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  • Author or Editor: Tatsuo Aono x
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Abstract  

Five survey cruises were carried out from 2004 to 2007 to determine 137Cs concentrations in the water columns off Rokkasho Village, Aomori Prefecture, Japan, where the spent nuclear fuel reprocessing plant of Japan Nuclear Fuel Ltd has been undergoing test operation since March 2006. Seawater samples were collected with a large volume in situ filtration and concentration system at different depths in the water column. 137Cs in particulate form could not be detected in the survey area. Dissolved 137Cs showed temporal variation, especially in the surface water. Based on the results, it was concluded that no observable 137Cs contamination was present in the investigated area. The distribution of 137Cs concentrations was influenced by the mixing between the Tsugaru and Oyashio Currents.

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Abstract  

For safety assessments of geological repositories of nuclear waste, understanding of uranium (U) fate in estuarine areas is important because U chemical behavior in the areas is expected to be complex. Environmental transfer parameters such as sediment–water distribution coefficients (K d) and concentration ratios (CRs) for marine organisms are useful in mathematical models for the assessment. However, due to its low concentration in estuarine water, K d and CF data for U are scarce. Thus we studied a rapid method for separation and concentration of U from estuarine water samples using NOBIAS-CHELATE PA1 resin columns followed by inductively coupled plasma mass spectrometry (ICP-MS) for U measurement. Chemical recovery was about 100% at pH of 5.7 ± 0.1 from the water samples and alkali and alkaline earth metals were removed. The method was used to measure U concentrations in estuarine water samples collected at eight Japanese estuarine areas; they ranged from 0.1 to 3.8 μg L−1. We also measured U concentrations in sediment and marine organism samples by ICP-MS after acid digestion. Using these values, we observed K d (range: 39–284 L kg−1) and CRs (0.86–52 L kg−1 for macroalgae, 0.087–15 L kg−1 for crustaceans, and 0.52–93 L kg−1 for molluscs).

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