A Regulatory Inspection Tool in SDP Context

The Institute of Nuclear Energy Research (INER) is now developing a tool to help the inspectors to perform the Phase 2 SDP (Significance Determination Process) assessment. The purpose of this tool is to simplify the process of the assessment and help the inspectors to obtain the results quickly. Risk models for the calculation of core damage frequency (CDF) of internal initiating events will be used to determine the risk increase of specific inspection findings. The risk model used for the SDP tool was converted from the original Probabilistic Risk Assessment (PRA) model of the individual plant. The risk engine, INERISKEN, is adopted to perform the calculation. After input of the inspection findings are setup, all calculations can be done in less than one minute by INERISKEN. To perform the Phase 2 assessment, the inspector has to decide the affected components/systems and the impact to initiating events for his inspection findings. When changes of plant configuration are specified, the ΔCDF can be obtained by solving the risk model with new plant configuration. Simplified P&IDs for most of the safety systems are also available for user’s reference. If any inspector cannot make sure the response of the inspection findings to the affected systems or the initiating events, experiences and examples are also provided on user’s click. The ΔCCDP (Conditional Core Damage Probability) obtained can be related to one of the color (green, white, yellow or red) by the methodology defined in the counting rule worksheet of NRC inspection manual. Meanwhile, the status of the critical safety functions is also displayed according to the new plant configuration. These additional results will help the inspector to further understand the risk insight of inspection findings.