DOWN-BLENDING HIGH-ENRICHED URANIUM IN KAZAKHSTAN

To achieve the goal of reducing inventories of High Enriched Uranium (HEU) within its borders, the Government of Kazakhstan arranged to have surplus unirradiated HEU fuel from a shutdown reactor down blended at the Ulba metallurgical facility in Ust-Kamenogorsk. In the glove box line for processing HEU, uranium dioxide pellets were removed from the fuel rods and converted to U3O8 powder by oxidation in air. Because of criticality considerations the HEU powder was dryblended with low-enriched uranium (LEU) powder and dissolved so that the resulting LEU solution could be introduced to the parts of the plant that were certified for processing LEU with enrichment less than 15%. Since the down blending campaign would have limited duration, the IAEA determined that the most cost effective approach would be to use standard surveillance equipment, on-site nondestructive assay measurements, random sampling of nuclear material for destructive analysis and continuous inspector presence during active processing. Specially designed equipment (other than the IAEA’s standard optical surveillance system) to enable unattended or remote monitoring would not be cost effective for a simple, un-automated hands-on process. Inspectors carried out verification measurements on 100% of the HEU and observed the dissolution of the mixed powders to provide in-depth assurance that LEU could not be substituted to conceal diversion of HEU. This work demonstrated that the IAEA with the cooperation of the facility operator could provide unimpeachable assurance regarding the elimination of weapons-usable materials while simultaneously avoiding processing delays and using inspection resources most efficiently. The IAEA believes this model can be extended to future opportunities for downgrading HEU materials that are not covered under ongoing materials disposition programs. For example, the down blending facilities in Kazakhstan remain available to process materials from other sources. For each specific case the IAEA will present appropriate safeguards concepts that would be applicable to finite-duration campaigns at this or other facilities and that would provide a high level of safeguards assurance for downgrading HEU without continuous inspector presence, and without the installation of costly, specially designed instrumentation that would have limited flexibility to accommodate a variety of processes, and with acceptable impact on the processing operations.