Component function of self actuated shutdown system in the experimental fast reactor JOYO

Takamatsu, Misao ; Sekine, Takashi ; Uchita, Masato*; Harada, Kiyoshi*

Self actuated shutdown system (SASS) with a Curie point electromagnet (CPEM) is being developed for use in a large scale fast breeder reactor (FBR) in order to establish the passive shutdown capability against anticipated transient without scram (ATWS) events. In order to confirm the stability of CPEM in holding the control rod and demonstrate the functions of the driving system to re-connect and pull out the control rod under the actual reactor-operational environment, the component function test using the reduced-scale model experimental equipment of SASS was conducted in the experimental fast reactor JOYO MK-III. As a result of this test conducted for 117 days during the 1st and 2nd operational cycles of JOYO MK-III from May to Oct. 2004, the rod-holding stability and the recovering functions of the driving system were fully confirmed. A neutron fluence of over 61018n/cm2 (E0.1MeV) was obtained for CPEM. This corresponded to 60 years of use in a large-scale FBR and satisfied the required fluence for stability assurance. The results also will likely dispel the apprehensiveness about the operational trouble involving the unexpected drop of SASS.