1、Designation: C1703 18Standard Practice forSampling of Gaseous Uranium Hexafluoride for Enrichment1This standard is issued under the fixed designation C1703; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 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 practice covers methods for withdrawing represen-tative sample(s) of uranium hexafluoride (UF6) during atransfer occurring in t
3、he gas phase. Such transfer in the gasphase can take place during the filling of a cylinder during acontinuous production process, for example the distillationcolumn in a conversion facility. Such sample(s) may be usedfor determining compliance with the applicable commercialspecification, for exampl
4、e Specification C787.1.2 Since UF6sampling is taken during the filling process,this practice does not address any special additional arrange-ments that may be agreed upon between the buyer and theseller when the sampled bulk material is being added toresidues already present in a container (“heels r
5、ecycle”). Sucharrangements will be based on QA procedures such as trace-ability of cylinder origin (to prevent for example contaminationwith irradiated material).1.3 If the receiving cylinder is purged after filling andsampling, special verifications must be performed by the userto verify the repres
6、entativity of the sample(s). It is thenexpected that the results found on volatile impurities with gasphase sampling may be conservative.1.4 This practice is only applicable when the transfer occursin the gas phase. When the transfer is performed in the liquidphase, Practice C1052 should apply. This
7、 practice does notapply to gas sampling after the cylinder has been filled sincethe sample taken will not be representative of the cylinder.1.5 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 t
8、o establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Prin
9、ciples for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C761 Test Methods for Chemical, Mass Spectrometric,Spectrochemical, Nuclear, and Radiochemica
10、l Analysis ofUranium HexafluorideC787 Specification for Uranium Hexafluoride for Enrich-mentC859 Terminology Relating to Nuclear MaterialsC1052 Practice for Bulk Sampling of Liquid UraniumHexafluorideC1838 Practice for Cleaning for 1S and 2S Bottles2.2 Other Document:ISO 7195 Packaging of Uranium He
11、xafluoride (UF6) forTransport33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 containera vessel either holding or receiving bytransfer, the UF6to be sampled; it may consist of, for example,a fixed vessel in a UF6handling plant or a cylinder to be usedfor the transport of UF6.3
12、.1.2 sample vesselthe small vessel into which the sampleof UF6is withdrawn for analysis in the laboratory for charac-terization. It can be a 1S or 2S bottle or a PCTFE(polychlorotrifluoroethylene)/PTFE (polytetrafluoroethylene)pot or tube or any other type of cylinder compatible with UF6.3.2 For def
13、initions of terms used in this test method but notdefined herein, refer to Terminology C859.4. Summary of Practices4.1 A common method of withdrawing gas UF6for sam-pling utilizes a continuous withdrawal using for example acapillary to produce one sample. Depending on the pressure1This practice is u
14、nder the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.02 on Fuel andFertile Material Specifications.Current edition approved Feb. 1, 2018. Published February 2018. Originallyapproved in 2008. Last previous edition approved in 2013 as C1
15、703 08 (2013).DOI: 10.1520/C1703-18.2For 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 American
16、National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recogniz
17、ed principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1and temperature conditions during the transfer, the sampledUF6is ei
18、ther liquefied or solidified in the sample vessel.4.2 An example of this is the sampling of UF6coming froma distillation column. In such case, the sampled gas UF6can becondensed in the liquid phase in the sampling vessel. Therepresentative sample is then homogenized before analysis atthe laboratory.
19、 It is assumed that the flow rate from thedistillation is either constant (for example using a mass flowcontroller) or that the capillary will take its variation inaccount.4.3 During sampling, the presence of residues may havesignificant implications for the quality of the UF6. For safetyand quality
20、 reasons, cylinders and bottles shall be clean, dry,and empty before filling.5. Significance and Use5.1 Uranium hexafluoride is normally produced and handledin large (typically 1 to 14-ton) quantities and must, therefore,be characterized by reference to representative samples (seeISO 7195). The samp
21、les are used to determine compliance withthe applicable commercial specification C787. The quantitiesinvolved, physical properties, chemical reactivity, and hazard-ous nature of UF6are such that for representative sampling,specially designed equipment must be used and operated inaccordance with the
22、most carefully controlled and stringentprocedures. This practice can be used by UF6converters toreview the effectiveness of existing procedures or as a guide tothe design of equipment and procedures for future use.5.2 The intention of this practice is to avoid liquid UF6sampling once the cylinder ha
23、s been filled. For safety reasons,manipulation of large quantities of liquid UF6should beavoided when possible.5.3 It is emphasized that this practice is not meant to addressconventional or nuclear criticality safety issues.6. Hazards6.1 Because of its chemical, radiochemical, and toxicproperties, U
24、F6is a hazardous material.7. Principles7.1 The essential purpose of the sample(s) is to be repre-sentative of the total material which has been transferred. It isthe responsibility of the user to determine the way of continu-ous sampling or the number of samples and time distributionthat are necessa
25、ry to be representative, depending on theprocess variability. For example, in case of the presence of highlevel of very volatile impurities, additional samples may haveto be taken at the beginning of the transfer.7.1.1 It is recommended to validate the gas sampling usinga comparison on several cylin
26、ders with liquid sampling afterfilling. Statistically significant sampling basis and requirementshould be established. Adequacy shall be demonstrated byquality assurance procedures.7.1.2 In case of the presence of volatile impurities close tothe specification (for example within 80 % of thespecifica
27、tion), a confirmation using liquid sampling may benecessary.7.2 Uranium hexafluoride is very reactive and corrosive. Itreacts readily with water, atmospheric moisture, certain metals,and many organic materials. For reasons of safety and to avoidcontamination, precautions must be taken to avoid conta
28、ct withsuch materials. The sampling equipment is therefore fabricatedto appropriate high standards of vacuum and high temperatureintegrity, and components in direct contact with UF6are madefrom nickel, high-nickel alloys, or materials having equivalentresistance to UF6corrosion. The formation of an
29、inert fluoridelayer is often an important feature of UF6corrosion resistance,and hence, internal surfaces are generally conditioned with asuitable fluorinating agent, sometimes UF6itself.7.3 Cross-contamination may occur between subsequentsamples taken using the same equipment, and appropriateprecau
30、tions 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 accomplished by taking an initialvolume which is then rejected and not used for definitiveanalysis.
31、 Alternative procedures to prevent cross-contamination are possible and should be validated individu-ally.8. Procedure for Continuous Sampling During Filling ofa Transport Cylinder8.1 Sample Preparation:8.1.1 The equipment consists of a continuous samplingvessel that has the ability to collect a des
32、ired weight/volume ofUF6during the filling of a UF6transport cylinder, and a samplemanifold used for obtaining the aliquot of UF6from thecontinuous sampling vessel. The sampling manifold can be apermanent (fixed) manifold, and can be the same manifoldused for sampling straight from a container. The
33、continuoussampling vessel should be fed gaseous UF6from a slip streamat the exit of the supplying source (for example, a distillationcolumn) that is supplying UF6to a transport cylinder.8.1.2 The continuous sampling vessel should be maintainedat a temperature and pressure adequate for condensing and
34、maintaining UF6in liquid phase, to allow for homogenizationby the action of convection currents within the bulk liquid. Thecontinuous sampling vessel should be operated so that acomposite sample of UF6could be withdrawn during the entirefilling cycle of a transport cylinder. The continuous samplingv
35、essel should be able to be isolated from the supply so thatadequate purging of the vessel and supply lines can beaccomplished after the sampling cycle is complete.8.1.3 The continuous sampling vessel should be opened todraw a sample from the UF6feed line at the beginning of fillingof the transport c
36、ylinder. At the completion of filling thetransport cylinder the continuous sampler should be isolatedfrom the feed line.8.1.4 The sampling manifold should be appropriately sizedto contain the quantity of UF6required for a single sample andnormally, consists of the manifold and associated pipe work o
37、rmay also include an additional metering volume (pipette). Thetotal graduated volume of the connected equipment (excludingthe vacuum system) should not exceed the designated maxi-mum fill volume of the attached sample vessels. Certain valvesC1703 182may be remotely operated as necessary. The samplin
38、g equip-ment should be heated to prevent the solidification of UF6.8.1.5 The weight/volume of UF6collected in the continuoussampling vessel should be monitored by load cell, so to notoverfill the continuous sampling vessel. This sample volumeshould be adequate for flushing the piping between thecont
39、inuous sampling vessel and the sampling manifold, as wellas the manifold itself. The total volume of the sample manifoldshould be transferred to the sample cylinder without anyventing.8.2 Sampling:8.2.1 The UF6can now be sampled into a desired number ofsample vessels from the continuous sampling ves
40、sel.8.2.2 Attach the sample vessel to the sampling manifold (ifa fixed manifold is used) or attach the sampling equipment,including sample vessels, at the relevant location on the UF6runoff line from the continuous sampler. Evacuate and test theequipment to ensure vacuum integrity. Isolate the sampl
41、evessels from the sample manifold.8.2.3 Open the valves on the continuous sampling vessel toallow liquid UF6to flow to the sampling manifold.8.2.4 Establish liquid transfer of UF6from the UF6continu-ous sampling vessel to the sampling manifold.Allow a suitableamount of UF6to flush the sampling manif
42、old and piping fromthe continuous sampler to manifold.8.2.5 At an appropriate time, open the valve and withdrawthe required quantity of UF6into the graduated volume. Thismay be indicated by the use of suitable temperature sensors,pressure transducers, strain gauges, a line of sight window atthe top
43、of the transfer pipette, or combinations thereof.8.2.6 Close the manifold valve and open the first samplevessel valve to transfer the sample. The equipment should bedesigned to allow transfers to take place using the influence ofgravity and differential pressures induced by temperaturegradients. For
44、 this reason, it may be necessary to cool thereceiving vessels.8.2.7 The first sample may be used to condition internalsurfaces of the equipment by suitable manipulation of thevacuum system or rejected to prevent cross-contaminationfrom earlier materials or both.8.2.8 Isolate the sample vessel from
45、the sampling manifold.8.2.9 If successive samples are to be taken, repeat 8.2.5 and8.2.6.8.2.10 At the completion of sampling, close all the samplevessel valves. Any residual UF6in the equipment, samplinglines, and continuous sampling vessel is withdrawn using drygas or evacuated into a UF6trap. Pur
46、ge all equipment with drygas several times to assure any residual vapors have beenremoved.8.2.11 Remove, identify, cap, and weigh the sample vessels.Local safety regulations may demand that the UF6be allowedto cool and solidify before this operation is carried out.9. Keywords9.1 bulk sampling; nucle
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