1、Designation: C 1673 07e1Standard Terminology ofC26.10 Nondestructive Assay Methods1This standard is issued under the fixed designation C 1673; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTECorrections were made throughout editorially in October 2007.1. Scope1.1 The terminology defined in this document is associatedwith nondestructive assa
3、y of nuclear material.1.2 All of the definitions are associated with measurementtechniques that measure nuclear emissions (that is, neutrons,gamma-rays, or heat) directly or indirectly.1.3 definitions are relevant to any standards and guideswritten by subcommittee C26.10.2. Referenced Documents2.1 A
4、STM Standards:2E 456 Terminology Relating to Quality and Statistics2.2 DOE Orders:3DOE Order 435.1 Low-level Waste RequirementsDOE Order 5820.2 Radioactive Waste Management3. Terminology(alpha, n) reaction, na reaction that occurs when energeticalpha particles collide with low atomic number nucleire
5、sulting in the emission of a neutron240Pu-effective mass, nthe mass of240Pu that would pro-duce the same coincident neutron response in the instrumentas the assay item.DISCUSSIONIt is a function of the quantity of even mass isotopes ofplutonium in the assay item and fundamental nuclear constants,som
6、etimes referred to as effective240Pu mass.absorber foils, nfoils, usually of copper, tin, cadmium, orlead, used to attenuate the gamma flux reaching a detector.DISCUSSIONAbsorber foils are used to reduce the count rate,typically from intense low-energy X or gamma rays.accidentals, nthe detection of
7、multiple neutron eventswithin the gate width that are not produced from the samefission.DISCUSSIONAccidental events take their name from the fact that itis the accidental or random summing of neutrons, which are not timecorrelated with a common origin (fission or cosmic-ray burst), that giverise to
8、the appearance of a signature like that from genuine correlatedevents.accuracy, n(1) bias; (2) the closeness of a measured value tothe true value; and (3) the closeness of a measured value toan accepted reference or standard value.active assay, nassay based on the observation of radiation(s)induced
9、by irradiation from an external source.alpha, a, nthe ratio of the uncorrelated neutron emissionrate from (a, n) reactions to the spontaneous neutronemission rate from a non-multiplying item.aperture, nthe size of the opening in the collimator throughwhich the radiation of interest is intended to pa
10、ss.assay, vto determine quantitatively the amount of one ormore nuclides of interest contained in an item.attenuation correction, ncorrection to the measured countrate for attenuation of radiation that provides an estimate ofthe unattenuated radiation emission rate of the radionuclidesbeing assayed.
11、attenuation, nreduction of radiation flux due to the interac-tion of radiation with material between the source of theradiation and the detector.background, nextraneous signal superimposed on the signalof interest.Beers Law, nthe fraction of uncollided gamma rays trans-mitted through layers of equal
12、 thickness of an absorber is aconstant.benign matrix, nbulk material that has a negligible effect onthe result of the measured parameter.blank, na prepared item containing a matrix as similar aspractical to the items being measured that is free, to theextent possible, of the radionuclides of interes
13、t.1This terminology is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.10 on NonDestructive Assay.Current edition approved June 1, 2007. Published July 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orc
14、ontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from the U.S. Department of Energy (DOE), 1000 IndependenceAve., SW Washington, DC 20585.1Copyright ASTM International, 100
15、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.DISCUSSIONThe most important matrix parameters are those thataffect the result of the measurement technique being used.calibration standard, nan item similar to the items to beassayed, for which the parameters of intere
16、st and all prop-erties to which the measurement technique is sensitive areknown.calorimeter, na device to measure heat or rate-of-heatgeneration.calorimetric assay, ndetermination of the mass of radioac-tive material through the measurement of its thermal powerby calorimetry and the use of nuclear d
17、ecay constants and, ifnecessary, additional isotopic measurements.certification, na written declaration from a certifying bodyor its legitimate designee that a particular measurementprocess or measurement personnel comply with stated crite-ria or that a measured item has the stated characteristics.c
18、ode validation, nprocess to determine that the softwareperforms its intended functions correctly, ensure that itperforms no unintended functions, and provides informationabout its quality and reliability.coincidence gate length, nthe time interval following thedetection of a neutron during which add
19、itional neutrons areconsidered to be in coincidence with the original neutron.coincident neutrons, ntwo or more neutrons emitted simul-taneously from a single event, such as from a nucleus duringfission.collimated detector, na detector surrounded by a shield thatimposes a directional response on the
20、 collimated detector.collimator, na shield that imposes a directional response onthe detector. Generally, for gamma ray detection the colli-mator is a hollow cylinder or rectangular prism of highatomic number (Z) and high density material, mountedcoaxially to the detector and extending over the dete
21、ctor andbeyond the detector face.Compton scattering, nscattering of gamma rays that may ormay not be from the radionuclide of interest.DISCUSSIONThe scattering reduces the energy of the gamma ray andresults in a continuum of gamma ray puted tomography, nsee tomography.confidence interval, nThe range
22、 of values, calculated fromthe probability distribution (often sufficiently well character-ized by the estimate of the mean and standard deviation),which is expected to include the population mean with astated level of confidence or likelihood.DISCUSSIONFor more details see Test Method E 456.contact
23、 measurement, na special case of a near-fieldmeasurement in which measurements are made with thedetector assembly in contact with the item, for example,tank, pipe, ductwork, being assayed.control chart, na graphical plot of test results with respectto time or sequence of measurement together with li
24、mits inwhich they are expected to lie when the system is in a stateof statistical control.control limits, nthe limits beyond which it is statisticallyhighly improbable that one or several point(s) could lie whilethe system remains in a state of statistical control.data quality objective, nmeasuremen
25、t uncertainty and con-fidence levels specified by the scope of work.dead time, nthe period following the detection of an eventduring which the detection electronics cannot register asubsequent event.DISCUSSIONDead time is usually expressed as a percentage ofelapsed time.delayed neutrons, nneutrons e
26、mitted by the item that areproduced from decay of the fission products.DISCUSSIONThese neutrons are produced at a time after the initialfission event.depleted uranium, nuranium containing less than the natu-rally occurring fraction of235U isotopes ( 0.7 weightpercent).die-away time, nthe average lif
27、e time of the neutronpopulation as measured from the time of emission todetection, escape, or absorption. The average lifetime is thetime required for the neutron population to decrease by afactor of 1/e.doubles, nthe detection of neutron pairs produced from thesame fission event.DISCUSSIONThe doubl
28、es terminology is often used in reference tomultiplicity counting, but it is the same as the reals from coincidencecounting.effective specific power, peff, nthe rate of energy emissionper unit mass of radionuclide at the time of measurement.far-field measurement, na measurement geometry wherethe ana
29、lyst can assume that all gamma rays emitted from theitem enter the detector along paths parallel to each other.field of view, nthe entire solid angle subtended by thecollimated detector.fissile isotopes, nisotopes that can be induced to fission bythermal neutrons.DISCUSSION233U,235U,239Pu, and241Pu
30、are the most commonfissile isotopes.flux monitors, ndetectors in the measurement chamber thatmeasure the neutron flux of interrogating neutrons (cavityflux monitor) or item neutrons (drum flux monitor).heat-flow calorimeter, na calorimeter so constructed thatthe heat generated in the calorimeter flo
31、ws past a tempera-ture sensing element, through a thermal resistance, to aconstant temperature heat sink.holdup, nthe residual nuclear material remaining in processequipment and facilities.homogeneous matrix, na matrix whose characteristics im-portant to the measurement result is uniform throughout
32、theitem.infinite thickness, nthe thickness of material through which99.9 % of the gamma rays of the designated energy cannotpenetrate.DISCUSSIONThis is nominally equal to 7 mean-free paths in purematerial.item, nmaterial potentially containing radioisotope to bemeasured.C167307e12low level waste, ni
33、s radioactive containing material that isnot classified as high-level waste, transuranic waste, spentnuclear fuel, or by-product material.lower limit of detectability, na stated limiting value whichdesignates the lowest concentration, mass, or activity thatcan be detected with confidence and which i
34、s specific to aparticular measurement.lump, nthat contiguous mass of nuclear material that issufficiently large to affect the measured signal.matrix, nthe material that comprises the bulk of the item,except for the radionuclide(s) of interest and the container.matrix-specific calibration, na calibra
35、tion that uses a ma-trix similar to the matrix to be measured.DISCUSSIONNo matrix correction factors are used. This calibrationis normally not appropriate for other matrices.model validation, nprocess to determine the suitability ofthe model for a given application.multiplicity distribution, nthis i
36、s the distribution of thenumber of neutrons emitted in fission events.near-field measurement, nmeasurement made at interme-diate or close distances from the item where the measuredradiation enters the detector from a variety of distances andangles.neutron absorbers, nmaterials which have relatively
37、largethermal-neutron capture cross-sections.DISCUSSIONAbsorbers with the largest capture cross-sections arecommonly known as neutron poisons. Some examples are boron,cadmium, gadolinium and lithium.neutron moderators, nmaterials which efficiently slowdown neutrons. Materials containing large amounts
38、 of lowatomic weight materials, such as hydrogen are highly mod-erating.neutron multiplication, nmultiplication takes place when aneutron interaction yields more than one neutron as aproduct.DISCUSSIONInduced fission is the primary mechanism for neutronmultiplication, however (n, 2n) interactions ar
39、e also multiplicationevents.nondestructive assay, NDA, nan analysis of an item inwhich the chemical and physical properties of that item andcontainer remain essentially unaltered.nuclide, nan atomic species characterized by the composi-tion of its nucleus, that is, by the number of protons andneutro
40、ns it contains.one pass assay, na gamma ray measurement in which thetransmission and emission data are collected simultaneously.passive assay, nassay based on the observation of naturallyoccurring or spontaneous nuclear radiation(s).passive mode, na technique used to determine thespontaneously-fissi
41、oning mass in the measured item throughthe detection of spontaneously emitted neutrons rather thanneutrons induced by external interrogation sources.peaked background, ngamma rays of the assay energy,which originate in sources other than the item material beingassayed.point model, nthe mathematical
42、model used to analyzemeasurements of radioactive items where the item is repre-sented as a point source.point source, nsource material confined to a volume whosedimensions are small compared with the distance betweenthe source and detector.pre-delay, nthe coincidence circuit has a time period imme-d
43、iately after a neutron has been detected during whichsignals are not accepted.prompt neutrons, nneutrons released within approximately114s of the fission.rate-loss correction, na correction for count rate relatedlosses that are used for some gamma-ray NDA techniques.reals, R, ndetection of neutron p
44、airs produced from the samefission event.DISCUSSIONThe reals terminology is often used in reference tocoincidence counting, but it is the same as the doubles from multiplicitycounting.sample, na portion of a population or lot. In the context ofNDA measurements, it may consist of measurements ofitems
45、 that are part of a larger group that could have beenconsidered.scrap, nmaterials that contain sufficient quantities of radio-active material to be worthy of recovery.screening, nrapid, that is, short-count time, measurements atspecific locations or with a moving gamma-ray detector(sometimes with a
46、neutron probe) along an item to qualita-tively identify the presence and rough distribution of radio-active material.DISCUSSIONThe information from the screening can be used tooptimize the assay procedure for the item(s).secular equilibrium, nthe state of equilibrium that existswhen a series of daug
47、hter radioisotopes have constantactivity levels determined by the parent activity rate.self-attenuation, nthe attenuation of emitted radiation bythe emitting material itself.sensitivity, nthe capability of methodology or instrumenta-tion to discriminate between items having differing concen-trations
48、 or containing differing amounts of a radioactivematerial or no radioactive material.singles, S, nthe sum of all detected neutrons in multiplicitycounting. Discussionequivalent to the totals from coinci-dence counting.special nuclear material, nplutonium,233U, uranium en-riched in235U and any other
49、materials defined as SNM undertheAtomic EnergyAct of 1954 as amended and DOE orders.spontaneously-fissioning nuclei, nthose nuclei which donot require an external neutron source to undergo significantfission.DISCUSSIONThe most common isotopes are238,240,242Pu,242,244Cm,and252Cf.total measurement uncertainty (TMU), nan estimatedparameter, either mass, activity, concentration, or fractional,used to quantify the overall confidence in the assay result ata prescribed level including
