Simulation of the atmospheric dispersion of Kr from a reprocessing plant over a coastal area; Performance examination of an emergency environmental radiation dose evaluation code system "SIERRA-II"

Takeyasu, Masanori ; Iida, Takao*; Watanabe, Hitoshi; Takeishi, Minoru ; Yamamoto, Asao*

The performance of the computer code system "SIERRA-II" for calculating the environmental radiation dose due to an accident was assessed using the environmental monitoring data around the coastally located Tokai Reprocessing Plant (TRP) when Kr was discharged during its operation. The agreement within a factor of 5 between the calculated and observed air concentrations of Kr in areas of a few km from the TRP was achieved in 57% of the comparison data, and the agreement within a factor of 2 was obtained in 29%, disregarding the internal boundary layer. According to the vertical profile of atmospheric temperatures, the internal boundary layer was modeled in the SIERRA-II and the agreement became better than when the internal boundary layer was not considered.