Impacts of C-uptake by plants on the spatial distribution of14C accumulated in vegetation around a nuclear facility-Application of a sophisticated land surface14C model to the Rokkasho reprocessing plant, Japan.
The impacts of carbon uptake by plants on the spatial distribution of radiocarbon (14C) accumulated in vegetation around a nuclear facility were investigated by numerical simulations using a sophisticated land surface14C model (SOLVEG-II). In the simulation, SOLVEG-II was combined with a mesoscale meteorological model and an atmospheric dispersion model. The model combination was applied to simulate the transfer of14CO2and to assess the radiological impact of14C accumulation in rice grains during test operations of the Rokkasho reprocessing plant (RRP), Japan, in 2007. The calculated14C-specific activities in rice grains agreed with the observed activities in paddy fields around the RRP within a factor of four. The annual effective dose delivered from14C in the rice grain was estimated to be less than 0.7 μSv, only 0.07% of the annual effective dose limit of 1 mSv for the public. Numerical experiments of hypothetical continuous atmospheric14CO2release from the RRP showed that the14C-specific activities of rice plants at harvest differed from the annual mean activities in the air. The difference was attributed to seasonal variations in the atmospheric14CO2concentration and the growth of the rice plant. Accumulation of14C in the rice plant significantly increased when14CO2releases were limited during daytime hours, compared with the results observed during the nighttime. These results indicated that plant growth stages and diurnal photosynthesis should be considered in predictions of the ingestion dose of14C for long-term chronic releases and short-term diurnal releases of14CO2, respectively.
Research Group for Environmental Science, Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan. Electronic address: ohta.masakazu@jaea.go.jp.
Masakazu
M
Ota
Research Group for Environmental Science, Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan.
Genki
G
Katata
Research Group for Environmental Science, Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan.
Haruyasu
H
Nagai
Research Group for Environmental Science, Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan.
Hiroaki
H
Terada
D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000032:analysis* / Q000378:metabolism*; D007564:Japan; D008962:Models, Theoretical; D012275:Oryza / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology; D011834:Radiation Monitoring / Q000379:methods*
D002250:Carbon Radioisotopes; D002245:Carbon Dioxide
(14)C; Atmospheric dispersion model; Dose estimation; Land surface model; Photosynthesis; Rice plant