Abstract
A method was developed to calculate radionuclides concentration in the Japan Sea. The concentration of radioactive fallout (137Cs, 239'240Pu) due to atmospheric nuclear weapons tests was calculated to verify in the Japan Sea the method by comparison between calculated and observed values. The flow field was calculated by Japan Sea circulation model, which was improved in vertical resolution. We confirmed that influence of seasonal change of flow field was small on calculated results of fallout concentration. Therefore, annual mean flow field was adapted for this method. 137Cs and 239'240Pu concentrations were calculated by this method. Calculated 137Cs concentration agrees well with observed value. However, calculated 239'240Pu concentration was underestimated. This result suggests that 239'240Pu concentration in the Japan Sea might be affected by not only global fallout but also another source.
