n (non-uniform distribution factor)
A factor, termed at various times the "non-uniform distribution factor" or "the relative hazard factor," used to adjust the absorbed dose in bone for observed differences in the biological effectiveness of different radionuclides not dependent on radiation quality.
(NCRP 84)

N_I
Inhalability of particles, fraction of particles that enters the nose or mouth of those present in the volume of ambient air that is inspired.
(ICRP 66)

N_i
Deposition efficiency of region, i, of the respiratory tract.
(ICRP 66)

N-type semiconductor, electron semiconductor
An extrinsic semiconductor in which the conduction electron density exceeds the mobile hole density under conditions of thermal equilibrium.
(IEC 50-394-1993)

N-unit
The quantity of neutron radiation measured in a condenser R-meter that will produce the same amount of ionization as one roentgen of x radiation.
(RHH)

NaK
Alloy of sodium (Na) and potassium (K) which in some ranges of composition is molten below room temperature.
(ANSI N1.1-1976)

Nano
A prefix that divides a basic unit by one billion (10⁹).
(USAEC-1974)

Nanocurie
See curie.
(HPJ 60)

Nanocurie (nCi)
A one billionth (10^-9) part of a curie or 37 nuclear transformations per second.
(NCRP 65)

Nanophase particles
Particles with sizes of the order of nanometers.
(AM-1993)

Narrow beam
In beam attenuation measurements, a beam in which only the unscattered and small angle forward scattered radiation reach the detector.
(ANSI N1.1-1976)

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

NAS/NRC
National Academy of Sciences/National Research Council. The National Research Council is a unit of the National Academy of Sciences.
(NCRP 98)

Nasal Septum
Wall or septum between the two nasal cavities.
(NCRP 125)

Nasal Turbinates
Three scroll-like bones coming from the outer walls of the superior, middle, and inferior passages in the main nasal cavity that provide filtration, temperature control and aeration in the nose.
(NCRP 125)

Nasal Valve
Smallest part of the nasal airway forming the anteriorposterior portion of the nose that filters the incoming air.
(NCRP 125)

Naso-Oro-Pharyngo-Laryngeal (NOPL) Region
Nasal, oral, pharyngeal and laryngeal portion of the upper respiratory tract.
(NCRP 125)

Nasopharyngeal compartment
A portion of the respiratory tract between the epiglottis and the anterior nares.
(AM-1993)

National radioactivity standard source
A calibrated radioactive source prepared and distributed as a standard reference material by the U.S. National Bureau of Standards.
(ANSI N42.14-1978)

National response center
The federal government center to which releases of hazardous substances should be reported. The Center is operated by the U.S. Coast Guard and provides technical assistance and communications support for responding federal agencies.
(NCRP 118)

National standard
An instrument, source or other system or device maintained and promulgated as such by the US National Bureau of Standards.
(ANSI N317-1980)

National standards
In countries with a primary standardizing laboratory, national standards are primary radiation standards, maintained in the national standardizing laboratory, that depend on measurement of length, mass, time, temperature, and charge. An essential requirement of national primary standards is comparison with the national primary standards of other countries. In countries without a primary standardizing laboratory, national standards may be instruments calibrated against the primary standards of another country. In this instance, the national standard is a secondary standard.
(NCRP 69)

Natural (or normal uranium)
Naturally occurring uranium, atomic number 92 and atomic weight 238.07, is a mixture consisting of 99.28 percent U-238, 0.71 percent U-235, and 0.00580 percent U-234 (formed by decay of U-238). All three isotopes are a-active with half-lives of 4.51 x 10⁹ y, 7.13 x 10⁸ y, and 2.48 x 10⁵ y, respectively. Natural uranium has a specific a activity of 1502.0 ± 1.5 dpm per mg, of which 737.4 ± 1.6 dpm (49.1 percent) is due to U-234, 27.2 ± 3.5 dpm (1.8 percent) is due to U-235, and 737.4 ± 1.6 dpm (49.1 percent) is due to U-238. The term "natural uranium" or the alternate term "normal uranium" as used in this standard may apply to the metal, the metallic alloys, or to uranium compounds (oxides, carbides, etc.).
(ANSI N7.2-1963)

Natural background radiation
The radiation in the earth's natural environment, including radiation originating outside the earth's atmosphere and radiation from the naturally occurring radioactive elements on earth. These elements may be found both in the environment and inside the bodies of men and animals.
(NCRP 118)

Natural background radiation
Radiation originating in natural sources; for example, cosmic rays, naturally occurring radioactive materials, naturally occurring radioactive carbon-14, and potassium-40 in the body.
(NCRP 105)

Natural circulation reactor
A reactor in which the coolant (usually water)is made to circulate without pumping, that is, by natural convection resulting from the different densities of its cold and reactor-heated portions.
(USAEC-1974)

Natural radiation, natural radioactivity
Background radiation.
(USAEC-1974)

Natural radioactivity
Radioactivity of naturally occurring nuclides.
(IEC 50-393-1993)

Natural radioactivity
See radioactivity.
(HPJ 60)

Natural thorium
Thorium with the naturally occurring distribution of thorium isotopes (essentially 100 weight percent thorium-232).
(10CFR71.4)

Natural thorium
Thorium with the naturally occurring distribution of thorium isotopes (essentially 100 weight percent thorium-232).
(49CFR173.403)

Natural thorium
Natural thorium is a mixture of two isotopes of element number 90, Th-232 and Th-228. Both of these isotopes occurring in the thorium radioactive series, Th-232 being the series parent and Th-228 its daughter by one a and two b transformations. Both isotopes are a emitters with respective half-lives of 1.39 x 10¹⁰ years and 1.91 years. The specific a activity of the mixture is 4.9 x 10² dpm per mg. The approximate proportions by weight, in nature or at time of separation, is approximately seven billion parts of Th-232 to one part of Th-228. Thorium-228 fathers a line of a, b and g emitters having short half-lives. In-growth of these daughters following separation is dependent upon the 3.64 day half-life of radium-224 (ThX) which is the first daughter of Th-228. Natural thorium, therefore, is free from daughter radiations for only brief period of time following its separation.
(ANSI N7.2-1963)

Natural uranium
The mixture of uranium as it is found in nature, i.e., 99.3% ²³⁸U, 0.7% ²³⁵U, and 0.0058% ²³⁴U by weight. The alpha activity comes mostly, and in about equal amounts, from ²³⁸U and ²³⁴U. The specific activity of this mixture is 2.6 x 10⁷ Bq kg^-1 (0.7 pCi mg^-1).
(ANSI/HPS N13.22-1995)

Natural uranium
Uranium with the naturally occurring distribution of uranium isotopes (approximately 0.711 weight percent uranium-235 and the remainder essentially uranium-238).
(10CFR71.4)

Natural uranium
Uranium with the naturally occurring distribution of uranium isotopes (approximately 0.711 weight percent uranium-235 and the remainder essentially uranium-238).
(49CFR173.403)

Natural uranium
Uranium as found in nature, containing 0.7% of ²³⁵U, 99.3% of ²³⁸U, and a trace of ²³⁴U. It is also called normal uranium. (See uranium.)
(USAEC-1974)

Natural uranium reactor
Reactor fueled with natural uranium.
(IEC 50-393-1993)

Naturally occurring
Occurring naturally in the soil. Not caused by industrial or other human activity.
(RRM)

Nauplii
Unsegmented larvae of crustaceans having a simple median eye and three pairs of appendages.
(NCRP 109)

Naval architect
A naval architect is an individual or firm with the technical expertise to design or analyze a vessel for the intended service, or to design and analyze the vessel. The naval architect transforms codes, standards, regulations, and the requirements of the shipper or carrier into hardware.
(ANSI N14.24-1985)

Near field region
A region in the field of an antenna, located near the antenna, in which the electric and magnetic fields do not have a substantially plane-wave character, but vary considerably from point to point. The term "near field region" is only vaguely defined and has different meanings for large and small antennas. The near field region is further subdivided into the reactive near field region which is closest to the antenna and contains most or nearly all the stored energy associated with the field of the antenna, and the radiating near field region. See also: "antenna, field region of", "reactive near field region", "Fresnel region", and "far field region".
(NCRP 67)

Near-surface disposal facility
A determination by a person having responsibility for protecting Safeguards Information that a proposed recipient's access to Safeguards Information is necessary in the performance of official, contractual, or licensee duties of employment.
(10CFR61.2)

Near-wall contribution
The component of dose to cells in tube walls which arises from radiation passing only through tissue (and not air). See far-wall contribution.
(ENV RAD)

Nebulizer
A device in which droplet aerosols are produced by dispersion of a bulk liquid.
(AM-1993)

Need to know
A determination by a person having responsibility for protecting Safeguards Information that a proposed recipient's access to Safeguards Information is necessary in the performance of official, contractual, or licensee duties of employment.
(10CFR73.2)

Negative pressure respirator
A respirator in which the air pressure inside the respirator-inlet covering is positive during exhalation in relation to the air pressure of the outside atmosphere and negative during inhalation in relation to the air pressure of the outside atmosphere.
(ANSI Z88.2-1980)

Negative temperature coefficient
See temperature coefficient of reactivity.
(USAEC-1974)

Negligible individual dose (NID)
A level of effective dose to an individual that may be dismissed. The NID is 0.01 mSv y^-1.
(NCRP 121)

Negligible individual risk level (NIRL)
A level of risk that can be dismissed, nominally an annual risk of 10^-7. This risk is that associated with an annual effective dose equivalent of 0.01 mSv.
(NCRP 107)

Negligible individual risk level (NIRL)
A level of risk that can be dismissed. Namely, an annual risk of 10^-7. This risk is that associated with an annual effective dose equivalent of 0.01 mSv (0.001 rem).
(NCRP 91)

Neocortex
That portion of the gray matter covering the cerebral hemispheres showing stratification and organization characteristic of the most highly evolved type.
(ICRP 49)

Neonate
Newly born animal.
(NCRP 109)

Neoplasm
A pathological lesion characterized by the progressive or uncontrolled proliferation of cells.
(NCRP 109)

Neoplasm
Any new and abnormal growth, such as a tumor. The term "neoplastic disease" refers to any disease which forms tumors, malignant or benign.
(BEIR I)

Neoplasm
A new growth of cells which is more or less unrestrained and not governed by the usual limitations of normal reproduction. Benign - Some degree of growth restraint and no spread to distant parts. Malignant - growth invades tissues or spreads to distant parts, or both.
(RHH)

Neoplasms
Any new or abnormal growth, such as a tumor; neoplastic disease refers to any disease that forms tumors, whether malignant or benign.
(BEIR V)

Neoplasms
Any new or abnormal growth, such as a tumor; neoplastic disease refers to any disease that forms tumors, whether malignant or benign.
(NCRP 98)

Neoplasms
Any new or abnormal growth, such as a tumor; neoplastic disease refers to any disease that forms tumors, whether malignant or benign.
(BEIR IV)

Neoplasms
Any new or abnormal growth, such as a tumor; neoplastic disease refers to any disease that forms tumors, whether malignant or benign.
(BEIR III)

NEPA
The National Environmental Policy Act of 1969 including any amendments thereto.
(10CFR72.3)

NEPA
The National Environmental Policy Act of 1969, as amended (Pub. L. 91-190, 83 Stat. 852, 856, as amended by Pub. L. 94-83, 89 Stat. 424, 42 U.S.C. 4321, et seq.).
(10CFR51.14)

NEPA
The National Environmental Policy Act of 1969, as amended (Pub. L. 91-190, 83 Stat. 852, 856, as amended by Pub. L. 94-83, 89 Stat. 424, 42 U.S.C. 4321, et seq.)
(10CFR51.15)

Nephelometer
An instrument that measures the amount of light scattered from a particle cloud; also called a photometer.
(AM-1993)

Neptunium series (sequence)
The series of nuclides resulting from the radioactive decay of the man-made nuclide, neptunium-237. Many other man-made nuclides decay into this sequence. The end-product of the series is stable bismuth-209, which is the only nuclide in the series that occurs in nature. (See decay, radioactive; radioactive series.)
(USAEC-1974)

Neuroglia
A highly branched cell that makes up the supportive structure of the nervous tissue.
(ICRP 49)

Neuron
The nerve cell with it processes, collaterals and terminations; it is regarded as the structural unit of the nervous system. Under normal circumstances, the neuron is a nonproliferating cell.
(ICRP 49)

Neutralizing
Reduction in electronic charge on particles by exposure of the aerosol to ion clouds (often produced by radioactive sources).
(AM-1993)

Neutrino
Stable elementary particle with zero charge, spin 1/2, and rest mass zero or less than one thousandth of that of the electron.
(IEC 50-393-1993)

Neutrino
[Symbol v (nu)] An electrically neutral elementary Particle with a negligible mass. It interacts very weakly with matter and hence is difficult to detect. It is produced in many nuclear reactions, for example, in beta decay, and has high penetrating power; neutrinos from the sun usually pass right through the earth. (See cosmic rays, neutron, nuclear reaction.)
(USAEC-1974)

Neutrino
A neutral particle of very small rest mass originally postulated to account for the continuous distribution of energy among particles in the beta-decay process.
(RHH)

Neutron
Particle having no electric charge, a rest mass of approximately 1.674 93 x 10^-27 kg, and a mean life in the free state for beta decay of about 1108 s.
(IEC 50-393-1993)

Neutron
Particle with a mass similar to that of a proton, but with no electrical charge.
(NCRP 114)

Neutron
An elementary nuclear particle with a mass approximately the same as that of a hydrogen atom and electrically neutral; its mass is 1.008982 mass units. Neutrons are commonly divided into subclassifications according to their energies as follows: thermal, around 0.025 eV; epithermal, 0.1 to 100 eV; slow, less than 100 eV; intermediate, 102 eV; fast, greater that 0.1 MeV.
(HPJ 60)

Neutron
Uncharged subatomic particle capable of producing ionization in matter by collision with charged particles.
(BEIR V)

Neutron
An uncharged elementary particle with a mass slightly greater than that of the proton and found in the nucleus of every atom heavier than hydrogen. A free neutron is unstable and decays with a half-life of about 13 minutes into an electron, proton, and neutrino. Neutrons sustain the fission chain reaction in a nuclear reactor. (NCRP 65)

Neutron
An elementary particle having no electric charge, a rest mass of 1.67495 x 10^-27 kg, and a mean life of 1000 s.
(ANSI N1.1-1976)

Neutron
[Symbol n] An uncharged elementary particle with a mass slightly greater than that of the proton, and found in the nucleus of every atom heavier than hydrogen. A free neutron is unstable and decays with a half-life of about 13 minutes into an electron, proton, and neutrino. Neutrons sustain the fission chain reaction in a nuclear reactor. (See fast neutron, intermediate neutron, and thermal neutron.)
(USAEC-1974)

Neutron (number) density
The number of free neutrons per unit volume. Partial densities may be defined for neutrons characterized by such parameters as energy and direction.
(ANSI N1.1-1976)

Neutron absorber
Material with which neutrons interact significantly by reactions resulting in their disappearance as free particles.
(IEC 50-393-1993)

Neutron activation analysis
Activation analysis in which neutrons are the activating agent.
(USAEC-1974)

Neutron capture
See capture.
(HPJ 60)

Neutron capture
A process in which a neutron becomes part of the nucleus with which is collides without release of another heavy particle.
(NCRP 51)

Neutron capture
The process in which an atomic nucleus absorbs or captures a neutron. The probability that a given material will capture neutrons is measured by its neutron capture cross section, which depends on the energy of the neutrons and on the nature of the material. (See capture, nuclear reaction, radiative capture.)
(USAEC-1974)

Neutron converter
Device placed in a flux of slow neutrons to produce fission neutrons and so increase the proportion of fast neutrons.
(IEC 50-393-1993)

Neutron cycle
Evolution in time of the average energy, interaction and migration history of neutrons in a reactor, beginning with fission and continuing until they have leaked out or have been absorbed.
(IEC 50-393-1993)

Neutron cycle
The average energy, interaction and migration history of neutrons in a reactor, beginning with fission and continuing until they have leaked out or have been absorbed.
(ANSI N1.1-1976)

Neutron cycle
The average energy, interaction and migration history of neutrons in a reactor, beginning with fission and continuing until they have leaked out or have been absorbed.
(RHH)

Neutron density
Number of free neutrons per unit volume.
(IEC 50-393-1993)

Neutron density
The number of neutrons per cubic centimeter in the core of a reactor. (See flux.)
(USAEC-1974)

Neutron diffusion
Phenomenon in which neutrons in a medium tend, through a process of successive scattering collisions, to migrate from regions of high concentration to regions of low concentration.
(IEC 50-393-1993)

Neutron diffusion
A phenomenon in which neutrons in a medium tend, through a process of successive scattering collisions, to migrate from regions of high concentration to regions of low concentration.
(ANSI N1.1-1976)

Neutron economy
Balance account, in a reactor, of the neutrons created and the neutrons lost uselessly, and problems related thereto.
(IEC 50-393-1993)

Neutron economy
(1) In a nuclear rector, the detailed account of neutrons produced and lost.
(2) A qualitative term referring to the extent to which neutrons are used in desired ways instead of being lost by leakage or useless absorptions.
(ANSI N1.1-1976)

Neutron economy
The degree to which neutrons in a reactor are used for desired ends instead of being lost by leakage or nonproductive absorption. The ends may include propagation of the chain reaction, converting fertile to fissionable material, producing isotopes, or research. (See leakage, Reactivity.)
(USAEC-1974)

Neutron energy classifications
Neutron energy ranges that are discussed in the Handbook are defined below.

Classification	Energy
Slow	Thermal to 0.1 kev
Intermediate	0.1 kev to 0.02 Mev
Fast	0.02 Mev to 10 Mev
High Energy	10 Mev to 500 Mev

(NBS 55)

Neutron energy group
One or a set of groups consisting of neutrons having energy within arbitrarily chosen intervals.
(IEC 50-393-1993)

Neutron energy group
One of a set of groups consisting of neutrons having energies within arbitrarily chosen intervals. Each group may be assigned effective values for the characteristics of the neutrons within the group.
(ANSI N1.1-1976)

Neutron flux
See flux density, neutron.
(ANSI N1.1-1976)

Neutron flux
See flux.
(USAEC-1974)

Neutron flux
The number of neutrons which, per unit time, traverse a sphere of unit cross-sectional area centered about the point of interest. It is usually expressed in n cm^-2 sec^-1. The correct term for this quantity is neutron flux density, but in common use the incorrect term "flux" is almost invariably employed.
(NBS 63)

Neutron generator
Charged particle accelerator having a target for producing neutron fluxes.
(IEC 50-393-1993)

Neutron generator
A type of accelerator in which the ion beam or the x-ray beam is used mainly for the production of neutrons; e.g., low-voltage deuteron accelerators.
(NCRP 51)

Neutron multiplication
Process in which a neutron produces on the average more than one neutron, when it is captured in a medium containing fissionable material.
(IEC 50-393-1993)

Neutron source
An apparatus or a material emitting, or capable of emitting, neutrons.
(ANSI N1.1-1976)

Neutron temperature
The temperature assigned to a population of neutrons which can be described by a Maxwellian distribution.
(ANSI N1.1-1976)

Neutron thermopile
Neutron detector in which the hot junctions of thermocouples are in thermal contact with a material which is heated by absorption of particles resulting from neutron induced reactions.
(IEC 50-394-1993)

Neutron yield per absorption
The average number of primary fission neutrons (including delayed neutrons) emitted per neutron absorbed by a fissionable nuclide or by a nuclear fuel, as specified. It is a function of the energy of the absorbed neutrons.
(ANSI N1.1-1976)

Neutron yield per absorption, eta factor (h)
Average number of primary fission neutrons, including delayed neutrons, emitted per neutron absorbed by a fissionable nuclide or by a nuclear fuel as specified.
(IEC 50-393-1993)

Neutron yield per fission
The average number of primary fission neutrons (including delayed neutrons) emitted per fission. It is a function of the energy of the absorbed neutrons.
(ANSI N1.1-1976)

Neutrons
Particles with a mass similar to that of a proton, but with no electrical charge. Because they are electrically neutral, they cannot be accelerated in an electrical device.
(NCRP 98)

Neutrons
(1) Fast Neutrons - Neutrons of kinetic energy greater than some specified value. This value can vary over a wide range and will be dependent upon the application. In concrete shield analyses, the specified value is normally 0.1 MeV when calculating tissue doses and 1 MeV when determining radiation damage to materials.
(2) Intermediate Energy Neutrons - Neutrons greater in energy than thermal neutrons and less than the energy associated with fast neutrons. This range includes the resonance neutrons energy range in which many nuclides exhibit strong neutron absorption, referred to as resonance absorption.
(3) Thermal Neutrons - Very low energy neutrons that are in thermal equilibrium with the atoms (or molecules) of the medium in which they are present at a temperature of 20 °C, thermal neutrons having an average velocity of 2,200 meters/second and a corresponding energy of 0.025 eV.
(ANSI/ANS-6.4-1985)

Neutrons, delayed
Neutrons emitted by nuclei in excited states which have been formed in the process of beta decay. (The neutron emission itself is prompt, so that the observed delay is that of the preceding beta emission or emissions.)
(ANSI N1.1-1976)

Neutrons, epicadmium
Neutrons of kinetic energy greater than the effective cadmium cutoff.
(ANSI N1.1-1976)

Neutrons, epithermal
Neutrons of kinetic energy greater than that of thermal agitation. The term is often restricted to energies just above thermal, that is, energies comparable with those of chemical bonds.
(ANSI N1.1-1976)

Neutrons, fast
Neutrons with kinetic energy greater than some specified value. This value may vary over a wide range and will be dependent upon the application, such as reactor physics, shielding, or dosimetry. In reactor physics the value is frequently chosen to be 0.1 MeV.
(ANSI N1.1-1976)

Neutrons, fission
Neutrons originating in the fission process which have retained their original energy.
(ANSI N1.1-1976)

Neutrons, intermediate
Neutrons of kinetic energy between the energies of slow and fast neutrons. In reactor physics the range is often chosen to be 1 eV to 0.1 MeV.
(ANSI N1.1-1976)

Neutrons, prompt
Neutrons accompanying the fission process without measurable delay.
(ANSI N1.1-1976)

Neutrons, prompt
Neutrons accompanying the fission process without measurable delay.
(RHH)

Neutrons, resonance
Neutrons having kinetic energy in the resonance energy range, that is, in the range for which the resonance level structure is evident from the variations in cross sections with energy.
(ANSI N1.1-1976)

Neutrons, slow
Neutrons of kinetic energy less than some specified value. This value may vary over a wide range and depends on the application, such as reactor physics, shielding, or dosimetry. In reactor physics the value is frequently chosen to be 1 eV; in dosimetry the effective cadmium cutoff is used.
(ANSI N1.1-1976)

Neutrons, subcadmium
Neutrons of kinetic energy less than the effective cadmium cutoff.
(ANSI N1.1-1976)

Neutrons, thermal
Neutrons of kinetic energy less than the effective cadmium cutoff.
(ANSI N1.1-1976)

Neutrons, virgin
Neutrons from any source, before they make a collision.
(ANSI N1.1-1976)

New bone
As used in ICRP 20: All bone formed after time zero, the time of injection.
(ICRP 20)

New cylinder
An unused cylinder that has been cleaned to remove fabrication debris.
(ANSI N14.1-1990)

New source
Any stationary source, the construction or modification of which is commenced after the publication in the FEDERAL REGISTER of proposed national emission standards for hazardous air pollutants which will be applicable to such source.
(40CFR61.02)

Newton
The unit of force, which when applied to one kilogram mass will give it an acceleration of one meter per second per second. (1 N = 1 kg x 1 m/s²).
(RHH)

NNES
National Nuclear Energy Series. The series of volumes published by McGraw-Hill Book Company containing significant results of the MED research in all fields.
(RAH)

Noble gas effluent monitor for accident conditions
Radiation monitor designed for the continuous measurement of the total radioactive volume emission of noble gas effluents discharged to the environment during accident and post accident conditions.
(IEC 50-394-1993)

Noise
A colloquial expression referring to the fluctuations resulting from the quantized and random nature of natural processes, for example the emission and absorption of x-ray and light photons.
(NCRP 68)

Noise diagnostic system (of a nuclear reactor)
System for monitoring and analysis of nuclear reactor parameters, such as, fluctuations of neutron fluence, coolant pressure, vibrations, for the purpose of early detection of latent defects of components of a reactor.
(IEC 50-394-1993)

Noise equivalent quanta (NEQ)
The equivalent input exposure deduced from the measured noise and signal transfer characteristics for a photographic or radiographic system is

where g is the slope of the curve of the density vs. log exposure, MTF the modulation transfer function and W_DD the noise power spectrum at the operating point of interest. Analogous quantities for other modalities are found throughout the image assessment literature with the large area factor K in the place of g(log₁₀ e). They are often loosely referred to as NEQ because they play the same role as NEQ in the ideal-observer signal-to-noise ratio.
(ICRU 54)

Noise power spectrum
An alternative name for the Wiener spectrum.
(ICRU 54)

Non-blind testing
Testing of capabilities when the service laboratory is aware that they are being tested for conformance.
(ANSI N13.30-1989D)

Non-controlled area
Any area to which access is not controlled for purposes of radiation protection.
(ANSI N43.2-1977)

Non-elastic interaction
Any interaction other than elastic scattering.
(NCRP 38)

Non-federal disposal facility
A low-level radioactive waste disposal facility that is commercially operated or is operated by a State.
(10CFR62.2)

Non-fixed radioactive contamination
Radioactive contamination that can be readily removed from a surface by wiping with an absorbent material. Non-fixed (removable) radioactive contamination is not significant if it does not exceed the limits specified in §173.443.
(49CFR173.403)

Non-leachable
Term used to convey that the radioactive material is virtually insoluble in water and is not convertible into dispersible products.
(ANSI N542-1977)

Non-linear detector
Radiation detector in which the output signal is a non-linear function of a quantity related to the incident radiation.
(IEC 50-394-1993)

Non-nuclear weapon state
Any State not a nuclear weapon State as defined in the Treaty on the Non-Proliferation of Nuclear Weapons.
(10CFR110.2)

Non-power reactor
A research or test reactor licensed under Secs. 50.21(c) or 50.22 of this part for research and development.
(10CFR50.2)

Non-prewhitening matched filter (NPWMF)
The NPWMF is a sub-optimal observer in that, while using all known information regarding the signal parameters perfectly, is unable to undo any correlations in the data. The NPWMF observer uses a template matched to the expected difference image to form a test statistic, regardless of the sources of variability in the data.
(ICRU 54)

Non-proliferation act
The Nuclear Non-Proliferation Act of 1978 (Pub. L. 95-242).
(10CFR110.2)

Non-routine respirator use
Wearing a respirator when carrying out a special task that occurs infrequently.
(ANSI Z88.2-1980)

Non-Stochastic Effects
Those effects for which the severity varies with the dose and for which a threshold may therefore occur.
(HPS N13.42-1997)

Non-stochastic effects
In radiation protection, those health effects for which the severity of the effect in the affected individuals varies with the dose, and for which a threshold may therefore occur. For example, cataracts of the lens of the eye.
(NCRP 111)

Non-stochastic effects
Effects for which the severity of the effect varies with dose, and for which a threshold may therefore exist.
(NCRP 101)

Non-stochastic effects
Health effects for which the severity of the effect in affected individuals varies with dose, and for which a threshold is assumed to exist.
(FGR 11)

Non-stochastic effects
Effects for which the severity of the effect varies with dose, and for which a threshold may therefore exist.
(NCRP 91)

Non-stochastic effects
Effects for which the severity of the effect varies with dose, and for which a threshold may therefore exist.
(NCRP 93)

Non-stochastic effects
Effects for which the severity of the effect varies with the dose, and for which a threshold may therefore occur.
(NCRP 84)

Non-stochastic effects
Effects such as opacity of the lens of the eye for which the severity of the effect varies with the dose, and for which a threshold may therefore occur.
(ICRP 30)

Non-stochastic effects
Effects due to radiation exposure for which the severity varies with the dose and for which a threshold normally exists (e.g., radiation-induced opacities within the lens of the eye).
(???)

Non-thermal effect
A change in a medium or system that is not directly associated with heat production when electromagnetic energy is absorbed.
(NCRP 67)

Non-uniform exposure
The irradiation is nonuniform if the ratio of maximum dose to minimum dose is greater than 1.30, i.e., 1.30 < D_max/D_min.
(ICRU 30)

Nonconformance
The condition of a characteristic, documentation, or procedure which renders the quality of an item or activity unacceptable or indeterminate.
(ANSI N46.2-1978)

Noncontrolled area
Any space not meeting the definition of a controlled area. This area designation is equivalent to an unrestricted area as defined by the U.S. Nuclear Regulatory Commission.
(NCRP 102)

Noncontrolled area
Any space not meeting the definition of a controlled area.
(NCRP 51)

Noncontrolled area
Any space not meeting the definition of a controlled area.
(NCRP 49)

Nondestructive assay (NDA)
The observation of spontaneous or stimulated radiations, interpreted to estimate the amount of one or more nuclides of interest in the item assayed, without affecting the physical or chemical form of the material.
(ANSI N15.36-1983)

Nondestructive assay (NDA)
The determination of a parameter of interest without significantly altering the chemical or physical form of the material.
(ANSI N15.35-1983)

Nondestructive assay (NDA)
The observation of spontaneous or stimulated phenomena, interpreted to estimate the item assayed, without affecting the physical or chemical form of the material.
(ANSI N15.37-1981)

Nondestructive testing
Testing to detect internal and concealed defects in materials using techniques that do not damage or destroy the items being tested. X rays, isotopic radiation and ultrasonics are frequently used.
(USAEC-1974)

Nonoccupational exposure
Radiation exposure received by an individual that is not expected as part of his normal occupation.
(NCRP 51)

Nonpenetrating radiation
A general term used to describe external radiations of such low penetrating power that the absorbed dose from exposures to man is principally in the skin and does not reach deeper organs to any significant extent. It refers to alpha, beta and very soft gamma or x-ray radiations.
(NCRP 65)

Nonpenetration radiation (np)
Those particles emitted in the source that contribute a negligible dose to organs other than the source organ. For these radiations, the source organ is the only target organ and the absorbed fraction is unity.
(MIRD)

Nonprofit Educational Institution
A public or nonprofit educational institution whose primary function is education, whose programs are accredited by a nationally recognized accrediting agency or association, who is legally authorized to provide a program of organized instruction or study, who provides an educational program for which it awards academic degrees, and whose educational programs are available to the public.
(10CFR170.3)

Nonprofit Educational Institution
A public or nonprofit educational institution whose primary function is education, whose programs are accredited by a nationally recognized accrediting agency or association, who is legally authorized to provide a program of organized instruction or study, who provides an educational program for which it awards academic degrees, and whose educational programs are available to the public.
(10CFR171.5)

Nonshielded x-ray tube assembly
An x-ray tube assembly which does not meet the shielding requirements defined in ANSI N537-1976.
(ANSI N537-1976)

Nonstochastic
Describes effects whose severity is a function of dose; for these, a threshold may occur; some nonstochastic somatic effects are cataract induction, nonmalignant damage to the skin, hematological deficiencies, and impairment of fertility.
(BEIR V)

Nonstochastic
Describes effects whose severity is a function of dose; for these, a threshold may occur; some nonstochastic somatic effects are cataract induction, nonmalignant damage to the skin, hematological deficiencies, and impairment of fertility.
(BEIR III)

Nonstochastic
Describes effects whose severity is a function of dose; for these, a threshold may occur; some nonstochastic somatic effects are cataract induction, nonmalignant damage to the skin, hematological deficiencies, and impairment of fertility.
(NCRP 98)

Nonstochastic
Describes effects whose severity is a function of dose; for these, a threshold may occur; some nonstochastic somatic effects are cataract induction, nonmalignant damage to the skin, hematological deficiencies, and impairment of fertility.
(BEIR IV)

Nonstochastic effect
Health effects, the severity of which varies with the dose and for which a threshold is believed to exist. Radiation-induced cataract formation is an example of a nonstochastic effect (also called a deterministic effect).
(10CFR20.1003)

Nonstochastic effects
Effects, for which the severity of the effect in affected individuals varies with dose, and for which a threshold exists.
(NCRP 105)

Nonstochastic effects
Effects for which the severity of the effect in affected individuals varies with dose, and for which a threshold usually exists.
(NCRP 102)

Noradrenaline
Norepinephrine; a crystalline compound C₈H₁₁NO₃ that occurs with epinephrine, has a strong vasoconstrictor action, and mediates transmission of sympathetic nerve impulses.
(HPJ 60)

Normal conditions (normal conditions of transport)
Those conditions that are specified in 10CFR71.71.
(ANSI N14.19-1986)

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

Normal form radioactive material
Radioactive material which has not been demonstrated to qualify as "special form radioactive material."
(49CFR173.403)

Normal form radioactive material
Radioactive material which has not been demonstrated to qualify as "special form radioactive material."
(10CFR71.4)

Normal monitoring programs
Normal monitoring programs include both routine monitoring, that is, monitoring carried out at prescribed intervals, and monitoring related to certain operations or conditions that can be foreseen. For example, a normal monitoring program for a nuclear power plant would include routine surveillance of absorbed dose rates in air and discharges. It would also make provision for additional monitoring required during planned operations when greater exposures could occur, and provision for monitoring required in the event of an unusual but predictable occurrence. The normal monitoring program will also provide baseline values for use in investigations of unusual occurrences.
(ICRP 43)

Normal off-gas
The normal gaseous discharge from a process or process equipment item.
(ERDA 76-21)

Normal operating conditions
Normal variation in operating parameters affecting control of radioactive materials in the offgas during startup, operation, shutdown, and maintenance of the facility.
(ANSI N303-1978)

Normal operation
Operation of a nuclear power plant within specified operational limits and conditions including shut-down, power operation, shutting down, starting up, maintenance, testing and refueling.
(IEC 50-393-1993)

Normal operation
Operation under conditions suitable for collecting data as recommended by a manufacturer of the x-ray system. Recommended shielding and barriers shall be in place.
(ANSI N43.2-1977)

Normal shut-down safety assembly
Safety assembly which performs a nuclear reactor shut-down by reducing the neutron flux in the core of a reactor.
(IEC 50-394-1993)

Normal size distribution
Particle size distribution characterized by a bell-shaped or Gaussian distribution shape when plotted on a linear size scale.
(AM-1993)

Normal uranium
Natural uranium.
(USAEC-1974)

Normal-form radioactive material
A radioactive material that has not been demonstrated to qualify as special-form radioactive material. UF6 is classified as a normal-form material.
(ANSI N14.1-1990)

Normalized output (X_n)
The exposure rate (in roentgens per minute) per unit target current (in milliamperes) and measured at one meter from the source, after transmission through the barrier. The unit is Rm²/(mA min).
(NCRP 49)

Nose clamp
A device used with a respirator equipped with a mouthpiece that closes the nostrils of the wearer (sometimes called a nose clip).
(ANSI Z88.2-1980)

Not immediately dangerous to life or health
Any hazardous atmosphere which may produce physical discomfort immediately, chronic poisoning after repeated exposure, or acute adverse physiological symptoms after prolonged exposure.
(ANSI Z88.2-1980)

Notice of intent
A notice that an environmental impact statement will be prepared and considered.
(10CFR51.14)

Notification
The telephonic communication to the NRC Operations Center or written transmittal of information to the NRC Document Control Desk.
(10CFR50.2)

NPT
The Treaty on the Non-Proliferation of Nuclear Weapons (TIAS 6839).
(10CFR110.2)

NRC
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR20.1003)

NRC
The Nuclear Regulatory Commission, the agency established by Title II of the Energy Reorganization Act of 1974, as amended.
(10CFR51.4)

NRC licensee
The holder of a license issued by the NRC under the regulations in 10 CFR 30 through 35, 40, 50, 60, 61, 70, or 72.
(ANSI N14.24-1985)

NRC records
Any documentary material made by, in the possession of, or under the control of the Commission under Federal law or in connection with the transaction of public business as evidence of any of the Commission's activities.
(10CFR110.2)

NRC Staff
Any NRC officer or employee or his/her authorized representative, except a Commissioner, a member of a Commissioner's immediate staff, an Atomic Safety and Licensing Board, an Atomic Safety and Licensing Appeal Board, a presiding officer, an administrative judge, an administrative law judge, or any other officer or employee of the Commission who performs adjudicatory functions.
(10CFR51.4)

NRC Staff Director
Executive Director for Operations; Director, Office of Nuclear Reactor Regulation; Director, Office of Nuclear Material Safety and Safeguards; Director, Office of Nuclear Regulatory Research; Director, Office of Governmental and Public Affairs; and the designee of any NRC staff director.
(10CFR51.4)

NRC-licensed facility
Any facility licensed by the Nuclear Regulatory Commission or any Agreement State to receive title to, receive, possess, use, transfer, or deliver any source, by-product, or special nuclear material.
(40CFR61.101)

Nu factor
See neutron yield per fission.
(ANSI N1.1-1976)

Nuclear battery
A device in which power is continuously derived from the emission of charged particles from a radionuclide. A potential is achieved by collection of the charged particles on a suitable grid or plate.
(ANSI N1.1-1976)

Nuclear battery
A radioisotopic generator.
(USAEC-1974)

Nuclear chain reaction
Series of nuclear reactions in which one of the agents necessary to the series is itself produced by the reactions so as to cause like reactions.
(IEC 50-393-1993)

Nuclear chemistry
That part of chemistry which deals with the study of nuclei and nuclear reactions using chemical methods.
(ANSI N1.1-1976)

Nuclear compounds
Relatively pure and well-characterized chemical compounds (commonly oxide) of uranium, plutonium, thorium (or a mixture of these compounds) used in preparing calibration material by mixing with the matrix material.
(ANSI N15.35-1983)

Nuclear decay parameters
The various parameters associated with radioactive decay. These include, among others, the half-life, and the energies and probabilities of various transitions associated with specified decay modes.
(ANSI N15.22-1987)

Nuclear disintegration
Transformation of an atomic nucleus, involving the splitting into two or more nuclei or emission of particles, with the emission of energy.
(IEC 50-393-1993)

Nuclear disintegration
See disintegration.
(HPJ 60)

Nuclear disintegration
Transformation of a nucleus, possibly a compound nucleus, involving a splitting into more nuclei of the emission of particles.
(ANSI N1.1-1976)

Nuclear emulsion
Layer of photographic emulsion in which individual tracks of charged particles are evaluated after proper development.
(IEC 50-394-1993)

Nuclear energy
Energy released in nuclear reactions or transitions.
(IEC 50-393-1993)

Nuclear energy
Energy released in nuclear reactions or transitions.
(ANSI N1.1-1976)

Nuclear energy
The energy liberated by a nuclear reaction (fission or fusion) or by radioactive decay. (See decay, radioactive; fission; fusion; nuclear explosive; nuclear reactor.)
(USAEC-1974)

Nuclear experience
Experience acquired in reactor facility startup activities or operation. Experience in design, construction, maintenance, or related technical services that is job-related may also be considered. On-the-job training at the reactor facility may qualify as equivalent nuclear experience on a one-for-one time basis. Appropriate research, or teaching, or both may be included as nuclear experience.
(ANSI/ANS-15.4-1988)

Nuclear explosive
An explosive based on fission or fusion of atomic nuclei. (See device, nuclear; nuclear weapons.)
(USAEC-1974)

Nuclear fission
See fission.
(USAEC-1974)

Nuclear fuel
Material containing fissile nuclides which, when placed in a reactor, enables a chain reaction to be achieved.
(IEC 50-393-1993)

Nuclear fuel reprocessing facility
A plant engaged in the processing of irradiated nuclear fuels and in ancillary activities for the purpose of separating, recovering, purifying and packaging nuclear materials.
(ANSI N303-1978)

Nuclear fusion
See fusion.
(USAEC-1974)

Nuclear fusion reaction
Reaction between two light nuclei resulting in the production of at least one nuclear species heavier than either initial nucleus, together with excess energy.
(IEC 50-393-1993)

Nuclear grade graphite
Graphite with a boron equivalent content of less than 5 parts per million and density greater than 1.5 grams per cubic centimeter.
(10CFR110.2)

Nuclear instrumentation
Equipment or instruments for measuring quantities relating to ionizing radiation, and for controlling equipment or processes involving ionizing radiation.
(IEC 50-394-1993)

Nuclear insurer
The private nuclear insurer or underwriter (or pools thereof) provides financial protection to the shipper, carrier, and any other directly or indirectly related party from liability or property damage or loss claims arising from the hazardous properties of the radioactive materials.
(ANSI N14.24-1985)

Nuclear magnetic resonance spectrometer
Equipment which utilizes nuclear magnetic resonance to determine the number of nuclei per unit volume of a specific nuclide.
(IEC 50-394-1993)

Nuclear magnetic resonance, NMR
Phenomenon used to identify molecules in diluted substances through resonance between specific spin of their nuclei and the radio frequency field to which the substance is subjected while within an intense static magnetic field.
(IEC 50-393-1993)

Nuclear material
Any source material or any special nuclear material.
(10CFR75.4)

Nuclear materials
Those types and composition of matter specified in requirements applicable to a safeguards system.
(ANSI N15.38-1982)

Nuclear materials control
The establishment, documentation, and maintenance of the quantity, form, and location of nuclear material.
(ANSI N15.37-1981)

Nuclear medicine
A medical specialty that utilizes radioactive pharmaceuticals for diagnosis, therapy and research.
(NCRP 83)

Nuclear medicine
Diagnostic or therapeutic use of radionuclides.
(NCRP 48)

Nuclear poison
Substance which, because of its high neutron absorption cross section, can reduce reactivity.
(IEC 50-393-1993)

Nuclear Power Plant
A nuclear power facility of a type described in 10 CFR 50.21(b) or 50.22.
(10CFR54.3)

Nuclear power plant
A nuclear power facility of a type described in 10CFR50.21(b) or 50.22.
(10CFR54.4)

Nuclear power plant
Any device, machine, or assembly that converts nuclear energy into some form of useful power, such as mechanical or electrical power. In a nuclear electric power plant, heat produced by a reactor is generally used to make steam to drive a turbine that in turn drives an electric generator.
(USAEC-1974)

Nuclear power station, nuclear power plant
A power plant generating electrical or thermal energy by means of one or several nuclear reactors.
(IEC 50-393-1993)

Nuclear radiation
Ionizing radiation emitted from atomic nuclei, such as alpha radiation and beta radiation, gamma radiation, neutron radiation.
(IEC 50-393-1993)

Nuclear radius
That somewhat ill-defined distance from the center of a nucleus at which the density of nuclear matter drops sharply.
(ANSI N1.1-1976)

Nuclear reaction
Event in which one or more atomic nuclei are involved, resulting in a change of mass, charge or energy state.
(IEC 50-393-1993)

Nuclear reaction
An interaction between a photon, particle or nucleus and a target nucleus, leading to the emission of one or more particles and/or photons.
(NCRP 51)

Nuclear reaction
A reaction involving a change in an atomic nucleus, such as fission, fusion, neutron capture, or radioactive decay, as distinct from a chemical reaction, which is limited to changes in the electron structure surrounding the nucleus.
(USAEC-1974)

Nuclear reaction
Interaction between two or more particles including at least one nucleus and leading to emission of different particles.
(NCRP 38)

Nuclear reaction
Collision between nuclear particles leading to release of different particles.
(NBS 63)

Nuclear reactor
An apparatus, other than an atomic weapon or nuclear explosive device, designed or used to sustain nuclear fission in a self-supporting chain reaction.
(10CFR110.2)

Nuclear reactor
An apparatus, other than an atomic weapon, used to sustain fission in a self-supporting chain reaction.
(10CFR171.5)

Nuclear reactor
An apparatus, other than an atomic weapon, designed or used to sustain nuclear fission in a self-supporting chain reaction.
(10CFR50.2)

Nuclear reactor
An apparatus, other than an atomic weapon, designed or used to sustain nuclear fission in a self-supporting chain reaction.
(10CFR170.3)

Nuclear reactor
Device containing fissionable material in sufficient quantity and so arranged as to be capable of maintaining a controlled self-sustaining nuclear fission chain reaction.
(IEC 50-393-1993)

Nuclear reactor
An apparatus in which nuclear fission may be sustained as a self-sustaining chain reaction.
(NCRP 81)

Nuclear reactor
An apparatus in which a chain reaction of fissionable material is initiated and controlled.
(ERDA 76-21)

Nuclear reactor
A device in which a fission chain reaction can be initiated, maintained, and controlled. Its essential component is a core with fissionable fuel. It usually has a moderator, a reflector, shielding, coolant, and control mechanisms. Sometimes called an atomic "furnace", it is the basic machine of nuclear energy. (See fission.)
(USAEC-1974)

Nuclear reactor instrumentation
Electronic and electrical equipment or instruments for ensuring the proper control and monitoring of a nuclear reactor, including all control and safety related instrumentation.
(IEC 50-394-1993)

Nuclear Referral List (NRL)
The nuclear-related, dual-use commodities on the Commerce Control List that are subject to the nuclear non-proliferation export licensing controls of the Department of Commerce. They are contained in Supplement No. 1 to 15 CFR part 799 of the Department of Commerce's Export Administration Regulations and are designated by the symbol (NP) as the reason for control.
(10CFR110.2)

Nuclear rocket
A rocket powered by an engine that obtains energy for heating a propellant fluid (such as hydrogen) from a nuclear reactor, rather than from chemical combustion. (See Rover.)
(USAEC-1974)

Nuclear safety
Set of arrangements taken in all stages of design, construction, operation and, finally, the definitive closure of a nuclear plant in order to forestall accidents (and limit their effects).
(IEC 50-393-1993)

Nuclear security (in nuclear power plants)
Set of arrangements taken for ensuring protection of personnel and of goods against dangers, or all other inconveniences resulting from the presence of natural or induced radioactive substances in the nuclear plant or during their transport.
(IEC 50-393-1993)

Nuclear spin
The intrinsic angular momentum of a nucleus expressed in unit of h where h is Plank's constant divided by 2p.
(ANSI N1.1-1976)

Nuclear steam supply system
The reactor core, reactor coolant system, and related auxiliary systems including the emergency core cooling system; decay heat removal system; and chemical volume and control system.
(10CFR170.3)

Nuclear superheat
The use of thermal energy from a nuclear reactor to heat a vapor above its saturation temperature.
(ANSI N1.1-1976)

Nuclear superheating
Superheating the steam produced in a reactor by using additional heat from a reactor. Two methods are commonly employed: recirculating the steam through the same core in which it is first produced (integral superheating) or passing the steam through a second and separate reactor. (See superheating.)
(USAEC-1974)

Nuclear track detector
See solid state nuclear track detector.
(NCRP 97)

Nuclear transformation
The spontaneous transformation of one radionuclide into a different nuclide or into a different energy state of the same nuclide.
(FGR 11)

Nuclear weapon state
Any State which has manufactured and exploded a nuclear weapon or other nuclear explosive device prior to January 1, 1967.
(10CFR110.2)

Nuclear weapons
A collective term for atomic bombs and hydrogen bombs. Any weapons based on a nuclear explosive.
(USAEC-1974)

Nucleation
Process of initial formation of particles from a vapor.
(AM-1993)

Nuclei
Plural of nucleus.
(USAEC-1974)

Nuclei mode
Smallest mode in atmospheric particle size distributions, formed by condensation of atmospheric gases or emissions from hot processes, typically containing particles < 0.1 µm in size.
(AM-1993)

Nucleon
Constituent of an atomic nucleus, either proton or neutron.
(IEC 50-393-1993)

Nucleon
Any particle found in the structure of an atomic nucleus, i.e., neutron or proton.
(NCRP 94)

Nucleon
A proton or a neutron.
(ANSI N1.1-1976)

Nucleon
Any particle found in the structure of an atomic nucleus, i.e., neutron or proton.
(NCRP 45)

Nucleon
A constituent of an atomic nucleus, that is, a proton or a neutron.
(USAEC-1974)

Nucleon
Common name for a constituent particle of the nucleus. Applied to a proton or a neutron.
(RHH)

Nucleonics
The science and technology of nuclear energy and its applications.
(USAEC-1974)

Nucleoside
A compound of a sugar (notably ribose or deoxyribose) with a purine or pyrimidine base by way of an N-glycosyl link.
(HPJ 60)

Nucleus
The small positively charged core of an atom. It is only about 1/10,000 the diameter of the atom but contains nearly all of the atom's mass. All nuclei contain both protons and neutrons, except the nucleus of ordinary hydrogen, which contains a single proton.
(HPJ 60)

Nucleus
The small positively charged core of an atom. It is only about 1/10,000 the diameter of the atom but contains nearly all of the atom's mass. All nuclei contain both protons and neutrons, except the nucleus of ordinary hydrogen, which contains a single proton.
(USAEC-1974)

Nucleus
Biological - A definitely delineated body within a cell, containing the chromosomes.
Nuclear - That part of an atom in which the total positive electric charge and most of the mass is concentrated.
(RHH)

Nucleus (atomic nucleus)
The positively charged central portion of an atom, with which is associated almost the whole mass of the atom, but only a minute part of its volume.
(ANSI N1.1-1976)

Nuclide
Species of atom characterized by its mass number and atomic number.
(IEC 50-393-1993)

Nuclide
A species of atom characterized by the constitution of its nucleus.
(NCRP 118)

Nuclide
A species of atom characterized by the constitution of its nucleus, which is specified by the number of protons (Z), number of neutrons (N), and energy content or, alternatively, by the atomic number (Z), mass number (A = N + Z), and atomic mass; to be regarded as a distinct nuclide, an atom must be capable of existing for a measurable time; thus, nuclear isomers are separate nuclides, whereas promptly decaying excited nuclear states and unstable intermediates in nuclear reactions are not.
(HPJ 60)

Nuclide
A species of atom characterized by the constitution of its nucleus and hence by the number of protons, the number of neutrons, and the energy content.
(NCRP 111)

Nuclide
A species of atom characterized by the constitution of its nucleus, which is specified by its atomic mass and atomic number (A), or by its number of protons (Z), number of neutrons (N), and energy content.
(BEIR V)

Nuclide
A species of atoms characterized by its atomic number, mass number, and nuclear energy state, provided that the mean life in that state is long enough to be observable.
(NCRP 105)

Nuclide
Any nuclear species.
(ANSI N15.54-1988)

Nuclide
A species of atom characterized by the constitution of its nucleus, which is specified by its atomic mass and atomic number (A), or by its number of protons (Z), number of neutrons (N), and energy content.
(BEIR IV)

Nuclide
Any nuclear species.
(ANSI N15.22-1987)

Nuclide
A species of atom characterized by the constitution of its nucleus.
(NCRP 87)

Nuclide
A species of atom characterized by the constitution of its nucleus.
(NCRP 84)

Nuclide
A species of atom characterized by the constitution of its nucleus, which is specified by the number of protons (Z), number of neutrons (N), and energy content or, alternatively, by the atomic number (Z), mass number (A = N + Z), and atomic mass; to be regarded as a distinct nuclide, an atom must be capable of existing for a measurable time; thus, nuclear isomers are separate nuclides, whereas promptly decaying excited nuclear states and unstable intermediates in nuclear reactions are not.
(BEIR III)

Nuclide
A general term applicable to all atomic forms of the elements. The term is often erroneously used as a synonym of "isotope," which properly has a more limited definition. Whereas isotopes are the various forms of a single element (hence are a family of nuclides) and all have the same atomic members, nuclides comprise all the isotopic forms of all the elements.
(NCRP 65)

Nuclide
A species of atom characterized by its mass number, atomic number, and nuclear energy state, provided that the mean life in that state is long enough to be observable.
(ANSI N1.1-1976)

Nuclide
A general term applicable to all atomic forms of the elements. The term is often erroneously used as a synonym for "isotope", which properly has a more limited definition. Whereas isotopes are the various forms of a single element (hence are a family of nuclides) and all have the same atomic number and number of protons, nuclides comprise all the isotopic forms of all the elements. Nuclides are distinguished by their atomic number, atomic mass, and energy state.
(USAEC-1974)

Nuclide
A species of atom characterized by the constitution of its nucleus. The nuclear constitution is specified by the number of protons (Z), number of neutrons (N), and energy content; or, alternatively, by the atomic number (Z), mass number A=(N+Z), and atomic mass. To be regarded as a distinct nuclide, the atom must be capable of existing for a measurable time. Thus, nuclear isomers are separate nuclides, whereas promptly decaying excited nuclear states and unstble intermediates in nuclear reactions are not so considered.
(BEIR I)

Nuclide
A species of atom having a specified numbers of neutrons and protons in its nucleus.
(ICRU 19)

Nuclide
A species of atom having a specified numbers of neutrons and protons in its nucleus.
(ICRU 33)

Nuclide
A species of atom characterized by the constitution of its nucleus, which is specified by the number of protons (Z), number of neutrons (N), and energy content or, alternatively, by the atomic number (Z), mass number (A = N + Z), and atomic mass; to be regarded as a distinct nuclide, an atom must be capable of existing for a measurable time; thus, nuclear isomers are separate nuclides, whereas promptly decaying excited nuclear states and unstable intermediates in nuclear reactions are not.
(RHH)

Nuclide
A nuclide is a species of atom having a specified numbers of neutrons and protons in its nucleus.
(NBS 92)

Nuclide
A species of atom having a specified numbers of neutrons and protons in its nucleus.
(ICRU 10f)

Nuclide
A species of atom having a specified numbers of neutrons and protons in its nucleus.
(NCRP 51)

Nuclide
A species of atom having a specified numbers of neutrons and protons in its nucleus.
(ICRU 10b)

Nuclide
A species of atom characterized by the constitution of its nucleus, i.e., by the number of protons, number of neutrons, and energy content.
(NBS 66)

Null
The potential difference across the calorimeter bridge when the calorimeter is empty and at equilibrium. Also referred to as the "zero" of the calorimeter.
(ANSI N15.54-1988)

Number of particles, n_i
The number of particles of type-i radiation emitted per nuclear transition.
(MIRD)

NUREG documents
NUREG's are issued by the United Stated Nuclear Regulatory Commission as a form of guidance on compliance with regulations. These documents provide, in addition to methodology, the technical basis for implementation of programs or requirements. These documents are not substitutes for regulations, and compliance is not required.
(HPJ 60)

NWPA
The Nuclear Waste Policy Act of 1982 including any amendments thereto.
(10CFR72.3)

Nyquist frequency
Highest frequency component in a signal; twice this frequency is the minimum sampling rate that can be used without biasing the measured values.
(AM-1993)

Note: References shown in ()