Development of probabilistic safety assessment method for mixed oxide fuel fabrication facilities

Tamaki, Hitoshi ; Yoshida, Kazuo ; Watanabe, Norio; Muramatsu, Ken

A Probabilistic Safety Assessment (PSA) procedure for Mixed Oxide (MOX) fuel fabrication facilities was developed. The procedure is a "two-part five-step" approach which takes characteristics of MOX fuel fabrication facilities into consideration. In the first part, so-called preliminary PSA, the hazard analysis approach was applied, which consists of two analysis steps: Functional Failure Modes and Effects Analysis (FFMEA) and Risk Matrix Analysis. The FFMEA analyzes a variety of functions of equipment composing the facility to identify potential abnormal events exhaustively. In the Risk Matrix Analysis, these potential events are screened to select abnormal events as candidates to be analyzed in the second part, using two-dimensional matrix based on the likelihood evaluated by probabilistic index method and maximum unmitigated radioactive release calculated by the Five Factor Formula. For the selected abnormal events, in the second part, so-called detailed PSA, accident sequences, their occurrence frequencies and consequences are analyzed. These three analysis steps correspond to PSA procedure for nuclear power plant. The applicability of the PSA procedure was demonstrated through the trial application to model plant of MOX fuel fabrication facility.