1、Designation: C 1457 00 (Reapproved 2005)Standard Test Method forDetermination of Total Hydrogen Content of Uranium OxidePowders and Pellets by Carrier Gas Extraction1This standard is issued under the fixed designation C 1457; the number immediately following the designation indicates the year oforig
2、inal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method applies to the determination of hydro-gen in
3、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 a procedure for measuring thetotal hydrogen content of ura
4、nium 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 residual hydrogen.1.4 This test method describes an electro
5、de 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 This standard does not purport to address all of thesafety concerns, if a
6、ny, 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 753 Specification for Nuclear-Grade, Sinterable
7、 UraniumDioxide PowderC 776 Specification for Sintered Uranium Dioxide PelletsC 888 Specification for Nuclear-Grade Gadolinium Oxide(Gd2O3) PowderC 922 Specification for Sintered Gadolinium Oxide-Uranium Dioxide Pellets3. Summary of Test Method3.1 The total hydrogen content is determined using a hy-
8、drogen analyzer. The hydrogen analyzer is based on the carriergas method using argon or nitrogen as carrier gas. The actualconfiguration 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
9、morethan 1700C in a graphite crucible. At that temperaturehydrogen, oxygen, nitrogen, and carbon monoxide (oxygen isconverted 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 chr
10、omatographic means and analyzed in a thermal conduc-tivity detector.4. Significance and Use4.1 Uranium dioxide is used as 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
11、 content. This test method isdesigned to determine whether the hydrogen content meetsSpecifications C 753, C 776, C 888, and C 922.5. Interferences5.1 Contamination of carrier gas, crucibles, or samples withextraneous sources of hydrogen may cause a positive bias. Ablank correction will help to mini
12、mize the bias from carrier gasand crucibles. Interference from adsorbed hydrogen onsamples may be eliminated by keeping the sample in an inertatmosphere or vacuum.5.2 The purification system typically associated with therecommended combustion and detection equipment is de-signed to minimize other ex
13、pected sources of interferences,such as sulfur, halogens, carbon monoxide, carbon dioxide, andwater.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, 2005.
14、Published December 2005. Originallyapproved in 2000. Last previous edition approved in 2000 as C 145700.2For 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 standard
15、s Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2.1 The nitrogen and hydrogen peaks are close togetherand must be well-separated to prevent falsely high result fromthe nitrogen. The molecu
16、lar sieve must be sufficiently long toseparate the peaks and must be changed when the columnbecomes 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 c
17、omplete. The temperature willdepend upon the instrument and type of graphite crucible used.Single 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
18、 more than 2200C uranium metalmay be formed, and carbon dioxide released because ofreduction of UO2by the graphite crucible.5.5.1 Carbon dioxide will interfere with the thermal con-ductivity measurement. This is normally covered by use ofchemical absorption, or a molecular sieve column, or both.5.5.
19、2 Excess temperature, from too much power, or cruciblehot spots, from misaligned electrodes may cause analysiserrors. Uranium samples should be evenly fused and shouldfall out freely of the crucibles and contain very little uraniummetal.6. Apparatus6.1 Hydrogen Analyzer, consisting of an electrode f
20、urnacecapable of operation at least up to 2200 to 2500C, a thermalconductivity detector for measuring, 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,
21、 it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical 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 i
22、ts use without lessening theaccuracy of the determination.7.2 Carrier GasNitrogen $ 99.998 % or 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(s
23、odium hydroxide3reacts with CO2to yield water; themolecular sieve separates N2and H2).7.5 Schutze Reagent, iodine pentoxide over silica gel (con-verts CO to CO2).7.6 Magnesium Perchlorate4removes water.7.7 Silicone Vacuum Grease.7.8 Tin Flux, if Zr or Ti hydride standards are to be used.7.9 Graphite
24、 Crucibles.7.10 Tin Capsules.7.11 Aluminum Oxide (Al2O3), to check furnace tempera-ture.7.12 Hydrogen Standard MaterialsCalibrate the instru-ment using either high purity (99.9999 %) certified hydrogengas or NIST-traceable, or equivalent, metal standards. Steelstandards5are the preferred metal stand
25、ards because no flux isused, and this best matches the conditions used to analyzeuranium oxide 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 Precau
26、tions8.1 Take proper safety precautions to prevent inhalation oringestion of uranium dioxide 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 haz
27、ardous chemicals. Use appro-priate precautions for handling corrosives, oxidizers, andgases.9. 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
28、 is recommended. A properlyfunctioning furnace, set at normal operating parameters shouldfuse 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
29、 apparatus by combustion of severalblanks prepared with sample crucible and accelerator, if any, 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 u
30、nits and the tightness of the equipment. Blankvalues of more than6 0.03 g H2require adequate 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 rec
31、ommended. The numberof standards and calibration range will depend upon theavailability, assay accuracy, and homogeneity of availablestandards.3Ascarite marketed by J.T. Baker has been found to perform satisfactorily.4Anhydrone marketed by J.T. Baker has been found to perform satisfactorily.5NIST-tr
32、aceable steel standards marketed by LECO have been found to performsatisfactorily.C 1457 00 (2005)210.2 Load and combust the standards according to themanufacturers recommended operating conditions.10.3 Calibrate the instrument according to operating in-structions. Calibration coefficients normally
33、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 that the instrument is failing to meetperformance criteria.10
34、.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 deviation of the calibration values ofmore than 2 % from th
35、e normal requires as 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 may differ from the certifiedvalues by not more than 10 %. If
36、 not, the calibration isrepeated.Alternately, for better safety, helium gas may be used,if the correlation between the response of the helium andhydrogen gas is established.11. Sample Preparation11.1 Powder SamplesThe sample shall be exposed toambient conditions for not longer than five minutes beca
37、usealterations of the powder sample due to moisture adsorption ordesorption or oxidation have to be avoided. The sample has tobe stored in tight containers. The gas volume in the containershould be as low as possible.11.2 Powder SamplesPowder samples are filled into tincapsules, which subsequently a
38、re 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 have to behandled with forceps. The sample
39、should be representative ofthe manufacturing process, for example, 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 great care. The possibility of i
40、ncreasing 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 concentrations.12.2 Load the cruci
41、ble 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, andmeasure the hydrogen content (
42、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 specimen,Hb= micrograms of hydr
43、ogen 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. Precision and Bias14.1 The precis
44、ion and bias for this method will dependupon the instrument used and the operating conditions. Thefollowing data6are provided as an example of method capa-bility.714.2 The relative standard deviation for a 5 g/g steelstandard was 5.8 % (1 s.d.). The bias, as measured by percentrecovery of the standa
45、rds 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 percent recovery of the standard
46、svalue, 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 oxide6Data were obtained from a LECO model 404.7Supporting data
47、 have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: C261009.C 1457 00 (2005)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard a
48、re 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 reviewed every five years andif not
49、 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 International, 100 Barr Harbor Drive,
