The integration of Nuclear Power Plants (NPPs) with Proton Exchange Membrane (PEM) electrolyzers is a promising pathway for low-emission hydrogen production and expansion of the nuclear power plant capabilities. Co-located hydrogen production facilities and nuclear power plants are one aspect of the advanced Integrated Energy Systems (IES) concepts being developed across the U.S. However, co-location of these facilities introduces new physical and functional interdependencies that are not explicitly captured in conventional Probabilistic Risk Assessments (PRA). This work presents a probabilistic framework to model risk scenarios and escalation pathways between a PEM electrolyzer facility and an NPP. Hydrogen leak frequencies and ignition probabilities are combined with overpressure consequence modeling and fragility-based damage estimation to quantify the potential impact of hydrogen explosions on shared electrical infrastructure, including switchyards, transformers, and transmission assets. In addition to overpressure effects, the framework also accounts for overcurrent events in the shared electrical infrastructure, which may lead to damages to the NPP turbine. Both overpressure and overcurrent-induced failures are mapped to site-level initiating events (i.e., Loss Of Offsite Power (LOOP) and Loss of Heat Sink (LHS)), which are integrated into a dynamic PRA model to estimate the increase in Core Damage Frequency (CDF) caused by the PEM integration. A distance-dependent analysis is then performed to quantify how spatial configuration influences escalation frequencies and site risk. Preliminary results show that, while hydrogen-related escalation frequencies are generally low, shared electrical infrastructure can represent a critical vulnerability. The proposed methodology enables risk-informed siting and design decisions for nuclear-hydrogen integrated systems and provides a foundation for further extensions to broader IES configurations.
Keywords: Nuclear Power Plant (NPP), Hydrogen production, Proton Exchange Membrane (PEM) electrolyzers, Probabilistic Risk Assessment (PRA), Integrated Energy System (IES).