Research of Probabilistic Safety Assessment of CPR1000 Considering Aging Effects

In order to quantify aging impact to core damage risk of CPR1000 units which are widely distributed in China, it is necessary to develop a technical framework of probabilistic safety assessment (PSA) considering aging effects. Several basic technical elements affected were identified. At first, general rules were established to identify and screen structures, systems and components (SSCs) based on their risk contributions and aging sensitivities. No further work was required for SSCs screened out. Some SSCs which are not included in current PSA model should be added if aging effects are considered, e.g. pipes and cables. Secondly, a formula to calculate the aging failure rate was developed, considering aging effects and aging management actions. Thirdly, a method of integrating aging effects into current PSA model was developed, including the development of aging basic events and handling of different failure rates with different operating time. The accident of large break loss of coolant was selected for case analysis. A brief PSA model was developed and a quantitative result was generated for the selected accident. The result of the case analysis showed that aging effect could have a significant influence to the core damage frequency and relevant risk insights of PSA for a CPR1000 nuclear power unit.