Simulation of spread and dispersion of Kr and Xe noble gas radionuclides in a hypothetical accident in the Tehran Research Reactor.

Understanding the atmospheric transport and dispersion of radioactive materials following a nuclear accident is essential for effective emergency response and environmental monitoring. In this study, a hypothetical accident scenario involving a 10% core meltdown at the Tehran Research Reactor was analyzed. The core radionuclide inventory was first calculated using the ORIGEN 2.0 code. Subsequently, the atmospheric transport, dispersion, and deposition of released radionuclides were simulated using the HYSPLIT 5.2 model, driven by the Global Data Assimilation System (GDAS) and Global Forecast System (GFS) meteorological data. Seasonal variations were investigated to evaluate concentration patterns at different distances from the release point. Particular attention was given to identifying optimal sampling locations for measuring the activity of noble gases, specifically krypton (Kr) and xenon (Xe). A novel feature of this study is the development of a spatial monitoring strategy that moves beyond traditional dose assessment to provide actionable data for emergency responders. The results indicate that, across all seasons, distances between 5 and 10 km from the reactor site provide the most suitable conditions for air sampling and noble gas activity measurements. This finding establishes a critical technical benchmark for the deployment of automated sampling systems in the event of a TRR accident.