Validation of the Advanced Environmental Transfer and Dose Assessment Model forRadionuclides Released from the Nuclear Fuel Reprocessing Plant in Rokkasho
Hidenao HASEGAWA, Hideki KAKIUCHI, Yuhi SATOH, Shinji UEDA
Yuichi TAKAKU, Shun’ichi HISAMATSU
Department of Radioecology
Abstract
The first commercial nuclear fuel reprocessing plant in Japan, located in Rokkasho, Aomori Prefecturefinished its final testing using actual spent nuclear fuels and is now under safety assessment by the Nuclear
Regulation Authority. The advanced environmental transfer and dose assessment model (AdvETDAM) wasdeveloped for estimating areal and temporal distributions of the radionuclides around the plant and theradiation doses resulting from these radionuclides. To validate the model using actual field data, we measured
the concentrations of radionuclides (3H, 14C, 129I, etc.) in environmental, agricultural, and livestock samples
collected at points around the plant and the environmental -ray dose rates at IES. In FY2016, an experimental
agricultural field was set up in IES, in which the atmospheric deposition and concentration of radionuclides
are being measured, to study the transfer process of radionuclides to agricultural products. In addition, longterm observations of suspended substance (SS) flux were started in two rivers, Futamata and Oippe Rivers,around the reprocessing plant to evaluate discharge rate of radionuclides with SS through the rivers.
Because no nuclear fuel rods have been sheared or dissolved at the plant since October 2008, we foundconcentration levels of the radionuclides in most environmental samples collected in FY 2016 were similar tothe background ones before the plant test operation, excluding several samples. Iodine-129 deposited on soil
and lake sediment surfaces around the plant has still remained at a higher level than each background level.
Since the AdvETDAM simulated the maximum 129I atmospheric deposition during the plant test
operation period at an unexpected point on the mountainside north of the reprocessing plant, we collected soil
samples at the point and analyzed them for 129I. However, the measured 129I inventory was lower than that of
the west side of the plant, showing that further study of both measurements and simulations is necessary.
To improve the accuracy of the model prediction in AdvETDAM, we investigated the distributions andtransfer of radionuclides in terrestrial environment in Fukushima Prefecture after the accident at theFukushima Dai-ichi Nuclear Power Plant. In FY 2016, we studied the following subjects: 1) the re-suspension
rate of radiocesium and 2) the discharge rate of radiocesium via rivers. The wind direction weighted mean resuspension factor of 137Cs in Namie Town (1.0×10-11 - 1.0×10-9 in FY 2013 - 2016) has become similar to orlower than the annual mean resuspension factor, (atmospheric 137Cs concentration)/(137Cs deposition density),
observed at Chernobyl and in European countries (1×10-10 - 1×10-6). The discharge rate of 137Cs from the rivercatchments of the two small rivers in Iitate Village during 2016 was less than 2% of 137Cs deposited in thecatchments, showing that most of the radiocesium has still remained on the soil surface in the catchments.

Fig.1 Distribution map of measured excess 129I inventories from background in Rokkasho Village with a color
map showing values predicted by AdvETDAM. RP indicates the nuclear fuel reprocessing plant.