Accident-based standoff distances for nuclear-powered container ships in port environments

The deployment of nuclear-powered container ships has emerged as a promising option for maritime decarbonization. However, Pressurized Water Reactor (PWR)-based technology has often taken a backseat to other unproven nuclear concepts because of perceived risks of offsite consequences upon a severe accident. The lack of a quantitative linkage between accident progression and spatial siting constraints of modern PWR-based Small Modular Reactor (SMR) technology has led ship developers to leverage military PWR ship consequences that feature significantly different power density and radionuclide inventory. In this study, accident consequences of a PWR-based SMR propulsion system for a Neo-Panamax container ship are evaluated using state-of-the-art tools for nuclear severe accident progression and offsite consequence analysis. Representative accident scenarios, including maritime-specific capsized conditions, are analyzed to quantify mechanistic source terms and offsite radiological consequences at major U.S. ports. The results indicate that offsite dose responses are strongly influenced by accident progression characteristics and meteorological conditions, with variations observed across port environments. Capsized conditions are identified as the bounding scenario, underscoring the importance of maritime-specific accident considerations. These findings can be extended to other maritime reactor concepts to provide a practical foundation for evaluating the feasibility of nuclear-powered shipping and informing future regulatory frameworks.