The Sensitivity Improvement of Passive Shutdown System Based on Curie Point Alloy in a Fast Reactor

The magnetic properties will be lost when the temperature of Curie point alloy is above the Curie point temperature. The physical properties of Curie point alloy are used for Passive Actuated Shutdown System (PASS) in the Fast Reactor, for example American, Japan, the shutdown systems are called Self Actuated Shutdown System (SASS). The shutdown device is composed of the up assembly and the down assembly. The up one is a magnetic material and the down one is Curie point alloy. The reliability of PASS in normal condition, and whereabouts of sensitivity are determined by the properties of Curie point alloy. The Reactor-type Experiment Furnace and related circuits were designed to carry out static and dynamic experiments under the high temperature. Cylindrical alloy functions were investigated through the high temperature experiments outside of the reactor. The results showed that improvement was necessary because of long response time. In order to improve the sensitivity of PASS, different shapes were designed for Curie point alloy, under the premise that PASS was reliable. The response times of different sharps were calculated by finite element software, ANSYS, in abnormal condition. Comparison of response times of cylinder, quincunx and fins model under the same conditions, quincunx structure had the shortest response time when the temperature of Curie point ally was above the Curie point temperature. The results obtained from the high-temperature experiments, also showed that the quincunx has the shortest response time. These results showed the quincunx structure was superior to the other models.