Atmospheric-dispersion database system that can immediately provide calculation results for various source term and meteorological conditions

We have estimated source term and analyzed processes of atmospheric dispersion against atmospheric discharge of radioactive materials due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident by atmospheric-dispersion calculation using the Worldwide version of System for Environmental Emergency Dose Information (WSPEEDI). On the basis of this experience, we developed an atmospheric-dispersion calculation method that can respond to various needs for dispersion prediction in a nuclear emergency and provide useful information for emergency-response planning. By this method, if a release point, such as a nuclear facility, is known, it is possible to immediately obtain the prediction results by applying provided source term (released radionuclides, release rate, and release period) to the database of dispersion-calculation results prepared in advance without specifying source term. With this function, it is easy to compare results by applying many kinds of source term with monitoring data, and to find out the optimum source term. By preparing a database by this calculation with past long-term meteorological data, we can immediately get dispersion-calculation results for various source term and meteorological conditions. This database is useful for pre-accident planning, such as optimization of a monitoring plan and understanding of events to be supposed in considering emergency countermeasures.