Blend Down Monitoring System Fissile Mass Flow Monitor Implementation at the Siberian Chemical Enterprise, Seversk, Russia

摘要

In this paper the implementation plans and preparations for installation of the Fissile Mass Flow Monitor (FMFM) equipment at the Siberian Chemical Enterprise (SChE), Seversk, Russia, will be presented. The FMFM, developed by Oak Ridge National Laboratory (ORNL), is part of the Blend Down Monitoring System (BDMS) for the U.S. Department of Energy (DOE) Highly Enriched Uranium (HEU) Transparency Implementation Program (TIP). The BDMS provides confidence to the United States that the Russian nuclear facilities supplying the lower assay (~4%) product low enriched uranium (P-LEU) to the United States from down-blended weapon-grade HEU are meeting the nonproliferation goals of the 1993 HEU Purchase Agreement signed between the Russian Federation and the United States. The first BDMS has been operational at Ural Electrochemical Integrated Plant (UEIP), Novouralsk, since February 1999. The second BDMS became operational at Electro Chemical Plant (ECP), Zelenogorsk, in March 2003. These systems are successfully providing HEU transparency data to the United States. The third BDMS was successfully installed on the HEU down-blending tee in the SChE Enrichment Plant in October 2004. The FMFM makes use of a set of thermalized californium-252 (252Cf) spontaneous neutron sources for modulated fission activation of the uranium hexafluoride (UF6) gas stream for measuring the 235U fissile mass flow rate. To do this, the FMFM measures the transport time of the fission fragments created from the fission activation process under the modulated source to the downstream detectors by detecting the delayed gamma rays from the fission fragments retained in the flow. The FMFM provides unattended nonintrusive measurements of the 235U mass flow of the UF6 gas in the blending tee legs of HEU, the LEU blend stock, and the resulting P-LEU. The FMFM also confirms that HEUF6 gas identified in the HEU leg flows through the blending tee into the P-LEU leg. This paper will discuss details of the SChE FMFM equipment characteristics as well as the technical installation requirements.