Atmospheric Dispersion of Radioactive Material according to the Local Wind Patterns around the Kori Nuclear Power Plant using WRF/HYSPLIT Model

Abstract

The characteristics of atmospheric dispersion of radioactive material (i.e. 137 Cs) related to local wind patterns around the Kori nuclear power plant (KNPP) were studied using WRF/HYSPLIT model. The cluster analysis using observed winds from 28 weather stations during a year (2012) was performed in order to obtain representative local wind patterns. The cluster analysis identified eight local wind patterns (P1, P2, P3, P4-1, P4-2, P4-3, P4-4, P4-5) over the KNPP region. P1, P2 and P3 accounted for 14.5%, 27.0% and 14.5%, respectively. Both P1 and P2 are related to westerly/northwesterly synoptic flows in winter and P3 includes the Changma or typhoons days. The simulations of P1, P2 and P3 with high wind velocities and constant wind directions show that 137 Cs emitted from the KNPP during 0900~1400 LST (Local Standard Time) are dispersed to the east sea, southeast sea and southwestern inland, respectively. On the other hands, 5 sub-category of P4 have various local wind distributions under weak synoptic forcing and accounted for less than 10% of all. While the simulated 137 Cs for P4-2 is dispersed to southwest inland due to northeasterly flows, 137 Cs dispersed northward for the other patterns. The simulated average 137Cs concentrations of each local wind pattern are 564. 1~1076.3 Bqm -3 . The highest average concentration appeared P4-4 due to dispersion in a narrow zone and weak wind environment. On the other hands, the lowest average concentration appeared P1 and P2 due to rapid dispersion to the sea. The simulated 137 Cs concentrations and dispersion locations of each local wind pattern are different according to the local wind conditions.