WSPEEDI(Worldwide Version of SPEEDI) : A computer code system for the prediction of radiological impacts on Japanese due to a nuclear accident in foreign countries

A computer code system has been developed for near real-time dose assessment during radiological emergencies. The system WSPEEDI, the worldwide version of SPEEDI (System for Prediction of Environmental Emergency Dose Information) aims at predicting the radiological impact on Japanese due to a nuclear accident in foreign countries. WSPEEDI consists of a mass-consistent wind model WSYNOP for large-scale wind fields and a particle random walk model GEARN for atmospheric dispersion and dry and wet deposition of radioactivity. The models are integrated into a computer code system together with a system control software, worldwide geographic database, meteorological data processor and graphic software. The performance of the models has been evaluated using the Chernobyl case with reliable source terms, well-established meteorological data and a comprehensive monitoring database. Furthermore, the response of the system has been examined by near real-time simulations of the European Tracer Experiment (ETEX), carried out over about 2,000 km area in Europe.