Inventories of 239+240Pu and 137Cs in sediment cores from brackish Lake Obuchi, Rokkasho Village, Japan, bordered by nuclear fuel cycle facilities

The aim of this study was to measure the distribution and inventories of 239+240Pu and 137Cs in sediment core samples from brackish Lake Obuchi, Which is bordered by nuclear fuel facilities in Rokkasho Village, Japan. The inventories of the 239+240Pu activity in the sediment samples from the estuary of a freshwater river, the central point of the lake, and the deepest point in the lake were 0.18, 0.29, and 0.24 kBq m-2, respectively. The inventories of 137Cs in sediments were 0.83-1.2 kBq m-2. the mean 239+240Pu/137Cs activity ratio was 0.23. The 239+240Pu/137Cs activity ratio was approximately 10 times the ratio expected from global fallout. The inventory of 239+240Pu in sediments was higher than the inventory expected from atmospheric fallout, but the 137Cs inventory was significantly lower than expected. (author)