VVER-1000 SFAT-Specification of an industrial prototype: Interim report on Task FIN A 1073 of the Finnish Support Programme to IAEA Safeguards

The project to develop a Spent Fuel Attribute Tester (SFAT) for Ukrainian VVER-1000 facilities is going on under the Task FIN A 1073 of the Finnish Support Programme to the IAEA safeguards. In the SFAT method [1] the verification is based on an unambiguous detection of gamma radiation of the fission products. This is implemented by detecting the radiation emitted by a fuel assembly with a mobile gamma-spectroscopic instrument consisting of a collimator arrangement and a detector unit. The fuel assemblies stored in a wet storage are not moved during the verification measurement. The principal target is the radiation characteristic to 137Cs. For short cooled assemblies also 144Pr can be used as the target fission product nuclide. The generic IAEA SFAT concept has been adapted to the special conditions at the Ukrainian facilities. The requirements of the End User (IAEA), the State Nuclear Safety Authority (NRA) and the facilities have been taken into account and included in the specifications. Since the issuance of the first interim report [2], additional measurements were conducted at the Zaporozhye NPP to ensure the feasibility of the suggested measurement geometry and to test whether the SFAT device could be operated using the refuelling machine. A clear answer to the optimal measurement geometry and the detector choice was also obtained during this first phase of the task. Basing on the measurement results and the operational experience, the technical specifications for an industrial SFAT prototype are formulated. The technical specifications presented in this report and in the previous report [2] have been approved by the Ukrainian State Authority and one of the facility operators, the Zaporozhye NPP. A procedure has been started for getting the approval of the other Ukrainian operators. Lyhyt englanninkielinen tiivistelmä JURE-tietokantaa varten (vapaaehtoinen osio, ei koske VTT:n julkaisusarjoja) The project to develop a Spent Fuel Attribute Tester (SFAT) for Ukrainian VVER-1000 facilities is going on under the Task FIN A 1073 of the Finnish Support Programme to the IAEA safeguards. In the SFAT method [1] the verification is based on an unambiguous detection of gamma radiation of the fission products. This is implemented by detecting the radiation emitted by a fuel assembly with a mobile gamma-spectroscopic instrument consisting of a collimator arrangement and a detector unit. The fuel assemblies stored in a wet storage are not moved during the verification measurement. The principal target is the radiation characteristic to 137Cs. For short cooled assemblies also 144Pr can be used as the target fission product nuclide. The generic IAEA SFAT concept has been adapted to the special conditions at the Ukrainian facilities. The requirements of the End User (IAEA), the State Nuclear Safety Authority (NRA) and the facilities have been taken into account and included in the specifications. Since the issuance of the first interim report [2], additional measurements were conducted at the Zaporozhye NPP to ensure the feasibility of the suggested measurement geometry and to test whether the SFAT device could be operated using the refuelling machine. A clear answer to the optimal measurement geometry and the detector choice was also obtained during this first phase of the task. Basing on the measurement results and the operational experience, the technical specifications for an industrial SFAT prototype are formulated. The technical specifications presented in this report and in the previous report [2] have been approved by the Ukrainian State Authority and one of the facility operators, the Zaporozhye NPP. A procedure has been started for getting the approval of the other Ukrainian operators.