Establishment of the Basis for Safety Evaluation and Risk Assessment of Ships Using Ammonia as Fuel

Ammonia fuel presents a greater potential for the formation of a toxic atmosphere than an explosive atmosphere, distinguishing it from conventional and other alternative fuels. Pioneers shall obtain acceptance from the Administration by demonstrating that the design of ships using ammonia as fuel can achieve an equivalent level of safety to ships using conventional fuels. However, a basis for defining release scenarios and evaluating whether safety criteria can be met through safeguards for those scenarios has yet to be established. This poses challenges in decision-making not only for those involved in ship design but also for those responsible for conducting safety evaluation and risk assessment, and for granting approval based on the evaluation. A basis was originally prepared for an ammonia-fuelled gas carrier project and refined through this paper, providing technical justification to ensure that safety functions are appropriately designed to meet safety criteria within a specific context. The basis categorizes the operational situations into normal operation, accidental situation, and emergency and focuses on minimizing the probability of crews being exposed to the toxic atmosphere in each situation.

Keywords: Ammonia fuel, Toxicity risk, Release scenarios, Safety criteria, Safety evaluation, Risk assessment.