1、Designation: C1457 00 (Reapproved 2010)1C1457 18Standard Test Method forDetermination of Total Hydrogen Content of Uranium OxidePowders and Pellets by Carrier Gas Extraction1This standard is issued under the fixed designation C1457; the number immediately following the designation indicates the year
2、 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 NOTEEditorial corrections were made throughout in June 2010.1. Sco
3、pe1.1 This test method applies to the determination of hydrogen in nuclear-grade uranium oxide powders and pellets to determinecompliance with specifications. Gadolinium oxide (Gd2O3) and gadolinium oxide-uranium oxide powders and pellets may also beanalyzed using this test method.1.2 This standard
4、describes a procedure for measuring the total hydrogen content of uranium oxides. The total hydrogen contentresults from absorbed water, water of crystallization, hydro-carbides and other hydrogenated compounds which may exist as fuelsimpurities.1.3 This test method covers the determination of 0.05
5、to 200 g of residual hydrogen.1.4 This test method describes an electrode furnace carrier gas combustion system equipped with a thermal conductivitydetector.1.5 The preferred system of units is micrograms hydrogen per gram of sample (g/g sample) or micrograms hydrogen per gramof uranium (g/g U).1.6
6、The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appro
7、priate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. For specific hazard statements, see Section 9.1.8 This international standard was developed in accordance with internationally recognized principles on standardizati
8、onestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C753 Specification for Nuclear-Grade, Sinterable Uranium
9、 Dioxide PowderC776 Specification for Sintered Uranium Dioxide Pellets for Light Water ReactorsC859 Terminology Relating to Nuclear MaterialsC888 Specification for Nuclear-Grade Gadolinium Oxide (Gd2O3) PowderC922 Specification for Sintered Gadolinium Oxide-Uranium Dioxide Pellets3. Terminology3.1 D
10、efinitions:3.1.1 For definitions of terms relating to the nuclear fuel cycle, refer to Terminology C859.4. Summary of Test Method4.1 The total hydrogen content is determined using a hydrogen analyzer. The hydrogen analyzer is based on the carrier gasmethod using argon or nitrogen as carrier gas. The
11、 actual configuration of the system may vary with vendor and model.1 This test method is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test.Current edition approved June 1, 2010Feb. 1, 2018. Published June 201
12、0February 2018. Originally approved in 2000. Last previous edition approved in 20052010 asC1457 00 (2005).(2010)1. DOI: 10.1520/C1457-00R10E01.10.1520/C1457-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of
13、ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically
14、 possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C70
15、0, West Conshohocken, PA 19428-2959. United States14.2 The samples to be analyzed are dropped into a preheated graphite crucible, and then, heated up to a temperature of morethan 1700C in a graphite crucible. At that temperature hydrogen, oxygen, nitrogen, and carbon monoxide (oxygen is convertedto
16、CO when it reacts with the crucible) are released. The release gas is purified in the carrier gas stream by oxidation and absorptioncolumns. The hydrogen is separated by chromatographic means and analyzed in a thermal conductivity detector.5. Significance and Use5.1 Uranium dioxide is used as a nucl
17、ear-reactor fuel. Gadolinium oxide is used as an additive to uranium dioxide. In order tobe suitable for this purpose, these materials must meet certain criteria for impurity content. This test method is designed todetermine whether the hydrogen content meets Specifications C753, C776, C888, and C92
18、2.6. Interferences6.1 Contamination of carrier gas, crucibles, or samples with extraneous sources of hydrogen may cause a positive bias.Ablankcorrection will help to minimize the bias from carrier gas and crucibles. Interference from adsorbed hydrogen on samples may beeliminated by keeping the sampl
19、e in an inert atmosphere or vacuum.6.2 The purification system typically associated with the recommended combustion and detection equipment is designed tominimize other expected sources of interferences, such as sulfur, halogens, carbon monoxide, carbon dioxide, and water.6.2.1 The nitrogen and hydr
20、ogen peaks are close together and must be well-separated to prevent falsely high result from thenitrogen. The molecular sieve must be sufficiently long to separate the peaks and must be changed when the column becomesloaded with contaminants that prevent proper peak separation.6.3 The temperature of
21、 17001800C must be reached. If not, the decomposition of the released water to hydrogen and carbonmonoxide may not be complete. The temperature will depend upon the instrument and type of graphite crucible used. Single wallcrucibles will require a lower temperature (power) than double wall crucibles
22、.6.4 Incomplete fusion may result in partial or a late release of hydrogen resulting in low results.6.5 At temperatures of more than 2200C uranium metal may be formed, and carbon dioxide released because of reduction ofUO2 by the graphite crucible.6.5.1 Carbon dioxide will interfere with the thermal
23、 conductivity measurement. This interference can be minimized by use ofchemical absorption, or a molecular sieve column, or both.6.5.2 Excess temperature, from too much power, crucible hot spots, or from misaligned electrodes may cause analysis errors.Uranium samples should be evenly fused, fall out
24、 freely of the crucibles and contain very little uranium metal.7. Apparatus7.1 Hydrogen Analyzer, consisting of an electrode furnace capable of operation at least up to 2200 to 2500C, a thermalconductivity detector for measuring, and auxiliary purification systems.7.2 Balance, with precision of 6 1
25、mg.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are
26、 available.3 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.8.2 Carrier GasNitrogen 99.998 % or Argon 99.995 %.8.3 Carrier Gas Purifiers:8.3.1 Copper Oxide, or rare earth
27、copper oxide (converts H to H2O), or8.3.2 Copper Turnings, or granules.8.4 Molecular Sieve-Sodium Hydroxide, on a fiber support (sodium hydroxide reacts with CO2 to yield water; the molecularsieve separates N2 and H2).8.5 Schutze Reagent, iodine pentoxide over silica gel (converts CO to CO2).8.6 Mag
28、nesium Perchlorateremoves water.8.7 Silicone Vacuum Grease.8.8 Tin Flux, if Zr or Ti hydride standards are to be used.3 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemica
29、l Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.C1457 1828.9 Graphite Crucibles.8.10 Tin Capsules.8.11 Aluminum Oxide (Al2O3), to check furnace
30、 temperature.8.12 Hydrogen Standard MaterialsCalibrate the instrument using either high purity (99.9999 %) certified hydrogen gas orNIST-traceable, or equivalent, metal standards. Steel standards4 are the preferred metal standards because no flux is used, and thisbest matches the conditions used to
31、analyze uranium oxide samples. Zr- or Ti-hydride standards may be used, but require the useof a flux metal.8.13 Sodium Tartrate or Sodium Tungstate may be used as check standards for uranium powder analyses.9. Hazards and Precautions9.1 Take proper safety precautions to prevent inhalation or ingesti
32、on of uranium dioxide powders or dust during grinding orhandling operations.9.2 Operation of equipment presents electrical and thermal hazards. Follow the manufacturers recommendations for safeoperation.9.3 This procedure uses hazardous chemicals. Use appropriate precautions for handling corrosives,
33、 oxidizers, and gases.10. Preparation of Apparatus10.1 Inspect and change instrument column packing and reagents as recommended by manufacturer.10.2 Check to ensure that the furnace heats properly on a periodic basis. A quarterly check is recommended. A properlyfunctioning furnace, set at normal ope
34、rating parameters should fuse Al2O3 (approximately 2050C melting point, depending uponform).10.3 Set the operating controls of the instrument system according to the operating instructions for the specific equipment used.10.4 Condition the apparatus by combustion of several blanks prepared with samp
35、le crucible and accelerator, if any, in theamount to be used with the samples. Successive blanks should approach a constant value, allowing for normal statisticalfluctuations.10.5 The blank measurements prove the integrity of the purifying units and the tightness of the equipment. Blank values of mo
36、rethan 60.03 g H2 require adequate measures of correction.11. Calibration Using Metal Standards11.1 The calibration range and number of standards will depend upon the instrument used. Three to five standards, containing3 to 6 g hydrogen are recommended. The number of standards and calibration range
37、will depend upon the availability, assayaccuracy, and homogeneity of available standards.11.2 Load and combust the standards according to the manufacturers recommended operating conditions.11.3 Calibrate the instrument according to operating instructions. Calibration coefficients normally are stored
38、 in themicroprocessor memory.11.4 Recalibration frequency will depend upon the type of instrument used. As a minimum, recalibration is required whencritical instrument components are changed or when control standards data indicate that the instrument is failing to meetperformance criteria.11.5 Calib
39、ration of the Analyzer Using Gas Dosing:11.5.1 Instrument CalibrationA well-defined volume of hydrogen calibration gas, which is corrected on standard conditions,is inserted and analyzed. This calibration is performed three times. A deviation of the calibration values of more than 2 % fromthe normal
40、 requires a readjustment.11.5.2 Check of the CalibrationAtitanium, zirconium, or steel hydride standard is weighed to 1-mg 1 mg accuracy and meltedwith the aid of tin granules. The released hydrogen is determined. The measured values must be between 10 % of the certifiedvalues. If not, the calibrati
41、on is repeated. Alternately, for better safety, helium gas may be used, if the correlation between theresponse of the helium and hydrogen gas is established.12. Sample Preparation12.1 Powder SamplesThe samples must be stored in tight containers and shall not be exposed to ambient conditions for long
42、erthan five minutes because alterations of the powder sample due to moisture adsorption or desorption or oxidation have to beavoided. The gas volume in the container should be as low as possible.4 NIST-traceable steel standards marketed by LECO have been found to perform satisfactorily.C1457 18312.2
43、 Powder SamplesPowder samples are placed into tin capsules, which subsequently are closed. Alternatively, the powdersamples may be inserted as pressed bodies. Sampling is done with a tube shaped powder sampler having aan inner diameter ofmore than 2.5 times of the maximum powder particle size.12.3 P
44、elletsDuring pellet sampling the pellets must be handled with forceps. The sample should be representative of themanufacturing process, including storage of the pellets.12.4 PelletsPellets may be analyzed whole or may be crushed to particles as small as 1 mm (18 mesh). mm. Crushing pelletswill incre
45、ase sample surface area and must be performed with great care. The possibility of increasing moisture adsorption andobtaining falsely elevated hydrogen results is very high.13. Procedure13.1 Weigh a portion of sample, to the nearest 1 mg, into the crucible. The sample size should be chosen to provid
46、e adequatesensitivity and accuracy at low hydrogen concentrations.13.2 Load the crucible into the furnace and combust the sample according to the manufacturers recommended operatingconditions: Purify the empty graphite crucible in the carrier gas stream by heating at a temperature above 17001800C. D
47、rop thesample into the crucible, heat to 17001800C, and measure the hydrogen content (combustion time will vary with the instrumentused).13.3 Remove the sample crucible and examine it for proper fusion. See 5.46.4 and 5.56.5.14. Calculation14.1 Calculate the hydrogen content as follows:g H per gof s
48、ample5Hs 2Hb!/W (1)where:Hs = micrograms of hydrogen in test specimen,Hb = micrograms of hydrogen in a blank run, entered if a blank correction is desired, andW = grams of test specimen.14.2 For samples requiring hydrogen results expressed as g hydrogen per g U, convert results to uranium basis as f
49、ollows:H,g/g U basis5 H g/g3100%U content of sample (2)15. Precision and Bias515.1 The precision and bias for this method will depend upon the instrument used and the operating conditions. The followingdata6 are provided as an example of method capability.15.2 The relative standard deviation for a 5 g/g steel standard was 5.8 % (1 s.d.). The bias, as measured by percent recoveryof the standards value, was + 0.1 %. These data represent 102 standards measured by seven operators using one instrument, overa one-year period.15.3 The relative
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