1、Designation: C1854 17Standard Test Method forDetermination of Hydrogen (total from all sources) in MixedOxide (U, Pu)O2) Sintered Pellets by the Inert Gas FusionTechnique Followed by Thermal Conductivity Measurement1This standard is issued under the fixed designation C1854; the number immediately fo
2、llowing the designation indicates the year oforiginal 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 meth
3、od covers the determination of hydrogenin nuclear-grade mixed oxides of uranium and plutonium (U,Pu)O2) sintered fuel pellets. This test method is an alternativeto Test Method C698 for the determination of moisture innuclear-grade sintered mixed oxide (MOX) fuel pellets. TestMethod C698 describes th
4、e detection of moisture in mixedoxides using a coulometric, electrolytic moisture analyzer.Although the main source of H2in the fuel pellets is moisture,there could be other sources. The MOX pellet SpecificationC833 specifies a limit for hydrogen from all sources, not onlymoisture. The inert gas fus
5、ion followed by thermal conductiv-ity detector specified in this test method allows for detection ofhydrogen from all sources. Therefore, this test method can beused to determine the limit specified in C833.1.2 The values stated in SI units are to be regarded asstandard. No other units of measuremen
6、t are included in thisstandard.1.3 This standard does not purport to address all of thesafety 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 limitatio
7、ns prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization Tech
8、nicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C698 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade Mixed Ox-ides (U, Pu)O2)C753 Specification for Nuclear-Grade, Sinterable UraniumDioxide PowderC757 Specification for Nucl
9、ear-Grade Plutonium DioxidePowder for Light Water ReactorsC833 Specification for Sintered (Uranium-Plutonium) Diox-ide Pellets for Light Water ReactorsC859 Terminology Relating to Nuclear MaterialsC1068 Guide for Qualification of Measurement Methods bya Laboratory Within the Nuclear Industry3. Termi
10、nology3.1 For definitions of terms used in this test method but notdefined herein, refer to Terminology C859.3.2 Definitions of Terms Specific to This Standard:3.2.1 MOXnuclear fuel composed of a mixture of uraniumand plutonium oxides (U, Pu)O2).3.2.2 reference materialmaterial traceable to a refere
11、ncematerial from a national standards body such as the U.S.National Institute for Standards and Technology (NIST) orequivalent.3.2.3 sinteringto increase the bonding in a mass of pow-der or a compact by heating below the melting point of themain constituent.3.3 Acronyms:3.3.1 LIMSLaboratory Informat
12、ion Management System3.3.2 TCDThermal Conductivity Detector4. Summary of Test Method4.1 The method for the determination of total hydrogen (H2)from all sources presented in this test method consists of fusion1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and i
13、s the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2017. Published June 2017. DOI: 10.1520/C1854-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStan
14、dards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principle
15、s on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1of the sample in an electrode impulse furnace in a stream ofnitrogen (N2) or ar
16、gon (Ar) gas at a temperature sufficient torelease all hydrogen in the sample. The stream of gas carriesthe released hydrogen through a series of filters to removeinterfering impurities and the hydrogen is measured by TCD.4.2 The specimen, a single MOX pellet weighing approxi-mately 6 g, contained i
17、n a small single-use graphite crucible, isfused under a flowing nitrogen (N2) or argon (Ar) atmosphereand at a temperature greater than 1770C. Hydrogen present inthe sample is released as molecular hydrogen into the flowingcarrier gas. Other gases are also liberated into the carrier gas,such as carb
18、on monoxide, and need to be removed before theyreach the thermal conductivity detector as they interfere withthe measurement. These sample impurities are swept by thecarrier gas through a series of filters to remove dust and waterand then the gases flow through a quartz tube filled withSchuetze reag
19、ent (see 8.3) and activated charcoal. The Schue-tze reagent acts as an oxidizing agent to convert carbonmonoxide (CO) to carbon dioxide (CO2). The gas then flowsthrough a molecular sieve to separate nitrogen from hydrogenby size, delaying the larger nitrogen molecule and allowing thehydrogen to reac
20、h the TCD before the nitrogen.4.3 The carrier gas, now free of interfering species thenflows through the measurement branch of the thermal conduc-tivity cell which is where the quantitative detection of thehydrogen released from the sample takes place. The hydrogenconcentration in the carrier gas is
21、 measured by the TCD whichdetects small changes in the thermal conductivity of the carriergas containing the liberated hydrogen gas compared to thethermal conductivity of the carrier gas alone.4.4 The detector signal plotted versus time is a function ofthe concentration of the H2in a carrier gas. Th
22、e area below thecurve (integral) corresponds to the total amount of hydrogen inthe sample. The peak is integrated by the software and theconcentration is calculated taking into account the calibrationfactor, the blank analysis and the sample weight. The calibra-tion of the analyzer is made by means
23、of a reference material.Blank values are obtained from analyzing the empty crucibles.The blank results are stored. The final sample result iscorrected by the blank value and the results are expressed in ghydrogen/g MOX.5. Significance and Use5.1 MOX is used as a nuclear-reactor fuel. This test metho
24、dis designed to determine whether the hydrogen content of thepellets meet the requirements of fuel specification. Examplesof these requirements are given in Specification C833. Otherrequirements may apply based on agreements between thesupplier and the customer.5.2 This method is suitable for all si
25、ntered MOX pelletscontaining up to 15 weight % PuO2when the UO2and PuO2meet the requirements of Specifications C753 and C757. Themethod uncertainty is related to the concentration of thehydrogen in the sample. At lower concentrations, the relativeuncertainty increases.At hydrogen contents close to t
26、he typicalhydrogen content specification limit (1.3 g hydrogen/gU+Pumetal); the combined relative uncertainty at the 95 % confi-dence level (k = 2) is approximately 30 %.6. Interferences6.1 After the sample fusion, the carrier gas containing thecarbon dioxide and other potentially interfering impuri
27、ties(sulfur, water, and small particulate matter) pass through aseries of filters and purifying reagents that remove theseimpurities from the carrier gas stream leaving only H2in thestream at the detector. If the MOX pellets are made from UO2and PuO2that meet the requirements of Specifications C753a
28、nd C757, all interferences are eliminated by the purificationsystem.6.2 The crucibles, if they contain hydrogen, will yielderroneously high results for the sample. The analytical methodrequires running blanks to correct for this potential interferencein the calculation of the results (see 12.2).6.3
29、The nitrogen (N2) or argon (Ar) carrier gas couldcontain water and CO2and is filtered prior to injection in thesample combustion chamber to remove these potentially inter-fering components.6.4 Weighing uncertainty of the samples is critical to themethod. If the balance meets the specification in 7.1
30、,iscalibrated in accordance with manufacturers guidance, and ischecked by procedure, the potential for the balance to be asource of error is insignificant.6.5 When using nitrogen gas with graphite crucible asecondary reaction occurs at high temperatures (3000C)where HCN is created, causing a bias th
31、at increases withtemperature.Argon as carrier gas is used at higher temperaturesto avoid this reaction.7. Apparatus7.1 Analytical Balance, with precision 60.1 mg.7.2 Graphite CruciblesUse the crucibles of size recom-mended by the manufacturer of the instrument. Crucibles shallbe composed of high pur
32、ity graphite.7.3 Hydrogen analyzer, consisting of an electrode impulsefurnace suitable for operation at 1770 to 2200C, a TCD formeasuring H2, a nitrogen or argon carrier gas injection system,auxiliary gas purification systems, and a chiller to cool theelectrodes. The analyzer typically has an integr
33、ated datacollection and analysis software system that allows for efficientcollection and analysis of data.7.4 Tongs and Forceps, for handling crucibles.7.5 Stainless Steel Scoops and Spatulas, for handling pelletsand reference materials.8. Reagents and Materials8.1 Purity of ReagentsReagent grade ch
34、emicals shall beused in all tests. Unless otherwise indicated, it is intended thatC1854 172all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first
35、 ascertained that the reagent is ofsufficiently high purity to permit its use without compromisingthe accuracy of the determination.8.2 Molecular Sieve (Zeolites of Silicon and Aluminum)Captures CO2from the carrier gas.8.3 Schuetze Reagent (I2O5and SiO2)Oxidizes CO toCO2.NOTE 1Schuetze reagent is co
36、mmercially available and is typicallynot prepared in-house. If the user of this test method wishes to prepare theSchuetze reagent in house, a procedure is given in Appendix X1.8.4 Activated Coal or Sodium Hydroxide (NaOH)absorbsCO2before and after the CO and CO2conversion.8.5 Quartz Wool, for dust t
37、raps and to plug the reagenttubes.8.6 Platinum Wire (if needed), for minimum furnace tem-perature verification, 1.0 mm diameter, 99.99 % trace metalbasis.8.7 Rhodium Wire (if needed), for maximum furnace tem-perature verification, 1.0 mm diameter, 99.9 % trace metalbasis.8.8 Nitrogen or Argon Carrie
38、r Gas, 99.999 % purity, inletpressure: 200 kPa or as specified by the equipment manufac-turer.8.9 Magnesium Perchlorate (Mg(ClO4)2), removes H2O.9. Reference Materials9.1 The calibration of the analyzer is made by measuringmaterials with hydrogen content in the range of concentrationexpected in the
39、MOX pellet (1.3 ppm) traceable to a referencematerial from a national standards body such as the U.S.National Institute for Standards and Technology (NIST) orequivalent. Suitable materials traceable to a reference materialin steel matrices (steel pins, steel rings, steel granules, and steelpowder) a
40、re available and have been found satisfactory. Matrixmatched reference materials for MOX pellets are not available.10. Precautions10.1 Because of the toxicity of plutonium, all operationsshould be performed within an approved glove box fitted withappropriate filters to contain any small particle of
41、plutonium.Adetailed discussion of the necessary precautions is beyond thescope of this test method. Personnel involved in these analysesshould be familiar with safe handling practices for radiologi-cally controlled materials.10.2 The furnace, sample tube and sample crucibles areheated to 1770C. Care
42、 should be taken to avoid contactinggloves with hot surfaces. Typically these hot surfaces areguarded and inaccessible during the heating process andtherefore do not pose a risk to the operator.10.3 Exercise appropriate caution when working with com-pressed gases.10.4 This procedure uses hazardous c
43、hemicals. Use appro-priate precautions for handling corrosives, oxidizers, andgases.11. Preparation and Verification of Apparatus Prior toSample Analysis11.1 Turn on the analyzer and set the operating controls ofthe instrument system according to the operating instructionsfor the specific equipment
44、used.11.2 Verification of the GasesCarrier gas flow and systempressure are two essential parameters that must be controlled toensure satisfactory performance of the instrument. Most ana-lyzers are equipped with pressure regulation and electronicflow control.11.2.1 Ensure that the regulator valve is
45、set to the correctvalue for the nitrogen line per manufacturers recommenda-tions.11.3 Verification of the ReagentsChange instrument col-umn packing and reagents as recommended by manufacturer.11.3.1 The molecular sieve is usually changed or regener-ated after eight hours of continuous analysis, but
46、exact changeout times vary based on analyzer model and use.11.3.2 The Schuetze reagent and activated carbon should bereplaced approximately 40 % of the color of the Schuetzereagent changes from lemon yellow to pink or brown.11.3.3 The quartz wool should be replaced when visibleparticulate matter is
47、observed.11.3.4 At regular intervals and at each replacement of thereagents, the O-rings at the reagent tube holders must beinspected for wear and tear and replaced when appropriate.11.4 Verification of the Furnace TemperatureIn somecases, the furnace is designed with an automatic temperaturesensor
48、or pyrometer. In these cases, temperature verificationcan easily be performed per the manufacturers instructions. Inother cases where automatic temperature sensors are notavailable, it is necessary to use pure metal standards withknown melting points to verify furnace temperature above1770C and well
49、 below 2200C. Metals such as platinum andrhodium can be used. For example, if platinum melts, andrhodium does not melt, the verification is successful. If thesample is heated above 2200C, significant amounts of carbondioxide can be released as a result of the reduction of UO2bythe graphite crucible which could interfere with the detectionof the hydrogen by the TCD. Therefore avoiding temperaturesnear 2200C is important.11.5 Cleaning the AnalyzerIt is typically recommendedthat furnace cleaning should be performed after approximately20 samples have been
