Application of PSA to review and define technical specifications for advanced nuclear power plants

As part of the design certification process, probabilistic safety assessments (PSAS) are performed at the design stage for each advanced nuclear power plant. Among other usages, these PSAs are important inputs in defining the Technical Specifications (TSs) for these plants. Knowledge gained from their use in improving the TSs for operating nuclear power plants is providing methods and insights for using PSAs at this early stage. Evaluating the safety or the risk significance of the TSs to be defined for an advanced plant encompasses diverse aspects: (a) determining the basic limiting condition for operation (LCO); (b) structuring conditions associated with the LCO; (c) defining completion times (equivalent to allowed outage times in the TS for conventional plants); and, (d) prescribing required actions to be taken within the specified completion times. In this paper, we consider the use of PSA in defining the TSs for an advanced nuclear plant, namely General Electric`s Advanced Boiling Water Reactor (ABWR). Similar approaches are being taken for ABB-CE`s System 80+ and Westinghouse`s AP-600. We discuss the general features of an advanced reactor`s TS, how PSA is being used in reviewing the TSs, and we give an example where the TS submittal was reviewed using a PSA-based analysis to arrive at the requirements for the plant