Research on the Impact Vector Evaluation Methods of Common Cause Failure in PSA of Nuclear Power Plants

Common cause failure analysis is an important component of probabilistic safety analysis (PSA) for nuclear power plants. The evaluation of the impact vector of common cause failure events is the foundation of common cause failure analysis. At present, the quantitative mathematical method for calculating the impact vector of common cause failure events applicable to any system sizes has not been clearly established. Therefore, the definition and classification of impact vectors are studied in this paper, the mathematical expressions for evaluating impact vectors under incomplete common cause failure events are systematically demonstrated, as well as the mapping calculation method of impact vectors of common cause failure between different system sizes. Furthermore, the evaluation process of the total common cause failure impact vectors of any system sizes is proposed, and the total common cause failure impact vectors of the system is calculated by taking the system with four redundant components as an example. Considering the impact vectors in the target system and the impact vectors mapped from the external system to the target system, the total impact vectors in the case of common cause failure of the target system are (3.03, 23.26, 11.40, 3.72, 3.07). This method can calculate the impact vector of common cause failures with any system sizes, and could provide input data for common cause parameter estimation model.