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  • 1 Japan Atomic Energy Agency Nuclear Fuel Cycyle Engineering Laboratories 4-33, Muramatsu, Tokai-mura, Naka-gun Ibaraki 319-1194 Japan
  • 2 Nagoya University Graduate School of Engineering Furo-cho, Chikusa-ku Nagoya 464-8063 Japan
  • 3 Hitachi Engineering Co., Ltd. Electric Power Systems Group 3-2-1, Saiwai-cho, Hitachi-shi Ibaraki 317-0073 Japan
  • 4 Ministry of Education, Culture, Sports, Science and Technology Mito Atomic Energy Office 4-1, Atago-cho, Mito-shi Ibaraki 310-0054 Japan
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The performance of the computer code system, SIERRA-II, for calculating the environmental radiation dose due to an accident was assessed over a coastal area, using the environmental monitoring data around the coastally located Tokai Reprocessing Plant (TRP) when 85Kr was discharged during its operation. The agreement within a factor of 5 between the calculated and observed air concentrations of 85Kr in areas of a few km from the TRP was achieved in 57% of the comparison data, disregarding the internal boundary layer. The mean fraction bias was −0.6, which meant a slight overestimation. According to the vertical profile of the atmospheric temperatures, the internal boundary layer was modeled with the SIERRA-II and the agreement became better than when the internal boundary layer was not considered.