CA Carrier added. J.
CADMIUM CUTOFF In neutron irradiations, the energy value which, for a given experimental configuration, is determined by the condition that if a cadmium cover surrounding a detector were replaced by a fictitious cover black to neutrons below this value and transparent to neutrons with energy above this value, the observed detector response would be unchanged. NM.
CADMIUM RATIO The ratio of the response of an uncovered neutron detector to that of the same detector under identical conditions when it is covered with cadmium of a specified thickness. M.
CAMAC MODULE A standardized modular instrument compatible with a bin or crate that houses and powers the instrument and that also has a built-in digital data bus to provide computer communications with the unit.
CANDU Canadian heavy-water moderated nuclear reactor using natural uranium as fuel.
CAPTURE A process in which an atomic or nuclear system acquires an additional particle . In general a specification is added of the type of the captured particle or its energy. IUPAC82..
CAPTURE CROSS-SECTION The cross section for capture . IUPAC82.
CAPTURE, ELECTRON A nuclear transformation in which the nucleus captures an orbital electron . Often the shell from which the electron is captured is indicated. (K-, L-, etc.) IUPAC82..
CAPTURE GAMMA RADIATION The gamma radiation emitted in radiative capture . IUPAC82..
CAPTURE, RADIATIVE Capture of a particle by a nucleus followed by immediate emission of gamma radiation . IUPAC82..
CAPTURE, RESONANT Capture of a particle exactly matching the product's resonance energy .
CARRIER An inactive material deliberately added to a specified radioactive substance to ensure that the radioactivity will behave normally in all subsequent chemical and physical processes.
CARRIER-FREE A preparation of a radioactive isotope which is 'free' from stable isotopes of the element in question. More precisely, a preparation of a radioactive isotope of high specific activity to which no isotopic carrier was intentionally added and which was not produced by irradiation of stable isotope of the same element.
CARRIER, HOLD-BACK A non-radioactive carrier of a radioactive nuclide used to prevent that particular radioactive species from contaminating other radioactive species in a chemical operation.
CARRIER, ISOTOPIC A carrier which differs only in isotopic composition from the trace substance it has to carry.
CARRIER, NONISOTOPIC A carrier which is not an isotope (that is, it is a different element) of the trace substance or substances it has to carry. A scavenger of radioactive elements.
CARRIER PROTEINS Macroscopic amounts of nonlabeled proteins present with trace amounts of radiolabeled proteins. NM.
CASCADE, AUGER In the Auger effect , when the emission of an Auger electron leads to the creation of a new vacancy that relaxes by a subsequent Auger effect.
CASCADE, GAMMA See gamma cascade .
CATCHER FOIL In an irradiation of a target, a foil used to stop and retain nuclear reaction products that recoil out of the target.
CATION EXCHANGE The process of exchanging cations between solution and a cation exchanger . C.
CATION EXCHANGER An ion exchanger with cations as counter-ions. C.
CBA See competitive binding assay .
CDD Concentration dependent distribution.
CELL, HOT See hot cell .
CEMA An intermediate dosimetric quantity: the converted energy, per unit mass, expended by charged primary particles which in turn had been produced by uncharged particles. (Radiation Research, 130 15 [1992].)
CEMS Conversion electron Mssbauer spectroscopy.
CERENKOV DETECTOR A charged particle detector based on the Cerenkov effect . IUPAC82..
CERENKOV EFFECT Emission of radiation in the visible and ultraviolet spectrum arising when a charged particle crosses a medium with a velocity greater than that of light in the same medium. IUPAC82..
CERENKOV RADIATION Radiation resulting from the Cerenkov effect . IUPAC82..
CHAIN FISSION YIELD The fraction of fissions giving rise to fission fragments of a particular mass number .
CHAIN REACTION In nuclear reactions, a process in which a reaction produces more than one reaction product (such as neutrons) that induces subsequent nuclear reactions.
CHARACTERISTIC CURVE (OF A GM COUNTER) The dependence of the response of a (Geiger-Mller) detector on the applied voltage. GM counters are operated in the "plateau" voltage region of the characteristic curve where the count rate is essentially unaffected by small changes in the operating voltage.
CHARACTERISTIC X-RADIATION X-radiation consisting of discrete wavelengths which are characteristic of the emitting element.
CHARGE EXCHANGE In the interaction between two particles at least one of which is charged, the exchange of charge by those particles.
CHARGED-PARTICLE ACTIVATION ANALYSIS Nuclear activation analysis in which the irradiation is done using charged particles such as protons or alphas.
CHARGE TRAPPING In a semiconductor detector, once electrons and holes are formed by radiation, they can become immobilized for relatively long periods by impurities in the crystal lattice and this "trapping" can prevent the charge carrier from contributing to the measured pulse.
CHELATE A chemical which can undergo or has undergone chelation with an element.
CHELATING RESIN An ion exchange resin in which the counter-ions are retained by a chelate functional group on the resin.
CHELATION In molecular or complex ion structure, the formation or presence of bonds (or other attractive forces) from two or more separate binding sites within the same ligand to a single central atom. C.
CHEMICAL DOSIMETER A dosimeter in which the dose is measured by observing the extent, under specified conditions, of a chemical reaction caused by the ionizing radiation to be measured. IUPAC82..
CHEMICAL ISOTOPE EXCHANGE Exchange of isotopes of a given element between different molecules or between different chemical forms of this element in the course of a chemical reaction.
CHEMICAL NEUTRON ACTIVATION ANALYSIS (CNAA) A variation of activation analysis where a single element or group separations are employed prior to irradiation. Synonymous with activation analysis with preconcentration .
CHEMICAL YIELD The fraction of the amount of an element or chemical compound (remaining) following a specified chemical reaction or separation. IUPAC82..
CHEMILUMINESCENCE Emission of light as a result of a chemical reaction in which there is no apparent change in temperature. M.
CHEMISORPTION Adsorption in which the forces involved are valence forces of the same kind as those operating in the formation of chemical compounds. C.
CHEMISTRY, NUCLEAR The scientific discipline dealing with understanding and applying effects of a chemical and physicochemical nature caused by the nucleus of an atom, its transformations through decay and reactions, and nuclear radiation.
CHEMISTRY, RADIATION See radiation chemistry .
CHEMONUCLEAR REACTION A chemical reaction induced by nuclear radiation or fission fragments. NM.
CHOPPER A mechanical device, conceptually like a camera shutter, for controlling the precise timing of a beam .
CHLORAMINE-T A common oxidizing agent used in radioiodination of proteins. N-chloro-4-methylbenzenesulfonamide sodium salt. NM.
CHROMATOGRAM A graphical or other representation of a detector response, effluent concentration, or other quantity used as a measure of effluent concentration versus time or the volume of the effluent. C.
CHROMATOGRAPH 1.) To separate by chromatography . C. 2.) The assembly of apparatus for carrying out chromatographic separations. CAN.
CHROMATOGRAPHY A method used primarily for the separation of the compounds of a sample in which components are distributed between two phases, one of which is stationary while the other moves. C.
Ci Symbol for the curie , a unit of activity equal to 3.7 X 1010 becquerels . (Not a SI unit.)
CINAA Cyclic instrumental neutron activation analysis. See cyclic activation analysis .
CLADDING An external layer of material (usually of Zircalloy, stainless steel, magnesium), directly surrounding nuclear fuel or other substance that seals and protects it from the environment and protects the environment from radioactive material produced during irradiation. WASTE.
CLATHRATE An inclusion compound; that is, a complex in which one compound (the host) forms a crystal lattice containing spaces in the shape of long tunnels or channels in which molecular entities of a second chemical species (the guest) are located. If the host spaces are closed on all sides so that the guest is "trapped", such compounds are known as clathrates or "cage compounds". C.
CMCP Coincident measurement of complementary particles.
CNAA Chemical neutron activation analysis.
COCKROFT-WALTON GENERATOR An electrostatic device for generating high voltages through staged rectifiers and transformers. The generators are used to accelerate charged particles. FFKM.
COCKTAIL (a) In nuclear medicine; ingested mixture containing radioactive or isotopic tracers for medical studies. (b) in liquid scintillation counting, a mixture of organic solvents and fluors into which the sample is dispensed for counting. NM.
COCRYSTALLISATION See Coprecipitation .
COINCIDENCE The occurrence of two or more events at the same time; equivalent to a Boolean "and".
COINCIDENCE CIRCUIT An electronic circuit which produces a usable output pulse only when each of its inputs receives a pulse within a specified time interval. IUPAC82..
COINCIDENCE, DELAYED The occurrence of two or more events separated by a short but measurable time interval. IUPAC82..
COINCIDENCE, PROMPT The occurrence of two or more events separated by a time interval which is less than a specified small value. IUPAC82..
COINCIDENCE, RANDOM A coincidence of events occurring in different atoms or between measured atoms and other atoms, including background and unknown sources.
COINCIDENCE, TRUE A coincidence of events triggered by a single cause. (Contrast with random coincidence above.)
COINCIDENCE CORRECTION A correction to the count rate of a radiation due to losses or gains when two radiations arrive at and are processed by the detector within the coincidence resolving time .
COINCIDENCE RESOLVING TIME The greatest time interval that can elapse between the occurrence of two or more consecutive signal pulses, in order that the measuring device processes them as a coincidence . IUPAC82..
COINCIDENT MEASUREMENT OF CHARGED PARTICLES A technique used in charged particle activation analysis of light elements in thin targets in which an emitted charged particle is detected in coincidence with the recoiling product nucleus. CRC.
COLD TEST A test of method, process, apparatus, or instrumentation with highly radioactive materials replaced by inactive materials or materials that may contain radioactive tracers. NM.
COLLATERAL SERIES A radioactive decay series, initiated by transmutation, that eventually joins one of the four natural actinide decay chains. Also called a collateral chain. M
COLLECTION EFFICIENCY The chemical yield of a particular collection step in a separation, the step being either chemical or physical in nature.
COLLECTRON A neutron detector in which an electric current is produced without the application of an external power source though the emission of b particles by a short-lived radionuclide. This radionuclide is produced by neutron activation in the part of the detector called the "emitter". NM.
COLLIMATION The limiting of a beam of radiation to the required dimensions and angular spread. IUPAC82..
COLLIMATOR An arrangement of absorbers used for collimation . IUPAC82..
COLLISION DENSITY In neutron transport theory, the number of collisions per cm3/s undergone by a neutron with energy E, equal to the neutron flux divided by the scattering mean free path. NM.
COLUMN (IN CHROMATOGRAPHY) The tube that contains the stationary phase and through which the mobile phase passes. C.
COLUMN GENERATOR See radioisotope generator .
COMPARATIVE LIFETIME See ft value .
COMPARATOR A known amount of an element, capable of being activated, that is simultaneously irradiated with the test portion in the context of activation analysis . If one comparator is used (single comparator method) , it is essentially identical to a flux monitor (except that this term is not necessarily linked to activation analysis).
COMPETITIVE BINDING ASSAY Assay based on the competition between a labeled and an unlabeled ligand in the reaction with a receptor binding agent (e.g. antibody, receptor, transport protein). IUPAC94.
COMPETITIVE PROTEIN-BINDING ASSAY A competitive binding assay in which the binding agent is a protein. KE.
COMPLEX A molecular entity formed by a loose association involving two or more component molecular entities (ionic or uncharged) or the corresponding chemical species. The binding between the components is normally weaker than in a covalent bond. C.
COMPOUND NUCLEUS A transient nucleus formed when two nuclear particles fuse completely; analogous to the activated complex in the transition state theory of chemical reactions.
COMPTON EDGE In a gamma-ray spectrum, the maximum energy deposited by gamma-rays which are scattered by the Compton effect and consequently deposit less than the full energy peak . A continuum of measured energies is detected below the edge determined by the Compton effect.
COMPTON EFFECT The inelastic scattering of a photon by a free or weakly bound electron which afterwards occurs as a free electron. Part of the energy and momentum of the incident photon is transferred to the electron and the remaining part is carried away by the scattered photon. Synonymous with Compton scattering .
COMPTON ELECTRON The energetic electron resulting from the Compton effect. IUPAC82..
COMPTON SCATTERING See Compton effect .
COMPTON SHIFT The change in wavelength or energy of scattered radiation due to the Compton effect . M.
COMPTON SUPPRESSION SPECTROMETER See gamma-ray spectrometer, anti-Compton .
CONTAINMENT Any procedure which prevents the transport of radioactivity .
CONTAMINATION The presence of an unwanted radioactivity in a material or the environment in a concentration exceeding the required limit or natural background.
CONVERSION ELECTRON Electron ejected from the atom in the process of internal conversion . IUPAC82..
CONVERSION, INTERNAL A transition between two energy states of a nucleus where the energy difference is given to an orbital electron which is thereby ejected from the atom . IUPAC82..
CONVERSION COEFFICIENT, INTERNAL For a transition between two specified energy levels of a nuclide , the ratio of the transition probabilities for internal conversion and gamma ray emission. IUPAC82..
COOLING, RADIOACTIVE Of a strongly radioactive material, the decrease of its activity by nuclear decay . IUPAC82..
COORDINATION The formation of a covalent bond, the two shared electrons of which have come from only one of the two parts of the molecular entity linked by it, as in the reaction between a Lewis acid and a Lewis base to form a Lewis adduct; alternatively, the bonding formed in this way. C.
COPRECIPITATION The simultaneous precipitation of a normally soluble component with a macro-component from the same solution by the formation of mixed crystals, by adsorption , occlusion, or mechanical entrapment. (Applies generally to a radionuclide at the tracer level.) C.
COSMIC RAYS High-energy particles irradiating the earth, including electrons, muons, protons, alphas, and heavy-ions, which originate extraterrestrially from the sun and from galactic and extra-galactic sources.
COULOMB BARRIER The repulsive potential energy between two charged particles at a separation distance corresponding approximately to contact.
COUNT 1. Information corresponding to a pulse processed for counting. 2. Number of pulses recorded during a measurement. IUPAC82..
COUNTER, RADIATION A radiation detector which measures a count rate but does not perform energy spectrum analysis .
COUNTER TUBE Radiation detector consisting of a gas-filled tube or valve whose gas amplification is much greater than one, and in which the individual ionizing events give rise to discrete electrical pulses. Often an expression is added indicating the geometry (e. g. end window), composition of the gas (e. g. helium) or the physical process essential for its operation (e. g. proton recoil, fission). IUPAC82..
COUNTER TUBE, GEIGER-MLLER A counter tube operated under such conditions that the magnitude of each pulse is independent of the amount of energy deposited in it. IUPAC82..
COUNTER TUBE, PROPORTIONAL A counter tube operated under such conditions that the magnitude of each pulse is proportional to the amount of energy deposited in it. IUPAC82..
COUNTER, WELL-TYPE A radiation detector shaped with a cylindrical cavity or well into which a sample may be placed for counting in a geometry that approaches 4p.
COUNTING, ABSOLUTE A measurement under such well-defined conditions that the activity of a sample can be derived directly from the observed counting rate . IUPAC94.
COUNTING EFFICIENCY The ratio between the number of particles or photons counted with a radiation counter and the number of similar particles or photons emitted by the radiation source . IUPAC82..
COUNTING LOSS A reduction of the counting rate resulting from phenomena such as the resolving time or the dead time . IUPAC82..
COUNTING RATE The number of counts occurring in unit time. CAN
COW See radioisotope generator .
CPAA Charged-particle activation analysis.
CPBA Competitive protein-binding assay .
CRAA Critical reflection activation analysis.
CRITICAL ABSORPTION In a pair of neighboring elements whose absorption edges for x-rays straddle the energy for a particular photon energy, the one that absorbs more strongly is called the critical absorber for the photon.
CRITICAL MASS The minimum amount of fissile material necessary to sustain a chain reaction .
CRITICAL REFLECTION ACTIVATION ANALYSIS An activation analysis procedure for depth profiling of impurities in which activation is measured as a function of the angle of neutron reflection. FR.
CROSS BOMBARDMENT A method for assigning the mass to a radioactive nuclide by producing it in different nuclear reactions. NM.
CROSS FIRE In autoradiography, the spread of images into film grains appearing over features other than those which emitted the particles. J.
CROSS-LINKING Covalent bonding between polymer chains.
CROSS REACTION Ability of substances other than the analyte to bind to the binding reagent and ability of substances other than the binding reagent to bind the analyte in competitive binding assays . IUPAC94.
CROSS SECTION See cross section, microscopic .
CROSS-SECTION, ACTIVATION The cross section for the formation of a radionuclide by a specified reaction. IUPAC82..
CROSS-SECTION, CAPTURE The cross section for capture . IUPAC82..
CROSS-SECTION, EFFECTIVE In neutron induced reactions, an average cross section used to calculate a reaction rate per nucleus when the flux from the neutron source is known. NAC.
CROSS-SECTION, EFFECTIVE THERMAL A fictitious cross section for a specified (neutron-induced) reaction which, when multiplied by the 2200 metre-per-second flux density , gives the correct reaction rate. Synonymous with Westcott cross section . IUPAC82..
CROSS-SECTION, MACROSCOPIC The cross section per unit volume of a given material for a specified process. For a pure nuclide , it is the product of the microscopic cross section and the number of target nuclei per unit volume; for a mixture of nuclides, it is the sum of such products. IUPAC82..
CROSS-SECTION, MICROSCOPIC A measure of the probability of a specific interaction or reaction between an incident radiation and a target particle or system of particles. It is the reaction rate per target particle for a specified process divided by the flux density of the incident radiation. See cross-section, Westcott . C.
CROSS-SECTION, PARTIAL See cross-section, microscopic
CROSS-SECTION, THERMAL The microscopic cross section appropriate to thermal neutrons .
CROSS-SECTION, TOTAL The sum of all partial cross sections .
CROSS-SECTION, WESTCOTT See cross section, effective thermal .
CRUD Insolubly bulky corrosion products from fuel elements, condenser systems, water purification systems, etc., inside (water-cooled) nuclear reactors.
CRYPTAND A molecular entity comprising a cyclic ligand assembly that contains three or more binding sites held together by covalent bonds and which defines a molecular cavity in such a way as to bind (and thus "hide" in the cavity) another molecular entity, the guest (a cation, anion, or a neutral species) more strongly than do the separate parts of the assembly (at the same total concentration of binding sites). The adduct thus formed is called a cryptate .
CRYPTATE The adduct formed between a cryptand and a "guest" molecular entity, trapped within the cryptand's structure.
CRYSTAL DIFFRACTION SPECTROMETER See spectrometer, crystal diffraction
CUMULATIVE FISSION YIELD The fraction of fissions which have resulted in the production of a given nuclide , either directly or indirectly, up to a specified time. If no time is specified, the yield is considered to be the asymptotic value at scission .
CUMULATIVE FRACTION RELEASED OR
CUMULATIVE PENETRATION A term for expressing leach rates of radionuclides from solidified waste forms based upon depletion of the radionuclide to a certain sample depth. WASTE
CURIE A unit of activity equal to exactly 3.7 X 1010 nuclear decays per second or 3.7 X 1010 becquerels. IUPAC82.. (Not capitalized. Not a SI unit. Symbol is "Ci".)
CURRENT DENSITY Rate of flow across a surface per unit area of that surface. M.
CUTIE PIE A colloquial term for a portable ionization chamber for determining relatively stable dose rates. NM.
CYCLIC ACTIVATION (ANALYSIS) Activation analysis in which the sensitivity for short-lived radioactivities is enhanced through accumulating spectra produced during repetitive short irradiations.
CYCLIC INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS See cyclic activation analysis .
CYCLOTRON A particle accelerator in which the particles travel in a succession of semicircular orbits of increasing radii under the influence of a magnetic field and are accelerated at the beginning of each such orbit by traversing an electric field produced by a high-frequency generator. IUPAC82.. These are sometimes classified as levels I, II, III, and IV, corresponding respectively to particle energies less than 10 MeV, 20 MeV, 45 MeV, and 200 MeV. NM.