A numerical model for the analysis and evaluation of global 137Cs fallout.

Abstract

Fallout 137Cs from atmospheric nuclear detonation tests has been monitored worldwide since the late 1950's. The deviation and the correlation among these monitoring data were analyzed, and their surface deposition characteristics were estimated by the compartment model developed in this research. In the analysis, the scale of space (i.e., size of each compartment) and the degree of detail (i.e., number of compartments) were statistically determined using the global distribution data of 137Cs. The mathematical model was evaluated by comparing the numerically stimulated results with the fallout monitoring data including the 137Cs concentration in sea water. The major findings obtained in this research include that the deposition pattern of 137Cs is dependent on the latitude zone but not on the longitude, the mathematical model is promising for evaluating the dynamic performance of 137Cs in global atmospheric environment and its surface deposition, 137Cs is accumulated more in both the surface and deep ocean water of the North Pacific Ocean and the North Atlantic Ocean than that of other oceans, the 137Cs inventory is decreasing after the peak time in 1965, and the 137Cs inventory in the deep ocean water is decreasing more slowly than that in the surface ocean water.