Improvement of the Advanced Environmental Transfer and Dose Assessment Model forRadionuclides Released from the Nuclear Fuel Reprocessing Plant in Rokkasho
Takashi IYOGI, Koichi ABE, Shinji UEDA, Hidenao HASEGAWA, Toshihiro SHIBATA,
Shun’ichi HISAMATSU
Department of Radioecology
Abstract
We have developed the advanced environmental transfer and dose assessment model (AdvETDAM 1.1) forradionuclides released from the first Japanese commercial nuclear fuel reprocessing plant located in Rokkasho.
The computer code system was developed on personal computers to describe atmospheric dispersion, terrestrial
and aquatic transfers, and dose calculations for the released radionuclides. The model consists of an atmosphericdispersion model with a meteorological model (MM5), a terrestrial transfer model, an aquatic transfer model in
Lake Obuchi, which is a brackish lake neighboring the reprocessing plant, and its catchment area, and a coastal
marine model for the Rokkasho coast.
In FY 2013, to extend the aquatic transfer model to Lake Takahoko and its catchment area, we examined
the basic design of the models. Coastal Sea Modeling System for Hydrodynamic Process (COSMOS) andPrinceton Ocean Model (POM) were selected as candidates to simulate water currents in Lake Takahoko. In FY
2014, both models will be implemented and tested, and the better one will be adopted as the hydrological model.
Also, as candidates to simulate water transfer in the catchment area in Lake Takahoko, Soil and Water
Assessment Tool (SWAT) and Water and Energy Transfer Process (WEP) were selected and will be tested.
Radionuclide transfer models will be added to the selected hydrological models in FY 2015.
We have collected basic hydrological data for Lake Takahoko to construct the hydrodynamic model,including the water currents in Lake Takahoko and characteristics in the lake bottom sediment (organic mattercontent, etc.). To construct the hydrological model for the Lake Takahoko catchment area, basic hydrological
data, such as water flow rates in rivers flowing into Lake Takahoko and groundwater levels, have been collected.
In FY 2013, electrical resistivity tomography in the subsurface ground was carried out in the river mouth areas toevaluated intrusion of seawater into these areas. In addition, a surface run-off ratio during a storm event, which isone of the most important factors for the hydrological model in a catchment area, was measured for theMuronokubo River and Tokusari River by using the difference of the stable isotopic ratios of oxygen in
rainwater and groundwater. As a result, we estimated the surface run-off ratios in a storm event were 15% and
10% for the Muronokubo River and Tokusari River, respectively.

-82
Muronokubo River

-11

1.5

Discharge rate (m3 s-1 )

0.5

-14

Oxygen isotope ratio inprecipitation
Discharge-17-20-802Tokusari River
1.5
1Oxygen isotope ratio in river water-14

Discharge

0.5

Oxygen isotope ratio inprecipitation

0-11-17-20

Sampling date and time (month/day time)
Fig. 1 Temporal variations of discharge (solid line) and oxygen isotope ratio of stream water (solid line withopen triangles) during a storm event from 1:00 on October 16th to 15:00 on the 17th (JST). The
broken line indicates the oxygen isotope ratio of precipitation during the storm in the Tokusari River
catchment area.

Oxygen isotope ratio (‰)

Oxygen isotope ratio in river water1