Nuclear technology for hydrogen generation: Pathways, coupling physics, and the niche role of γ-radiolysis

Nuclear-generated hydrogen spans electricity-driven low-temperature electrolysis (LTE), heat-assisted high-temperature steam electrolysis (HTSE/SOEC), heat-dominant thermochemical or hybrid cycles, and a niche direct ionizing-radiation route via water radiolysis. This review now situates nuclear hydrogen within the wider hydrogen-production landscape, including fossil-based reforming with and without carbon capture, renewable electrolysis, biomass- and waste-derived routes, and emerging geological hydrogen. The decisive engineering variables are not stack efficiency in isolation but exportable heat quality and its opportunity cost against electricity generation, nuclear-hydrogen coupling architecture and safety classification boundaries, degradation and lifetime under realistic duty cycles, and balance-of-plant parasitics such as steam generation, recuperation, compression, drying, water treatment, and storage. The review further expands the practical discussion of industrial deployment barriers, licensing interfaces, safety zoning, infrastructure requirements, commercialization prospects, and radiation-protection materials relevant to co-located nuclear-hydrogen systems. Finally, gamma-radiolytic water splitting is critically assessed as a mechanistically valid but specialized pathway whose realistic role is likely to be process-intensification, waste-radiation utilization, materials-screening, and niche production rather than bulk hydrogen supply.