 [A]- AAO Acid aluminum oxide, an inorganic ion-exchanger.
- ABSOLUTE ACTIVATION ANALYSIS See activation analysis, absolute
- ABSOLUTE ACTIVITY See Activity
- ABSOLUTE COUNTING A measurement performed under such well-defined conditions that the absolute activity of a sample can be derived directly from the observed count rate.
- ABSOLUTE FULL ENERGY PEAK See full energy peak efficiency, absolute
- ABSOLUTE PHOTOPEAK EFFICIENCY See photopeak efficiency, absolute
- ABSORBED DOSE See dose, absorbed
- ABSORBER A substance used to absorb energy from any type of radiation.
- ABSORPTION (ENERGY) A phenomenon in which radiation transfers to matter which it traverses some or all of its energy. CAN.
- ABSORPTION COEFFICIENT (ENERGY) See absorption coefficient, linear
- ABSORPTION COEFFICIENT, LINEAR Of a substance, for a parallel beam of electromagnetic radiation of specified energy: the quantity m in the expression mDx for the fraction of the energy removed by absorption in passing through a thin layer of thickness Dx of that substance.
- ABSORPTION COEFFICIENT, MASS Absorption coefficient (linear ) in which the layer of thickness Dx is expressed in units of mass per unit area so that the units for the quantity m are area per unit mass.
- ABSORPTION CROSS SECTION For incident neutrons, the sum of all the microscopic or partial cross sections in which the incident neutron does not reappear as a product.
- ABSORPTION CURVE A graph showing the relationship between the fraction of radiation absorbed and its energy, range, or wavelength. M.
 ABSORPTION EDGE The energy or wavelength corresponding to a discontinuity in the absorption coefficient of a substance towards radiation. M.- ABUNDANCE, ISOTOPIC The relative number of atoms of a particular isotope in a mixture of the isotopes of an element, expressed as a fraction of all the atoms of the element.
- ABUNDANCE, NATURAL ISOTOPIC Of a specified isotope of an element, the isotopic abundance in the element as found in nature.
- ABUNDANCE RATIO, ISOTOPIC See abundance, isotopic
- ACCELERATED TEST METHOD A procedure, preferably one for which a standard protocol has been developed, that is used in a laboratory to produce in a reasonably short time (days or months) effects that would otherwise be observed only over much longer times (decades to millennia). Generally this requires adjusting parameters such as temperature (and pressure), radioactive dose rate, etc., that affect the kinetics of a chemical reaction. WASTE.
- ACCELERATOR A device for generating a beam of high-velocity charged particles.
- ACCELERATOR MASS SPECTROMETRY A highly sensitive technique of mass spectrometry in which the sample, after ionization, is separated not only by mass but also by atomic number. To accomplish this, ions in the beam are accelerated to several MeV per mass number.
- ACCEPTABLE LIMIT Limit acceptable to the regulatory body. See authorized limit. WASTE.
- ACCEPTOR In a solid state detector, an atom of a substance added to a semiconductor crystal to increase the number of holes in the conduction band. M.
- ACCOUNTABILITY Quantitative accounting for nuclear material, inventories, and transfers, through a system of measurements, records and reports. GNST
- ACID DIGESTION In treating samples, the use of acid to chemically decompose a material into its simpler constituents (usually soluble) thereby releasing the analytes for subsequent analysis.
- ACTINIDE An element which is any of the second (5f) series of f-block elements or inner transition elements commencing with actinium at atomic number 89 and ending with lawrencium at atomic number 103.
- ACTINIUM SERIES The naturally occurring decay chain commencing with 235U (formerly known as actino-uranium) and with 207Pb as the stable end product. The mass number of each radioactive member of the actinium series is representable as 4n+3 where n is an integer. FKKM.
- ACTINOIDS See actinides
- ACTINOMETER Any instrument, based on observable chemical reaction, used to measure the intensity of radiant energy. M.
- ACTIVATED SLUDGE Term sometimes used with reference to radioactive effluent treatment processes employing biological slimes and sludges to concentrate the radioactive materials. NM.
- ACTIVATION The process of inducing radioactivity by irradiation. In general, a specification is added of the type of incident radiation (e.g., nuclear, neutron, photon) or its energy (e. g. thermal, fast).
- ACTIVATION ANALYSIS A method of elemental or isotopic analysis based on the measurement of characteristic radiation) from nuclides formed directly or indirectly by activation). In general, a specification is added of the type of the incident radiation (e. g. neutron, proton) and its energy (e. g. , thermal, fast).
- ACTIVATION ANALYSIS, ABSOLUTE A method of activation analysis in which the elemental concentrations in the material are calculated from known nuclear constants, irradiation and measurement parameters, rather than by comparing with known standards.
- ACTIVATION ANALYSIS, INSTRUMENTAL A method of activation analysis in which element specificity is obtained by using appropriate irradiation conditions, radiation measurement techniques and mathematical techniques for the interpretation of the measurement results.
- ACTIVATION ANALYSIS, NEUTRON See activation analysis.
- ACTIVATION ANALYSIS, NON-DESTRUCTIVE An activation analysis procedure in which after the irradiation , no chemical and physical operations are applied which cause a change of any properties of the sample.
- ACTIVATION ANALYSIS, POST Synonymous with activation analysis, post , which is preferred.
- ACTIVATION ANALYSIS, RADIOCHEMICAL A method of activation analysis in which, after the irradiation , chemical or physical separation is applied.
- ACTIVATION CROSS SECTION See cross section, microscopic
- ACTIVATION DETECTOR A radiation detector in which the induced radioactivity produced by exposure in a radiation field is used to determine particle flux density or particle fluence. NM.
- ACTIVATION FOIL An activation detector in the form of a foil. NM.
- ACTIVATION PRODUCT] An element made radioactive by bombardment with charged particles, photons, or neutrons.
- ACTIVE DEPOSIT The non-gaseous, radioactive descendants of radon from the natural radioactive series (decay chain). FKMM.
- ACTIVE (NEUTRON) ASSAY OR INTERROGATION A non-destructive measurement technique in which the sample is exposed to (neutron) irradiation which causes a reaction (usually nuclear) that can be measured. GNST
- ACTIVITY The number of nuclear decays occurring in a given quantity of material in a time interval, divided by that time interval. Synonymous with disintegration rate.
- ACTIVITY CONCENTRATION For a specified radionuclide , the activity of a material divided by its volume.
- ACTIVITY CURVE See decay curve. NM.
- ACTIVITY, MOLAR For a specified isotope in a compound, the activity of one mole of the compound.
- ACTIVITY, SPECIFIC For a specified radionuclide , the activity of a material divided by the mass or volume of that material.
- ADC Analog-to-digital converter
- ADSORBENT A material that has the property of adsorbing radionuclides (see adsorption). WASTE.
- ADSORPTION The enrichment of one or more components in an interfacial layer. C.
- AES Auger electron spectroscopy.
- AGE, NEUTRON See Fermi age.
- AGE, RADIOACTIVE See radioactive age
- AGGREGATE RECOIL An atom of the source material which is ejected from the surface of a radioactive source. This occurs principally in a-particle disintegrations. NM.
- AGONIST A chemical which can not only combine with a receptor , like an antagonist , but when it does so stimulates it, resulting in an observable effect. (Oxford English Dictionary, 2nd ed.)
- AIRBORN DEBRIS OR WASTE Radioactively contaminated matter, generally small solid particles or liquid droplets, that has become suspended by the air. WASTE.
- AIR EQUIVALENT A measure of the effectiveness of an absorber of radiation equal to the thickness of a layer of air at STP that absorbs the same fraction of radiation or results in the same energy degradation as the air. M.
- ALARA As low as reasonably achievable, in reference to radiation hazards. NCRP.
- ALBEDO The reflection factor a surface, such as paraffin, has for neutrons. M.
- ALI Annual limit of intake.
- ALPHA See alpha particle.
- ALPHA-DECAY Radioactive decay in which an alpha particle is emitted.
- ALPHA-EMITTER A nucleus that undergoes radioactive decay by emitting an alpha particle.
- ALPHA-PARTICLE Alpha-particle. A 4He nucleus emitted during a nuclear transformation. Also called an a-ray or just an alpha.
- AMALGAM EXCHANGE A rapid and efficient separation procedure for a number of cations from aqueous solution into a mercury amalgam of their elements. NAC.
- AMPLIFIER, BIASED LINEAR PULSE A pulse amplifier which, within the limits of its normal operating characteristics, has a constant gain for that portion of an input pulse that exceeds the threshold value and that produces no output for pulses whose amplitude is below the threshold.
- AMPLIFIER, LINEAR PULSE A pulse amplifier which, within the limits of its normal operating characteristics, delivers an output pulse of amplitude proportional to that of the input pulse. (AMPLITUDE TO TIME CONVERTER)
- AMS Accelerator mass spectrometry.
- ANALOG TO DIGITAL CONVERTER (ADC) A pulse amplitude analyzer which produces an digital number proportional to the amplitude of the pulse presented at its input. The three types are the linear ramp converter (Wilkinson type), the successive approximation ADC, and the flash ADC.
- ANALYTE The substance in a specimen to be analyzed in an assay. NM.
- ANALYTICAL RADIOCHEMISTRY See radioanalytical chemistry.
- ANGULAR CORRELATION In reference to radiation in coincidence , the dependence of the direction of one radiation with respect to its coincident partner.
- ANGULAR CORRELATION COEFFICIENTS In the probability distribution W(q) for the angle q between two coincident radiations, the relative weighting factors, a2n for the cos2nq terms in W(q) 1+a2cos2q + a4cos4q +....
- ANION EXCHANGE The process of exchanging anions between solution and an anion exchanger. C.
- ANION EXCHANGER An ion exchanger with anions as counter-ions. C.
- ANNEALING In radiation of materials, the process of returning displaced atoms to their original position by heating or irradiation with electrons or gamma rays. The original displacement can have been caused by a variety of processes including recoils from nuclear transformations.
- ANNIHILATION An interaction between a particle and its antiparticle in which the pair is converted into annihilation photons.
- ANNIHILATION PHOTONS Photons produced as the result of annihilation of a particle with its antiparticle. The summed energy of the annihilation photons must equal the mass-energy equivalent of the summed masses of the annihilating particles.
- ANNIHILATION RADIATION Radiation resulting from annihilation.
- ANNUAL LIMIT OF INTAKE Annual limit of intake, in reference to radiation dose.
- ANTAGONIST A substance that binds to a receptor but does not activate it, in the process of blocking the binding of the natural agonist and so preventing its action. NM.
- ANTAGONISTIC EFFECT
- ANTIBODY A serum or cell-bound protein, part of which provides the specificity for binding an antigen.
- ANTICOINCIDENCE The occurrence of an event that is unaccompanied by one or more other specified events at the same time; equivalent to a Boolean "not".
- ANTI-COMPTON GAMMA-RAY SPECTROMETER See gamma-ray spectrometer, anti-Compton
- ANTIGEN Any substance that will induce antibody formation after parenteral application to a vertebrate animal. KE.
- ANTINEUTRINO The antiparticle of the neutrino, emitted with the negative beta particle in beta decay.
- ANTIPARTICLE Of a given particle , a particle with the same rest mass and opposite charge; the two can undergo annihilation.
- APPEARANCE POTENTIAL The minimum potential which the electron beam in an ion source must traverse in order to acquire enough energy to produce ions of a specified nuclide or molecular fragment. M.
- ARCHAEOMETRY The application of the measuring techniques of the hard sciences to the remains left by ancient peoples. P.
- ARTIFICIAL ELEMENT An element which has been produced through nuclear transformation and which does not otherwise exist in nature.
- ARTIFICIAL RADIOACTIVITY See induced radioactivity.
- ASHING Dry or wet mineralization as a method of preconcentration of trace substances. C.
- ASSAY 1. The quantitative determination of a specified analyte. 2. The measurement of the quantity of a chemical constituent, or of the activity of an enzyme, hormone or other biological compound, or biological potency of a drug in a biological material.
- ASSAY KIT A set of components (reagents and other necessary materials) and procedural instructions packaged together and designed for the estimation in vitro of a specified analyte, when used according to the instruction.
- ASSAY METER An instrument used for the assay of radioactive material. It can comprise a radiation detector sensitive to the emissions from the radioactive material and a counting rate-meter or a scaler. NM.
- ASYMMETRY Denoting absence of symmetry. Sometimes a quantitative measure of a peak so characterized.
- ATOM The smallest unit quantity of an element that is capable of existence whether alone or in chemical combination with other atoms of the same element or other elements. NIC.
- ATOMIC MASS Rest mass of an atom in its nuclear and atomic ground state.
- ATOMIC MASS, RELATIVE The ratio of the mass per atom of an element, averaged over a specified nuclidic composition, to 1/12 of the mass of an atom of nuclide 12C. The term atomic weight is also used for this quantity.
- ATOMIC MASS UNIT A special unit of mass, equal to 1/12 of the rest mass of an atom of nuclide 12C in its nuclear and atomic ground state.
- ATOMIC NUMBER Number of protons contained in a nucleus. Synonymous with proton number.
- ATOMIC PILE An obsolete synonym for a nuclear reactor. NM.
- ATOMIC WEIGHT Atomic mass
- ATTENUATION The reduction of a radiation quantity upon its passage through matter. Attenuation results from interactions of the radiation with the matter it traverses.
- ATTENUATION COEFFICIENT Of a substance, for parallel beam of specified radiation , the quantity m in the expression mDx for the fraction removed by attenuation in passing through a thin layer of thickness Dx of that substance. According as Dx is expressed in terms of length, mass per unit area, moles or atoms per unit, m is called respectively the linear, mass, molar, or atomic attenuation coefficient.
- ATTENUATION FACTOR A measure of the opacity of a layer of material for radiation traversing it; the ratio of the incident intensity to the transmitted intensity. NM.
- AUGER EFFECT The emission of an electron from an atom ; accompanies the filling of a vacancy in an inner electron shell.
- AUGER ELECTRON Electron originating in the Auger effect.
- AUGER ELECTRON SPECTROSCOPY Any technique in which a specimen is bombarded with keV-energy electrons or X-rays, and the energy distribution of the electrons (Auger electrons ) produced through radiationless de-excitation of the atoms in the sample is recorded. C.
- AUGER (ELECTRON) YIELD The fraction of the atoms having a vacancy in an inner orbital which relaxes by emission of an Auger electron. C.
- AUTHORIZED LIMIT Limit set for a given radionuclide or source or for a given environment by a national or international environmental authority. WASTE.
- AUTO-IONIZATION The radiationless transition from an atom to an equal energy level in the continuum of an ion. M.
- AUTORADIOGRAM See autoradiograph
- AUTORADIOGRAPH A radiograph of an object containing radioactive substance, produced by itself when it is placed upon photographic plate or film.
- AUTORADIOGRAPHY A collection of techniques whereby radioactivity is visually localized within solid specimens by means of the close apposition of a detector layer. J.
- AUTORADIOGRAPHY, WHOLE BODY Autoradiography of cross-sectional slices. J.
- AUTORADIOLYSIS Radiolysis of a radioactive material resulting directly or indirectly from its radioactive decay.
- AVERAGE LIFE The average life of an atom or nuclear system in a specified state. For an exponentially decaying system, it is the average time for the number of atoms or nuclei in a specified state to decrease by a factor e. Synonymous with mean life.
- AVERAGE LOGARITHMIC ENERGY DECREMENT In moderation of neutrons, it is the average of the natural logarithm of the ratio of the energy of a neutron before a collision to that after a collision.
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