Probabilistic Fracture Assessment of Wall Thinning Pipe

This paper describes failure probability assessment of thinning pipe of a nuclear-power plant. The rupture of the feed water piping in the turbine building due to wall thinning happened in Kansai Electric Power Company (KEPCO) Mihama nuclear power plant Unit-3 on August 9, 2004. The variation between the prediction and measured wear rate was evaluated using the published data from KEPCO, and the probability density function was created. Using this probability density function, the failure probability of wall thinning pipe was evaluated using Monte Carlo simulation. The parameters of this evaluation are thinning patterns, wear rate, an applied stress and an inspection interval. The requirements to the inspection were clarified from the probability of failure.