SHAKE-RoverD Framework for Nuclear Power Plants: A Streamlined Approach for Seismic Risk Assessment

A major challenge facing the nuclear energy industry is to remain competitive under current market conditions. Utility operators are searching for innovative methods to reduce nuclear power plant (NPP) operation and maintenance costs while complying with safety and reliability requirements. To support these goals, the authors suggest a streamlined approach that implements a conservative risk-informed method to reduce the costs of satisfying emergent regulatory requirements. As a streamlined approach, the Risk-informed Over Deterministic (RoverD) method was developed by some of the authors of the current paper to resolve the concerns associated with Generic Safety Issue 191 (GSI-191). The RoverD method is designed around U.S. Nuclear Regulatory Commission Regulatory Guide 1.174 (RG 1.174), which defines “risk-informed” regulation as comprising a blend of risk-based and deterministically based elements. This paper offers the Safety Hazard Analysis for earthquaKE (SHAKE)–RoverD (SHAKE-RoverD) methodology, an extension of the original RoverD methodology developed for GSI-191, to evaluate the impact of an increased seismic hazard on the performance of NPP protective systems. SHAKE-RoverD aims to reduce the cost required for developing, validating, and documenting detailed fragility curves in seismic probabilistic risk assessment by using deterministic fragility curves. The SHAKE-RoverD methodology assesses whether an increase in a seismic hazard would result in an unacceptable increase in NPP risk. If the conservative estimate of plant risk, computed by the streamlined approach, satisfies the regulatory acceptance criteria (e.g., Regulatory Guide 1.174), the plant likely would not need to make a design change (as long as defense in depth and adequate safety margin are satisfied); therefore, the use of streamlined methodology could lead to significant cost savings for the utility operator. Future work will advance SHAKE-RoverD and analyze risk management strategies based on this method.