AVLIS Criticality risk assessment

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Evaluation of criticality safety has become an important task in preparing for the Atomic Vapor Laser Isotope Separation (AVLIS) uranium enrichment runs that will take place during the Integrated Process Demonstration (IPD) at Lawrence Livermore National Laboratory (LLNL). This integrated operation of AVLIS systems under plant-like conditions will be used to verify the performance of process equipment and to demonstrate the sustained integrated enrichment performance of these systems using operating parameters that are similar to production plant specifications. Because of the potential criticality concerns associated with enriched uranium, substantial effort has been aimed towards understanding the potential system failures of ... continued below

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11 p.

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Brereton, S. J. April 29, 1998.

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Evaluation of criticality safety has become an important task in preparing for the Atomic Vapor Laser Isotope Separation (AVLIS) uranium enrichment runs that will take place during the Integrated Process Demonstration (IPD) at Lawrence Livermore National Laboratory (LLNL). This integrated operation of AVLIS systems under plant-like conditions will be used to verify the performance of process equipment and to demonstrate the sustained integrated enrichment performance of these systems using operating parameters that are similar to production plant specifications. Because of the potential criticality concerns associated with enriched uranium, substantial effort has been aimed towards understanding the potential system failures of interest from a criticality standpoint, and evaluating them in detail. The AVLIS process is based on selective photoionization of uranium atoms of atomic weight 235 (U-235) in a vapor stream, followed by electrostatic extraction. The process is illustrated in Figure 1. Two major subsystems are involved: the uranium separator and the laser system. In the separator, metallic uranium is fed into a crucible where it is heated and vaporized by an electron beam. The atomic U-235/U-238 vapor stream moves away from the molten uranium and is illuminated by precisely tuned beams of dye laser light. Upon absorption of the tuned dye laser light, the U-235 atoms become excited and eject electrons (become photoionized), giving them a net positive charge. The ions of U-235 are moved preferentially by an electrostatic field to condense on the product collector, forming the enriched uranium product. The remaining vapor, which is depleted in U-235 (tails), passes unaffected through the photoionization/extractor zone and accumulates on collectors in the top of the separator. Tails and product collector surfaces operate at elevated temperatures so that deposited materials flow as segregated liquid streams. The separated uranium condensates (uranium enriched in U-235 and uranium depleted in U-235) are cooled and accumulated in solid metallic form in canisters. The collected product and tails material is weighed and transferred into certified, critically safe, shipping containers (DOT specification 6M with 2R containment vessel). These will be temporarily stored, and then shipped offsite either for use by a fuel fabricator, or for disposal. Tails material will be packaged for disposal. A criticality risk assessment was performed for AVLIS IPD runs. In this analysis, the likelihood of occurrence of a criticality was examined. For the AVLIS process, there are a number of areas that have been specifically examined to assess whether or not the frequency of occurrence of a criticality is credible (frequency of occurrence > 10-6/yr). In this paper, we discuss only two of the areas: the separator and canister operations.

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11 p.

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OSTI as DE98058847

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  • Conference on integrating safety analysis into safety management, Park City, UT (United States), 15-19 Jun 1998

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  • Other: DE98058847
  • Report No.: UCRL-JC--130693
  • Report No.: CONF-980616--
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 672324
  • Archival Resource Key: ark:/67531/metadc710289

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • April 29, 1998

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  • Sept. 12, 2015, 6:31 a.m.

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  • May 8, 2017, 12:42 p.m.

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Brereton, S. J. AVLIS Criticality risk assessment, article, April 29, 1998; California. (digital.library.unt.edu/ark:/67531/metadc710289/: accessed October 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.