Lagrangian models for nuclear studies; Examples and applications

Arnold, D.*; Seibert, P.*; Nagai, Haruyasu  ; Wotawa, G.*; Skomorowski, P.*; Baumann-Stanzer, K.*; Polreich, E.*; Langer, M.*; Jones, A.*; Hort, M.*; Andronopoulos, S.*; Bartzis, J. G.*; Davakis, E.*; Kaufmann, P.*; Vargas, A.*

WSPEEDI uses a combination of non-hydrostatic mesoscale atmospheric model MM5 and Lagrangian particle dispersion model GEARN. MM5 is a community model having many users all over the world and is used for the official weather forecast by some countries. GEARN calculates the atmospheric dispersion of radionuclides by tracing the trajectories of a large number of marker particles discharged from a release point. Japan Atomic Energy Agency (JAEA) has been undertaking the task to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Plant accident by using both environmental monitoring data and computer simulation on the dispersion of radioactive materials in the environment. As the first step, the source term of radioactive materials discharged into the atmosphere was estimated. Then, by using the estimated source term, detailed analysis on the local atmospheric dispersion around the Fukushima Daiichi Nuclear Power Plant has been carried out.