Diverse monitoring approaches reveal C dispersion pattern and its impact on the environment around the Tokai reprocessing plant

Koarashi, Jun   ; Fujita, Hiroki; Watanabe, Hitoshi; Sumiya, Shuichi 

Carbon-14 (C) is of great interest in dose assessment due to the nuclear industry. We collected terrestrial environmental samples at various locations at different time intervals around the Tokai Reprocessing Plant (TRP), and measured their C concentrations. The results consistently gave the picture of C dispersion pattern that the prevailing wind conveyed C plume, and as a result caused elevated C concentrations in the area 2-3 km southwest of the main stack. The C increases were however quite temporary. The C concentrations in vegetations generally followed those in atmospheric CO, but seemed different in the integrated period of reflecting the atmospheric C level between vegetations. We found the highest C concentration of 374 Bq/kg-C. The annual effective dose due to C was estimated to be only 0.07% of the annual effective dose limit. Thus, we conclude that the C releases from the TRP have a very slight impact both on the environment and on the public.