2021 年 87 巻 893 号 p. 19-00420
The self-actuated shutdown system (SASS) is a reactor shutdown system that is able to achieve passively de-tach the absorber rod based on the coolant temperature rise under the any type of abnormal conditions and then the absorber rods will be inserted by the gravity forces within a few seconds. This capability is possible to add the active shutdown system, if a Curie-point temperature magnet system would be adopted. The temperature sensing alloy is designed and fabricated for de-tach under Unprotected Loss of Flow, Unprotected Transient Overpower, and Unprotected Loss of Heat Sink accidents, whereas the control rods would be well hold under the normal operating conditions. Since its impact on the reactor core design is less, its installation is excellent both in the safety enhancement and also in cost effectiveness. The SASS has been developed as a safety enhancement measure against the failures of the reactor shutdown system in sodium-cooled fast reactors. This paper contains the results of experimental studies in order to select appropriate materials for SASS. As a result, the feasibility and the reliability of candidate material for SASS has been confirmed.
