An Example for improving accuracy of environmental dose assessment with site-specific constants

Mathematical models are usually used to estimate environmental doses for routine and accidental discharge of radionuclides from nuclear installations. To get the best estimate, some adjustment of constants and parameters to be used in the mathematical models should be considered with measurement data. Iodine-129 (129I) was discharged in the environment from the routine operation of Tokai reprocessing plant (TRP). The concentration of 129I in cultivated soil was measured at 1 km, 2 km, 3 km and 8 km southwest of TRP. Site-specific deposition velocities and weathering factors were estimated from data of the atmospheric discharges and the concentrations in soil samples. The deposition velocities and the weathering factors were estimated as 0.5 - 1.5 cm y-1 and 0.0052 - 0.066 y-1, respectively. With the site-specific constants, the estimated results of the concentrations of 129I in soil were improved to show good agreement with the measured ones. (author)