Abstract
The brackish Lake Obuchi in Rokkasho-Village, Aomori, Japan, is bordered by nuclear fuel
facilities including a nuclear spent-fuel reprocessing plant under construction. Small amount of
radionuclides will be released from the reprocessing plant, when it will be in operation. These
radionuclides may enter this lake from the ocean by tides, from the land by rivers, and from
the atmosphere by fallout. Therefore, it is necessary to evaluate the impact of released radioac
tive substances to assess the safety of the surrounding environment and develop a radionuclide
transport model in this lake. As the part for constructing for a radionuclide transport model, a
3-D hydrodynamic model was developed for lake current, salinity and water temperature in Lake
and calculated from May to October 1998.
The numerical results were compared favorably with the field measurements of water current
and salinity indicating the validity and predictive capability of the model in this lake. Field ob
servations showed that the model could simulate a formation and elimination of the halocline.
Moreover, the model could well describe flow to a back swamp in the ebb-current of the lake's
lower layer in the spring. However, as a point of the nonconformity, the salinity of middle layer
in the model result was estimated a little lower than field measurement, and it was not possible
to express internal wave of a short time period (1.5 to 6 hours) in the model results.
