1、Designation: C1430 07 (Reapproved 2011)1Standard 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 C1430; the numb
2、er immediately following 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.1NOTEA un
3、its statement was added editorially in June 2011.1. Scope1.1 This test method 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-centra
4、tion of up to 12 weight %. The O/M calculations assumethat the gadolinium and uranium oxides are present in a metaldioxide solid solution.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to
5、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 limitations prior to use. For specific hazardsstatements, see Section 8.2. Ref
6、erenced Documents2.1 ASTM Standards:2C696 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade Uranium Di-oxide Powders and PelletsC776 Specification for Sintered Uranium Dioxide PelletsC922 Specification for Sintered Gadolinium Oxide-Uranium Dioxide PelletsC96
7、8 Test Methods for Analysis of Sintered GadoliniumOxide-Uranium Dioxide PelletsC1287 Test Method for Determination of Impurities inNuclear Grade Uranium Compounds by InductivelyCoupled Plasma Mass Spectrometry3. Summary of Test Method3.1 The uranium, and either O/U or O/M, are determined bymeasuring
8、 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 boat. The boat is placed in a tube furnacecapable of holding a temperature of 800 6 10C. The furnaceis purg
9、ed 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. The furnace then is turned off andallowed to cool, with gas purge on, to room temperature. Thesamples are
10、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 Uranium dioxide is used as a nuclear-reactor fuel. Thistest method is designed to determine whether the percentur
11、anium and O/U or O/M content meet Specifications C776and C922.5. Interferences5.1 Parameters for temperature, gas composition, gas flow,and moist air purge must be monitored and maintained care-fully within the limits set in the procedure.5.2 This test method assumes that chemical impurities meetSpe
12、cifications C776 and C922 limits. Potential method inter-ferences from higher impurity concentrations will requireevaluation.5.3 Furnace tubes or boats made from metals that oxidizeunder the test conditions may prevent proper equilibration byconsuming available oxygen.1This test method is under the
13、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, 2011. Published June 2011. Originallyapproved in 2000. Last previous edition approved in 2007 as C143007. DOI:10.1520/C1430-07R11E01.2For
14、 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 ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700
15、, West Conshohocken, PA 19428-2959, United States.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.5.6 This test method assumes that pellets are sintered. Itdoes not correct
16、 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 10.2).6. Apparatus6.1 Analytical Balance, capable of weighing to 6 0.0001 g.6.2 Tube Fu
17、rnace, 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 purge gas is passed through a humidifier,into the tube furnace. A bubbler flask is attach
18、ed 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 perform satisfactorily.6.7 Purge Gas Humidifier, with heater and controller ca-pable of mai
19、ntaining 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 safety precautions for handling uranium.8.2 The furnace, sample tube and sample boats a
20、re 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 sample size is 510-g pellet. Smallerpellets may need to be composited (two pellets/test)
21、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 will not stabilize, do notproceed.NOTE 1The extremely small weight changes that are bei
22、ng 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.3Available from the New Brunswick Laboratory, 9800 S. Cass Ave., Argonne,IL.FIG. 1 Assorted Connectors, Tubing, Fl
23、asks, Stoppers, and Delivery TubesC1430 07 (2011)129.4 Create a boat map to maintain 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.
24、Repeat for each pellet.9.6 Include one or two equilibrated standard control pelletswith 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.9.8 Fit the purge gas connection to end of tube and clamp.Make certai
25、n 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 forapproximately five minutes.NOTE 2The flow rate of the purge gas and the leng
26、th 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 inside thesample chamber.9.10 Attach a Pyrext delivery tube with ground glass fi
27、ttingto 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 toequilibrate for a minimum of 4 h. Monitor the system occa-sionally during
28、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 thecarrier gas and allow the pellets to cool to room temperature.NOTE 3If t
29、he 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 condensation but low enough to prevent oxidation by room air.9.14 Remove the sample boa
30、t 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 sample before equilibration, g,W2= Weight of sample after equilibration, g,AW
31、o= 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 equilibra-tion, g,W2= Weight of sample after equilibra-tion, g,%Gd2O3= Measured Gd
32、, expressed as stoi-chiometric 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 solution,this factor should be evaluated todetermine if modification is neces
33、-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 impurities, expressed as weight %impurity oxides in UO2. Add the weight % of ea
34、chdetected 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 satisfactory results. See Table 1 toobtain conversion factors to convert co
35、mmon im-purity elements to oxides.The list of impurities to be tested for will dependupon specification requirements (see SpecificationsC776 and C922), elements obtained from multiele-ment methods (see Test Methods C696, C968, andC1287), and fuel processing conditions. In somecases, a nominal value
36、for impurities is adequate.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 237.96 may be used. For accuracy better than0.03 %, or for U-235 enrichments 5 %,
37、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 NBL-125 UO2standards by five opera-tors in one laboratory over a two month period,
38、 using a singlespectrometric measurement for total impurities (%I) and asingle measured value for atomic weight (AW). The certifiedC1430 07 (2011)13value of the standard is 88.079 % uranium. The bias was +0.005 % (absolute), with an average result of 88.0841 %. Theprecision was 0.0004 % (1 s.d.).10.
39、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 onelaboratory. The nominal value of the standard pellets whichwere made by equilibrat
40、ing 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 MeasurementUncertaintiesThe uncertainties associated with samplingand measurement of imp
41、urities 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 UncertaintiesUncertainties associated with the equilibration procedure, suchas weighing error
42、s, 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 own precision and bias evaluation.11. Keywords11.1 atmospheric equilib
43、ration; 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-lanthanide solutions gives a set ofequations relating the atmospheric
44、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 intersection of curves representing thehypo and hyper stoichiometric comositi
45、on 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 6U2/3Gd2/3O8/3(X1.1)RTln(rO2) (J/mol) = 753 600 + 196.7 T+6RTln(1.5 z)3RTl
46、n(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 eliminated by adding 0.4times the first equations to 0.6 times the latter
47、 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. Sutton, Journal American Ceramic Society, Vol 71, p. 553,1988.TABLE 1
48、 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 Dy2O31.15Eu Eu2O31.16Fe Fe2O31.43Gd Gd2O31.15Hf Hf O21.18Li Li2O 2.15Mg
49、 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 defined as grams oxide per gram of element.C1430 07 (2011)14RTln(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
