Under-Sodium Endurance Experiment of Selector Valve in Failed-Fuel Detection and Location System of JSFR

A conceptual design study of Japan Sodium-cooled Fast Reactor (JSFR) is in progress in the Fast Reactor Cycle Technology Development (FaCT) project in Japan. In the design of JSFR, a selector valve mechanism is adopted for its failed-fuel detection and location (FFDL) system. Since JSFR has only two FFDL units for [approximately]600 fuel subassemblies due to its compact design of the reactor vessel, one FFDL unit must handle a much larger number of subassemblies than in previous designs. In addition, during the long plant life of 60 years, the wear length of the selector valve will become longer than those of past reactors. Therefore, the endurance of the selector valve becomes important. To demonstrate the manufacturability and endurance of the selector valve, a full-size mockup valve including coating to protect the sliding mechanism was manufactured, and an endurance experiment of the mockup model under high-temperature sodium was conducted. Dimensional inspections and seal performance showed manufacturability of the selector valve. The cross-section observation, hardness measurement, and chemical assay results after the endurance experiment showed that the coating layer on the sliding surface still remains. Thus, the endurance of the JSFR selector valve was demonstrated.