ASTM C1689-2008 Standard Practice for Subsampling of Uranium Hexafluoride.pdf

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1、Designation: C 1689 08Standard 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 paren

2、theses 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 conformance

3、 with C 1052, intosmaller sample containers, which are required for laboratoryanalyses.1.2 It is assumed that the liquid UF6being sampled com-prises a single quality and quantity of material. This practicedoes not address any special additional arrangement that mightbe required for taking proportion

4、al or composite samples.1.3 The number of samples to be taken, their nominalsample weight, and their disposition shall be agreed uponbetween the parties.1.4 The scope of this practice does not include provisionsfor preventing criticality incidents.1.5 This standard does not purport to address all of

5、 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:2C 787 Specification for

6、Uranium Hexafluoride for Enrich-mentC 859 Terminology Relating to Nuclear Materials3C 996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC 761 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemical Analysis ofUranium HexafluorideC 1052 Practice

7、for Bulk Sampling of Liquid UraniumHexafluoride2.2 Other Documents:ANSI N14.1 Uranium Hexafluoride: Packaging for Trans-port4ISO/DIS 7195 Packaging of Uranium Hexafluoride (UF6)for Transport5USEC-651 The UF6Manual: Good Handling Practices forUranium Hexafluoride, latest revision63. Terminology3.1 Te

8、rms 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859 except for the following:3.1.1 sample bottlethe vessel (typically a 1S or 2S bottle)into which the sample of UF6is withdrawn from the containerfor transfer to the laboratory, analysis or dispatch to thecustomer.3.1.2 subsample tubethe small ve

9、ssel (for example, a P10tube7) into which a subsample of UF6is withdrawn from thesample bottle for analysis of UF6quality or dispatch to thecustomer.3.1.3 subsample rigthe equipment to perform the transferof liquid UF6from the sample bottle into the subsample tube,typically a vacuum manifold equippe

10、d 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) homogenizing of liquefied UF6by agitation before liquidtransfer and (2) homogenizing of liquefied UF6by convectionbefore l

11、iquid transfer. The first method involves homogeniza-tion of liquified UF6in sample bottle by vigorous shaking.Subsequently the sample bottle is inverted and connected to thetop of a heated vacuum-manifold system, and the subsample1This practice is under the jurisdiction of ASTM Committee C26 on Nuc

12、learFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved Aug. 1, 2008. Published September 2008.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSt

13、andards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from International Organization for Standardization (ISO),

14、1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.6Available from United States Enrichment Corp., 6903 Rockledge Dr., Bethesda,MD 20817, http:/.7Polychlorotrifluoroethylene P10 tubes are widely accepted by the industry forsubsample collection and subsequent

15、UF6quality analyses or dispatch to thecustomer. Other types of subsample tubes, for example P-20, P-80 or 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

16、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.tube 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 containin

17、g solid UF6is connected to the top of amanifold system, and a subsample tube is attached to theappropriate 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 all

18、ow for complete homogenization ofthe liquid UF6by convection. Subsequently the liquid UF6isallowed to flow 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. For

19、safety and quality reasons, sample bottles and an subsampletubes shall be clean, dry, and empty before filling.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 g

20、iven type of sample bottle, the detailed configuration,for example valve orientation, terminal fittings and the 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 norm

21、ally produced and handledin large (typically 1- to 14-ton) quantities and must, thereforebe characterized by reference to representative samples. Thequantities involved, physical properties, chemical reactivity,and hazardous nature of UF6are such that for representativesampling, specially designated

22、 equipment must be used andoperated in accordance with the most carefully controlled andstringent procedures. This practice indicates appropriate prin-ciples, equipment and procedures currently in use for subsam-pling of liquid UF6. It is used by UF6converters, enrichers andfuel fabricators to revie

23、w the effectiveness of existing proce-dures or to design equipment and procedures for future use.Other subsampling procedures such as UF6vapor sampling arenot directly representative of the chemical quality of liquidUF6.5.2 It is emphasized that this test guide is not meant toaddress conventional or

24、 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 nickel, high nickel alloys, ormaterials having comparable resistance to UF6corrosion.6.3

25、Polychlorotrifluoroethylene Subsample Tube and Clos-ing Disc (Fig. 3)The tube must be of uniform density, freefrom cracks or occlusions and able to withstand temperaturesfrom 195C to +150C. Materials of construction in directcontact with liquid UF6are made from polychlorotrifluoroet-hylene, PTFE/TFE

26、 (gaskets), or materials having comparableresistance to UF6corrosion.6.4 Flare Nut and PlugFlare nuts and plugs for subsampletube closure, storage and transport can be constructed fromMonel, nickel, high nickel alloys or 316 SS.6.5 Gaseous Isotopic Abundance Sample Tube (Fig. 4).NOTE 1All lines are3

27、8 in. (9.5 mm) Monel tubing.NOTE 2All valves are Monel diaphragm type 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 polychlorotrifluoroethyl

28、ene tube is isolated fromthe system, but the lines from valve 1 to valve 3 and to the bulk container are open.FIG. 1 Subsample Rig Used for Procedure 1C16890826.6 Polychlorotrifluoroethylene Knockout Cylinder (Fig. 5),closed with a Cajon M-16 VCR-1 female nut and an M-16VCR-4 male nut or equivalent.

29、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 chromium (Fig.6).NOTE 2The filterdisc should weigh approximately 1 g. It should bemade of nickel p

30、owder 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 Flask, for liquid nitrogen, stainless steel.7. Hazards7.1 Uranium hexafluoride (UF6) is radioact

31、ive, 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 Follow all safety procedures for handling UF6as pro-vided by your facility.7.3 Review Material S

32、afety 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 inspectionsto ensure proper airflow.7.5 When released to atmosphere, gaseous UF6reacts withmoisture to

33、 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 is mandatory aftercontact with HF or UF6. When water-soluble UO2F2is inhaledor ingested in lar

34、ge 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 material specification. Toensure that the sample is representative for this purpose, certainpri

35、nciples, 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 hence easy mobilityof liquid UF6facilitates the process of homogenization by theaction of conv

36、ection currents within the bulk upon heating. Itis necessary to determine and establish for each set ofNOTE 1All lines in direct contact with liquid UF6are38 in. (9.5 mm) Monel tubing.NOTE 2All other lines are “ in. (9.5 mm) RVS-316 tubing.NOTE 3Valves 13 are monel below sealed valves that can be op

37、erated from outside the hotbox.NOTE 4Valves 48 are RVS-316 below sealed valves.NOTE 5Flange connections are equipped with helicoflex (high pressure) gaskets.FIG. 2 Subsample Rig Used for Procedure 2C1689083subsampling equipment the physical conditions, normally acombination of the minimum time and t

38、emperature for whichliquefied uranium hexafluoride is held, which guaranty homo-geneity of the 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

39、 must be taken to avoid contact with suchFIG. 3 Isotopic Abundance Sample Tube.FIG. 4 Example of a Polychlorotrifluoroethylene Subsample TubeC1689084materials. The subsampling equipment and subsample tube aretherefore fabricated to appropriate high standards of vacuumintegrity, and components in dir

40、ect contact with liquid UF6aremade from nickel, high nickel alloys, or materials havingcomparable resistance to UF6corrosion. The formation of aninert fluoride layer is often an important feature of UF6FIG. 5 Example of a Polychlorotrifluoroethylene Knock-out TubeFIG. 6 Filter Disc Unit for Determin

41、ation of Soluble and Insoluble ChromiumC1689085corrosion resistance, and hence internal surfaces are generallyconditioned with a suitable fluorinating agent, sometimes UF6itself.8.4 Cross-contamination may occur between subsequentsamples taken using the same equipment, and appropriateprecautions mus

42、t 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 accomplished by taking an initialvolume which is then rejected and not used for definitiveanalysis. Alternat

43、ive 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 liquid UF6transfer forFTIR quantification, it is recommended, in order to minimizethe gas phase contri

44、bution 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 bottle (typically 1S or 2S bottle) depends both on thesampling requirements (natural UF6, enriched UF6an

45、d 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 isotopic abundance analyses can be performedusing a isotopic abundance sample tube (Fig. 3, uraniumcontent

46、 appr.4g),apolychlorotrifluoroethylene tube (P10,Fig. 4, UF6 content7g)oralternatively measured directly inthe gas phase using the 1S or 2S sample bottle.9.3 For uranium purity determination a polychlorotrifluoro-ethylene tube (P10, Fig. 4) containing7gofUF6can beused.9.4 Determination of (metallic)

47、 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-formed using a nickel filter disc (Fig. 6) and a polychlorotrif-luoroethylene tube (UF6content 15-20 g).9.6 S

48、ubsampling for hydro-, chloro-, and halohydrocarbonanalysis can be performed using a gas sample cylinder # 75mm Hg (# 9.99 3 103Pa). Alternatively the analysis can beperformed directly on the 1S or 2S sample bottle.9.7 In order to achieve the typically required detectionlimits for the determination

49、impurities in reprocessed UF6(Pu,Np,232U, g-activity of fission products), larger amounts of UF6are required (typically 50 g). For this purpose either apolychlorotrifluoroethylene knock-out cylinder (Fig. 5)oranumber of polychlorotrifluoroethylene tubes (P10, Fig. 4) canbe used.9.8 Finally, it has to be emphasized that other types ofsubsample holders can also be used as long as the requirementsin 8.3 are met.10. Procedure 110.1 System Preparation:10.1.1 Place the bulk sample container in a water bath at90C 6 3C.10.1.2 After the UF6has been