1、Designation: C 1689 08aStandard Practice forSubsampling of Uranium Hexafluoride1This standard is issued under the fixed designation C 1689; 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 practice is applicable to subsampling uraniumhexafluoride (UF6), using heat liquefaction techniques, frombulk containers, obtained in conformanc
3、e with C 1052, intosmaller sample containers, which are required for laboratoryanalyses.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 It is assumed that the liquid UF6being sampled com-prises a single quality and quant
4、ity of material. This practicedoes not address any special additional arrangement that mightbe required for taking proportional or composite samples.1.4 The number of samples to be taken, their nominalsample weight, and their disposition shall be agreed uponbetween the parties.1.5 The scope of this
5、practice does not include provisionsfor preventing criticality incidents.1.6 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
6、the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 787 Specification for Uranium Hexafluoride for Enrich-mentC 859 Terminology Relating to Nuclear MaterialsC 996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC 761 Test Methods
7、for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofUranium HexafluorideC 1052 Practice for Bulk Sampling of Liquid UraniumHexafluoride2.2 Other Documents:ANSI N14.1 Uranium Hexafluoride: Packaging for Trans-port3ISO/DIS 7195 Packaging of Uranium Hexafluoride (UF6
8、)for Transport4USEC-651 The UF6Manual: Good Handling Practices forUranium Hexafluoride, latest revision53. Terminology3.1 Terms shall be defined in accordance with TerminologyC 859 except for the following:3.1.1 sample bottlethe vessel (typically a 1S or 2S bottle)into which the sample of UF6is with
9、drawn from the containerfor transfer to the laboratory, analysis or dispatch to thecustomer.3.1.2 subsample tubethe small vessel (for example, a P10tube6) into which a subsample of UF6is withdrawn from thesample bottle for analysis of UF6quality or dispatch to thecustomer.3.1.3 subsample rigthe equi
10、pment to perform the transferof liquid UF6from the sample bottle into the subsample tube,typically a vacuum manifold equipped with heating and aliquid nitrogen trap.4. Summary of Practice4.1 Two methods of withdrawing a subsample of UF6aredescribed which differ based on safety requirements namely:(1
11、) homogenizing of liquefied UF6by agitation before liquidtransfer and (2) homogenizing of liquefied UF6by convectionbefore liquid transfer. The first method involves homogeniza-tion of liquified UF6in a sample bottle by vigorous shaking.Subsequently the sample bottle is inverted and connected to the
12、top of a heated vacuum-manifold system, and the subsample1This practice is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved Dec. 1, 2008. Published January 2009. Originallyapproved in
13、2008. Last previous edition approved in 2008 as C 1689 08.2For 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.3Av
14、ailable from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.5Available fro
15、m United States Enrichment Corp., 6903 Rockledge Dr., Bethesda,MD 20817, http:/.6Polychlorotrifluoroethylene P10 tubes are widely accepted by the industry forsubsample collection and subsequent UF6quality analyses or dispatch to thecustomer. Other types of subsample tubes, for example P-20, P-80 or
16、P100 , can beused for internal subsample collection and processing. Dispatch of these subsampletubes may be agreed upon by buyer and seller and subject to (local) transportregulations.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.t
17、ube is attached to the appropriate port of the system. Thesystem is evacuated and the liquid UF6allowed to flow bygravity into the subsample tube. In the second method thesample bottle containing solid UF6is connected to the top of amanifold system, and a subsample tube is attached to theappropriate
18、 port of the system. The whole system is enclosed insecondary containment that can be heated (hot-box). Afterevacuation the complete system is heated for specific period(typically 1.5 hr) to allow for complete homogenization ofthe liquid UF6by convection. Subsequently the liquid UF6isallowed to flow
19、 by gravity either directly or via graduatedvolume into the subsample tube.4.2 For both methods of sampling, the presence of residuesmay have significant implications for the quality of UF6. Forsafety and quality reasons, sample bottles and subsample tubesshall be clean, dry, and empty before fillin
20、g.4.3 Various types of sample bottles and tubes are in use andare described in detail in the applicable national and interna-tional standards, for example, ANSI N14.1 and ISO/DIS 7195.For a given type of sample bottle, the detailed configuration,for example valve orientation, terminal fittings and t
21、he like,may vary. Hence the type and configuration of bottles used forthe withdrawal of samples shall be agreed upon between theparties.5. Significance and Use5.1 Uranium hexafluoride is normally produced and handledin large (typically 1- to 14-ton) quantities and must, thereforebe characterized by
22、reference to representative samples. Thesamples are used to determine compliance with the applicablecommercial Specifications C 996 and C 787 by means of theappropriate test method (for example, Test Method C 761 andreferences therein). The quantities involved, physical proper-ties, chemical reactiv
23、ity, and hazardous nature of UF6are suchthat for representative sampling, specially designated equip-ment must be used and operated in accordance with the mostcarefully controlled and stringent procedures. This practiceindicates appropriate principles, equipment and procedurescurrently in use for su
24、bsampling of liquid UF6. It is used byUF6converters, enrichers and fuel fabricators to review theeffectiveness of existing procedures or to design equipment andprocedures for future use. Other subsampling procedures suchas UF6vapor sampling are not directly representative of thechemical quality of l
25、iquid UF6.5.2 It is emphasized that this test guide is not meant toaddress conventional or nuclear criticality safety issues.6. Apparatus6.1 Hot Water Bath.6.2 Subsample RigFor Procedure 1 see Fig. 1 and Proce-dure 2 see Fig. 2. Materials of construction in direct contactwith liquid UF6are made from
26、 nickel, high nickel alloys, ormaterials having comparable resistance to UF6corrosion.6.3 Gaseous Isotopic Abundance Sample Tube (Fig. 3).6.4 Polychlorotrifluoroethylene Subsample Tube and Clos-ing Disc (Fig. 4)The tube must be of uniform density, freefrom cracks or occlusions and able to withstand
27、temperaturesfrom 195C to +150C. Materials of construction in directcontact with liquid UF6are made from polychlorotrifluoroet-hylene, PTFE/TFE (gaskets), or materials having comparableresistance to UF6corrosion.NOTE 1All lines are38 in. (9.5 mm) Monel tubing.NOTE 2All valves are Monel diaphragm type
28、 valves.NOTE 3The valves and lines are wrapped with heating tape to maintain a system temperature of about 80C.NOTE 4Valve 2 is a 3-way valve modified to make it a 4-way valve. When the valve is closed, the polychlorotrifluoroethylene tube is isolated fromthe system, but the lines from valve 1 to va
29、lve 3 and to the bulk container are open.FIG. 1 Subsample Rig Used for Procedure 1C 1689 08a26.5 Flare Nut and PlugFlare nuts and plugs for subsampletube closure, storage and transport can be constructed fromMonel, nickel, high nickel alloys or 316 SS.6.6 Polychlorotrifluoroethylene Knockout Cylinde
30、r (Fig. 5),closed with a Cajon M-16 VCR-1 female nut and an M-16VCR-4 male nut or equivalent.NOTE 1Brand names mentioned in this practice are intended to betypical, not limiting. Another brand with comparable characteristics couldperform equally well.6.7 Nickel Filter Disc, porous, 2m, free of chrom
31、ium (Fig.6).NOTE 2The filterdisc should weigh approximately 1 g. It should bemade of nickel powder produced from carbonyl nickel and formed by theno pressure sintering method in graphite or ceramic molds.6.8 Gas Sample Cylinder.6.9 Heat SourcesHeat gun (or an equivalent) and heatlamps.6.10 Dewar Fla
32、sk, for liquid nitrogen, stainless steel.7. Hazards7.1 Uranium hexafluoride (UF6) is radioactive, toxic andhighly reactive especially in the presence of reducing sub-stances and moisture. Safe techniques must be utilized whenhandling UF6. Suitable handling procedures are described inUSEC-651.7.2 Fol
33、low all safety procedures for handling UF6as pro-vided by your facility.7.3 Review Material Safety Data Sheets for UF6and allchemicals associated with this method prior to performance.7.4 Perform subsampling operations in a fume hood that hasbeen verified operable and has undergone regular inspectio
34、nsto ensure proper airflow.7.5 When released to atmosphere, gaseous UF6reacts withmoisture to produce HF gas and UO2F2particulates (a whiteamorphous solid) and becomes readily visible as a white cloud.The corrosive nature of HF and UF6can result in skin burnsand lung impairment. Medical evaluation i
35、s mandatory aftercontact with HF or UF6. When water-soluble UO2F2is inhaledor ingested in large quantities it can be toxic to the kidneys.8. Principles8.1 The essential purpose of the sample is to be represen-tative of the bulk material for the purpose of determiningcompliance with the applicable ma
36、terial specification. Toensure that the sample is representative for this purpose, certainprinciples, as described below, must be observed.8.2 Special attention must be given to ensuring that the bulkmaterial, from which the sample is withdrawn, is homoge-neous. In practice, the low viscosity, and h
37、ence easy mobilityof liquid UF6facilitates the process of homogenization by theaction of convection currents within the bulk upon heating. ItNOTE 1All lines in direct contact with liquid UF6are38 in. (9.5 mm) Monel tubing.NOTE 2All other lines are “ in. (9.5 mm) 316 SS tubing.NOTE 3Valves 13 are Mon
38、el below sealed valves that can be operated from outside the hotbox.NOTE 4Valves 48 are 316 SS below sealed valves.NOTE 5Flange connections are equipped with helicoflex (high pressure) gaskets.FIG. 2 Subsample Rig Used for Procedure 2C 1689 08a3is necessary to determine and establish for each set of
39、 subsampling equipment the physical conditions, normally aFIG. 3 Isotopic Abundance Sample Tube.FIG. 4 Example of a Polychlorotrifluoroethylene Subsample TubeC 1689 08a4combination of the minimum time and temperature for whichliquefied uranium hexafluoride is held, which guaranty homo-geneity of the
40、 bulk UF6.8.3 Uranium hexafluoride is very reactive and corrosive. Itreacts readily with water, atmospheric moisture and manyorganic materials. For reasons of safety and to avoid contami-nation, precautions must be taken to avoid contact with suchmaterials. The subsampling equipment and subsample tu
41、be aretherefore fabricated to appropriate high standards of vacuumintegrity, and components in direct contact with liquid UF6areFIG. 5 Example of a Polychlorotrifluoroethylene Knock-out TubeFIG. 6 Filter Disc Unit for Determination of Soluble and Insoluble ChromiumC 1689 08a5made from nickel, high n
42、ickel alloys, or materials havingcomparable resistance to UF6corrosion. The formation of aninert fluoride layer is often an important feature of UF6corrosion resistance, and hence internal surfaces are generallyconditioned with a suitable fluorinating agent, sometimes UF6itself.8.4 Cross-contaminati
43、on may occur between subsequentsamples taken using the same equipment, and appropriateprecautions must be taken to prevent this. It is thereforerecommended that, before taking definitive samples, the equip-ment is flushed through with an aliquot of the material to besampled. This is normally accompl
44、ished by taking an initialvolume which is then rejected and not used for definitiveanalysis. Alternative procedures to prevent cross-contamination are possible and should be validated individu-ally.8.5 If sample bottles are taken for an analytical need such asliquid UF6subsampling for P10 tubes or l
45、iquid UF6transfer forFTIR quantification, it is recommended, in order to minimizethe gas phase contribution to the sample bottle, to fill the bottlewith more than 10 % of its total volume.9. Subsampling Schemes for UF6Specification Analyses9.1 The number and type of subsamples taken from asample bot
46、tle (typically 1S or 2S bottle) depends both on thesampling requirements (natural UF6, enriched UF6and particu-lar agreements between buyer and seller) and the availableequipment. Below are some typical examples of analyses thatcan be performed and their appropriate subsample tubes.9.2 Uranium isoto
47、pic abundance analyses can be performedusing a isotopic abundance sample tube (Fig. 3, uraniumcontent appr. 4 g), a polychlorotrifluoroethylene tube (P10, Fig.4, UF6 content7g)oralternatively measured directly in thegas phase using the 1S or 2S sample bottle.9.3 For uranium purity determination a po
48、lychlorotrifluoro-ethylene tube (P10, Fig. 4) containing7gofUF6can beused.9.4 Determination of (metallic) impurities, for example B,Si, Tc, Cl, Br, etc., can be performed using a polychlorotrif-luoroethylene tube (P-10, Fig. 4,UF6content7g).9.5 Soluble and insoluble chromium analyses can be per-form
49、ed using a nickel filter disc (Fig. 6) and a polychlorotrif-luoroethylene tube (UF6content 15-20 g).9.6 Subsampling for hydro-, chloro-, and halohydrocarbonanalysis can be performed using a gas sample cylinder # 9.993 103Pa. Alternatively the analysis can be performed directlyon the 1S or 2S sample bottle.9.7 In order to achieve the typically required detectionlimits for the determination impurities in reprocessed UF6(Pu,Np,232U, g-activity of fission products), larger amounts of UF6are required (typically 50 g). For this purpose eithe
