The Development of model and computer program for radioactivity diffusion in global ocean

not registered ; not registered; Maruo, Yoshihiro

To evaluate the long-term environmental effect from the liquid radioactive effluent discharged to the ocean, the radioactivity diffusion model in global ocean and its computer program have been developed. This study consists of the method for the calculation of the velocity field for global ocean, movement and diffusion by particle chasing method, and the model validation by the simulation for the radioactive fallout from the atmospheric nuclear tests. The velocity field obtained by the diagnostic model represented real ocean very well. And it was confirmed that the result of the diffusion by random walk method was equal to that by the diffusion equation. Combined the current field obtained by the diagnosis model and random walk method, the simulation for the radioactive fallout from the atmospheric nuclear tests was carried out. As for Cs and Sr, the calculated value was agreed with the observed value. But as for Pu, the calculated value was not agreed because of the scavenging process. This result implied the necessity for adding Pu scavenging model to this diffusion code. The other side, the appropriate horizontal and vertical diffusion coefficients can be set up by the simulation with changing these coefficients.