Integrating proton exchange membrane (PEM) electrolyzers with nuclear power plants (NPPs) offers a pathway for large-scale, low-carbon hydrogen production, but co-location introduces hazards that require rigorous probabilistic safety assessment. In this work, we present our new quantitative risk assessment (QRA) framework for a 1 MW PEM electrolyzer integrated with an NPP, spanning hazard identification through consequence modeling and site risk quantification. We began by conducting a detailed failure modes and effects analysis (FMEA), identifying more than 850 modal-level failure scenarios that could result in hydrogen, oxygen, or nitrogen releases, or hydrogen and oxygen mixing. We then constructed and parameterized fault trees for key top events using reliability data to quantify failure frequencies, identify minimal cut sets, and calculate risk reduction and achievement worth importance measures. These results allowed us to rank dominant risk contributors and propose targeted mitigation strategies. To address ignition probability, we developed Bayesian network models to provide traceable probabilities for immediate and delayed ignition. To model the consequences of immediate ignition, we analytically modeled jet fires for multiple release scenarios using the HyRAM+ software toolkit. We quantified explosion overpressures using Kingery–Bulmash, Baker, and TNO methods and performed finite element analysis to evaluate structural vulnerability of critical piping. Finally, we integrated frequency, ignition, and consequence models into the QRA framework and used it to calculate location-specific individual and site risk (LSIR and LSSR). We performed Monte Carlo simulations to propagate scenario-level and system-level uncertainties through the risk metrics and inform safety system design. These results support risk-informed design decisions and setback distances. This work establishes a structured, specific QRA methodology that supports the safe deployment of nuclear-enabled hydrogen production systems.