Development of structural reliability evaluation method for aged piping considering uncertainties of seismic motions; How to evaluate the failure probability of aged piping in nuclear power plant due to earthquake

Ito, Hiroto; Onizawa, Kunio ; Sugino, Hideharu*

Magnitude of seismic motion and degradation such as crack initiation and growth on stress corrosion cracking have uncertainties in the evaluation for the structural integrity of reactor components under seismic motion. We have studied evaluation methods for the structural integrity of components such as piping, i.e. failure probabilities in operation time by probabilistic fracture mechanics (PFM) analysis method which evaluates the uncertainties quantitatively. The evaluation method for seismic motion considering uncertainties, which is most important to evaluate the safety of nuclear power plants under seismic motion, has also been developed. Though their evaluation methods were independent in past, we developed the evaluation method for the failure probabilities considering occurrence probabilities of seismic motion around a plant when seismic motion acts on aged piping by merging them together.