Designation: C1429 − 99 (Reapproved 2014)Standard Test Method forIsotopic Analysis of Uranium Hexafluoride by Double-Standard Multi-Collector Gas Mass Spectrometer1This standard is issued under the fixed designation C1429; the number 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.1. Scope1.1 This test method covers a quantitative test methodapplicable to determining the mass percent of uranium isotopesin uranium hexafluoride (UF6) samples. This method as de-scribed is for concentrations of235U between 0.1 and 10mass %, and234U and236U between 0.0001 and 0.1 mass %.1.2 This test method is for laboratory analysis by a gas massspectrometer with a multi-collector.1.3 This standard complements Test Methods C761, thedouble-standard method for gas mass spectrometers using asingle collector, by providing a method for spectrometers usinga multi-collector.1.4 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 applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C761 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and RadiochemicalAnalysis ofUranium HexafluorideC787 Specification for Uranium Hexafluoride for Enrich-mentC996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC1215 Guide for Preparing and Interpreting Precision andBias Statements in Test Method Standards Used in theNuclear Industry3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 A standard, n—the low-value standard of a standardpair that brackets the sample.3.1.2 B standard, n—the high-value standard of a standardpair that brackets the sample.3.1.3 determination, n—a single isotopic value, calculatedfrom a sequence of ratios; the most basic isotopic valuecalculated.3.1.4 Lagrange’s interpolation formula, n—a mathematicalequation designed to estimate values between two or moreknown values.3.1.5 run, n—a completed, six-entry symmetrical sequenceconsisting of A standard, sample, B standard, B standard,sample, and A standard from which a determination can becalculated for one or more isotopes.3.1.6 standard spread, n—the difference between the highand low standards; sometimes called standard range.3.1.7 test result, n—a reported value; the mean of two ormore determinations.4. Summary of Test Method4.1 Uranium hexafluoride gas is introduced into an ioniza-tion source. The resulting ions are accelerated down the flighttube into the magnetic field. The magnetic field separates theions into ion beams in accordance with the m/e ratio. Fourcollectors are stationed so the234UF5+,235UF5+,236UF5+,and238UF5+ion beams strike individual collectors.4.2 Two standards are chosen whose values bracket thedesired isotope of the sample. The sample and two standardsare introduced in a six-entry, symmetrical sequence. Then,measurements are taken that give the mole ratio of the desiredisotope to238U.4.3 Through Lagrange’s interpolation formula, these mea-surements are used to calculate the mass percent of the desiredisotope. If standards are available that bracket all isotopes, thenthe234U,235U, and236U mass percents are calculated from thesame six-entry run.1This test method is under the jurisdiction of ASTM CommitteeC26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1, 2014. Published June 2014. Originallyapproved in 1999. Last previous edition approved in 2009 as C1429 – 99 (2009)ε1.DOI: 10.1520/C1429-99R14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at

[email protected] For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.4 The results of two six-entry, symmetrical-sequence runsare averaged to find test results for each isotope. The238U masspercent is obtained by subtraction.5. Significance and Use5.1 Uranium hexafluoride used to produce nuclear-reactorfuel must meet certain criteria for its isotopic composition.This test method may be used to help determine if samplematerials meet the criteria described in Specifications C787and C996.6. Apparatus6.1 Mass spectrometer with the following features andcapabilities:6.1.1 An ion source with an accelerating voltage of approxi-mately 8 kV,6.1.2 A resolving power of greater than or equal to 500,6.1.3 A minimum of three points of attachment for stan-dards or samples,6.1.4 An ion collection system consisting of four collectorcups stationed to collect234UF5+,235UF5+,236UF5+, and238UF5+ions,6.1.5 An ion-current amplifier for each collector cup,6.1.6 A voltage-to-frequency (V-to-F) converter for eachamplifier,6.1.7 A counter for each V-to-F converter, and6.1.8 Computer control over opening and closing valves, thetiming, and the integration of analytical sequences.7. Procedure7.1 Select standards:7.1.1 Choose high and low standards that bracket thesample isotope(s) being evaluated. If the mass percentof234U,235U, and236U are all desired, then the two standardsmust bracket each of the three isotopes to permit calculation ofall isotopes for every run.7.1.2 If standards that bracket all isotopes are unavailable,analyze the isotope(s) bracketed by the originally selectedstandards, then select other standards to run the remainingisotope(s).7.2 Prepare Sample and Standards:7.2.1 Attach sample and standard containers to the spec-trometer.7.2.2 Open and close the appropriate valves to evacuate theair from the inlet system.7.2.3 Open the sample and standard containers individuallyand vent the gas phase to the cold trap. This is to removeimpurities that may bias the results or interfere with theionization. If necessary, freeze the UF6with ice water or amixture of crushed dry ice and isopropyl alcohol to permitlonger venting without losing large amounts of UF6.7.2.4 Permit exhaust system pressure to recover.7.2.5 Check to see if impurities have been sufficientlyremoved by introducing UF6into the ion source and observingpressure, or exhausting through the cold trap and observingpressure on the other side, or any other suitable means.7.2.6 If necessary, repeat 7.2.3 – 7.2.5 until samples areclean.7.3 Prepare Instrument:7.3.1 Adjust instrument parameters to focus ion beams inproper collectors and maximize the238UF5+current reading.7.3.2 Enter standard values and other information if neededfor calculations performed by computer.7.3.3 Program the spectrometer to run two of the followingsix-entry, symmetrical sequences: low standard, sample, highstandard, high standard, sample, low standard.7.4 Run the Analysis:7.4.1 Obtain measurements from all four collectors duringeach entry.8. Calculation8.1 Perform the following operations for each of the234U,235U, and236U isotopes:8.1.1 For each entry, obtain a ratio by dividing the UF5+ioncount of the desired isotope by the238UF5+ion count.8.1.2 Find the mean of the two low standard ratios anddesignate this A.8.1.3 Find the mean of the two sample ratios and designatethis X.8.1.4 Find the mean of the two high standard ratios anddesignate this B.NOTE 1—In a six-entry symmetrical run sequence,~r11r6!/2 5 A (1)~r21r5!/2 5 X (2)~r31r4!/2 5 B (3)where:rn= the ratio from the nthentry.8.1.5 Find the mass percent ratio of the low value standard(A standard) by dividing the mass percent of the desired isotopeby the mass percent238U.EA5 mass %234U/mass %238U (4)HA5 mass %235U/mass %238U (5)YA5 mass %236U/mass %238U (6)8.1.6 Find the equivalent mass percent ratio for the highvalue standard (B standard.) Label it either EB, HB,orYB.8.1.7 Find the difference (D) between the mass percentratios of the A and B standards.NOTE 2—EB− EA= DE, HB− HA= DH, and YB− YA= DY8.1.8 Find the mass percent ratio (desired isotope/238U) ofthe sample by calculating EX, HX,orYXas follows:EX5 ~~X 2 A!/~B 2 A!!·DE1EA(7)HX5 ~~X 2 A!/~B 2 A!!·DH1HA(8)YX5 ~~X 2 A!/~B 2 A!!·DY1YA(9)NOTE 3—Calculations in 8.1.8 are based on an algebraic manipulationof Lagrange’s interpolation formula using two known values of a function.8.2 Calculate the mass percent as follows:e 5 100%·EX/~11EX1HX1YX! (10)x 5 100%·HX/~11EX1HX1YX! (11)y 5 100%·YX/~11EX1HX1YX! (12)C1429 − 99 (2014)2where:e = mass %234U,x = mass %235U, andy = mass %236U.8.3 Average a minimum of two determinations for each testresult.8.4 Find the mass percent238U by subtracting the masspercent of the other isotopes from 100 %.9. Precision and Bias9.1 Seven standards traceable to National Institute of Stan-dards and Technology (NIST) were selected as referencevalues. Two pairs of standards, also traceable to NIST, werechosen to evaluate the234U,235U, and236U mass percentvalues of the seven reference standards. These standard pairswere obtained by selecting a low standard and two highstandards to create one standard spread that was narrower forall three of the desired isotopes and one standard spread thatwas wider for all three of the desired isotopes. The234U and236U reference values assigned to all of these standards weredetermined by thermal mass spectrometer (see Table 1) withthe exception of the mass percent236U value assigned toG015-1. This value was obtained on a single-collector gas-phase mass spectrometer. The235U reference values wereassigned through a combination of thermal and gas-phaseanalysis.9.2 The test deviated from single-day design because of theneed for a large number of test results for statistical purposes.However, each set of data for a specific combination ofreference value, standard pair, and mass spectrometer wasobtained within a 24-h period. Each reference standard was runby double-standard method 60 consecutive times for each oftwo standard pair on each of three mass spectrometers. Everyrun yielded three determinations, one for each isotope. Twoconsecutive determinations were then averaged for a test result.This produced a test result for each isotope after every twoconsecutive runs. The completion of each reference standardanalysis yielded 30 test results per combination of spectrometerand standard pair for each of the234U,235U, and236U isotopes.The combined test data for all isotopes of all referencestandards yielded 7560 test determinations and 3780 testresults. These data were collected over a period of severalmonths.9.3 The one-analyst design was impractical because of theneed to accumulate such a large amount of data in as short atime as possible. After a reference standard was attached to aspectrometer, all the data for that combination of referencestandard and standard pair were obtained before the referencestandard was detached from the spectrometer. The contributionto variation due to different analysts should have been minimal.Pumping down the instrument and restarting the spectrometerby computer were the basic components of that variation.9.4 Due to the difficulties in movement and ownership ofnuclear materials, as referred to in Section 1.4 of Guide C1215,the reproducibility was obtained by treating the three spectrom-eters as three different laboratories. This should be taken intoaccount when considering the reproducibility results.9.5 Precision3—The precision was calculated based on masspercent units. The repeatability percent RSD for the235Uisotope was determined to be 0.006 % and was typicallyconsistent for all levels of mass percent. The reproducibilitypercent RSD for the235U isotope was determined to be0.010 % and tended to decrease as the assay increased.9.5.1 The repeatability percent RSD for the234U isotopewas determined to be 0.411 % and typically decreased asthe234U mass percent increased. The reproducibility percentRSD for the234U isotope was determined to be 0.722 %.9.5.2 The average repeatability percent RSD for the236Uisotope was determined to be 0.344 % and tended to decreaseas the236U assay increased. The reproducibility percent RSDfor the236U isotope was determined to be 1.664 % and tendedto decrease as the236U assay increased. The precision resultsfor the three uranium isotopes are listed in Table 2.9.6 Bias—The observed percent bias was calculated basedon mass percent units. The observed percent bias for the235Uisotope was determined to be −0.003 %. The observed percentbias for the234U isotope was determined to be −0.810 %. Theobserved percent bias for the236U isotope was determined tobe 3.711 %. The235U and234U data indicate no significant biasin the method. The236U data indicate there may be a slight biasfor that isotope. The bias results are listed in Table 2.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report: RR:C26-1008.TABLE 1 Reference Materials Used in the Test and TheirAssigned ValuesIdentity Function234U mass %235U mass %236U mass %G005 low std 0.0026 0.48347 0.0027G006 reference 0.0040 0.61074 0.0060G010–1 reference 0.0052 0.99151 0.0077G012 reference 0.0096 1.2250 0.0152AG015–1 reference 0.0060 1.5139 0.0152AG020-1 reference 0.0156 2.0123 0.0039G025 reference 0.0204A2.4719 0.0018BG030–1 reference 0.0224A3.0066 0.0040G030 high std 0.0186 3.0072 0.0108G050–1 high std 0.0264 4.9457 0.0369AThese values are outside the bracket of the narrow standard spread, and onlythe data obtained from the wider standard pair are used to determine the precisionand bias.BThis value is not within the bracket of either standard pair, and the data obtainedfor this value were not used to determine the precision and bias. The certainty inthe assigned values, expressed as 3 × % RSD is ± 2.2921 % for234U, ± 0.0646 %for235U, and ± 2.7263 % for236U.TABLE 2 Precision and Bias Test Results in Mass Percent UnitsIsotope %BiasASrB%RSDrCSRD%RSDRE235U −0.003 0.00010 0.006 0.00014 0.010234U −0.810 0.000032 0.411 0.000085 0.722236U 3.711 0.000026 0.344 0.000120 1.664A%Bias = (bias/reference value) × 100 %BSr= repeatability standard deviationC%RSDr= %RSD for repeatabilityDSR= reproducibility standard deviationE%RSDR= %RSD for reproducibilityN = 1260 for235U, 1080 for234U, 900 for236UC1429 − 99 (2014)310. Keywords10.1 double-standard; isotopic; mass spectrometer; multi-collector; spectrometer; uranium hexafluorideASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. 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 t