1、Designation: C787 15Standard Specification forUranium Hexafluoride for Enrichment1This standard is issued under the fixed designation C787; 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 pare
2、ntheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers uranium hexafluoride (UF6)intended for feeding to an enrichment plant. Included arespecifications for UF6derived from unirr
3、adiated natural ura-nium and UF6derived from irradiated uranium that has beenreprocessed and converted to UF6for enrichment and subse-quent reuse. The objectives of this specification are twofold:(1) To define the impurity and uranium isotope limits forCommercial Natural UF6feedstock; and (2) To def
4、ine addi-tional limits for Reprocessed UF6(or any mixture of Repro-cessed UF6and Commercial Natural UF6). For such UF6,special provisions may be needed to ensure that no extra hazardarises to the work force, process equipment, or the environ-ment.1.2 The scope of this specification does not comprehe
5、n-sively cover all provisions for preventing criticality accidentsor requirements for health and safety or for shipping. Obser-vance of this specification does not relieve the user of theobligation to conform to all international, federal, state, andlocal regulations for processing, shipping, or in
6、any other wayusing UF6(see, for example, TID-7016, DP-532, ORNL-NUREG-CSD-6, and DOE O 474.1).1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.2. Referenced Documents2.1 ASTM Standards:2C761 Test Methods for Chemical, Mass S
7、pectrometric,Spectrochemical, Nuclear, and RadiochemicalAnalysis ofUranium HexafluorideC859 Terminology Relating to Nuclear MaterialsC996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC1052 Practice for Bulk Sampling of Liquid UraniumHexafluorideC1295 Test Method for Gamma Energ
8、y Emission fromFission and Decay Products in Uranium Hexafluoride andUranyl Nitrate SolutionC1703 Practice for Sampling of Gaseous UraniumHexafluoride2.2 ANSI Standard:N14.1 Packaging of Uranium Hexafluoride for Transport32.3 U.S. Government Documents:Inspection, Weighing, and Sampling of Uranium He
9、xafluo-ride Cylinders, Procedures for Handling and Analysis ofUranium Hexafluoride, Vol. 1, Department of EnergyReport ORO-671-1, latest revision4The UF6Manual: Good Handling Practices for UraniumHexafluoride, United States Enrichment Corporation Re-port USEC-651, latest revision5Nuclear Safety Guid
10、e, U.S. Nuclear Regulatory CommissionReport TID-7016, Rev. 2, 1978, and ORNL-NUREG-CSD-64Clarke, H. K., Handbook of Nuclear Safety, Department ofEnergy Report DP-5324Control and Accountability of Nuclear Materials, DOEDirective O 474.143. Terminology3.1 Definitions of Terms Specific to This Standard
11、:3.1.1 Terms shall be defined in accordance with Terminol-ogy C859, except for the following:3.1.2 Commercial Natural UF6UF6from natural unirra-diated uranium (containing 0.711 6 0.004 g235U per 100 g U).3.1.2.1 DiscussionIt is recognized that some contamina-tion with reprocessed uranium may occur d
12、uring routineprocessing. This is acceptable provided that the UF6meets therequirements for Commercial Natural UF6.1This specification is under the jurisdiction of ASTM Committee C26 onNuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.02 on Fueland Fertile Material Specification
13、s.Current edition approved July 1, 2015. Published July 2015. Originally approvedin 1976. Last previous edition approved in 2011 as C787 11. DOI: 10.1520/C0787-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book
14、 of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute, 11 W. 42nd St., 13thFloor, New York, NY 10036.4Available from Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402
15、.5Available 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 States13.1.3 Reprocessed UF6any UF6made from uranium thathas been exposed in a neutron irradiation
16、 facility and subse-quently chemically separated from the fission products andtransuranic isotopes so generated.3.1.3.1 DiscussionThe requirements for Reprocessed UF6given in this specification are intended to be typical ofreprocessed spent fuel that has achieved burnup levels of up to50 000 Megawat
17、t days per tonne of uranium in light waterreactors and has been cooled for ten years after discharge. It isrecognized that different limits would be necessary to accom-modate different fuel histories.4. Safety, Health Physics, and Criticality Requirements4.1 The UF6concentration shall be not less th
18、an 99.5 g UF6per 100 g of sample in order to limit the potential hydrogencontent for nuclear criticality safety.4.2 The total absolute vapor pressure shall not exceed thevalues given below:380 kPa at 80C (55 psia at 176F), or517 kPa at 93C (75 psia at 200F), or862 kPa at 112C (125 psia at 235F)Addit
19、ionally, if a measurement is taken over solid UF6, thenthe vapor pressure shall not exceed the values given below:50 kPa at 20C (7 psia at 68F), or69 kPa at 35C (10 psia at 95F)The purpose of the pressure check is to limit the hydrogenfluoride, air, or other volatile components that might causeoverp
20、ressure when heating the shipping container to obtain aliquid sample or withdraw the contents.4.2.1 If the temperature differs from 20C or 35C, atemperature correction must be performed which takes thechange in vapor pressure of UF6into account. For example, anacceptable correction would be that the
21、 pressure must remainbelow PUF6(T) + 39.3 kPa, where PUF6(T) is the vapor pressureof pure UF6over solid at temperature T and PUF6(T) is givenaccording to Log PUF6= 12.77 (2562.46/T), with P in PascalandTinK.6Other methods or equations to assure that thepressure limits above are met are acceptable pr
22、ovided thatvalidated temperature compensation is made.4.3 The total hydrocarbon, chlorocarbon, and partially sub-stituted halohydrocarbon content shall not exceed 0.01 mol %of the UF6. The reason for the exclusion of these materials isto prevent a vigorous reaction with UF6upon heating or withstrong
23、er-fluorinating agents which may be present in enrich-ment plants. It is essential that contamination of the UF6containers, such as by vacuum pump oil, be prevented since itis not practical to obtain a sample without heating the UF6. Forfully substituted chlorofluorocarbons a maximum limit may beagr
24、eed upon between the parties concerned.4.3.1 Measures should be taken to minimize contaminationby hydrocarbons, chlorocarbons, and partially substituted ha-lohydrocarbons in the receiving cylinder before filling and it isgood practice to minimize such contact during UF6processing.4.3.2 If UF6has bee
25、n liquefied, either during filling orduring sampling of the final shipping container, compliancecan be assumed. If the UF6has not been liquefied, compliancemust be demonstrated. An alternative means of demonstratingcompliance with this requirement, other than by directmeasurement, may be agreed upon
26、 between the parties con-cerned.4.4 For Reprocessed UF6the gamma radiation from fissionproducts shall not exceed 1.1 105MeV Bq/kgU (1.1 105MeV/sec kgU). The measurements are made in accordancewith Test Method C1295 or equivalent. The purpose of thisrequirement is to limit the gamma dose from fission
27、 products towhich plant workers might be exposed to a level less than 20 %of the gamma dose from aged natural uranium, and to limit thequantity of fission products in effluent from enrichment andfuel fabrication plants.4.5 For Reprocessed UF6, the alpha activity from neptunium(Np) and plutonium (Pu)
28、 isotopes may be specified in either oftwo ways as agreed upon between the parties concerned:4.5.1 The total alpha activity from Np and Pu in the cylindershall be limited to 25 000 Bq/kgU (1.5 106disintegrationsper minute per kilogram of uranium). This criterion is con-cerned with both the volatile
29、components and those that remainon the inner surfaces and in the heel, so it can be measuredpractically only by sampling from the inflow during the fillingof the shipping container; or4.5.2 The volatile alpha activity from Np and Pu in theliquid sample from the shipping container shall be limited to
30、3300 Bq/kgU (0.2 106disintegrations per minute per kilo-gram of uranium). To prevent nonvolatile particles from beingincluded in this measurement, the liquid sample must befiltered through a porous nickel filter as described in TestMethods C761.5. Chemical, Physical, and Isotopic Requirements5.1 Pla
31、nts preparing UF6will have to control the purity ofprocess chemicals and also employ low corrosion equipment tobe successful in meeting the specifications for most impurities.Both Commercial Natural UF6and Reprocessed UF6will haveto meet the same specification criteria for most elements. Inaddition,
32、 Reprocessed UF6must meet additional specificationlimits for artificially created radioactive species. For evaluatingCommercial Natural UF6, the measured concentration of236Uwill be used as an indicator for contamination with reprocesseduranium, on the assumption that there is no opportunity forcont
33、amination with irradiated uranium that has not beenprocessed to remove the majority of fission products. Providedthat this isotope does not exceed the concentration limit forCommercial Natural UF6listed in 5.5, the expected concentra-tions of artificial isotopes would be so far below normaldetection
34、 limits that measurements to determine compliancewith the separate limits are not appropriate. Uranium hexafluo-ride that fails to meet Commercial Natural UF6limits wouldrequire further testing to determine its acceptability as Repro-cessed UF6.5.2 The UF6content shall be reported as gUF6/100 g ofsa
35、mple.5.3 The total of all the following listed elements that formnonvolatile fluorides shall not exceed 300 g/g of uranium:6Comprehensive Nuclear Materials, Volume 2, The U-F System, Ed. R.J.M.Konings, p. 209, Elsevier 2012.C787 152aluminumarsenic iron sodiumbarium lead strontiumberyllium lithium th
36、oriumbismuth magnesium tincadmium manganese zinccalcium nickel zirconiumchromium potassiumcopper silverNOTE 1The list of nonvolatile fluorides and their limits weredetermined based upon their vapor pressure and likelihood to remain inthe UF6heel following transfer. These elements form fluorides with
37、 avapor pressure below 101.3 kPa at 300C and are always nonvolatile.Additionally some elements may form both volatile and nonvolatilecompounds and that is why in 5.4 we specifically limit the volatilecomponent of each element.5.3.1 If the concentration of an impurity element is given asa less-than v
38、alue (this is a concentration expressed as being lessthan the lower detection limit of the analytical method), thisless-than value shall be taken as the concentration of thatelement in determining the total impurity content.5.4 The volatile component of the following elements shallnot exceed the val
39、ues listed below:Element Value, g/g of uraniumantimony 1arsenic 3 (see Note 2)boron 1bromine 5chlorine 100chromium 10 (see Note 2)molybdenum 5 (see Note 2)niobium 1phosphorus 50ruthenium 1silicon 100tantalum 1titanium 1tungsten 2vanadium 2NOTE 2Total chromium, molybdenum, and arsenic are usually ex-
40、pected to be well below 10g/gU, 5g/gU, and 3g/gU, respectively. If thetotal value of the element (noted hereafter as E(total) is found to be abovethe limit in 5.4, the volatile component may be determined by either of thefollowing techniques as described in Test Method C761:by measuring the insolubl
41、e component of the Element, and deducingthe volatile component by:Evolatile!5Etotal!2Enonvolatile!5Etotal!2Einsoluble!or, by vapor transfer of a sample UF6(taken according to PracticeC1052) from its original sample container to a new container. Measuringthe Element in the hydrolysed UF6of the new co
42、ntainer will yield thevolatile component of the Element initially present, providing the transferhas been made in the vapor phase Evolatile!5Etotal!2Enonvolatile!5Eafter gas transfer!If E(total)exceeds the value in 5.4, then agreement in advance betweenthe parties (for example, supplier, receiver) s
43、hall be required to accept thematerial.5.5 Minor IsotopesThese items shall not exceed the limitsgiven as micrograms per gram of total uranium (g/gU).Commercial Natural UF6Reprocessed UF6232U 0.00001 0.005234U 62 480.0 (see Note 3)236U 20 8400.05.5.1 It is recognized that variability in natural urani
44、umdoes occur and affects the234U level.234U levels in the rangeof 5662 g/gU have been identified in a small part of naturaluranium production. For compliance with Specification C996after enrichment, a234U content of 56 g/gU or less inCommercial Natural UF6is generally required to yield En-riched Com
45、mercial Grade UF6that does not exceed 10.0 103g234U/g235U (Specification C996 requires agreement inadvance between the parties to accept Enriched CommercialGrade UF6above 10.0 103g234U/g235U).A234U content of5762 g/gU will yield Enriched Commercial Grade UF6thatmay exceed this level, but will genera
46、lly comply with the limitin Specification C996 of 11.0 103g234U/g235U. Therefore,prior to any delivery of Commercial Natural UF6containing234U above 56 g/gU, the234U level shall be reported and shallrequire agreement in advance between the parties (for example,converter, enricher) to accept the mate
47、rial.5.5.2 Values at or below the above limit for232UinCommercial Natural UF6may be assumed without measure-ment provided that it can be demonstrated that the materialmeets the236U limits.5.5.3 For Commercial Natural UF6, isotopic concentrationsshall be reported for234U,235U, and236U unless it can b
48、eotherwise demonstrated that the UF6conforms to the appro-priate isotopic specifications (for example, through the sellersquality assurance records). For Commercial Natural UF6fromverifiable natural uranium sources the analysis of236Uisnotnormally required unless otherwise agreed upon between thebuy
49、er and seller.5.5.4 Unirradiated UF6at any235U concentration other thanthat of Commercial Natural UF6might be delivered as feedmaterial if this is acceptable to the enricher. Renegotiation ofthe impurity limits may be needed under these circumstances.5.5.5 For Reprocessed UF6, isotopic concentrations shall bemeasured and reported for232U,234U,235U, and236U.NOTE 3If the234U level (expressed here in wt %) in reprocessed UF6exceeds the following limit: (0.036 wt %235U) 0.004, then in orderto ensure compliance with Speci
