Development of an Atmospheric Dispersion Model for Accidental Discharge of Radionuclides with the Function of Simultaneous Prediction for Multiple Domains and its Evaluation by Application to the Chernobyl Nuclear Accident

Abstract

A particle random-walk model GEARN for nuclear emergency response system, Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI), was improved to predict the atmospheric dispersion of radionuclides in detail around a release point as well as on a regional scale for a transboundary nuclear accident. The main improvement is simultaneous atmospheric dispersion calculations of two nested domains, local and regional areas, achieved by exchanging particle information between the domains. In the application of the model to the Chernobyl accident, the distribution of surface deposition of 137Cs was predicted well in the local area around Chernobyl and the European regional area. The improvements were mainly due to the consideration of the reentry of particles from the regional area to the local one and the enhancement of prediction accuracy for precipitation by the nesting calculation in the meteorological model MM5 combined with GEARN. It is concluded that the nesting model developed in this paper is appropriate for nuclear emergencies in which the prediction of both local and regional scale dispersions are required.