A PIDA-PDA integrated parametric approach for establishing safety zone for hydrogen, ammonia and LNG bunkering operations

This paper proposes a comprehensive methodology that systematically integrates Population-Independent Analysis (PIDA) and Population-Dependent Analysis (PDA), providing both spatial hazard delineation and human risk quantification. By utilizing scenario-based simulations with varying leak diameters (5 mm, 10 mm, and 100 mm) and distinct bunkering methods (ship-to-ship, truck-to-ship, and facility-to-ship), the research elucidates fuel-specific risk profiles under diverse operating conditions. Key findings indicate that ammonia's high toxicity can produce a toxic exclusion zone extending beyond 600 m in worst-case scenarios, while compressed hydrogen often yields a similarly large hazard radius—exceeding 200 m—primarily driven by its proclivity to form flammable and explosive vapour clouds. In contrast, liquefied hydrogen exhibits a more constrained dispersal pattern, with average outer-zone radii near 25 m, albeit still presenting significant explosion hazards in enclosed spaces. These quantitative results underscore the importance of robust leak detection and rapid emergency shutdowns, which effectively reduce total leak volumes and resultant hazard footprints. The integrated PIDA-PDA framework offers distinct benefits over conventional single-method approaches. PIDA quantifies worst-case hazard boundaries for each scenario, ensuring stringent protective measures within clear safety zones. PDA then refines these zones by incorporating actual population densities and exposure rates, enabling stakeholders to prioritize areas of high casualty potential for intensified safety measures. This complementary approach avoids overly conservative restrictions while preserving critical safety margins. Ultimately, the results advance more resilient strategies for adopting LNG, ammonia, and hydrogen as viable pathways to decarbonised maritime transport.