Efforts for utilizing risk information at Ikata Power Station. Current state and plans for the future

Shikoku Electric Power Co. has taken lessons from the TEPCO Fukushima Daiichi Nuclear Power Station accident and is performing activities aiming at improving the safety of Ikata Power Station without being caught by the framework of regulations. The company believes that for improving safety it is important to utilize risk information for day-to-day operations. As part of this, the company is making efforts to build a risk-informed decision-making (RIDM) process making use of risk information including probabilistic risk assessment (PRA) in the fields of plant remodeling, maintenance, operation, etc., and to promote risk management. In RIDM, risk is quantified by the use of PRA, and the following merits can be considered. (1) Using common indices such as core damage frequency and risk importance degree, the importance on nuclear safety can be shared among the people involved. (2) In addition to the merits in the maintenance and remodeling of facilities, the improvements of operation procedures, accident response drills, patrolling methods, work procedures, work environment, etc. can be expected. As measures for challenging the introduction of RIDM, the company is making efforts for establishing business processes/mechanisms and upgrading PRA. The company is promoting the integrated process utilizing risk information and the sophistication/elaboration of event tree, equipment failure rate data, human reliability evaluation, etc. Thus, the improvement of safety level, countermeasures for performance deterioration, and response to changes in authorization base would become possible, which would contribute to safety. (A.O.)