IAEA Neutron Multiplicity Measurements at the KAMS Facility

Since 1994, the International Atomic Energy Agency (IAEA) has been safeguarding approximately one metric ton of excess weapons plutonium at the Rocky Flats Environmental Technology Site (RFETS). The IAEA has been verifying the mass of these materials using a neutron multiplicity counter [1]. The materials are being shipped to the K-Area Material Storage (KAMS) facility at Westinghouse Savannah River Site (WSRS) because of the closure of RFETS. Transferring safeguards from RFETS to the KAMS facility present many difficult measurement challenges. The materials are being shipped in 9975-shipping containers and are required to remain in these containers while the materials are stored at the KAMS facility. The fabrication of these containers substantially affects the radiation signature used to assay the mass. A neutron multiplicity counter specifically designed to measure items inside 9975-shipping containers was used by the IAEA to measure materials. Since this counter belongs to the KAMS facility, the IAEA is using its own computers and electronics to assay the items. In addition, the IAEA uses different software with different calibration parameters than are used by the KAMS facility. The IAEA developed three working reference standards at RFETS to test the performance of the KAMS neutron multiplicity counter prior to beginning the Initial Physical Inventory Verification (IPIV). These standards included a pure oxide, an impure oxide, and a mixed oxide. Also, a 252Cf reference source was procured for IAEA use to ensure that the counter is working properly. This source was also used to evaluate the effect that the 9975-shipping container has on the assay. We will present the measurements of the 252Cf source and the working reference standards at KAMS. We will also present results from the IPIV at KAMS.