1、Designation: C1457 00 (Reapproved 2010)1Standard 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 oforigi
2、nal 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.1NOTEEditorial corrections were made throughout in June 2010.1. Scope1.1 Thi
3、s test method applies to the determination of hydro-gen in nuclear-grade uranium oxide powders and pellets todetermine compliance with specifications. Gadolinium oxide(Gd2O3) and gadolinium oxide-uranium oxide powders andpellets may also be analyzed using this test method.1.2 This standard describes
4、 a procedure for measuring thetotal hydrogen content of uranium oxides. The total hydrogencontent results from absorbed water, water of crystallization,hydro-carbides and other hydrogenated compounds which mayexist as fuels impurities.1.3 This test method covers the determination of 0.05 to 200g of
5、residual hydrogen.1.4 This test method describes an electrode furnace carriergas combustion system equipped with a thermal conductivitydetector.1.5 The preferred system of units is micrograms hydrogenper gram of sample (g/g sample) or micrograms hydrogen pergram of uranium (g/g U).1.6 The values sta
6、ted in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 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 an
7、d health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C753 Specification for Nuclear-Grade, Sinterable UraniumDioxide PowderC776 Specification for Sintered Uranium Dioxide PelletsC888 Specification for Nuclear-Grade Gado
8、linium Oxide(Gd2O3) PowderC922 Specification for Sintered Gadolinium Oxide-Uranium Dioxide Pellets3. Summary of Test Method3.1 The total hydrogen content is determined using a hy-drogen analyzer. The hydrogen analyzer is based on the carriergas method using argon or nitrogen as carrier gas. The actu
9、alconfiguration of the system may vary with vendor and model.3.2 The samples to be analyzed are dropped into a preheatedgraphite crucible, and then, heated up to a temperature of morethan 1700C in a graphite crucible. At that temperaturehydrogen, oxygen, nitrogen, and carbon monoxide (oxygen isconve
10、rted to CO when it reacts with the crucible) are released.The release gas is purified in the carrier gas stream byoxidation and absorption columns. The hydrogen is separatedby chromatographic means and analyzed in a thermal conduc-tivity detector.4. Significance and Use4.1 Uranium dioxide is used as
11、 a nuclear-reactor fuel.Gadolinium oxide is used as an additive to uranium dioxide. Inorder to be suitable for this purpose, these materials must meetcertain criteria for impurity content. This test method isdesigned to determine whether the hydrogen content meetsSpecifications C753, C776, C888, and
12、 C922.5. Interferences5.1 Contamination of carrier gas, crucibles, or samples withextraneous sources of hydrogen may cause a positive bias. Ablank correction will help to minimize the bias from carrier gasand crucibles. Interference from adsorbed hydrogen onsamples may be eliminated by keeping the s
13、ample in an inertatmosphere or vacuum.1This test method is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2010. Published June 2010. Originallyapproved in 2000. Last previous
14、 edition approved in 2005 as C1457 00 (2005).DOI: 10.1520/C1457-00R10E01.2For 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 standards Document Summary page onthe A
15、STM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 The purification system typically associated with therecommended combustion and detection equipment is de-signed to minimize other expected sources of interferences,such
16、 as sulfur, halogens, carbon monoxide, carbon dioxide, andwater.5.2.1 The nitrogen and hydrogen peaks are close togetherand must be well-separated to prevent falsely high result fromthe nitrogen. The molecular sieve must be sufficiently long toseparate the peaks and must be changed when the columnbe
17、comes loaded with contaminants that prevent proper peakseparation.5.3 The temperature of 17001800C must be reached. Ifnot, the decomposition of the released water to hydrogen andcarbon monoxide may not be complete. The temperature willdepend upon the instrument and type of graphite crucible used.Sin
18、gle wall crucibles will require a lower temperature (power)than double wall crucibles.5.4 Incomplete fusion may result in partial or a late releaseof hydrogen resulting in low results.5.5 At temperatures of more than 2200C uranium metalmay be formed, and carbon dioxide released because ofreduction o
19、f UO2by the graphite crucible.5.5.1 Carbon dioxide will interfere with the thermal con-ductivity measurement. This interference can be minimized byuse of chemical absorption, or a molecular sieve column, orboth.5.5.2 Excess temperature, from too much power, cruciblehot spots, or from misaligned elec
20、trodes may cause analysiserrors. Uranium samples should be evenly fused, fall out freelyof the crucibles and contain very little uranium metal.6. Apparatus6.1 Hydrogen Analyzer, consisting of an electrode furnacecapable of operation at least up to 2200 to 2500C, a thermalconductivity detector for me
21、asuring, and auxiliary purificationsystems.6.2 Balance, with precision of 6 1 mg.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Anal
22、ytical Reagents of the American Chemical Society,where such specifications are available. Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Carrier GasNitrogen $ 99.998 % o
23、r Argon $99.995 %.7.3 Carrier Gas Purifiers:7.3.1 Copper Oxide, or rare earth copper oxide (converts Hto H2O), or7.3.2 Copper Turnings, or granules.7.4 Molecular Sieve-Sodium Hydroxide, on a fiber support(sodium hydroxide reacts with CO2to yield water; the molecu-lar sieve separates N2and H2).7.5 Sc
24、hutze Reagent, iodine pentoxide over silica gel (con-verts CO to CO2).7.6 Magnesium Perchlorateremoves water.7.7 Silicone Vacuum Grease.7.8 Tin Flux, if Zr or Ti hydride standards are to be used.7.9 Graphite Crucibles.7.10 Tin Capsules.7.11 Aluminum Oxide (Al2O3), to check furnace tempera-ture.7.12
25、Hydrogen Standard MaterialsCalibrate the instru-ment using either high purity (99.9999 %) certified hydrogengas or NIST-traceable, or equivalent, metal standards. Steelstandards3are the preferred metal standards because no flux isused, and this best matches the conditions used to analyzeuranium oxid
26、e samples. Zr- or Ti-hydride standards may beused, but require the use of a flux metal.7.13 Sodium Tartrate or Sodium Tungstate may be used ascheck standards for uranium powder analyses.8. Hazards and Precautions8.1 Take proper safety precautions to prevent inhalation oringestion of uranium dioxide
27、powders or dust during grindingor handling operations.8.2 Operation of equipment presents electrical and thermalhazards. Follow the manufacturers recommendations for safeoperation.8.3 This procedure uses hazardous chemicals. Use appro-priate precautions for handling corrosives, oxidizers, andgases.9
28、. Preparation of Apparatus9.1 Inspect and change instrument column packing andreagents as recommended by manufacturer.9.2 Check to ensure that the furnace heats properly on aperiodic basis. A quarterly check is recommended. A properlyfunctioning furnace, set at normal operating parameters shouldfuse
29、 Al2O3(approximately 2050C melting point, dependingupon form).9.3 Set the operating controls of the instrument systemaccording to the operating instructions for the specific equip-ment used.9.4 Condition the apparatus by combustion of severalblanks prepared with sample crucible and accelerator, if a
30、ny, inthe amount to be used with the samples. Successive blanksshould approach a constant value, allowing for normal statis-tical fluctuations.9.5 The blank measurements prove the integrity of thepurifying units and the tightness of the equipment. Blankvalues of more than6 0.03 g H2require adequate
31、measures ofcorrection.10. Calibration Using Metal Standards10.1 The calibration range and number of standards willdepend upon the instrument used. Three to five standards,containing 3 to 6 g hydrogen are recommended. The numberof standards and calibration range will depend upon theavailability, assa
32、y accuracy, and homogeneity of availablestandards.3NIST-traceable steel standards marketed by LECO have been found to performsatisfactorily.C1457 00 (2010)1210.2 Load and combust the standards according to themanufacturers recommended operating conditions.10.3 Calibrate the instrument according to o
33、perating in-structions. Calibration coefficients normally are stored in themicroprocessor memory.10.4 Recalibration frequency will depend upon the type ofinstrument used. As a minimum, recalibration is required whencritical instrument components are changed or when controlstandards data indicate tha
34、t the instrument is failing to meetperformance criteria.10.5 Calibration of the Analyzer Using Gas Dosing:10.5.1 Instrument CalibrationA well-defined volume ofhydrogen calibration gas, which is corrected on standardconditions, is inserted and analyzed. This calibration is per-formed three times. A d
35、eviation of the calibration values ofmore than 2 % from the normal requires a readjustment.10.5.2 Check of the CalibrationA titanium, zirconium, orsteel hydride standard is weighed to 1-mg accuracy and meltedwith the aid of tin granules. The released hydrogen is deter-mined. The measured values must
36、 be between 10 % of thecertified values. If not, the calibration is repeated. Alternately,for better safety, helium gas may be used, if the correlationbetween the response of the helium and hydrogen gas isestablished.11. Sample Preparation11.1 Powder SamplesThe sample must be stored in tightcontaine
37、rs and shall not be exposed to ambient conditions forlonger than five minutes because alterations of the powdersample due to moisture adsorption or desorption or oxidationhave to be avoided. The gas volume in the container should beas low as possible.11.2 Powder SamplesPowder samples are placed into
38、 tincapsules, which subsequently are closed. Alternatively, thepowder samples may be inserted as pressed bodies. Samplingis done with a tube shaped powder sampler having a innerdiameter of more than 2.5 times of the maximum powderparticle size.11.3 PelletsDuring pellet sampling the pellets must beha
39、ndled with forceps. The sample should be representative ofthe manufacturing process, including storage of the pellets.11.4 PelletsPellets may be analyzed whole or may becrushed to particles as small as 1 mm (18 mesh). Crushingpellets will increase sample surface area and must be per-formed with grea
40、t care. The possibility of increasing moistureadsorption and obtaining falsely elevated hydrogen results isvery high.12. Procedure12.1 Weigh a portion of sample, to the nearest 1 mg, into thecrucible. The sample size should be chosen to provide adequatesensitivity and accuracy at low hydrogen concen
41、trations.12.2 Load the crucible into the furnace and combust thesample according to the manufacturers recommended operat-ing conditions: Purify the empty graphite crucible in the carriergas stream by heating at a temperature above 17001800C.Drop the sample into the crucible, heat to 17001800C, andme
42、asure the hydrogen content (combustion time will vary withthe instrument used).12.3 Remove the sample crucible and examine it for properfusion. See 5.4 and 5.5.13. Calculation13.1 Calculate the hydrogen content as follows:g H per g of sample 5 Hs Hb!/W (1)where:Hs= micrograms of hydrogen in test spe
43、cimen,Hb= micrograms of hydrogen in a blank run, entered if ablank correction is desired, andW = grams of test specimen.13.2 For samples requiring hydrogen results expressed as ghydrogen per g U, convert results to uranium basis as follows:H, g/g U basis 5H g/g 3 100% U content of sample(2)14. Preci
44、sion and Bias414.1 The precision and bias for this method will dependupon the instrument used and the operating conditions. Thefollowing data5are provided as an example of method capa-bility.14.2 The relative standard deviation for a 5 g/g steelstandard was 5.8 % (1 s.d.). The bias, as measured by p
45、ercentrecovery of the standards value, was + 0.1 %. These datarepresent 102 standards measured by seven operators using oneinstrument, over a one-year period.14.3 The relative standard deviation for a 12 000 g/gworking sodium tungstate powder standard was 4.2 % (1 s.d.).The bias, as measured by perc
46、ent recovery of the standardsvalue, was 5.7 %. These data represent 102 standards mea-sured by seven operators using one instrument, over a one-yearperiod.15. Keywords15.1 gadolinium oxide; gadolinium oxide-uranium oxide;hydrogen content; impurity content; uranium oxide4Supporting data have been fil
47、ed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:C26-1009.5Data were obtained from a LECO model 404.C1457 00 (2010)13ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standa
48、rd. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewe
49、d every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Int
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