Thesis

An integrated qualitative- quantitative risk assessment framework for the determination of safety and hazardous zones on hydrogen-fuelled ships

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T18184
Person Identifier (Local)
  • 202288761
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Department, School or Faculty
Abstract
  • The maritime industry is undergoing a transition towards decarbonisation, driven by the International Maritime Organization's net-zero emissions target. Among the candidate zero-carbon fuels, hydrogen has emerged as one of the most strategically significant, with ammonia receiving complementary attention as a hydrogen carrier suitable for onboard energy conversion. However, the practical deployment of hydrogen as a marine fuel remains constrained by unresolved safety challenges. Current regulations, most notably the IGF Code, prescribe distances for the placement of fuel system components but do not define the spatial extent of the safety and hazardous zones that bound the consequences of an accidental release. Although the principles of integrated and probabilistic risk assessment are well established in the offshore oil and gas industry, existing maritime studies have applied qualitative and quantitative methods in isolation, relied on deterministic worst-case assumptions, and treated environmental and operational parameters as fixed inputs. This thesis addresses these gaps by developing a structured and integrated qualitative–quantitative risk assessment framework that adapts established risk assessment principles to the determination of safety and hazardous zones on hydrogen-fuelled ships. The framework comprises five phases, namely scenario and system definition, qualitative hazard identification and risk screening, quantitative risk assessment, risk integration, and general observations. Its originality lies in the structured procedural integration of these phases, through an explicit linkage between the qualitative and quantitative stages, a formal parametric scenario analysis sub-phase, a direct link between integrated risk results and the spatial determination of zones, and comparative risk profiling across fuel types under standardised conditions. The framework is applied through two case studies. The first provides an overall demonstration of the framework for bunkering operations at the Port of Hamburg, establishing safety zones for liquefied natural gas (LNG), liquid ammonia (LNH₃), liquefied hydrogen (LH₂), and compressed gaseous hydrogen (GH₂) across three bunkering methods and 76 parametric scenarios through the Population-Independent and Population-Dependent Analysis (PIDA-PDA) integrated parametric approach. Ammonia produced the largest safety zones, with an outer zone boundary of approximately 601 m under default conditions extending to approximately 924 m at the largest leaked fuel quantity, whereas liquefied hydrogen produced the smallest. The parameters governing the zones differed between fuels, and compressed hydrogen, despite its intermediate zone extent, presented the highest societal risk, indicating that a safety zone alone is insufficient to achieve tolerable risk for compressed hydrogen bunkering at the scale modelled. The second case study provides an in-depth application of selected components of the framework to an onboard ammonia cracking system on an 18 m hydrogen fuel cell ferry. HAZID identified five release points, which were analysed through 75 transient CFD simulations using FLACS and STAR-CCM+ and evaluated probabilistically against a frequency criterion of 10⁻⁴ per year. The resulting toxic zones of approximately 7 m for the ammonia tank connection and 5 m for the cracking system, with no separate zone required at the remaining release points, replaced deterministic distances of several times the vessel length. The risk informed zone confirmed the prescriptive requirement where the risk justified it and reduced it where it did not, and the zone definitions formed part of the basis on which approval of the vessel was obtained from the Korean Register. The research establishes that risk-informed zones are both more practical and more discriminating than uniform prescriptive distances, and that zone determination must be accompanied by an explicit evaluation of risk tolerability. The framework provides ship designers, port authorities, classification societies, and regulatory bodies with a structured and transparent route for determining and demonstrating the adequacy of safety and hazardous zones, and its outputs offer technical input to the development of performance-based safety requirements for hydrogen-fuelled ships.
Advisor / supervisor
  • Jeong, Byongug
Resource Type
DOI

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