantage factor
In a reactor cell, the ratio of the average neutron flux density in a material to that in the fuel.
(IEC 50-393-1993)

Discharge noise (of a corona counter tube)
Current or voltage fluctuations of a stable corona discharge in the absence of radiation.
(IEC 50-394-1993)

Disclaimed opinion
A statement that the nuclear material balance report was not examined in accordance with ANSI N15.38-1982 and, accordingly, no opinion is stated.
(ANSI N15.11-1983)

Discovery
The completion of the documentation first identifying the existence of a deviation or failure to comply potentially associated with a substantial safety hazard within the evaluation procedures discussed in Sec. 50.55(e)(1).
(10CFR50.2)

Discretization
A mathematical approximation in which values of a variable under consideration are taken to be constants over small ranges of space and/or time.
(ICRP 29)

Discriminator
Sub-assembly which produces an output logic pulse only if its input signal exceeds a preset threshold level.
(IEC 50-394-1993)

Discriminator
An electronic circuit which selects signal pulses according to their pulse height or voltage. It is used to delete extraneous radiation counts or background radiation, or as the basis for energy spectrum analysis.
(USAEC-1974)

Discriminator curve
Curve showing the counting rate as a function of the discriminator threshold.
(IEC 50-394-1993)

Discriminator, pulse height
A circuit that produces an output signal if it receives an input pulse whose amplitude exceeds an assigned value.
(ANSI N42.15-1980)

Discriminator, pulse height
A circuit designed to select and pass voltage pulses of a certain specified amplitude.
(RHH)

Disinfection
Destruction of the majority of microorganisms, not necessarily of all the spores.
(AM-1993)

Disinfection
The destruction and removal of pathogenic organisms, especially by means of chemical substances.
(ANSI Z88.2-1969)

Disintegration (radioactive)
Breaking down of a radioactive atom, with discharge of alpha, beta, gamma or other radiation.
(NCRP 48)

Disintegration constant
The fraction of the number of atoms of a radioactive nuclide which decay in unit time; l in the equation N = N_oe^-lt, where N_o is the initial number of atoms present, and N is the number of atoms present after some time, t.
(HPJ 60)

Disintegration energy
Energy obtained by a given nuclear disintegration.
(IEC 50-393-1993)

Disintegration energy (Q)
For a given nuclear disintegration: the amount of energy released.
(ANSI N1.1-1976)

Disintegration, nuclear
A spontaneous nuclear transformation (radioactivity) characterized by the emission of energy and/or mass from the nucleus. When numbers of nuclei are involved, the process is characterized by a definite half-life.
(HPJ 60)

Disintegration, radioactive
Equivalent to radioactive decay.
(USAEC-1974)

Disordering
Any process by which atoms are displaced from or rearranged among their positions in a crystal lattice, e.g., by ionizing radiation.
(ANSI N1.1-1976)

Dispatcher
Any person or persons within the carrier's organization responsible for contact with the carrier's drivers.
(ANSI N14.27-1986)

Dispersion
A system consisting of particles suspended in a fluid.
(AM-1993)

Dispersion coefficient
A measure of the spreading of a flowing substance due to the nature of the porous medium.
(NCRP 123I)

Dispersion coefficient
A measure of the spreading of a flowing substance due to the nature of the porous medium.
(NCRP 76)

Dispersion fuel
A fuel mixture in which the fuel bearing phase is dispersed in a matrix of nonfissionable material.
(ANSI N1.1-1976)

Dispersivity
A geometric property of a porous medium which determines the dispersion characteristics of the medium by relating the components of pore velocity to the dispersion coefficient.
(NCRP 123I)

Displacement
See electric flux density.
(NCRP 67)

Displacement factor (displacement correction)
When a dosimeter, calibrated in air with respect to exposure, is introduced into a phantom, the exposure averaged over the "hole" is determined. To deduce the exposure at the same point in the phantom, in the absence of the dosimeter, it is necessary to correct for the attenuation in and scatter from the material displaced by it. The "hole" size is that of the dosimeter when it was calibrated and must include a build-up cap if one were used for the calibration. The correction factor is normally less than unity and has been taken as 0.985 for ionization chambers of external dimensions of about 1 cm (including build-up cap) for gamma rays from ⁶⁰Co or x rays generated by potentials in the neighborhood of 2 MV. It is normally assumed to be unity for x rays generated by potentials less than 400 kV.
(ICRU 24)

Displacement per atom
Number of displaced atoms per target atom in the solid, induced by bombardment with ionizing radiation.
(IEC 50-393-1993)

Disposal
The isolation of radioactive wastes from the biosphere inhabited by man and containing his food chains by emplacement in a land disposal facility.
(10CFR61.2)

Disposal
The permanent isolation of low-level radioactive waste pursuant to the requirements established by the Nuclear Regulatory Commission under applicable laws, or by an Agreement State if such isolation occurs in this Agreement State.
(10CFR62.2)

Disposal
The planned release of radioactive waste in a manner that precludes recovery or its placement in a manner that is considered permanent so that recovery is not planned.
(ANSI/HPS N13.45-1998)

Disposal
The isolation of radioactive wastes from the accessible environment.
(10CFR60.2)

Disposal
Permanent isolation of radioactive material from the surrounding environment.
(10CFR110.2)

Disposal site
That portion of a land disposal facility which is used for disposal of waste. It consists of disposal units and a buffer zone.
(10CFR61.2)

Disposal unit
A discrete portion of the disposal site into which waste is placed for disposal. For near-surface disposal the unit is usually a trench.
(10CFR61.2)

Disqualifying or disqualifying condition
Something which precludes medical approval for research reactor operator certification.
(ANSI/ANS-15.4-1988)

Dissolution Rate
Rate of change of a solid to a liquid form by immersion in a fluid of suitable character.
(NCRP 125)

Distal lung
The region of the lung farthest from the nose.
(ENV RAD)

Distinguishable from background
The detectable concentration of a radionuclide is statistically different from the background concentration of that radionuclide in the vicinity of the site or, in the case of structures, in similar materials using adequate measurement technology, survey, and statistical techniques.
(10CFR20.1003)

Distributed source
An area or volume source with at least one dimension large compared to the dimensions of the detector and which may produce radiations over a wide range of angles of incidence on the detector.
(NCRP 112)

Distribution coefficient
The quantity of a radionuclide sorbed by the solid per unit weight of solid divided by the quantity of radionuclide dissolved in the water per unit volume of water.
(NCRP 123I)

Distribution coefficient
The quantity of radionuclide sorbed by a solid per unit weight of the solid, divided by the concentration of the radionuclide dissolved in water.
(NUREG/CR 3332)

Distribution factor
A term used to express the modification of the effect of radiation in a biological system attributable to the nonuniform distribution of an internally deposited isotope, such as radium's being concentrated in bones. (See absorbed dose, dose equivalent, quality factor, relative biological effectiveness.)
(USAEC-1974)

Distribution factor (radiation protection)
The factor used in computing dose equivalent to allow for the non-uniform distribution of internally deposited radionuclides.
(ANSI N43.2-1977)

Distribution factor (radiation protection)
The factor used in computing dose equivalent to allow for the non-uniform distribution of internally deposited radionuclides.
(ANSI N1.1-1976)

Distribution function, fractional, a_h(t)
The ratio of the distribution function in organ h due to a bolus administrations, divided by the activity administered in the bolus.
(MIRD)

Distribution function, q_h(t)
The activity in organ h corrected for radioactive decay to a reference time.
(MIRD)

Disturbed zone
That portion of the controlled area the physical or chemical properties of which have changed as a result of underground facility construction or as a result of heat generated by the emplaced radioactive wastes such that the resultant change of properties may have a significant effect on the performance of the geologic repository.
(10CFR60.2)

Divergence
Growth of a reaction rate with time.
(IEC 50-393-1993)

Divergence
Growth of a reaction rate with time.
(ANSI N1.1-1976)

Divergent reaction
Nuclear chain reaction in which the number of reactions caused directly by one reaction is on the average greater than unity.
(IEC 50-393-1993)

Divergent reaction
See chain reaction, nuclear.
(ANSI N1.1-1976)

DNA Adduct
A chemical covalently bound to DNA.
(NCRP 125)

Documentation
Description of what a computer program does and how it does it, its assumptions, and its possible applications. An 'owners' and operators' manual' for a program.
(NUREG/CR 3332)

DOE
The U.S. Department of Energy or its duly authorized representatives.
(10CFR72.3)

DOE
The U.S. Department of Energy or its duly authorized representatives.
(10CFR74.4)

DOE
The U.S. Department of Energy or its duly authorized representatives.
(10CFR51.14)

DOE
The U.S. Department of Energy or its duly authorized representatives.
(10CFR60.2)

DOE activities
An activity taken for or by the DOE that has the potential to result in the occupational exposure of an individual to radiation or radioactive material. The activity may be, but is not limited to, design, construction, operation or decommissioning. To the extent appropriate, the activity may involve a single DOE facility or operation or a combination of facilities and operations, possibly in an entire site.
Editorial Note: This definition was removed from 10CFR835.2 in the 1998 revision.
(10CFR835.2-1993)

DOE Activity
An activity taken for or by DOE in a DOE operation or facility that has the potential to result in the occupational exposure of an individual to radiation or radioactive material. The activity may be, but is not limited to, design, construction, operation, or decommissioning. To the extent appropriate, the activity may involve a single DOE facility or operation or a combination of facilities and operations, possibly including an entire site or multiple DOE sites.
(10CFR835.2-1998)

DOE activity
An activity taken for or by the Department that has the potential to result in exposures of persons to ionizing radiation. The activity may involve a single DOE facility, or a combination of facilities and operations, possibly including an entire site or no fixed site at all.
(10CFR834.2)

DOE facility
Something that is built, installed, or established to serve a particular DOE activity.
(10CFR834.2)

DOE and Department of Energy
The Department of Energy established by the Department of Energy Organization Act (Pub. L. 95-91, 91 Stat. 565, 42 U.S.C. 7101 et seq.) to the extent that the Department, or its duly authorized representatives, exercises functions formerly vested in the U.S. Atomic Energy Commission, its Chairman, members, officers and components and transferred to the U.S. Energy Research and Development Administration and to the Administrator thereof pursuant to sections 104 (b), (c) and (d) of the Energy Reorganization Act of 1974 (Pub. L. 93-438, 88 Stat. 1233 at 1237, 42 U.S.C. 5814) and retransferred to the Secretary of Energy pursuant to section 301(a) of the Department of Energy Organization Act (Pub. L. 9591, 91 Stat. 565 at 577-578, 42 U.S.C. 7151).
(10CFR73.2)

Dollar
A unit of reactivity. One dollar is the maximum amount of reactivity in a reactor due to delayed neutrons alone. (See reactivity.)
(USAEC-1974)

Dollar (reactor technology)
A special unit of reactivity; equal to the amount of reactivity required to make a reactor critical on prompt neutrons only, and therefore equal to the effective delayed neutron fraction for that reactor.
(ANSI N1.1-1976)

Dominant mutation
The mutation is dominant if it produces its effect in the presence of an equivalent normal gene from the other parent.
(BEIR V)

Dominant mutation
The mutation is dominant if it produces its effect in the presence of an equivalent normal gene from the other parent.
(BEIR IV)

Donut
See acceleration chamber.
(NBS 55)

DOP aerosol
A dispersion of dioctyl phthalate (DOP) droplets in air. Monodisperse DOP is generated by controlled vaporization and condensation of liquid dioctyl phthalate to give a cloud of droplets with diameters of approximately 0.3 µm. Polydisperse DOP is generated by blowing compressed air through liquid dioctyl phthalate and exhausting through special nozzles under controlled conditions to produce a cloud of droplets with a light-scattering mean diameter of approximately 0.7 µm.
(ERDA 76-21)

Dopoamine
A decarboxylated form of DOPA found especially in the adrenal glands.
(HPJ 60)

Doppler broadening
In spectroscopy, the observed broadening of a spectral line resulting from the thermal motion of the molecules, atoms or nuclei. In reactor technology, it is the observed broadening of the energy width of a cross section resonance resulting from the thermal motion of the target particles.
(ANSI N1.1-1976)

Doppler coefficient
That part of the temperature coefficient of reactivity which arises from Doppler broadening.
(ANSI N1.1-1976)

Doppler effect
The change in the observed wave length of a radiation which results from the motion of its source relative to the observer.
(ANSI N1.1-1976)

Doppler effect
The shift with temperature of the interaction rate between neutrons and reactor materials, such as fuel rods, structural materials, and fertile materials. The shift can appreciably affect the neutron density and hence the reactivity of reactors. (See neutron density.)
(USAEC-1974)

Doppler effect
The change in the observed wave length of a radiation which results from the motion of its source relative to the observer.
(RHH)

Dose
A general term for absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, committed effective dose equivalent, or total effective dose equivalent as defined in this part.
(10CFR835.2-1998)

Dose
As used in the general sense, refers to deposition of energy by ionizing radiation.
(NCRP 121)

Dose
The quantity of radiation absorbed, per unit of mass, by the body or by any portion of the body.
(10CFR20.4)

Dose
A general term denoting the quantity of radiation or energy absorbed. For special purposes it must be appropriately qualified. If unqualified, it refers to absorbed dose. Unit of absorbed dose is the rad. The SI unit is the gray
(1 Gy = 1 J kg^-1 = 100 R).
(HPJ 60)

Dose
A general term denoting the quantity of radiation or energy absorbed; for special purposes, must be qualified; if unqualified, refers to absorbed dose.
(NCRP 98)

Dose
In ANSI/ANS-6.4, the term "dose" is to be taken as "dose equivalent," in particular, the maximum value of dose equivalent in an appropriated tissue phantom.
(ANSI/ANS-6.4-1985)

Dose
A general term denoting the quantity of radiation or energy absorbed. For special purposes, it must be appropriately qualified; if unqualified, it refers to absorbed dose. See for example: Absorbed Dose, Cumulative Dose, Depth Dose, Dose Equivalent, Exit Dose, Integral Dose, Maximum Permissible Dose Equivalent, Median Lethal Dose, Percentage Depth Dose, Permissible Dose, Skin Dose, Threshold Dose, Tissue Dose.
(BEIR III)

Dose
A colloquial term. For precision it should be appropriately qualified (see absorbed dose, absorbed dose index, dose equivalent, dose-equivalent index).
(NCRP 51)

Dose
The amount of ionizing radiation energy absorbed per unit mass of irradiated material at a specific location. In the human body it is measured in rems; in inanimate bodies it is measured in rads.
(ERDA 76-21)

Dose
See absorbed dose.
(NCRP 48)

Dose
See absorbed dose, biological dose, maximum permissible dose, threshold dose.
(USAEC-1974)

Dose
A general form denoting the quantity of radiation or energy absorbed. For special purposes it must be appropriately qualified. If unqualified, it refers to absorbed dose.
(BEIR I)

Dose
See absorbed dose, exposure dose, and RBE dose.
(NBS 73)

Dose
See absorbed dose.
(NBS 66)

Dose
As used in this Handbook, either absorbed dose or RBE dose. Doses and dose rates will be said to exist at some point in space even if tissue may not actually be located at such a point. In such instances such doses and dose rates are the maximum ones that would be obtained in a 30-cm-thick infinite slab of tissue.
(NBS 63)

Dose
The quantity of radiation delivered to a specified mass or volume. Dose units are: the roentgen (r) for gamma rays, the rad for gamma and beta rays. In radiology the dose may be specified in air, on the skin or at some depth beneath its surface; no statement of dose is complete without specification of location at which the dose is considered.
(NBS 54)

Dose
A measure of the energy imparted to a unit mass of a medium by the ionizing particles present in the place of interest. The term dose as used in this Handbook is expressed in ergs per gram. This is the unit recommended by the International Commission on Radiological Unit for use at energies above 3 Mev. See rad.
(NBS 55)

Dose
The radiation delivered to a specified volume or to the whole body. The unit is the roentgen.
(NBS 51)

Dose coefficient
Committed tissue equivalent dose per unit acute intake H_T(t) or committed effective dose per unit acute intake e(T), where T is the time period in years over which the dose is calculated (e.g. e(50)).
(ICRP 68)

Dose coefficient
Committed tissue equivalent dose per unit intake or committed effective dose per unit intake (Sv Bq-1).
(ICRP 67)

Dose coefficient
Committed or integrated tissue dose equivalent and effective dose equivalent per unit intake of activity. (Sv/Bq).
(ICRP 56)

Dose commitment
The total radiation dose to a part of the body that will result from retention in the body of radioactive material. For purposes of estimating the dose commitment, it is assumed that from the time of intake the period of exposure to retained material will not exceed 50 years.
(10CFR32.2)

Dose commitment
An early term for expression of the legacy of dose from a single intake of a radionuclide. No specific time interval is designated in contrast to "committed dose equivalent."
(NCRP 84)

Dose commitment
The dose commitment, as used in NCRP 75, refers to the radiation dose received during some period of immediate exposure plus the dose over the time period of interest while the material persists in the environment.
(NCRP 75)

Dose commitment
The infinite time integral of the per caput dose rate in a given organ or tissue for a specified population - the exposed population is not necessarily constant in number.
(ICRP 29)

Dose commitment (DC)
The total radiation dose-equivalent in the body or specified part of the body that would be received from an intake of radioactive material during a hypothetical 50-year period following the initial intake.
(ANSI N343-1978)

Dose committment
The dose committment (H_c,T or E_c) is a calculational tool. It can be assessed for a critical group as well as for the whole world population. It is defined as the infinite time integral of the per caput dose rate (H_T or E) due to a specified event, such as a unit of practice( e.g., a year of practice):

or

(ICRP 60)

Dose conversion convention
The method used to relate exposure to radon progeny expressed in WLM, to effective dose expressed in mSv on the basis of equal detriment.
(ICRP 65)

Dose conversion factor
The absorbed dose in rad per working level month.
(NCRP 78)

Dose conversion factor (Cl)
Conversion factor to obtain absorbed dose in water for ⁶⁰Co, ¹³⁷Cs and high-energy x-ray beams from measurements made with an ionization chamber in a water phantom when the chamber has been calibrated in air in exposure units using ⁶⁰Co or 2-MV x rays.
(NCRP 69)

Dose distribution factor
A factor used to modify the absorbed dose when distribution of the dose is not nominally uniform. It has usually been applied to gross rather than microscopic distributions.
(NCRP 84)

Dose equivalent
The product of absorbed dose in rad (or gray) in tissue, a quality factor, and all other modifying factors at the location of interest. Dose equivalent is expressed in units of rem (or sievert).
(10CFR834.2)

Dose equivalent
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose (D) and the quality factor Q. The name for the unit of dose equivalent (J kg^-1) is the sievert (Sv).
(NCRP 114)

Dose equivalent
A quantity used for radiation protection purposes that expresses on a common scale for all radiations the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose (D) in gray and the quality factor (Q). The unit of dose equivalent is the sievert (Sv).
(NCRP 111)

Dose equivalent
A quantity that expresses, for the purposes of radiation protection and control, an assumed equal biological effectiveness of a given absorbed dose on a common scale for all kinds of ionizing radiation. SI unit is the Sievert. (See Units).
(BEIR V)

Dose equivalent
The dose equivalent, H, is the product of Q and D at the point of interest in body tissue where D is the absorbed dose, Q is the quality factor weighting the absorbed dose for the biological effectiveness of the charged particles producing the absorbed dose.

Unit: J kg^-1. The special name for the unit of dose equivalent is sievert (Sv).
(ICRU 44)

Dose equivalent
A quantity, that expresses for the purposes of radiation protection, the assumed biological effectiveness of absorbed dose on a common scale for all kinds of ionizing radiation. The S.I. unit of dose equivalent is the sievert (Sv). One sievert equals one joule per kilogram.
(NCRP 103)

Dose equivalent
A quantity that expresses, for the purposes of radiation protection and control, the assumed effectiveness of dose on a common scale for all kinds of ionizing radiation. SI unit is the Sievert. (See Units).
(BEIR IV)

Dose equivalent
The product of the absorbed dose and the quality factor. Dose equivalent is considered to be related to radiation risk.
(NCRP 94)

Dose equivalent
The quantity that expresses the effects of all radiations on a common scale for calculating the effective absorbed dose. It is defined as the product of the absorbed dose, the quality factor, and other modifying factors. The unit of dose equivalent is the rem [the SI unit is the sievert (Sv), where 100 rem = 1 Sv].
(NUREG/CR 3332)

Dose equivalent
Quantity obtained by multiplying the absorbed dose by a factor to allow for the different harmfulness to tissue of various kind of ionizing radiation. Unit sievert, symbol Sv. Appropriate factors are recommended by the Commission.
(ICRP 36)

Dose equivalent
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose and certain modifying factors. The unit of dose equivalent is the rem. See rem.
(NCRP 68)

Dose equivalent
The dose equivalent, H, is the product of D, Q, and N, at the point of interest in tissue, where D is the absorbed dose, Q is the quality factor, and N is the product of any other modifying factors, H = DQN.
(ANSI N43.1-1978)

Dose equivalent
A quantity used for radiation protection purposes that expresses on a common scale for all radiations the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose in rads and certain modifying factors The special unit of absorbed dose is the rem.
(NCRP 59)

Dose equivalent
The absorbed dose weighted by modifying factor Q and N given in ICRP Publication 26. Dose equivalent is intended to correlate with the more important deleterious effects of exposure to radiation than does absorbed dose.
(ICRP 29)

Dose equivalent
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose and certain modifying factors. The unit of absorbed dose is the rem.
(NCRP 48)

Dose equivalent
The product of absorbed dose, quality factor, and other necessary modifying factors.
(ANSI N319-1976)

Dose equivalent
A term used to express the amount of effective radiation when modifying factors have been considered. The product of absorbed dose multiplied by a quality factor multiplied by a distribution factor. It is expressed numerically in rems.
(USAEC-1974)

Dose equivalent
The product of absorbed dose and the quality factor (QF). (Other modifying factors may also be employed.)
The special unit of dose equivalent is the rem; the dose equivalent is in rems if the absorbed dose is in rads. In the absence of recommended simple terminology, values of dose equivalent or dose equivalent rate will be said to "exist at" or be "delivered to" some location; the meaning that these values would be the most significant ones received by an individual if he were at that location. This quantity should be used for protection purposes only.
(NCRP 38)

Dose equivalent
Equal absorbed doses of radiation may not give rise to equal risks of a given biological effect, since the biological effectiveness may be affected by differences in type of radiation or irradiation conditions. To apply risk estimates obtained under a given set of conditions to situations in which other types of radiations are used or the conditions of irradiation differ, e.g., with regard to the spatial distribution of absorbed dose it is necessary to multiply the absorbed dose for each type of radiation by one or more weighting factors. In radiation protection the quantity obtained by thus weighting the absorbed dose in rads is called the dose equivalent (DE) and its unit is the rem. The dose equivalent for a given type of radiation and at a given location in the body is numerically equal to the product of the absorbed dose in rads for that radiation at that position and the modifying factors specified by the Commission. The dose equivalent for a given radiation may thus be expressed by the following equation: (DE) = D x (MF)₁ x (MF)₂ x ... (MF)_i, where (DE) is the dose equivalent in rems, D is the absorbed dose in rads, and (MF)₁ ... (MF)_i are appropriate modifying factors.
(ICRP 15)

Dose equivalent
The product of absorbed dose, quality factor, dose distribution factor, and other modifying factors necessary to express on a common scale, for all ionizing radiations, the irradiation incurred by exposed persons. It is applicable only when the maximum permissible dose is not exceeded. The unit is the rem.
(ANSI N13.6-1966)

Dose equivalent (abbr., DE)
A quantity used in radiation protection. It expresses all kinds of radiation on a common scale for calculating the effective absorbed dose; defined as the product of the absorbed dose in rads and modifying factors; unit of DE is the rem.
(BEIR III)

Dose Equivalent (DE)
The product of the absorbed dose (D), the quality factor (Q), and other modifying factors (N) at a point of interest in tissue [ICRP 26 (1977)].
(HPS N13.42-1997)

Dose equivalent (DE)
Quantity that expresses all radiations on a common scale for calculating the effective absorbed dose. It is defined as the product of the absorbed dose in rads and certain modifying factors. The unit of DE is the rem.
(BEIR I)

Dose equivalent (DE) or (H)
Defined by
H = D Q N,
where
D = absorbed dose from a particular radiation,
Q = quality factor for a particular radiation (more recently called the "radiation weighing factor" by the ICRP - see ICRP 60),
N = the product of all other modifying factors specified by the ICRP.
The ICRP has assigned a value of unity to N for the present. The value for Q is assumed to be 20 for alpha particles and 1 for photons and electrons. The SI unit of dose equivalent is the same as for absorbed dose, J kg^-1, in fundamental metric units; however, the unit is termed the sievert (Sv), which has different implications regarding radiation risks than the gray. (See ICRP 26 and ICRP 60.)
(ANSI/HPS N13.22-1995)

Dose equivalent (H_T)
The product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. The units of dose equivalent are the rem and the sievert (Sv).
(10CFR20.1003)

Dose equivalent (H)
The product of absorbed dose (D) in rad (or gray) in tissue, a quality factor (Q), other modifying factors (N). Dose equivalent is expressed in units of rem (or sievert)) (1 rem = 0.01 sievert).
(10CFR835.2-1993)

Dose equivalent (H)
Product of D, Q and N at the point of interest in tissue, where D is the absorbed dose, Q is the quality factor and N is the product of all other modifying factors.

(IEC 50-393-1993)

Dose equivalent (H)
Absorbed dose multiplied by the quality factor.
(NCRP 112)

Dose equivalent (H)
A quantity used in radiation protection. It expresses all radiations on a common scale for calculating the effective absorbed dose. It is defined as the product of the absorbed dose in rad and certain modifying factors. The unit of absorbed dose is the rem. In the new SI system, the special unit of dose equivalent will be the sievert (Sv); 1 Sv = 100 rem.
(HPJ 60)

Dose equivalent (H)
A quantity, defined for radiation protection purposes, that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose (D) and the quality factor (Q). The name for the unit of dose equivalent (J kg^-1) is the sievert (Sv).
(NCRP 107)

Dose equivalent (H)
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose, D, and the quality factor, Q. The name for the unit of dose equivalent (J kg^-1) is the sievert, Sv. 1 sievert = 100 rem. (See sievert, rem).
(NCRP 105)

Dose equivalent (H)
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose (D) and quality factor (Q). The name for the SI unit of dose equivalent (J kg-1) is the sievert (Sv). Still in use temporarily is the rem; 1 rem = 0.01 Sv.
(NCRP 101)

Dose equivalent (H)
Quantity that expresses the biological effect of interest in radiation protection for all kinds of radiation on common scale: defined as the product of the absorbed dose in rad or Gy and quality factor (Q) for the particular radiation, i.e., H=DQ; unit of H has been the rem and is now the Sievert (Sv) in SI units, 100 rem = 1 Sv.
(NCRP 98)

Dose equivalent (H)
A quantity, defined for radiation protection purposes, which is the product of the absorbed dose to the tissue and a quality factor "Q" determined by the properties of the radiation that produced the absorbed dose. For x rays, gamma rays and electrons, Q=1 and dose equivalent values are numerically equal to absorbed dose values when consistent units are used for both quantities. The SI unit for dose equivalent is joule per kilogram. The special name for the SI unit of dose equivalent is sievert (Sv). The previous special unit of dose equivalent, rem, is being replaced by the sievert. One sievert equals 100 rem.
(NCRP 102)

Dose equivalent (H)
The product of the absorbed dose (D), the quality factor (Q), and any other modifying factors (N). The SI unit of dose equivalent is the sievert (Sv); the conventional unit is the rem (1 rem = 0.01 Sv).
(FGR 11)

Dose equivalent (H)
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose and the quality factor. In SI units, the unit of dose equivalent is the sievert (Sv). Still in used temporarily is the rem; 1 rem = 0.01 Sv.
(NCRP 91)

Dose equivalent (H)
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose and the quality factor. In SI units, the unit of dose equivalent is the sievert (Sv). Still in used temporarily is the rem; 1 rem = 0.01 Sv.
(NCRP 93)

Dose equivalent (H)
The product of D, Q, and N, at the point of interest in tissue, where D is the absorbed dose, Q is the quality factor, N is the product of any other modifying factors. The special unit of dose equivalent is the rem. When D is expressed in rads, H is expressed in rems.
(ANSI N13.15-1985)

Dose equivalent (H)
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose and certain modifying factors. The unit of dose equivalent is currently the rem (see rem) or the sievert (see Sv).
(NCRP 84)

Dose equivalent (H)
The product of the absorbed dose in rads, the quality factor, and any other modifying factors. Dose equivalent is expressed in rems and is considered to be related to the radiation risk.
(NCRP 81)

Dose equivalent (H)
The product of D and Q, where D is the absorbed dose and Q is the quality factor. The concept of dose equivalent is intended for use only in radiation protection and only at levels of exposure smaller than or comparable with the dose equivalent limits recommended by the ICRP.
(ICRU 43)

Dose equivalent (H)
The product of D, Q, and N, at the point of interest in tissue, where D is the absorbed dose, Q is the quality factor, n is the product of any other modifying factors. The special unit of dose equivalent is the rem. When D is expressed in rads, H is expressed in rems. When D is expressed in grays, H is expressed in sieverts (Sv). 1 Sv = 100 rem.
(ANSI N13.11-1983)

Dose equivalent (H)
The product of D, Q and N, at the point of interest in tissue, where D is the absorbed dose, Q is the quality factor, and N is the product of all modifying factors.

(ICRU 33)

Dose equivalent (H)
The product of the absorbed dose, the quality factor (Q) and the product of any other modifying factors (N). (Currently N = 1).
(ICRP 30)

Dose equivalent (H)
The product of absorbed dose, D, quality factor, Q, and N, at the point of interest in tissue. N is the product of any modifying factors other than Q. For the purposes of this report, N = 1. The special unit of dose equivalent is the rem. With D expressed in rads, H is in rems. The dose equivalent is not defined for values larger than the order of the maximum permissible dose equivalent, HM. There is no such restriction of dose-equivalent rate.
(NCRP 51)

Dose equivalent (H)
A quantity used for radiation protection purposes that expresses on a common scale for all radiations, the irradiation incurred by exposed persons. It is defined as the product of the absorbed dose in rads and certain modifying factors. The unit of absorbed dose is the rem. (For radiation protection purposes of the report, the dose equivalent in rems may be considered numerically equivalent to the absorbed dose in rads and the exposure in roentgens.)
(NCRP 49)

Dose equivalent (H)
The product of D, Q and N, at the point of interest in tissue, where D is the absorbed dose, Q is the quality factor, and N is the product of any other modifying factors.

The special unit of dose equivalent is the rem. When D is expressed in rads, H is in rems.
(ICRU 19)

Dose equivalent (H)
In general, the biological effectiveness of a given absorbed dose depends on the type of radiation and on the irradiation conditions. In current radiation protection procedures, an indication of the effect upon a given organ is inferred by weighting the absorbed dose in that organ by certain modifying factors. The product of these modifying factors and absorbed dose is called the dose equivalent, H. The special unit of H is the rem. When D is expressed in rads, H is in rems.
(ICRU 20)

Dose equivalent (H)
The product of absorbed dose, quality factor, dose distribution factor, and other modifying factors necessary to express on a common scale, for all ionizing radiations, the irradiation incurred by exposed persons. The special unit of dose equivalent is the rem. For the purposes of criticality accident dosimetry, dose equivalent is considered to be the sum of the absorbed doses for gamma rays and neutrons modified by quality factors appropriate for acute, relatively massive amounts of radiation and, hence, the total dose equivalent is usually approximately equal to the total absorbed dose.
(ANSI N13.3-1969)

Dose equivalent (H_T)
The product of the absorbed dose in tissue, quality factor of radiation, and all other necessary modifying factors at the location of interest. The unit of dose equivalent is the sievert (Sv) or the rem. One rem is equal to 0.01 Sv.
(HPS N13.41-1997)

Dose equivalent (radiation protection)
The product of absorbed dose, quality factor, distribution factor, and other modifying factors necessary to obtain an evaluation of the effects of irradiation received by exposed persons, so that the different characteristics of the exposure are taken into account. It is commonly expressed in rems.
(ANSI N1.1-1976)

Dose equivalent commitment
The infinite-time integral of the per caput dose equivalent rate in any given organ or tissue for a specified population.
(NCRP 84)

Dose equivalent commitment
The time integral of the per capita dose equivalent rate.
(NUREG/CR 3332)

Dose equivalent index (H_I)
The dose equivalent index at a point is the maximum dose equivalent within a 30 cm-diameter sphere centered at this point and consisting of material equivalent to soft body tissue with a density of 1000 kg m^-3. An important consequence of this definition is that HI is not defined at distances closer than 15 cm from a surface or source. The center of the sphere is almost always at a different point than that at which the maximum dose equivalent occurs.
(ICRP 43)

Dose equivalent index (H_I)
Maximum dose equivalent within the ICRU sphere centered at the point in space to which the quantity is assigned. The outer 0.07 mm thick shell is ignored (see Maximum Dose Equivalent in a shell). It is also called the unrestricted dose equivalent index.
(ICRU 43)

Dose equivalent index (H_I) or absorbed-dose index (D_I) at a point
The maximum dose equivalent or absorbed dose 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 g cm^-3. 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 aa 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)

Dose equivalent index rate (H_I)
The quotient of dH_I by dt, where dH_I is the increment of dose equivalent index in the time interval dt.

(ICRU 33)

Dose equivalent limit (annual) (H_L)
The annual dose equivalent limit, H_L, defines the degree to which radiation exposure should be controlled to achieve an acceptable level of risk for workers and the general public, taking into account both somatic and genetic detriment. The present limit for annual occupational exposure if 50 mSv (5 rem) and the corresponding limit for exposure to the public is 1 mSv (0.1 rem) for continuous exposures and 5 mSv (0.5 rem) for infrequent exposures.
(NCRP 105)

Dose equivalent limits
Recommended maximum values of the effective dose equivalents in certain organs or tissues of the body. In the case of skin, the averaging procedure is subject to restrictions.
(ICRU 43)

Dose equivalent limits
Ceiling on effective dose equivalent and on dose equivalent to single organ or tissue for workers and members of the public as recommended by the Commission.
(ICRP 36)

Dose equivalent limits
The maximum values of committed dose equivalent incurred in 1 year by individual organs (non-stochastic limits), and by the uniformly irradiated whole body (stochastic limit) of an occupationally exposed person, which are recommended in ICRP Publication 26 (1977).
(ICRP 30)

Dose equivalent meter
Radiation meter used to evaluate the quantity dose equivalent.
(IEC 50-394-1993)

Dose equivalent monitor
Radiation monitor used to evaluate and check the quantity dose equivalent.
(IEC 50-394-1993)

Dose equivalent rate ()
Quotient of dH by dt, where dH is the increment of dose equivalent in the time interval dt.

(IEC 50-393-1993)

Dose equivalent rate ()
The quotient dH by dt, where dH is the increment of dose equivalent in the time interval dt.

(ICRU 33)

Dose equivalent ratemeter
Radiation meter used to evaluate the quantity dose equivalent rate.
(IEC 50-394-1993)

Dose equivalent residual (E_rd)
The accumulated dose corrected for such physiological recovery as has occurred at a specified time. It is based on the ability of the body to recover to some degree from radiation injury following exposure. It is used to predict immediate effects.
(ANSI N1.1-1976)

Dose equivalent to whole body (H_wb)
See whole body dose equivalent.
(NCRP 101)

Dose equivalent to whole body (H_wb)
See whole body dose equivalent.
(NCRP 91)

Dose equivalent, H
The product of D and Q at the point of interest in tissue, where D is the absorbed dose and Q is the quality factor. The special unit of dose equivalent is the rem. When D is expressed in rads, H is expressed in rems. When D is expressed in grays, H is expressed in sieverts (Sv). 1 Sv = 100 rem.
(ANSI/HPS N13.11-1993)

Dose equivalent, maximum permissible (MPDE)
The largest dose equivalent received within a specified period which is permitted by regulatory committee on the assumption that there is no appreciable probability of somatic or genetic injury. Different levels of MPDE may be set for different groups within a population.
(ANSI N1.1-1976)

Dose fractionation
A method of administering radiation in which relatively small doses are given daily or at longer intervals.
(BEIR III)

Dose fractionation
A method of administering radiation in which relatively small doses are given daily or at longer intervals.
(BEIR I)

Dose fractionation
A method of administering radiation in which relatively small doses are given daily or at longer intervals.
(RHH)

Dose limit
For radiation protection purposes, the maximum dose equivalent that the general public shall be allowed to receive in a stated period of time. See also maximum permissible dose equivalent.
(NCRP 51)

Dose limits
The Commission's limits of dose equivalents.
(ICRP 29)

Dose meter
An instrument used for measuring or evaluating the absorbed dose, exposure, or similar radiation quantity. (Also called dosimeter)
(ANSI N1.1-1976)

Dose meter
An instrument that measures radiation dose.
(NBS 51)

Dose meter, integrating
Ionization chamber and measuring system designed for determining total radiation administered during an exposure. In medical radiology the chamber is usually designed to be placed on the patients skin. A device may be included to terminate the exposure when it has reached a desired value.
(RHH)

Dose modification
A comprehensive statement of change in dose-response relationship resulting from a modifier, e.g., oxygen or a chemical present during the exposure. When dose-effect curves are available, and a simple factorial relationship does not exist between the two curves, the entire curves are required to specify the modification.
(ICRU 30)

Dose modification ratio
The ratio of the dose under reference conditions to that under the modified or test conditions to produce the same level of effect.
(ICRU 30)

Dose or radiation dose
A generic term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, committed effective dose equivalent, or total effective dose equivalent, as defined in other paragraphs of this section.
(10CFR20.1003)

Dose protraction
A method of administering radiation in which it is delivered continuously over a relatively long period at low dose rate.
(BEIR III)

Dose protraction
A method of administering radiation by delivering it continuously over a relatively long period at a low dose rate.
(BEIR I)

Dose protraction
A method of administering radiation in which it is delivered continuously over a relatively long period at low dose rate.
(RHH)

Dose ranges
Arbitrarily designated ranges of dose response curves.
Low dose - The straight or essentially straight, very low dose portion of the low-LET dose-response curve. For many endpoints, the dose range is roughly 0 to 20 rads. (In Tradescantia and for life shortening in mice, 20 rads is the dose at which significant deviations from the linear term can be detected.)
Intermediate dose - The portion of the curve with increasing slope, between the low dose range and the region of maximum slope (between about 20 and 250 rads, depending on the biological system).
High dose - From the region of maximum slope of where the slope becomes zero (about 250 and 400 rads, depending on the system).
Very-high dose - The remaining curves beyond the high dose region.
(NCRP 64)

Dose rate
The radiation dose delivered per unit time.
(NCRP 118)

Dose rate
The radiation dose delivered per unit of time. Measured, for example, in rad per hour.
(HPJ 60)

Dose rate
The quantity of absorbed dose delivered per unit time.
(BEIR V)

Dose rate
Absorbed dose delivered per unit time.
(NCRP 98)

Dose rate
Absorbed dose delivered per unit time.
(BEIR III)

Dose rate
See absorbed dose rate.
(NCRP 48)

Dose rate
Dose per unit time.
(NCRP 49)

Dose rate
The radiation dose delivered per unit time and measured, for instance, in rems per hour. (See absorbed dose, rem.)
(USAEC-1974)

Dose rate
Absorbed dose delivered per unit time.
(BEIR I)

Dose rate
Absorbed dose delivered per unit time.
(RHH)

Dose rate
Dose per unit time.
(NBS 73)

Dose rate
The rate of dose delivered averaged over a stated period. This may be different from instantaneous dose rate (e.g., in the operation of a pulsed generator the instantaneous dose rate greatly exceeds the dose rate averaged over 1 hour. This in turn may be higher than the dose rate averaged over 1 week if generator operation is intermittent).
(NBS 63)

Dose rate
Dose per unit time.
(NBS 54)

Dose rate
The dose delivered per unit time. Dose rates in this Handbook is expressed in ergs per gram per second.
(NBS 55)

Dose rate
The radiation dose delivered per unit time.
(NBS 51)

Dose rate effectiveness factor (DREF)
A factor by which the effect caused by a specific dose of radiation changes at low compared to high dose rates.
(BEIR V)

Dose rate effectiveness factor (DREF)
A factor used to account for the difference in effectiveness of low-LET radiations at low versus high dose rates. In NCRP Report No. 64 it is quantitated as: "The factor by which linear interpolation from data obtained at high doses and dose rates overestimates the risk per unit absorbed dose of radiation delivered at very low doses and/or dose rates. Using the a + bD² formulation, at a given dose it is (aD + bD²/aD)."
(NCRP 84)

Dose rate effectiveness factor (DREF)
The factor by which linear interpolation from data obtained at high doses and dose rates overestimates the risk per unit absorbed dose of radiation delivered at very low doses and/or dose rates. Using the aD + bD² formulation, at a given dose it is aD + bD²/aD.
(NCRP 64)

Dose rate meter
Instrument for measuring dose rate.
(NBS 73)

Dose rate meter
Instrument for measuring dose rate.
(NBS 54)

Dose rate ranges
Arbitrarily defined ranges of average dose rate are as follows:
Low average dose rate is equal to or below the range that would be expected to yield risk coefficients approximating alpha in the formulation I = aD + bD² in systems in which the model applies. In most systems this certainly should apply at dose rate of the order of 5 rads per year or less, a rate that includes those for background radiation exposure, and radiation protection guides for workers and the general public.
High average dose rate - A dose rate that would give the maximum or near maximum risk coefficients, of high dose rates. In most systems, this would correspond to a total dose of about 200 - 250 rads, delivered over minutes to about one-half day.
Intermediate average dose rates - Any rate in between low and high dose rates.
(NCRP 64)

Dose rate, absorbed
The absorbed dose per unit time.
(ANSI N43.2-1977)

Dose rate, absorbed
The increment in absorbed dose during a suitable small interval of time divided by the interval of time.
(ANSI N1.1-1976)

Dose ratemeter
Any instrument which measures radiation dose rate.
(RHH)

Dose reduction factor
The ratio of the dose rate inside a building to the corresponding dose rate outdoors.
(NUREG/CR 3332)

Dose, absorbed
The energy imparted to matter in a volume element by ionizing radiation divided by the mass of irradiated material in that volume element. The special unit of absorbed dose is the rad. One rad equals 100 ergs per gram. (Also commonly called dose.)
(ANSI N43.2-1977)

Dose, absorbed
The energy imparted to matter in a volume element by ionizing radiation divided by the mass of the irradiated material in that volume element. The SI derived unit of absorbed dose is the grey (Gy). (One Gy = 100 rad = J/kg). Also commonly called dose.
(ANSI N1.1-1976)

Dose, accumulated
The sum of the absorbed doses received by the system considered regardless of whether it is exposed to radiation in a continuous or discontinuous fashion. (Also called cumulative absorbed dose.)
(ANSI N1.1-1976)

Dose, D
Absorbed dose.
(MIRD)

Dose, emergency
The absorbed dose incurred when the maximum permissible dose equivalent is knowingly exceeded in the performance of an unusual task to protect individuals or valuable property.
(ANSI N1.1-1976)

Dose, exit
The absorbed dose at the surface of a body opposite to that upon which a beam is incident.
(ANSI N1.1-1976)

Dose, integral absorbed
The integral of absorbed dose dove the mass of irradiated matter in the volume under consideration. It is identical with the energy imparted to matter in that volume. It may be expressed in gram-greys or gram-rads.
(ANSI N1.1-1976)

Dose, maximum permissible (MPD)
Obsolete. (See dose equivalent, maximum permissible.)
(ANSI N1.1-1976)

Dose, mean lethal
Incorrect term for dose, median lethal.
(ANSI N1.1-1976)

Dose, median lethal (LD₅₀)
The absorbed dose which will kill, within a specified time, 50% of a large population of a given species.
(ANSI N1.1-1976)

Dose, occupational
The radiation dose received as a result of a person's work. It dose not include the dose from natural background radiation or the radiation dose from medical procedures.
(HPJ 60)

Dose, percentage depth
The ratio expressed as a percentage of the absorbed dose at any given depth within a body to the absorbed dose at some reference point of the body along the central ray. For x or gamma radiation, the location of the reference point depends on the energy of the incident radiation, It is at the surface for low energies or at the position of peak absorbed dose for high energies.
(ANSI N1.1-1976)

Dose, permissible
Obsolete. (See dose equivalent, maximum permissible.)
(ANSI N1.1-1976)

Dose, skin
The absorbed dose at a point on the skin.
(ANSI N1.1-1976)

Dose, threshold
The minimum absorbed dose that will produce a specified effect.
(ANSI N1.1-1976)

Dose, tolerance
Obsolete. (See dose equivalent, maximum permissible.)
(ANSI N1.1-1976)

Dose, transit
A measure of the primary radiation transmitted through a patient and measured along a central ray at some point beyond the patient.
(ANSI N1.1-1976)

Dose, volume
The product of absorbed dose and the volume of the absorbing mass. NOTE: The term is often confused with integral absorbed dose.
(ANSI N1.1-1976)

Dose-distribution factor
A factor which accounts for modification of the dose effectiveness in cases in which the radionuclide distribution in nonuniform.
(BEIR V)

Dose-distribution factor
A factor which accounts for modification of the dose effectiveness in cases in which the radionuclide distribution in nonuniform.
(BEIR IV)

Dose-effect (dose-response) model
A mathematical formulation of the way the effect (or biological response) depends on dose.
(BEIR V)

Dose-effect (dose-response) model
A mathematical formulation of the way the effect, or response, depends on dose.
(NCRP 98)

Dose-equivalent index (Hi)
The maximum dose equivalent 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. In general, the maximum values of the quality factor, Q, and the absorbed dose, D, occur at different locations in the sphere. However, Q_maxD_max is a conservative estimate for HI.
(NCRP 51)

Dose-response curve
A graphical characterization of the relationship between a defined biological endpoint and the dose received.
(NCRP 121)

Dose-response curve
The functional relationship between dose and effect.
(ENV RAD)

Dosemeter
Used in the general sense of any device measuring some form of radiation dose, e.g., a film badge.
(ICRP 35)

Dosemeter charger
Electrical device to prepare a dosemeter for operation.
(IEC 50-394-1993)

Dosemeter charger-reader
Instrument designed to charge a dosemeter and to read its stored information.
(IEC 50-394-1993)

Dosemeter reader
Instrument designed to read a dosemeter.
(IEC 50-394-1993)

Dosemeter, dosimeter (deprecated)
Radiation meter designed to measure the quantities absorbed dose or dose equivalent.
(IEC 50-394-1993)

Dosimeter
A wearable package of absorbers and radiation-sensitive elements used to estimate a cumulative absorbed dose or dose equivalent received by an individual during a specific time period.
(HPS N13.41-1997)

Dosimeter
Radiation-sensitive element(s) in a holder (the holder being considered a part of the dosimeter) used for personnel monitoring.
(ANSI/HPS N13.11-1993)

Dosimeter
A device, instrument or system that can be used to measure radiation or evaluate any quantity of irradiation for the purpose of deter-mining an individual's absorbed dose, exposure or similar radiation quan-tity.
(NCRP 114)

Dosimeter
Instrument to detect and measure accumulated radiation exposure. Examples are film badges, thermoluminescent dosimeters (TLD), and pocket chambers, all used for personnel monitoring.
(HPJ 60)

Dosimeter
Dose measuring device. See also personnel dosimeter.
(NCRP 105)

Dosimeter
A radiation sensitive element (or elements) and the holder carrying it.
(ANSI N13.15-1985)

Dosimeter
Radiation-sensitive element(s) in a holder (the holder being considered part of the dosimeter) used to provide a lifetime cumulative personal irradiation record of an individual.
(ANSI N13.11-1983)

Dosimeter
A device that measures radiation dose, such as a film badge or ionization chamber. (See radiation dosimetry.)
(USAEC-1974)

Dosimeter
Instrument to detect and measure accumulated radiation exposure. In common usage, a pencil-size ionization chamber with a self-reading electrometer, used for personnel monitoring.
(RHH)

Dosimeter
An instrument used for measuring or evaluating the absorbed dose, exposure, or similar radiation quantity.
(ANSI N13.6-1966)

Dosimeter
Instrument for measuring total dose.
(NBS 73)

Dosimeter
Instrument for measuring total dose.
(NBS 54)

Dosimeter (radon/radon daughter)
A term used to describe any device that can be used to estimate the concentration of radon or its daughter products.
(NCRP 97)

Dosimetrist
An individual, usually a radiographer or a medical physics assistant, with special training in radiation dosimetry and treatment planning.
(ICRP 44)

Dosimetry
The measurement or calculation of the energy absorbed by matter.
(NCRP 118)

Dosimetry
The measurement or calculation of the energy absorbed by matter from ionizing radiation.
(NCRP 111)

Dosimetry
The theory and application of the principles and techniques involved in the measurement and recording of radiation dose. Its practical aspect is concerned with the use of various types of radiation instruments with which measurements are made.
(HPJ 60)

Dosimetry
The science or technique of determining radiation dose.
(NCRP 105)

Dosimetry
The measurement or calculation of the energy absorbed by matter.
(NCRP 78)

Dosimetry
(See radiation dosimetry.)
(USAEC-1974)

Dosimetry period
The length of time that a dosimeter is issued to an individual for the purpose of dose determination; also commonly called the dosimeter exchange period.
(ANSI N319-1976)

Dosimetry processor
An individual or organization that processes and evaluates individual monitoring equipment in order to determine the radiation dose delivered to the equipment.
(10CFR20.1003)

Dosimetry processor
An individual or an organization that processes and evaluates individual monitoring equipment in order to determine the radiation dose delivered to the equipment.
(10CFR20.3)

Dosimetry System
A system used to assess dose equivalent from external radiation. This system includes the selection, placement, and processing of the dosimeters; interpretation and recording of results; and the means by which the quality of results is assured.
(HPS N13.41-1997)

Dosimetry system
The dosimeters, plus the related data collection and processing instruments, and techniques required to estimate the neutron dose equivalent received by exposed individuals.
(ANSI N319-1976)

Dosimetry system
The detecting devices or dosimeters plus the related data collection and processing instruments and techniques required to infer from the measurements the absorbed dose to exposed persons.
(ANSI N13.3-1969)

Dosimetry, personnel
The use of instruments and associated procedures (including calibration and quality assurance) to ascertain the radiation dose absorbed by personnel.
(HPJ 60)

Dosimetry, photographic
Determination of cumulative radiation dose with photographic film and density measurement.
(RHH)

Dot specification container
A container whose design has been published by the U.S. Department of Transportation (DOT) and is licensed under the general licensing provisions of the U.S. Nuclear Regulatory Commission (NRC). Its use is limited to the provisions prescribed for those containers in Title 49, CFR, Parts 173 and 178.
(ANSI N14.1-1990)

Double containment
An arrangement of double barriers in which the second barrier provides backup protection against leakage through or failure of the first.
(ERDA 76-21)

Double filtration
An arrangement of two filters in series with the second providing backup protection against leakage or failure of the first. Also a series arrangement intended to increase the total filtration efficiency.
(ERDA 76-21)

Double spherical harmonics method; yvon's method
An approximate method for solving the transport equation, related to the spherical harmonics method and based on two expansions of the angular dependence of the differential particle flux density, one in the forward direction and one in the backward direction. This method is used mainly when there is a marked change of neutron characteristics across a boundary.
(ANSI N1.1-1976)

Doubling dose
The amount of radiation needed to double the natural incidence of a genetic or somatic anomaly.
(BEIR V)

Doubling dose
The amount of radiation needed to double the natural incidence of a genetic or somatic anomaly.
(BEIR IV)

Doubling dose
The amount of radiation needed to double the natural incidence of a genetic or somatic anomaly.
(BEIR III)

Doubling dose
The amount of radiation needed to double the natural incidence of a genetic or somatic anomaly.
(BEIR I)

Doubling time
The time required for a breeder reactor to produce as much fissionable material as the amount usually contained in its core plus the amount tied up in its fuel cycle (fabrication, reprocessing, etc.). It is estimated as 10 to 20 years in typical reactors. (See breeder reactor, fuel cycle.)
(USAEC-1974)

Doubling time (breeder reactor technology)
(1) For a fuel charge in a given breeder reactor, the time required for the initial amount of fissile nuclides to be doubled by breeding.
(2) For the fuel inventory of an entire fuel cycle, the time required for the amount of fissile nuclides to be doubled by breeding.
(ANSI N1.1-1976)

Doubling time (reactor physics)
In a nuclear reactor with rising neutron flux density, the time taken for the flux density to double.
(ANSI N1.1-1976)

Doubly encapsulated sealed source
A sealed source in which the radioactive material is sealed within a capsule and that capsule is sealed within another capsule.
(10CFR36.2)

Drag coefficient
A coefficient that relates the particle's drag force to the velocity pressure.
(AM-1993)

Drag coefficient
The ratio of the fluid resistance to particle motion to the product of its cross section and the dynamic pressure.
(TID-26608)

Drag force
Resistance experienced by a particle when moving in a fluid.
(AM-1993)

Drain-tile ventilation
The process of using perforated pipes, called drain tiles, around the foundation of a house to remove radon.
(ENV RAD)

Drift
Change in readout, usually gradual, without concomitant change in the influence quantity.
(ANSI N42.17A-1989)

Drift
Change in readout, usually gradual, without concomitant change in the influence quantity.
(ANSI N42.17B-1989)

Drift
Change in readout, usually gradual, without concomitant change in the influence quantity.
(ANSI N42.17C-1989)

Drift tube
A series of hollow cylindrical conductors in a linear particle accelerator, with potential differences applied between successive tubes. The charged particles travel through the field-free drift tubes with uniform speed and are accelerated only at the gaps between successive tubes.
(NCRP 51)

Drill
Supervised instruction period intended to test, develop and maintain skills in a particular operation. A drill is often a component of an exercise.
(ANSI/ANS-3.8.1-1987)

Driven device
Device such as a pump or valve that is operated by a prime mover.
(IEC 50-394-1993)

Driver fuel
The nuclear fuel in the driver zone.
(ANSI N1.1-1976)

Driver zone
That zone which principally sustains the chain reaction in a multizone reactor core.
(ANSI N1.1-1976)

Drivers
Carrier's motor vehicle operators assigned to a given vehicle.
(ANSI N14.27-1986)

Droplet
A very small quantity of a liquid in the general form of a sphere.
(ANSI N13.1-1969)

Dry criticality
Reactor criticality achieved without a coolant. (Compare wet criticality; see criticality.)
(USAEC-1974)

Dry deposition
The process of deposition of airborne radioactive materials due to gravitational and surface processes.
(NUREG/CR 3332)

Dry-type filter
A filter having a medium that is not coated with an oil or adhesive to improve its retention of large particles.
(ERDA 76-21)

DTPA
Diethylenetriaminepentaacetic acid - a chelating agent
(RAH)

Dual-cycle reactor system
A reactor-turbine system in which part of the steam fed to the turbine is generated directly in the reactor and part in a separate heat exchanger. A combination of direct-cycle and indirect-cycle reactor systems.
(USAEC-1974)

Dual-load-path hoisting system
A system providing two distinct paths of support from the crane through the special lifting device to the container. Each path is capable of supporting the container in such a manner that no uncontrolled movement of the container will result from the failure or malfunction of a single part.
(ANSI N14.6-1986)

Dual-purpose reactor
A reactor designed to achieve two purposes, for example, to produce both electricity and new fissionable material.
(USAEC-1974)

Dummy element
An assembly without nuclear fuel intended to replace or to represent a fuel assembly.
(ANSI N1.1-1976)

Dummy source
Facsimile of a sealed source of exactly the same material and construction as a sealed source but containing, in place of the radioactive material, a substance resembling it as closely a practicable in physical and chemical properties.
(ANSI N542-1977)

Durability
A cycle of temperature, humidity, shock and vibration to simulate environmental exposure in an accelerated mode.
(ANSI N42.17C-1989)

Dust
Solid particles formed by erosion or other mechanical breakage of a parent material; generally consists of particles of irregular shape and larger than about 0.5 µm.
(AM-1993)

Dust
Suspension in a gaseous medium of dry solid particles with dimensions in the range generally between 2 µm and 2 mm.
(IEC 50-393-1993)

Dust
A solid mechanically produced particle with sizes varying from submicroscopic to visible or macroscopic.
(ANSI Z88.2-1980)

Dust
An aerosol made of solid particles derived from breaking up of larger solids.
(TID-26608)

Dust
A solid mechanically produced particle with sizes varying from submicroscopic to visible or macroscopic.
(ANSI Z88.2-1969)

Dust generator
A device used to disperse dry particles in the air in a controlled fashion.
(AM-1993)

Dusts
Solid particles generated by handling, crushing, grinding, rapid impact, detonation and decrepitation of organic or inorganic materials such as rock, ore, metal, coal, wood, grain, etc. Dusts do not tend to flocculate except under electrostatic forces; they do not diffuse in air but tend to settle under the influence of gravity.
(ANSI Z9.2-1971)

Duty cycle
The fraction of the operation cycle of an accelerator during which radiation is produced; the product of the pulse duration and the pulse repetition frequency.
(NCRP 51)

Duty cycle
The fraction of the total operating time of the accelerator during which X-rays are being produced. The duty cycle for an accelerator that produces a burst of X-rays during each magnetic-field cycle is the product of the X-ray burst time in seconds and the number of magnetic-field cycles per second.
(NBS 55)

Duty factor
The ratio of the pulse duration to the pulse period of a periodic pulse train.
(NCRP 67)

Dynamic logic signal
Periodically changing voltage or current, the frequency being consistent with the required system response time.
(IEC 50-393-1993)

Dynamic range
Quotient of the signal from the maximum measurable indication of a quantity to the signal from the minimum detectable value of that quantity.
(IEC 50-394-1993)

Dynamic shape factor
Ratio of the drag force on a particle to that on a sphere of equivalent diameter.
(AM-1993)

Dynamitron
A particle accelerator using a voltage multiplying circuit with the stages driven by high voltage capacitors in parallel. A radiofrequency power source is used to charge the capacitors.
(RHH)

Dyne
The unit of force which, when acting upon a mass of one gram, will produce an acceleration of one centimeter per second per second.
(RHH)

Dynode
A secondary-emission electrode so placed and operated relative to other electrodes that the number of secondary electrons leaving its surface exceeds the number of primary electrons incident upon it.
(IEC 50-394-1993)

Dysraphic
Pertaining to incomplete closure of the neural tube.
(ICRP 49)

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