ASTM_C_1428_-_11.pdf

Designation:C142811Standard Test Method forIsotopic Analysis of Uranium Hexafluoride bySingleStandard Gas Source Multiple Collector MassSpectrometer Method1This standard is issued under the fixed designation C1428;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 is applicable to the isotopic analysis ofuranium hexafluoride(UF6)with235U concentrations less thanor equal to 5%and234U,236U concentrations of 0.0002 to0.1%.1.2 This test method may be applicable to the analysis of theentire range of235U isotopic compositions providing thatadequate Certified Reference Materials(CRMs or traceablestandards)are available.1.3 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 health practices and determine the applicability ofregulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C787 Specification for Uranium Hexafluoride for Enrich-mentC996 Specification for Uranium Hexafluoride Enriched toLess Than 5%235U2.2 Other Document:USEC-651Uranium Hexafluoride:A Manual of GoodHandling Practices33.Summary of Test Method3.1 The unknown sample and a CRM or traceable standardwhose isotopic composition is close to that of the sample areintroduced in sequence into the mass spectrometer,and234U,235U,236U,and238U ions are focused through correspondingcollector slits to the four separate collectors.Measurements aremade that are proportional to the ratios of234U,235U,or236Uto238U.With the known composition of the CRM or traceablestandard,these ratios of molar ratios permit calculation of the234U,235U,and236U contents.Memory corrections areapplied based on the periodic measurement of two CRMs ortraceable standards.4.Significance and Use4.1 Uranium hexafluoride is a basic material used to pro-duce nuclear reactor fuel.To be suitable for this purpose,thematerial must meet criteria for isotopic composition.This testmethod is designed to determine whether the material meetsthe requirements described in Specifications C787 and C996.5.Apparatus5.1 A gas source multiple collector mass spectrometer withthe following attributes:5.1.1 The resolving power of the mass spectrometer is notless than 500.The resolving power(R)is calculated from theregistered mass spectrum of both the235UF5+and238UF5+isotopes as follows:R 5aMbDM(1)wherea=distance between centers of the235UF5+and238UF5+peaks,b=peak width of the238UF5+isotope(10%valley),M=333 mass(u)238UF5+,andDM=3=333 330,330 mass(u)235UF5+5.1.2 The abundance sensitivity of the mass spectrometer isspecified as less than 1105as contribution of mass 333(238UF5+)to mass 331(236UF5+).5.1.3 The four collectors have collector slits adjusted forions of masses 329,330,331,and 333.Ion currents areamplified by four amplifiers,having noise level less than 0.5mV.5.1.4 The ion beams are kept within the slits by an auto-matic beam positioner circuit.1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved March 1,2011.Published April 2011.Originallyapproved in 1999.Last previous edition approved in 2005 as C142899(2005).DOI:10.1520/C1428-11.2For 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 ASTM website.3Available from United States Enrichment Corporation,6903 Rockledge Drive,Bethesda,MD 20817.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.1.5 The pumping system of the mass spectrometer analy-ser tube shall maintain a pressure less than 5108torr with asample flowing into the ion source.5.1.6 The memory correction factor of the mass spectrom-eter as defined in 9.1 shall be consistent with the requiredaccuracy and precision,and shall not exceed 1.005.5.1.7 The sample inlet system shall be equipped with amanifold,including adjustable leak,and valves for introducingthe sample and CRM or traceable standard in sequence and forevacuating corresponding lines.The pumping system of theinlet system must maintain a pressure less than 2102torr byevacuating.6.Hazards6.1 Since UF6is radioactive,toxic,and highly reactive,especially with reducing substances and moisture(see USEC-651),appropriate facilities and practices for analysis shall beprovided.7.Calibration and Standardization7.1 Uranium Hexafluoride Isotopic7.1.1 Two CRMs or traceable standards are used to deter-mine the memory correction factor.The235U concentrationratio of upper CRM or traceable st