Analysis on the initiating phase of ATWS events for Gen-IV loop-type SFR with SAS4A

Kubota, Ryuzaburo; Suzuki, Toru; Kawada, Kenichi   ; Kubo, Shigenobu ; Yamano, Hidemasa   ; Koyama, Kazuya*; Moriwaki, Hiroyuki*; Yamada, Yumi*; Shimakawa, Yoshio*

A new methodology to obtain SAS4A input data of power and reactivity profile more consistent with the core design for various core states was consolidated. Using this methodology, SAS4A analyses on the initiating phase during ULOF and UTOP transients from the full power state and the low power state were performed. This analysis study suggests that the power excursion with prompt criticality leading to large mechanical energy release can be prevented in the initiating phase of the current design for the medium-scale Gen-IV loop-type SFR.