Spatiotemporal variation of radionuclide dispersion from nuclear power plant accidents using FLEXPART mini-ensemble modeling

Abstract

Abstract. We investigate the spatiotemporal distribution of the radionuclides including iodine-131 (131I) and cesium-137 (137Cs), transported to Qatar from fictitious accidents at the upwind Barakah nuclear power plant (B-NPP) in the United Arab Emirates (UAE). To model the dispersion of radionuclides, we use the Lagrangian particle–air parcel dispersion model FLEXible PARTicle (FLEXPART) and FLEXPART coupled with the Weather Research and Forecasting model (FLEXPART–WRF). A four-member mini-ensemble of meteorological inputs is used to investigate the impact of meteorological inputs on the radionuclide dispersion modeling. The mini-ensemble includes one forecast dataset (Global Forecast System, GFS) and three (re)analysis datasets (native-resolution and downscaled NCEP final analysis – FNL, as well as downscaled ERA5). Additionally, we explore the sensitivity of the radionuclide dispersion simulations to variations in the turbulence schemes, as well as the temporal and vertical emission profiles, and the location of emission sources. According to the simulated age spectrum of the Lagrangian particles, radionuclides enter southern Qatar about 20 to 30 h after release. Most of the radionuclide deposition in the study area occurs within 80 h after release. The most populated areas of Qatar coincide with moderate 131I concentrations and 137Cs deposition, while uninhabited areas in southern Qatar receive the highest amounts. A larger number of long-lived particles is found in the FNL-based simulations, which is interpreted as a greater dispersion of particles at a greater distance from the emission location. The highest simulated 131I and 137Cs deposition shows a pronounced spatiotemporal pattern. The largest impacts are found in the south and southeast of Qatar, during the early daytime development of the boundary layer, and during the cold period of the year. The results show remarkable differences in the spatiotemporal distribution of 131I and 137Cs simulations based on the FNL and GFS datasets, which share a common base meteorological model. As part of a sensitivity analysis involving different model setups, changing the emission point from B-NPP to Bushehr NPP (Bu-NPP) results in a reduced transfer of radioactive materials to Qatar, except in the spring season. Bu-NPP simulations reveal distinct spatial patterns, with peak 131I concentrations and 137Cs deposition observed in northern and eastern Qatar during winter and spring.