137Cs activity concentration in the ground-level air in the Ignalina NPP region

Abstract

Results of the Cs activity concentration measurements in the ground-level air in the Ignalina Nuclear Power Plant (Ignalina NPP) region in 1978–2006 are presented and discussed. The peculiarities of the trend of mean annual radiocaesium activity concentrations in the air during the studied period are explained and described empirically. The analysis of the radiocaesium concentration course after the Chernobyl accident shows that mean annual Cs activity concentrations in the air are decreasing slower than it is expected due to its radioactive decay and aerosol, as the Cs carrier, removal processes in the atmosphere. The Hybrid Single-Particle Lagrangian Integrated Trajectory model of the global dispersion and deposition of the admixture in the air is used to study episodic increases in the Cs activity concentration in the ground-level air of more than 8 μBq m. Modelling results show the transport of resuspended radiocaesium with air mass from the Chernobyl NPP accident polluted regions to be an important source of the radionuclide to the environment of the Ignalina NPP. It is shown that Cs emissions from its generation sources (nuclear industry objects) and, probably, the depositional flux of the radiocaesium from the stratospheric reservoir, can contribute up to 10% to the mean annual Cs activity concentration value. Mean arithmetic and mean geometric Cs activity concentrations in the air during a year are calculated and compared.