Tritium dispersion analysis using HotSpot code: a comparative study across reactor types and environmental conditions

Kenya is advancing plans to establish nuclear power plant in its coastal parts to boost its energy production. This study addresses the critical need for tritium monitoring and radiological dose assessment under a severe accident scenario. Tritium (³H), due to its high mobility and biological relevance, presents a key concern in post-accident dispersion, particularly in developing nuclear states with limited baseline data. Using the HotSpot health physics code, we simulated atmospheric dispersion of tritium in molecular (HT), oxidised (HTO), and organically bound (H(M)) isotopes over Kilifi County, Kenya. The model incorporated 2024 site-specific meteorological data, release height and hypothetical containment bypass and loss of coolant accident events across four reactors (heavy water reactors (HWR), pressurised water reactors, boiling water reactors, advanced gas cooled reactor). The highest total effective dose (TED) and ground deposition were9.0×10-1Sv5.0×1010kBq m^-2respectively at a wind velocity of 2 m s^-1, while maximum time-integrated air concentration was5.5×1011Bq.s m^-3, ground contamination extended to 162 km²under low rainfall. Rural terrain yielded higher TED than urban areas, stability class F produced highest dose. The highest target organ committed dose was8.0×10-5Sv, primarily to the lungs. The overall highest dose was recorded in the HWR reactor and exceeded the International Commission on Radiological Protection dose limit of1.0×10-3Sv yr^-1. However, with increasing downwind distance, the dose dropped below this limit. Sensitivity analysis identified wind velocity as the dominant dispersion driver. These results inform emergency planning, exclusion zone design, and regulatory frameworks for nuclear safety in Kenya and other nations exploring nuclear development.