RECONSTRUCTION OF THE RADIOACTIVE CONTAMINATION OF THE TERRITORY OF UKRAINE BY IODINE-131 DURING INITIAL PERIOD OF THE CHORNOBYL ACCIDENT USING THE RESULTS FROM NUMERICAL MODEL WRF

Abstract

Objective. To reconstruct the 131I activity concentrations in air and 131I ground deposition densities from 26 April to 7 May 1986 from the radioactivity release after the Chornobyl accident in the settlements of Ukraine using the mesoscale radionuclides atmospheric transport model LEDI and meteorological information from the numerical weather forecast model WRF and to compare the obtained results with those calculated previously as well as with available measurements of 131I activity in soil. Object of research: the near-ground layer of the atmosphere and the surface of the territory of Ukraine radioactively contaminated as a result of the Chornobyl accident. Materials and methods of research. The dispersion of 131I in the atmosphere and deposition on the ground surface in Ukraine were calculated using the Lagrangian-Eulerian diffusion model LEDI. The detailed fields of meteorological parameters calculated using the mesoscale weather forecast model WRF, which was adapted for the territory of Ukraine, were used as input data for the LEDI model. Results. The 131I daily-average activity concentrations in the surface air and 131I daily ground deposition densities from 26 April to 7 May 1986 were calculated using the up-to-date mesoscale model of numerical weather forecast WRF for 30,352 settlements in entire Ukraine, including 1,263 settlements in Kyiv, 1,717 – in Zhytomyr and 1,570 – in Chernihiv Oblasts. Conclusions. The method of mathematical modeling of the atmospheric transport of the radionuclides is combination with the up-to-date mesoscale model of numerical weather forecast WRF is a useful tool for reconstruction of radioactive contamination of the air and the ground surface after the Chornobyl accident. Calculated in this study 131I activity concentrations in air and 131I ground deposition densities were used to reconstruct the thyroid doses due to 131I intake to the population of Ukraine. Key words: Chornobyl accident, Iodine-131, atmospheric transport model.