ASTM C1458-2009 Standard Test Method for Nondestructive Assay of Plutonium Tritium and 241Am by Calorimetric Assay.pdf

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1、Designation: C 1458 09Standard 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.1. Scope1.1 This test method describes the nondestructive assay(NDA) of plutonium, tritium, and241Am using heat flowcalori

3、metry. 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 to 50 L. It has been used routinely to assay items whosethe

4、rmal 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 of tritiumcontent.1.4 This test method provides a measure

5、 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 thesafety concerns, if any, associated with its use. It is there

6、sponsibility 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, Mass Spectrometric, andSpectrochemical Analysis of Nucle

7、ar-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 Gamma-Ray SpectrometryC 1592 Guide for Nondestructive Ass

8、ay MeasurementsC 1673 Terminology of C26.10 Nondestructive AssayMethods2.2 ANSI Standards:3ANSI N15.22 PlutoniumBearing SolidsCalibrationTechniques for Calorimetric AssayANSI N15.54 Radiometric CalorimetersMeasurementControl Program3. Terminology3.1 Definitions: Terms shall be defined in accordance

9、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 electrical resistance heater with noheat-generating item in

10、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 the calorimeter chamber.3.1.5 passive mode, na mode of calo

11、rimeter 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 response perWatt of thermal power (usually in units of micro

12、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 a closed loop control system.3.1.8 specific power, nthe r

13、ate 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 on NonDestructive Assay.Current edition approved Feb. 1, 2

14、009. 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 Book of ASTMStandards volume information, refer to the stand

15、ards 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, West Conshohocken, PA 19428-2959, United States.3.1.9 therma

16、l 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 generatedin a radioactively decaying item.3.1.11 thermal resistance,

17、 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 value. An item container combination will havenumerous th

18、ermal 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 equilibrium, that is, the thermalpower, from the item is determ

19、ined 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-sured by the calorimeter.4.3 The mass (m) of Pu, tritium,

20、 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 calculation of Pefffor plutonium).4.3.1 When tritium is the onl

21、y 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 mass using the specificpower of241Am, Peff= (0.1142 6 0.00

22、042) (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 NDAtechnique forthe assay of many physical forms of Pu. Is

23、otopic 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, oxides, fluorides,mixed Pu-U oxides, mixed oxide fuel pi

24、ns, 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 last 40 years (2-9).5.1.2 Pu-bearing materials have been me

25、asured 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 and241Am to Puratio (see Test Method C 1030). Isotopic info

26、rmation 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 the only practical measurementtechnique available.5.3 Physic

27、al 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 method can be degraded formaterials with inhomogeneous isotopic

28、 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 used to prepare second-ary standards for neutron and gamm

29、a-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, W/gStandard Deviation, W/g References238Pu 87.74 0.04 (0

30、.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 (0.24 %)0.1159 31030.00026 3103(0.22 %) (34)241Am 433.6 1.

31、4 (0.32 %) 0.1142 0.00042 (0.37 %) (32,35)ANumbers in parentheses are % relative standard deviation (RSD).C14580925.6 Calorimetry measurement times are typically longerthan other NDA techniques. Four parameters of the item andthe item packaging affect measurement time. These fourparameters are densi

32、ty, 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 maintain a constant measurement welltemperature and have no

33、 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 may be reduced by using equilib-rium prediction techniques, b

34、y 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 power of theradionuclides being assayed. Some examples include

35、 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.7. Apparatus7.1 Calorimeters are designed to measure different sizes andquantities of nuclear mat

36、erial. 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 the heatflow generated by radioactive decay is directed through tem-perature sensors.7.1.1.1 An elec

37、trical 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 the chamber from outside temperature variations thatwould influence the thermal power measurement

38、. 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 Calorimeter CanThe item to be measured may beplaced in a special can that is designed to be inserted and

39、removed 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.7.1.3 Temperature SensorsTemperature sensors consist ofthermistors, thermocouples, temperature sens

40、itive 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 be awater bath, air bath, or a solid, usually metal, maintained at aconstant temperature.7.1.5 El

41、ectrical 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 the temperature sensors.The resolution of the voltmeters should be better than one partper million

42、 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 trace-able to a national measurement system may be used withcalibrated voltmeters to accurately dete

43、rmine 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, norare precision resistors required.7.1.5.4 For a calorimeter operated in the servo (powerreplacem

44、ent) 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 StandardsThermal power standards are re-quired to calibrate the calorimeter and may be used asmeasurement control

45、 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 powers.These standards are calibrated againstelectrical standards traceable to a national measurement

46、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 standard the power gener-ated by the heater must be measured with electrical equipmentregularly calib

47、rated 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 BridgeWhen temperature sensitive re-sistance wire is used as the sensor, it is arranged in aWheatst

48、one 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 voltages or resistancesat a fixed time frequency and be able to calculate and report apower value from

49、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-cally Al or Cu, or metal shot can be used in place of machinedmetal adapters. Smaller items may be pl