Vertical distributions of (99)Tc and the (99)Tc/(137)Cs activity ratio in the coastal water off Aomori, Japan |
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Authors: | Nakanishi Takahiro Zheng Jian Aono Tatsuo Yamada Masatoshi Kusakabe Masashi |
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Institution: | Nakaminato Laboratory for Marine Radioecology, National Institute of Radiological Sciences, Isozaki-cho 3609, Hitachinaka, Ibaraki 311-1202, Japan |
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Abstract: | Using a sector-field ICP-MS the vertical distributions of the 99Tc concentration and 99Tc/137Cs activity ratio were measured in the coastal waters off Aomori Prefecture, Japan, where a spent-nuclear-fuel reprocessing plant has begun test operation. The 99Tc concentrations in surface water ranged from 1.8 to 2.4 mBq/m3, no greater than the estimated background level. Relatively high 99Tc/137Cs activity ratios (10-12 × 10−4) would be caused by the inflow of the high-99Tc/137Cs water mass from the Japan Sea. There is no observable contamination from the reprocessing plant in the investigated area. The 99Tc concentration and the 99Tc/137Cs activity ratio in water column showed gradual decreases with depth. Our results implied that 99Tc behaves in a more conservative manner than 137Cs in marine environments. |
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Keywords: | 99Tc 137Cs Seawater Vertical distribution Western North Pacific |
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