1、Designation: C 1458 091Standard Test Method forNondestructive Assay of Plutonium, Tritium and241Am byCalorimetric Assay1This standard is issued under the fixed designation C 1458; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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.1NOTESection 6.2 was corrected editorially in March 2009.1. Scope1.1 This test method describes the nondestructive assay(
3、NDA) of plutonium, tritium, and241Am using heat flowcalorimetry. For plutonium the typical range of applicabilitycorresponds to 1 g to 2000 g quantities while for tritium thetypical range extends from 0.001 g to 10 g. This test methodcan be applied to materials in a wide range of container sizesup t
4、o 50 L. It has been used routinely to assay items whosethermal power ranges from 0.001 W to 135 W.1.2 This test method requires knowledge of the relativeabundances of the plutonium isotopes and the241Am/Pu massratio to determine the total plutonium mass.1.3 This test method provides a direct measure
5、 of tritiumcontent.1.4 This test method provides a measure of241Am either asa single isotope or mixed with plutonium.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesaf
6、ety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 697 Test Methods for Chemical
7、, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade PlutoniumDioxide Powders and PelletsC 1009 Guide for Establishing a Quality Assurance Pro-gram for Analytical Chemistry Laboratories Within theNuclear IndustryC 1030 Test Method for Determination of Plutonium Isoto-pic Composition by
8、 Gamma-Ray SpectrometryC 1592 Guide for Nondestructive Assay MeasurementsC 1673 Terminology of C26.10 Nondestructive AssayMethods2.2 ANSI Standards:3ANSI N15.22 PlutoniumBearing SolidsCalibrationTechniques for Calorimetric AssayANSI N15.54 Radiometric CalorimetersMeasurementControl Program3. Termino
9、logy3.1 Definitions: Terms shall be defined in accordance withC26.10 Terminology C 1673 except for the following:3.1.1 baseline, nthe calorimeter output signal with noheat-generating item in the calorimeter item chamber.3.1.2 basepower, na constant thermal power applied in acalorimeter through an el
10、ectrical resistance heater with noheat-generating item in the item chamber.3.1.3 equilibrium, nthe point at which the temperature ofthe calorimeter measurement cell and the item being measuredstops changing.3.1.4 heat distribution error, nthe bias arising from thelocation of the heat source within t
11、he calorimeter chamber.3.1.5 passive mode, na mode of calorimeter operationwhere no external power is applied to the calorimeter except inthe case of Wheatstone bridge temperature sensors whereelectrical current is needed to excite the bridge circuit.3.1.6 sensitivity, nthe change in calorimeter res
12、ponse perWatt of thermal power (usually in units of micro Volts perWatt) for a heat flow calorimeter.3.1.7 servo control mode, na mode of calorimeter opera-tion where a constant applied thermal power is maintained in acalorimeter measurement chamber through the use of anelectric resistance heater in
13、 a closed loop control system.3.1.8 specific power, nthe rate of energy emission byionizing radiation per unit mass of a radionuclide, suchas241Am or tritium.1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.10
14、on NonDestructive Assay.Current edition approved Feb. 1, 2009. Published March 2009. Originallyapproved in 2000. Last previous edition approved in 2000 as C 1458 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Bo
15、ok of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
16、st Conshohocken, PA 19428-2959, United States.3.1.9 thermal diffusivity, nthe ratio of thermal conductiv-ity to the heat capacity. It measures the ability of a material toconduct thermal energy relative to its ability to store thermalenergy.3.1.10 thermal power, nthe rate at which heat is generatedi
17、n a radioactively decaying item.3.1.11 thermal resistance, nratio of the temperature dif-ference at two different surfaces to the heat flux through thesurfaces at equilibrium.3.1.12 thermal time constant, nan exponential decay con-stant describing the rate at which a temperature approaches aconstant
18、 value. An item container combination will havenumerous thermal time constants.3.1.13 thermel, nthe THERMal ELement of the calorim-eter, including the item chamber, and temperature sensor.4. Summary of Test Method4.1 The item is placed in the calorimeter measurementchamber and the heat flow at equil
19、ibrium, that is, the thermalpower, from the item is determined by temperature sensors andassociated electronic equipment.4.2 The thermal power emitted by a test item is directlyrelated to the quantity of radioactive material in it. The powergenerated by ionizing radiation absorbed in the item is mea
20、-sured by the calorimeter.4.3 The mass (m) of Pu, tritium, or241Am is calculated fromthe measured thermal power of an item (Wi) using thefollowing relationship:m 5WiPeff(1)where:Peff= the effective specific power calculated from theisotopic composition of the item (see 11.3.2 fordetails of the calcu
21、lation of Pefffor plutonium).4.3.1 When tritium is the only heat source the measuredthermal power can be directly converted into mass using thespecific power of tritium, Peff= (0.3240 6 0.00045) (SD) W/g(1).44.3.2 For241Am as a single isotope the measured thermalpower can be directly converted into
22、mass using the specificpower of241Am, Peff= (0.1142 6 0.00042) (SD) W/g (seeTable 1).4.3.3 For241Am mixed with plutonium, the241Am mass,MAm, is determined byMAm5 RAmMPu(2)where:RAm= the mass ratio of241Am to Pu, andMPu= the mass of Pu.5. Significance and Use5.1 This test method is the most accurate
23、NDAtechnique forthe assay of many physical forms of Pu. Isotopic measurementsby gamma-ray spectroscopy or destructive analysis techniquesare part of the test method when it is applied to the assay of Pu.5.1.1 Calorimetry has been applied to a wide variety ofPu-bearing solids including metals, alloys
24、, oxides, fluorides,mixed Pu-U oxides, mixed oxide fuel pins, waste, and scrap,for example, ash, ash heels, salts, crucibles, and graphitescarfings) (2,3). This test method has been routinely used atU.S. and European facilities for Pu process measurements andnuclear material accountability for the l
25、ast 40 years (2-9).5.1.2 Pu-bearing materials have been measured in calorim-eter containers ranging in size from about 0.025 m to about0.60 m in diameter and from about 0.076 m to about 0.9 m inheight.5.1.3 Gamma-ray spectroscopy typically is used to deter-mine the Pu-relative isotopic composition a
26、nd241Am to Puratio (see Test Method C 1030). Isotopic information frommass spectrometry and alpha counting measurements may beused (see Test Method C 697).5.2 This test method is the most accurate NDA method forthe measurement of tritium. For many physical forms of tritiumcompounds calorimetry is th
27、e only practical measurementtechnique available.5.3 Physical standards representative of the materials beingassayed are not required for the test method.5.3.1 This test method is largely independent of the elemen-tal distribution of the nuclear materials in the matrix.5.3.2 The accuracy of the metho
28、d can be degraded formaterials with inhomogeneous isotopic composition.5.4 The thermal power measurement is traceable to nationalmeasurement systems through electrical standards used todirectly calibrate the calorimeters or to calibratesecondary238Pu heat standards.5.5 Heat-flow calorimetry has been
29、 used to prepare second-ary standards for neutron and gamma-ray assay systems (7-12).4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.TABLE 1 Nuclear Decay Parameters for Pu Calorimetric AssayAIsotopeHalf-Life,YearsStandard Deviation, YearsSpecificPower
30、, W/gStandard Deviation, W/g References238Pu 87.74 0.04 (0.05 %) 0.56757 0.00026 (0.05 %) (19,20)239Pu 24 119 16 (0.11 %)1.9288 31030.0003 3103(0.02 %) (20-22)240Pu 6564 11 (0.17 %)7.0824 31030.0020 3103(0.03 %) (23-28)241Pu 14.348 0.022 (0.15 %)3.412 31030.002 3103(0.06 %) (29-33)242Pu 376 300 900
31、(0.24 %)0.1159 31030.00026 3103(0.22 %) (34)241Am 433.6 1.4 (0.32 %) 0.1142 0.00042 (0.37 %) (32,35)ANumbers in parentheses are % relative standard deviation (RSD).C145809125.6 Calorimetry measurement times are typically longerthan other NDA techniques. Four parameters of the item andthe item packag
32、ing affect measurement time. These fourparameters are density, mass, thermal conductivity, and changein temperature. The measurement well of passive calorimeterswill also affect measurement time because it too will need tocome to the new equilibrium temperature. Calorimeters oper-ated in servo mode
33、maintain a constant measurement welltemperature and have no effect on measurement time.5.6.1 Calorimeter measurement times range from 20 min-utes (13) for smaller, temperature-conditioned, containers up to24 h for larger containers and items with long thermal-timeconstants.5.6.2 Measurement times ma
34、y be reduced by using equilib-rium prediction techniques, by temperature preconditioning ofthe item to be measured, or operating the calorimeter using theservo-control technique.6. Interferences6.1 Interferences for calorimetry are those processes thatwould add or subtract thermal power from the pow
35、er of theradionuclides being assayed. Some examples include phasechanges, endothermic or exothermic chemical reactions, suchas oxidation, radiolisis of liquids, and bacterial action.6.2 Heat-generating radionuclides that are not included inthe Peffdetermination will bias the measurement results high
36、.7. Apparatus7.1 Calorimeters are designed to measure different sizes andquantities of nuclear material. Different types of heat-flowcalorimeter systems share the common attributes listed below.7.1.1 Measurement ChamberHeat flow calorimeters havea cylindrical measurement chamber from which all of th
37、e heatflow generated by radioactive decay is directed through tem-perature sensors.7.1.1.1 An electrical heater may be built into the walls or thebase of the chamber to provide measured amounts of thermalpower into the calorimeter well.7.1.1.2 Insulation or active heaters (or both) are used toshield
38、 the chamber from outside temperature variations thatwould influence the thermal power measurement. Typically, aninsulated plug is inserted above the item container inside thecalorimeter. For some calorimeter types an insulating plug isinstalled permanently below the measurement chamber.7.1.2 Calori
39、meter CanThe item to be measured may beplaced in a special can that is designed to be inserted andremoved easily from the calorimeter. It will typically have onlya small air gap to provide good thermal conductivity betweenthe outer surface of the can and the inner surface of themeasurement chamber.7
40、.1.3 Temperature SensorsTemperature sensors consist ofthermistors, thermocouples, temperature sensitive resistancewire, or thermopiles.7.1.4 Thermal SinkThe temperature increases due to heatflows generated by items are measured against a referencetemperature of a thermal sink. The thermal sink could
41、 be awater bath, air bath, or a solid, usually metal, maintained at aconstant temperature.7.1.5 Electrical ComponentsSensitive, stable electroniccomponents are required for accurate calorimeter measure-ments.7.1.5.1 High precision voltmeters are required to measurethe voltage changes generated from
42、the temperature sensors.The resolution of the voltmeters should be better than one partper million of the voltage range.7.1.5.2 Stable power supplies are necessary to provideconstant current to Wheatstone bridge sensors and calorimeterheaters.7.1.5.3 Precision resistors with certified resistances tr
43、ace-able to a national measurement system may be used withcalibrated voltmeters to accurately determine electrical powerdelivered to heaters in the calorimeter chamber. If radioactiveheat standards are used as part of the measurement controlprogram the calorimeter voltmeters need not be calibrated,
44、norare precision resistors required.7.1.5.4 For a calorimeter operated in the servo (powerreplacement) mode digital-to-analog controller units are usedto supply power to an internal resistance heater to maintain aconstant temperature differential across thermal resistances.7.1.6 Heat StandardsTherma
45、l power standards are re-quired to calibrate the calorimeter and may be used asmeasurement control standards to check the stability of calo-rimeter performance (14-17).7.1.6.1 Radioactive heat standards, typically poweredby238Pu, also may be used to calibrate calorimeters over arange of thermal powe
46、rs.These standards are calibrated againstelectrical standards traceable to a national measurement sys-tem. The certified power is typically decay corrected to thenearest day using certified decay tables.7.1.6.2 Removable electrical heaters may be used to cali-brate calorimeters. For this type of sta
47、ndard the power gener-ated by the heater must be measured with electrical equipmentregularly calibrated against standards or standard methodstraceable to a national measurement system. The power sup-plied to the electrical calibration heater may be varied over thecalibration range.7.1.7 Wheatstone B
48、ridgeWhen temperature sensitive re-sistance wire is used as the sensor, it is arranged in aWheatstone bridge configuration shown in Fig. 1.7.1.8 Data Acquisition SystemCalorimeter data collectionis performed using computer-based data acquisition systems.The system should be able to read signal volta
49、ges or resistancesat a fixed time frequency and be able to calculate and report apower value from the item using software that detects equilib-rium. Graphics and numerical data indicating system powerand temperatures may be displayed to aid the operator.7.1.9 AdaptersLow mass cylindrical metal adapters maybe fabricated to accept smaller calorimeter containers in thecalorimeter well, and thus, provide good thermal contactbetween the outer container surface and calorimeter inner wall.Heat-conducting metal foil or metal gauze fill material, typi
