ASSESSING SAFETY PERFORMANCE BY PERFORMANCE INDICTORS, ACCIDENT SEQUENCE PRECURSOR ANALYSIS AND SAFETY SYSTEMS RELIABILITY ANALYSIS

摘要

The paper summarizes some of the activities carried out by the Spanish regulatory body, Consejo de Seguridad Nuclear (CSN), in assessing and measuring the safety performance of nucler power plants. To place the work of assessing performance in the proper context, the mechanisms needed to achieve the required operational safety level are briefly discussed, being one of those mechanisms of operational experience feedback from events or situations actually happening in the installations. Next, the regulatory body's objectives and needs are presented and some of the tools devoted to the analysis of performance, of results, are listed, three of them being discussed in the paper. First, the present status of the performance indicators programme of the CSN is described. The indicators tracked down and the content of the reports are presented and a discussion of the insights generated is provided, keeping in mind that the programme results are a starting point for a deeper analysis and a diagnosis from which particular actions are defined and taken. Several by-products of significant value from the performance indicators work are commented on. It is concluded that, for the Spanish situation, a programme of performance indicators is a tool of significant interest for the regulatory body, but that it should not used in isolation from other programmes that assess performance. Secondly, the ongoing activities in Accident Sequence Precursor Analysis, in the use of probabilistic safety assessment (PSA) for the analysis of events, are described, identifying the basic characteristics of the procedure used for the screening of events and the selection of the initial PSA models applied in the programme. Insights obtained are briefly discussed. Thirdly and finally, a description is given of studies of individual safety systems merging simplified PSA models with specific and detailed operational data to derive insights regarding the reliability of the safety system compared with the PSA results, and of the effectiveness of the testing performed in the system to identify the relevant failure modes, comparing it with actual failures in demand. The kinds of insight expected from this programme are presented. As a general conclusion on the use of the three tools mentioned above, it is indicated that the quality of data recorded at the plants regarding performance of the safety systems, and the fair and complete notification to the regulatory body, are essential to allow an increased use of the assessment of performance by the regulatory body.