ASTM C1430-2007 Standard Test Method for Determination of Uranium Oxygen to Uranium (O U) and Oxygen to Metal (O M) in Sintered Uranium Dioxide and Gadolinia-Uranium Dioxide Pellet.pdf

1、Designation: C 1430 07Standard Test Method forDetermination of Uranium, Oxygen to Uranium (O/U), andOxygen to Metal (O/M) in Sintered Uranium Dioxide andGadolinia-Uranium Dioxide Pellets by AtmosphericEquilibration1This standard is issued under the fixed designation C 1430; 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test met

3、hod applies to the determination of ura-nium, the oxygen to uranium (O/U) ratio in sintered uraniumdioxide pellets, and the oxygen to metal (O/M) ratio in sinteredgadolinium oxide-uranium dioxide pellets with a Gd2O3con-centration of up to 12 weight %. The O/M calculations assumethat the gadolinium

4、and uranium oxides are present in a metaldioxide solid solution.1.2 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 appli

5、ca-bility of regulatory limitations prior to use. For specific hazardsstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2C 696 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade Uranium Di-oxide Powders and PelletsC 776 Specification for Sin

6、tered Uranium Dioxide PelletsC 922 Specification for Sintered Gadolinium Oxide-Uranium Dioxide PelletsC 968 Test Methods for Analysis of Sintered GadoliniumOxide-Uranium Dioxide PelletsC 1287 Test Method for Determination of Impurities inNuclear Grade Uranium Compounds by InductivelyCoupled Plasma M

7、ass Spectrometry3. Summary of Test Method3.1 The uranium, and either O/U or O/M, are determined bymeasuring the weight change of a sintered pellet after it hasbeen exposed to an equilibrating atmosphere to bring it to thestoichiometric condition. Sintered pellets are weighed andloaded into a sample

8、boat. The boat is placed in a tube furnacecapable of holding a temperature of 800 6 10C. The furnaceis purged with a moist gas flow of 4 % hydrogen and 96 %argon or nitrogen to remove all air. The temperature of thefurnace is raised to 800C and held at this temperature withconstant gas flow for 4 h.

9、 The furnace then is turned off andallowed to cool, with gas purge on, to room temperature. Thesamples are removed from the furnace and reweighed.3.2 The weight change, gadolinia content, and chemicalimpurity content are used to calculate % uranium and the O/Uor O/M.4. Significance and Use4.1 Uraniu

10、m dioxide is used as a nuclear-reactor fuel. Thistest method is designed to determine whether the percenturanium and O/U or O/M content meet Specifications C 776and C 922.5. Interferences5.1 Parameters for temperature, gas composition, gas flow,and moist air purge must be monitored and maintained ca

11、re-fully within the limits set in the procedure.5.2 This test method assumes that chemical impurities meetSpecifications C 776 and C 922 limits. Potential method inter-ferences from higher impurity concentrations will requireevaluation.5.3 Furnace tubes or boats made from metals that oxidizeunder th

12、e test conditions may prevent proper equilibration byconsuming available oxygen.5.4 Precise weighing of samples is critical to the accuracy ofthis test method.5.5 Loss of weight due to pellet chipping would invalidatethe analysis. Handle pellets with care.1This test method is under the jurisdiction

13、of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved Feb. 1, 2007. Published March 2007. Originallyapproved in 2000. Last previous edition approved in 2000 as C 143000.2For referenced ASTM standards, visit the A

14、STM 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 ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni

15、ted States.5.6 This test method assumes that pellets are sintered. Itdoes not correct for moisture or volatile additives.5.7 This test method assumes that UO2-Gd2O3pellets haveformed a solid solution; however, the error from incompletedissolution of Gd2O3would be very small (see the calculationin 10

16、.2).6. Apparatus6.1 Analytical Balance, capable of weighing to 6 0.0001 g.6.2 Tube Furnace, capable of controlling temperatures at800 6 10C, that has been fitted with a fused quartz furnacetube.6.3 Fused Quartz Sample Boats.6.4 Assorted Connectors, Tubing, Flasks, Stoppers, andDelivery TubesThe purg

17、e gas is passed through a humidifier,into the tube furnace. A bubbler flask is attached to the furnaceoutlet to monitor gas flow (see Fig. 1).6.5 Gas Pressure Gage and Regulator.6.6 Purge Gas (4 % hydrogen, 96 % argon or 4 % hydro-gen and 96 % nitrogen. Gas purity of 99.995 % has been foundto perfor

18、m satisfactorily.6.7 Purge Gas Humidifier, with heater and controller ca-pable of maintaining water temperature at 35 6 10C.7. Standard Materials7.1 NBL3, NBL-traceable, or equivalent, uranium dioxidepellets. Analyze at least one standard pellet per batch.8. Hazards and Precautions8.1 Take proper sa

19、fety precautions for handling uranium.8.2 The furnace, sample tube and sample boats are heated to800C. Care must be taken to avoid burns.8.3 Exercise appropriate caution when working with com-pressed gasses.9. Procedure9.1 Analyze samples as whole pellets. No preparation isrequired. The nominal samp

20、le size is 510-g pellet. Smallerpellets may need to be composited (two pellets/test) to main-tain minimum weight. Avoid using chipped or cracked pellets.9.2 Place a small weighing tray or watch glass on thebalance pan. Tare the balance and check to ensure that thebalance is stable. If the balance wi

21、ll not stabilize, do notproceed.NOTE 1The extremely small weight changes that are being measuredin this test method make it critical that the balance is working properly.9.3 Weigh a check weight at least daily to confirm that theanalytical balance is operating correctly.9.4 Create a boat map to main

22、tain sample identity.9.5 Use a pair of tweezers and carefully weigh the pellet.Rezero the balance and repeat the pellet weighing until aconsistent weight is obtained. Carefully place the pellet in thequartz sample boat. Repeat for each pellet.9.6 Include one or two equilibrated standard control pell

23、etswith each sample batch.9.7 Carefully place the loaded boat into the sample tube.Position the boat as close to center of the furnace tube aspossible.3Available from the New Brunswick Laboratory, 9800 S. Cass Ave., Argonne,IL.FIG. 1 Assorted Connectors, Tubing, Flasks, Stoppers, and Delivery TubesC

24、14300729.8 Fit the purge gas connection to end of tube and clamp.Make certain that the water in the humidifying flask is at 35 610C (6 5C is optimal) and check the gas cylinder pressure toverify there is sufficient gas to complete the cycle.9.9 Turn on the gas flow and allow the chamber to purge for

25、approximately five minutes.NOTE 2The flow rate of the purge gas and the length of the purgecycle will vary with the size of the furnace tube. A purge of greater thanor equal to three furnace volumes/minute is the recommended minimum.The flow rate must be adequate to maintain a positive pressure insi

26、de thesample chamber.9.10 Attach a Pyrext delivery tube with ground glass fittingto the exit end of the furnace, and place the end in a containerof water to verify and monitor the gas flow.9.11 Turn on the furnace and bring the temperature to800C.9.12 After temperature is reached, allow the pellets

27、toequilibrate for a minimum of 4 h. Monitor the system occa-sionally during the run to ensure constant temperature and gasflow.9.13 At the end of the 4-h cycle, turn the furnace down to50C and allow the samples to cool. The purge gas flow mustbe maintained until the samples reach 50C. Then, turn off

28、 thecarrier gas and allow the pellets to cool to room temperature.NOTE 3If the samples are allowed to cool to room temperature whilethe purge gas is flowing, the water in the purge gas will begin to condenseinside the tube and on the pellets. A temperature of 50C is high enoughto prevent condensatio

29、n but low enough to prevent oxidation by room air.9.14 Remove the sample boat and reweigh the pelletsimmediately. Use multiple weighings as necessary to obtain aconsistent weight.10. Calculation10.1 O/U (UO2Pellets):5 2.000 W2 W1!W2! AWo!/AWu1 2 AWo!#(1)5 2.000 W2 W1!W2! 0.0593!where:W1= Weight of s

30、ample before equilibration, g,W2= Weight of sample after equilibration, g,AWo= Atomic weight of oxygen,AWu= Atomic weight of uranium, and0.0593 =AWo!AWu1 2 AWo!.10.2 O/M (UO2-Gd2O3Pellets):Pellet O/M 5 2.000 D O/M (2)5 2.000 W2 W1!W2! 0.0593 1%Gd2O33 0.00026!#where:W1= Weight of sample before equili

31、bra-tion, g,W2= Weight of sample after equilibra-tion, g,%Gd2O3= Measured Gd, expressed as sto-ichiometric weight % Gd2O3, and(% Gd2O3)(0.00026) = Correction factor for weight gaindue to formation of oxygen-richUO2-Gd2O3solid solution duringsintering. For processes that do notproduce a 100 % solid s

32、olution,this factor should be evaluated todetermine if modification is neces-sary (see Appendix X1).10.3 Percent Uranium:10.3.1 Percent Uranium, Based on Sample Weight:%U 5F100 G %I!15.9994GFO/M 3 G157.25GFO/MAWuG1F115.9994G(3)where:G = Weight % Gd = weight % Gd2O33 0.86759%I = Total nonvolatile imp

33、urities, expressed as weight %impurity oxides in UO2. Add the weight % of eachdetected impurity oxide plus a correction factor toaccount for less than threshold of detection impu-rities. This correction factor will need to be deter-mined for each facility. A factor of 0.01 % has beenfound to provide

34、 satisfactory results. See Table 1 toobtain conversion factors to convert common im-purity elements to oxides.The list of impurities to be tested for will dependupon specification requirements (see SpecificationsC 776 and C 922), elements obtained from multi-element methods (see Test Methods C 696,

35、C 968,and C 1287), and fuel processing conditions. Insome cases, a nominal value for impurities isadequate.O/M = Oxygen/uranium ratio or oxygen/metal ratio calcu-lated in 10.1 or 10.2, respectively.AWu= Atomic weight of uranium. Normally for U-235enrichment of approximately 4 %, a nominal valueof 23

36、7.96 may be used. For accuracy better than0.03 %, or for U-235 enrichments 5 %, calculatethe actual atomic weight.10.3.2 Percent Uranium, Corrected for % Gd2O3Content:%U, Corrected 5%U10.01! %Gd2O3!#(4)10.4 Precision and Bias:10.4.1 Percent Uranium UncertaintiesPercent uraniumwas determined on 29 NB

37、L-125 UO2standards by five opera-tors in one laboratory over a two month period, using a singlespectrometric measurement for total impurities (%I) and asingle measured value for atomic weight (AW). The certifiedvalue of the standard is 88.079 % uranium. The bias was +0.005 % (absolute), with an aver

38、age result of 88.0841 %. Theprecision was 0.0004 % (1 s.d.).10.4.2 O/U and O/M UncertaintiesCertified NBL, orequivalent, standards for O/M and O/U are not available. TheO/M ratio was determined on 27 working UO2-Gd2O3standardpellets over a two month period by five operators in oneC1430073laboratory.

39、 The nominal value of the standard pellets whichwere made by equilibrating a batch of 8 % Gd2O3productionpellets, is 2.000. The average result of 2.0002. The precisionwas 0.0002 (1 s.d.). The bias from the nominal value is notstatistically significant.10.4.3 Sampling and Impurities MeasurementUncert

40、aintiesThe uncertainties associated with samplingand measurement of impurities are not included in the preci-sion and bias information in 10.4.1 and 10.4.2. Uncertaintiesassociated with determination of values for % Gd2O3and %U-235 are negligible.10.4.4 Equilibration Procedure UncertaintiesUncertain

41、ties associated with the equilibration procedure, suchas weighing errors, furnace temperature, gas composition, gasflow, and pure gas humidity are included in the 10.4.1 and10.4.2 data. These errors, however, will vary with equipmentand the laboratory environment. Each laboratory should per-form its

42、 own precision and bias evaluation.11. Keywords11.1 atmospheric equilibration; equilibration; oxygen tometal; oxygen to uranium; uraniumAPPENDIXES(Nonmandatory Information)X1. MODEL FOR NONSTOICHIOMETRY OF URANIA-GADOLINIAX1.1 A thermodynamic analysis of the published oxygenpotential data for urania

43、-lanthanide solutions gives a set ofequations relating the atmospheric oxygen potential at which asolid solution specimen neither gains or loses oxygen, to thespecimen composition (lanthanide content and O/M) andtemperature. The oxygen potential for stoichiometry (O/M =2.00) is defined by the inters

44、ection of curves representing thehypo and hyper stoichiometric comosition ranges4,5,6.X1.2 The equations for the hypo and hyper stoichiometricregions are shown in X1.2.1-X1.2.3 and plotted in Fig. 2 forseveral gadolinia contents:X1.2.1 For hypostoichiometry, from the reaction:3Gd4/3O21 4UO21 O25 6U2

45、/3Gd2/3O8/3(X1.1)RTln(rO2) (J/mol) = 753 600 + 196.7 T+6RTln(1.5 z)3RTln(x)3RTln(1.5)4RTln(12z)X1.2.2 For hyperstoichiometry, from the reaction:4UO21 O25 2U2O5(X1.2)RTln(rO2) (J/mol) = 336 600 + 154.6 T +2RTln(X)4RTln(12z)+ (41 400 38.1 T)(2)(12z)2+108000(2)(12z)(2z)X1.2.3 The terms in ln (X) are el

46、iminated by adding 0.4times the first equations to 0.6 times the latter to give theoxygen potential for exact stoichiometry.4Lindemer and T.M. Bessman, Journal Nuclear Materials , Vol 130, p. 473,1985.5Lindemer and J. Brynestad, Journal American Ceramic Society, Vol 69, p. 867,1986.6Lindemer and A.L

47、. Sutton, Journal American Ceramic Society, Vol 71, p. 553,1988.TABLE 1 Stoichiometric Factors to Convert Metals to OxidesOxide Conversion Factors for Impurity CalculationAElement Oxide FactorAl Al2O31.89BB2O33.23Ba Ba O 1.12Be Be O 2.78Ca Ca O 1.40Cd Cd O 1.14Co Co2O31.41Cr Cr2O31.46Cu Cu O 1.25Dy

48、Dy2O31.15Eu Eu2O31.16Fe Fe2O31.43Gd Gd2O31.15Hf Hf O21.18Li Li2O 2.15Mg Mg O 1.66Mn MnO21.58Mo Mo O31.50Na Na2O 1.35Ni Ni O 1.27PP2O52.29Pb Pb O21.15Sb Sb2O41.26Si Si O22.14Sm Sm2O31.16Sn Sn O21.27Ta Ta2O51.22Th Th O21.14Ti Ti O21.67VV2O51.79WW31.26Zn Zn O 1.24Zr Zr O21.35AOxide conversion factor is

49、 defined as grams oxide per gram of element.C1430074RTln(rO2) (J/mol) = 503 400 + 167.4 T+ 2.4 RTln(1.5 z)4RTln(12z)+(108000)(1.2)(12z)(2z)+ (41 400 38.1 T)(1.2)(12z)2where:Z = the atom fraction in gadolinium,X = the deviation from stoichiometry,rO2= the oxygen pressure,R = the gas constant, andT = the temperature, K.X1.2.4 The equations predict that for temperatures around800C, and oxygen potentials near 350 KJ/mol (85 Kcal/mol), the range of gadolin