Modeling of radioactive contamination of the atmosphere due to natural fires in the Exclusion Zone in September 2024

The results of modeling the transport of radioactive aerosols released into the atmosphere as a result of fires in forest and grass areas in the Chornobyl Exclusion Zone from September 3 to 11, 2024 are presented. To assess the effects of natural fires, a set of models of emission, atmospheric transport and deposition of radionuclides on the underlying surface LEDI, developed at the Institute for Safety Problems of Nuclear Power Plants, the National Academy of Sciences of Ukraine, was used. Calculations of the dynamics of the 137Cs activity concentration field in the surface air at the regional scale (on the territory of Ukraine) were performed. The possible impact of atmospheric transboundary transport of radioactive combustion products on the radiation situation in neighboring countries was assessed. A comparative analysis of the results of estimates of the burning area based on the data of satellite radiometers of the NASA FIRMS fire tracking system and multispectral images of Sentinel 2 satellites was carried out. The coefficient of 137Cs emission to the atmosphere from the radioactively contaminated territory of the forest fire in the Exclusion Zone as of the current period is estimated at 0.4 % of the total activity inventory in the burning area. The area of the fires is estimated at 61.7 sq. km, including 35.1 sq. km of forest and 26.6 sq. km of meadows. The total 137Cs emission from natural fires in the Exclusion Zone during September 3−11, 2024 was estimated at about 50 GBq. Outside the Chornobyl Exclusion Zone, the average daily concentration of 137Cs activity in the surface air during the fires could reach units of mBq/m3, i.e. 2 orders of magnitude less than the established limit. It was concluded that there is no significant impact of radioactive contamination of the atmosphere due to natural fires in 2024 on the radiation status and health of the population in Ukraine and abroad.