Development of the Advanced Environmental Transfer and Dose Assessment Model forRadionuclides Released from the Nuclear Fuel Reprocessing Plant in Rokkasho
Shun’ichi HISAMATSU, Takashi IYOGI, Shinji UEDA, Hidenao HASEGAWA, Koichi ABE
Department of Radioecology
Abstract
We have developed an environmental transfer and dose assessment model (ETDAM) for radionuclides
released from the first commercial nuclear fuel reprocessing plant in Japan, located in Rokkasho. The
computer code system was developed on a PC to describe atmospheric dispersion, terrestrial and aquatictransfers, and dose calculations for the released radionuclides. We have used it to estimate areal and temporal
distributions of the radionuclides around the plant and the radiation doses resulting from them. The aquatictransfer model targeted transfer of radionuclides in Lake Obuchi, a brackish lake neighboring thereprocessing plant. The Lake Obuchi model consists of a water current model and an ecosystem model
including lower trophic level organisms. The advanced environmental transfer and dose assessment model(AdvETDAM) is now being developed. AdvETDAM will have the features of ETDAM, and furthermore
include a meteorological model (MM5) for the atmospheric dispersion model, a catchment area model for
Lake Obuchi, an ecosystem model of higher trophic level organisms for Lake Obuchi, and a coastal marine
model. Development of AdvETDAM will be completed at the end of FY 2010.
Meteorological elements such as wind direction and velocity calculated by the meteorological model,
were introduced into the dispersion model through the interface that was constructed in FY 2009. The windfield data from the meteorological model were also processed by the data nudging method to approximate
data observed locally. Meteorological data observed at IES and JNFL were used for the nudging. Gamma-ray
dose rate data at IES during 2007-2008 were affected by 85Kr released from the spent nuclear fuelreprocessing plant. The simulated gamma-ray dose rate using the nudging method agreed fairly well with themeasured data, however, there were occasional disagreements.
The catchment area model is being constructed to describe the inflow of radionuclides from theFutamata River, which is the main river flowing into Lake Obuchi. In FY 2009, the hydrological parametersdescribing water flow in the catchment area were optimized to represent observed water inflow data of theriver. A function to handle transport of radionuclides (3H and 137Cs) by water in the catchment area wasdeveloped, and added to the model. A sub-model of fishes and benthos in Obuchi Lake was developed as apart of the ecosystem model of higher trophic level organisms in the lake. Biomass of several organisms,
such as oysters and polychaete of the benthos, were not well simulated, and showed that parameters in thesub-model need to be optimized. The coastal marine model simulating water flow in the near-shore areaaround the release point of wastewater from the plant was also constructed. The near-shore current produced
from the tidal flow and waves was introduced into this model. The coastal marine model simulated fairly
well the flow data observed at the point located between the release point and Obuchi Fishing Port at themouth of Lake Obuchi. Concentration of 3H, which was released from the plant from July to December in2008, in seawater was estimated by the model. Simulated 3H concentrations in the fishing port agreed fairly
well with the measured data with some exceptions.

Simulated with 2009 atmospheric dispersion model
Simulated with z* atmospheric dispersion model coupled to meteorological model with data nudging
Observed

10
Dose rate (nGy h-1)

Dose rate (nGy h-1)

2015
10
50
2007/9/21
8:00

50
2007/9/21
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2007/9/21
12:00

2007/9/21
14:00

2007/9/21 2008/9/27
14:00
16:00

2008/9/27
16:00

2008/9/27
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2008/9/27
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2008/9/27
22:00

Fig.Fig.1
1 DoseDose
simulatedwith withERDAM
for 85forKr 85release
fromfrom
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simulatedETDAM
Kr release
the spentnuclear
reprocessing