1、Designation:C149309Standard Test Method forNon-Destructive Assay of Nuclear Material in Waste byPassive and Active Neutron Counting Using a DifferentialDie-Away System1This standard is issued under the fixed designation C1493;the number immediately following the designation indicates the year oforig
2、inal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a system that performs nonde-structive assay(N
3、DA)of uranium or plutonium,or both,usingthe active,differential die-away technique(DDT),and passiveneutron coincidence counting.Results from the active andpassive measurements are combined to determine the totalamount of fissile and spontaneously-fissioning material indrums of scrap or waste.Correct
4、ions are made to the measure-ments for the effects of neutron moderation and absorption,assuming that the effects are averaged over the volume of thedrum and that no significant lumps of nuclear material arepresent.These systems are most widely used to assay low-leveland transuranic waste,but may al
5、so be used for the measure-ment of scrap materials.The examples given within this testmethod are specific to the second-generation Los AlamosNational Laboratory(LANL)passive-active neutron assaysystem.1.1.1 In the active mode,the system measures fissile iso-topes such as235U and239Pu.The neutrons fr
6、om a pulsed,14-MeV neutron generator are thermalized to induce fission inthe assay item.Between generator pulses,the system detectsprompt-fission neutrons emitted from the fissile material.Thenumber of detected neutrons between pulses is proportional tothe mass of fissile material.This method is cal
7、led the differ-ential die-away technique.1.1.2 In the passive mode,the system detects time-coincident neutrons emitted from spontaneously fissioningisotopes.The primary isotopes measured are238Pu,240Pu,and242Pu;however,the system may be adapted for use onother spontaneously-fissioning isotopes as we
8、ll,such as kilo-gram quantities of238U.The number of coincident neutronsdetected is proportional to the mass of spontaneously-fissioning material.1.2 The active mode is used to assay fissile material in thefollowing ranges.1.2.1 For uranium-only bearing items,the DDT can mea-sure the235U content in
9、the range from about 0.02 to over 100g.Small mass uranium-bearing items are typically measuredusing the active mode and only large mass items are measuredin passive mode.1.2.2 For plutonium-only bearing items,the DDT methodmeasures the239Pu content in the range between about 0.01and 20 g.1.3 The pas
10、sive mode is capable of assaying spontaneously-fissioning nuclei,over a nominal range from 0.05 to 15 g240Puequivalent.1.4 This test method requires knowledge of the relativeabundances of the plutonium or uranium isotopes to determinethe total plutonium or uranium mass.1.5 This test method will give
11、 biased results when the wasteform does not meet the calibration specifications and themeasurement assumptions presented in this test method regard-ing the requirements for a homogeneous matrix,uniformsource distribution,and the absence of nuclear material lumps,to the extent that they effect the me
12、asurement.1.6 The complete active and passive assay of a 208 L drumis nominally 10 min or less but either mode can be extended tomeet data quality objectives.1.7 Some improvements to this test method have beenreported(1,2,3,4).2Discussions of these improvements arenot included in this test method al
13、though improvementscontinue to occur.1.8 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.9 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concer
14、ns,if any,associated with itsuse.It is the responsibility of the user of this standard to1This test method 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 Feb.1,2009.Published
15、 March 2009.Originallyapproved in 2001.Last previous edition approved in 2001 as C1493 01.DOI:10.1520/C1493-09.2The boldface numbers given in parentheses refer to a list of references at theend of the text.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959
16、.United States1 establish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.Specific precautionary statements are given in Section 8.2.Referenced Documents2.1 ASTM Standards:3C1030 Test Method for Determination of Plutonium IsotopicComposition by Gamma-Ray SpectrometryC1207 Test Method for Nondestructive Assay of Plutoniumin Scrap and Waste by Passive Neutron CoincidenceCountingC1215 Guide for Preparing and Interpreting Precision andB
