Development of likelihood estimation method for criticality accidents of Mixed Oxide fuel fabrication facilities

Tamaki, Hitoshi ; Kimoto, Tatsuya*; Hamaguchi, Yoshikane*; Yoshida, Kazuo 

A criticality accident in MOX fuel fabrication facility may occur depending on several parameters, such as mass inventory, plutonium enrichment. MOX handling units in the facility are designed and operated based on the double contingency principle to prevent criticality accident. Control failures of at least two parameters are needed for occurrence of criticality accident. To evaluate probability of such control failure, the criticality conditions of each parameter for a specific handling unit are necessary for accident scenario analysis to be clarified quantitatively with criticality analysis computer code. In addition to this issue, a computer-based control system for mass inventory is planed to be installed into MOX handling equipment in a commercial MOX fuel fabrication plant. The reliability analysis is another important issue to evaluate likelihood of control failure caused by software malfunction. A likelihood estimation method for criticality accident has been developed with taking these issues into consideration. In this paper, an example of analysis with the proposed method and the applicability of the method were also shown through a trial application to a model MOX fabrication facility.