Vertical distribution of uranium concentrations and 235U/238U atom ratios in the coastal water off Aomori, Japan: a survey prior to the operation of a nuclear fuel reprocessing facility

From the viewpoint of environmental radioactivity monitoring, the determination of uranium and its isotope ratio is important for identifying and assessing the environmental impact of any unexpected release from nuclear facilities. In this work, a survey was conducted to determine 238U concentrations and 235U/238U atom ratios in coastal waters off Rokkasho Village, Aomori, Japan, where several uranium-related nuclear facilities have been operating since 1992, and a newly constructed nuclear fuel reprocessing plant is scheduled to be commissioned in 2006. Seawater samples were analyzed directly after a 10-fold dilution using isotope dilution sector-field ICP-MS. Based on the obtained results we concluded that there is no observable uranium contamination in the investigated sites. In addition, for the first time, a correlation between uranium concentration and the salinity was established in coastal waters using the SF-ICP-MS technique