Fig. 4-17 Outline of WSPEEDI The main parts of the system consist of the wind field model and the dispersion model, which require a supercomputer for their large computations. Other system components including the user-friendly man-machine interface, the meteorological data acquisition system, and the graphical output functions are essential for quick and easy operation under emergency conditions.

Fig. 4-18 Surface air concentration of ETEX tracer gas predicted by WSPEEDI Concentration distribution at 48 hours after the release in France (marked as +) is depicted by the colored regions.

From the Chernobyl reactor accident, we have learned that an accident of that scale and severity might cause widespread radionuclide contamination. The number of nuclear power plants in the world is steadily increasing and no country can be free from the potential influence of a severe accident in another country. It is therefore important to have the capability to predict atmospheric transport of radionuclides from an accident site. JAERI has developed a real-time prediction system, SPEEDI (System for Prediction of Environmental Emergency Dose Information). The system has been fully operational and embodies all nuclear power plants in Japan. Recently, JAERI has developed a prototype, WSPEEDI (the worldwide version of SPEEDI) by enhancing the performance of prediction models and by enlarging the application scope. Utilizing a supercomputer with a network for worldwide meteorological data (Fig. 4-17), the new system can quickly trace the movement of a radioactive cloud over a large area up to the scale of a hemisphere. To examine the performance of this system, JAERI is participating in the international cooperative study, ETEX (European Tracer EXperiment). In the ETEX project, nontoxic artificial tracer gas was released and the concentration was measured at about 170 stations located over all of Europe. WSPEEDI, which was only informed of the release at release time, predicted the evolution of concentration distribution for the next 60 hours and returned the predicted results to the project center in Europe within three hours of release time. Figure 4-18 is an example of the concentration distribution calculated by WSPEEDI. The results will be meticulously compared with the experimental data.

Reference M. Chino et al., SPEEDI and WSPEEDI: Japanese Emergency Response System to Predict Radiological Impacts in Local and Worldwide Areas Due to Nuclear Accident, Radiation Protection Dosimetry , 50, 145 (1993).

Select a topic in left column