Risk Analysis of Large Thermal Extraction from a Nuclear Power Plant: FMEA and PRA of Greater than 25% Steam Extraction

This paper explores the feasibility and risks of extracting more than 25% thermal power from light water reactor (LWR) nuclear power plants (NPPs) to sustain the existing nuclear fleet. Building on prior research that examined 15-25% thermal power dispatch, this study investigates 30%, 50%, and 70% thermal extraction levels, with a focus on the bounding cases of 30% and 50% due to operational concerns at 70%. The increased thermal extraction levels pose unique challenges requiring comprehensive analysis, including adjustments to the failure modes and effects analysis (FMEA) and modifications to the heat extraction system (HES), such as advanced control systems and piping changes. The study employs the Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) tool to update the LWR probabilistic risk assessment (PRA) models, incorporating new risk contributors from the proposed design changes. The updated risk metrics, including initiating event frequency of affected sequences due to increased failure are compared against Nuclear Regulatory Commission (NRC) safety criteria to determine the feasibility of the modes, proposed thermal extraction levels within the regulatory framework. The goal is to ensure safe implementation of the thermal power extraction process without compromising NPP integrity and reliability. This research supports the sustainability of the current nuclear fleet by optimizing thermal energy utilization, thus enhancing the overall efficiency and economic viability of nuclear power as a key energy resource.