Development of level 2 PSA methodology for sodium-cooled fast reactors, 3; Development of technical basis in the transition phase of unprotected events

Yamano, Hidemasa  ; Tobita, Yoshiharu; Sato, Ikken 

A Level 2 PSA methodology is developed for the risk evaluation of sodium-cooled fast reactors (SFRs). For this purpose, the phenomenological event tree is developed as well as a technical basis to quantify the probability of event sequences in the Level 2 PSA, focusing on the transition phase in an unprotected loss of flow (ULOF) accident in this paper. In addition, dominant factors are also identified through parametric analyses using the SIMMER-III code. The experimental findings on the fuel discharge behavior and its driving force formation were summarized from the CABRI and EAGLE experiments. Using past experimental evidences, furthermore, the experimental database is developed to quantify the probability of the Level 2 PSA.