Consideration on HRA Implementation during LPSD Operation

During low power and shutdown operation, it has been pointed out that the important of human actions is significantly increased. Because automatic control may be disabled, most control room annunciation titles indicate alarm status, and procedures are insufficient, human operators plays a much larger role during outages and in lower power state. In this regards, in order to reduce human errors and secure nuclear power plant safety, it is necessary to identify and estimate human errors during LPSD operations. However, many researchers have argued that there is no comprehensive LPSD human reliability analysis (HRA) method so far. In this study, we reviewed and implemented the existing HRA methods during LPSD operations: Korean standard HRA (K-HRA), Simplified plant analysis risk HRA (SPAR-H), Caused based decision tree (CBDT), and human cognitive reliability/ operator reliability experiments (HCR/ORE). We reviewed HRA methods based on several reports related to the unique aspects of human operator during LPSD operation and HRA requirements. In addition, the existing HRA methods were implemented during various plant operating states (POS) of LPSD operation. Loss of shutdown cooling system (SCS) was selected as initiating event. As a result of review and implementation of HRA methods, we derived the some limitations of the existing HRA methods and related procedure during loss of SCS event. Keyword: Human reliability analysis (HRA), Low power and shutdown (LPSD)