Quantitative Risk Assessment (QRA)

A quantitative risk assessment (QRA) estimates risk as a number, combining the frequency of each hazardous scenario with its consequence to yield individual risk per year and societal risk as an F-N curve. For alternative-fuel ships it sizes leak scenarios, models toxic or flammable dispersion, and tests the result against an ALARP criterion and tolerability limits. QRA is the core of the IGF Code and IGC Code safety case for ammonia, hydrogen, and LNG bunkering, where it sets exclusion-zone distances and mitigation. It differs from qualitative HAZID and HAZOP by attaching probabilities and physical consequence distances rather than ranking hazards.