【国外标准】 Standard Practice for Sampling of Gaseous Enriched Uranium Hexafluoride

5.1 The standard method for taking representative UF6 sample from a cylinder is collecting from UF6 liquid phase. Homogeneity of material is obtained by the basic indicator, that is, content of uranium isotope. Representativeness of a sample by other indicators such as content of highly volatile admixtures (boron fluoride, silicon fluoride, organic impurities), admixtures generating non-volatile fluorides may not be satisfactory owing to differences between physical properties of admixture and UF6. Nevertheless, such sampling is widely applied during the product quality control due to the fact that liquid phase process is applied when filling transport containers both for feedstock UF6 and enriched one. Refer to Practice C1052 for UF6 liquid phase sampling practice.5.2 Uranium hexafluoride is normally produced and handled in large (typically 1 to 14-ton) quantities and must, therefore, be characterized by reference to representative samples (see ISO 7195:2005). The samples are used to determine compliance with the applicable commercial Specification C996. The quantities involved, physical properties, chemical reactivity, and hazardous nature of UF6 are such that for representative sampling, specially designed equipment must be used and operated in accordance with the most carefully controlled and stringent procedures. This practice can be used by UF6 enrichers to review the effectiveness of existing procedures or as a guide to the design of equipment and procedures for future use.5.3 It is emphasized that this practice is not meant to address conventional or nuclear criticality safety issues.1.1 This practice covers the methods for withdrawing samples of enriched uranium hexafluoride (UF6) during and after a transfer occurring in the gas phase in order to determine compliance with Specification C996. It is applicable to the filling of a transport UF6 container (30B cylinder or 1 m3 vertical container) at a centrifuge enrichment facility that has been fed with UF6 that complies with Specification C787.1.2 Since UF6 sampling is taken during the filling process, this practice does not address any special additional arrangements that may be agreed upon between the buyer and the seller when the sampled bulk material is being added to residues already present in a container (“heels recycle”). Such arrangements will be based on QA procedures such as traceability of cylinder origin (to prevent, for example, contamination with irradiated material).1.3 This practice is only applicable when the transfer occurs in the gas phase. When the transfer is performed in the liquid phase, Practice C1052 should apply.1.4 The scope of this practice does not include provisions for preventing criticality incidents.1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.