Safeguards in the prototype fast breeder reactor MONJU

The verification of the fuel assemblies flows is designed to be made with fuel flow monitors measuring radiation, which can abridge inspector attendance during the fuel handling. The monitors consist of ex-vessel radiation monitors (EVRMs) and an exit gate monitor (EXGM). EVRMs are linked to the ex-vessel transfer machine, which charges and discharges fuel assemblies into and out of the core and the EVST (a sodium tank located in an area adjacent to the reactor containment building which temporarily stores new and irradiated fuel assemblies). Flows of fuel assemblies into and out of the core and the EVST can be monitored by EVRMs, and the flows of irradiated fuel assemblies into the spent fuel pond (water pool) can be monitored by the EXGM, including the flow direction. These monitors have been developed through JASPAS (Japan Support Programme for Agency Safeguards) and through joint R and D by the Power Reactor and Nuclear Fuel Development Corporation and the US Department of Energy. As well as the above monitors, the IAEA installed an entrance gate monitor using a neutron coincidence counter and several optical surveillance cameras. Using this equipment the transfers of fuel assemblies inside the facility can be monitored in an unattended mode and routine inspections are made monthly. The paper describes details of the fuel transfers in the MONJU facility, their verification through flow monitors, and the functions of other safeguards equipment. (author). 3 refs, 5 figs, 1 tab