Concentrations of iodine-129 in coastal surface sediments around spent nuclear fuel reprocessing plant at Rokkasho, Japan, during and after its test operation

Concentrations of 129I in coastal surface sediment samples from the east coast of Aomori, Japan, 2–65 km away from the wastewater outlet of the nuclear fuel reprocessing plant at Rokkasho, Japan, were measured from 2006 to 2010. No clear effect on 129I/127I atom ratios in marine sediments was observed, although 129I was discharged from the plant, during its test operation using actual spent fuel, mainly between 2006 and 2008. The ratio in sediments collected at a fishing port at the mouth of a brackish lake increased in 2007, showing that the 129I migrated from the lake to the port.