A plant operating state analysis method in probabilistic safety assessment for multi-unit nuclear power plant

Abstract

The nuclear power plants (NPPs) with more than one unit have become widespread globally, and plant operating state (POS) is a key issue to understand and manage characteristics of NPPs, especially to the safety level. Probabilistic safety assessment (PSA) is an indispensable safety analysis tool for NPPs, while it almost addresses single unit in practice at present. To perform PSA for multi-unit NPPs, the definition and evaluation of POS related to all units should be presented as preconditions. In this paper, a general framework of multi-unit POS analysis method based on single-unit POS is proposed, and the corresponding algorithm is also implemented. A case study on high temperature gas-cooled reactor - pebble-bed module (HTR-PM) is realized to verify the feasibility of this method. All possible combinations of POSs and their risk profiles for HTR-PM are obtained which could provide guidance for the subsequent operation under low power and shutdown conditions.