Fukushima-derived radionuclides in sediments of the Japanese Pacific Ocean coast and various Japanese water samples (seawater, tap water, and coolant water of Fukushima Daiichi reactor unit 5)

We investigated Ocean sediments and seawater from inside the Fukushima exclusion zone and found radiocesium ((134)Cs and (137)Cs) up to 800 Bq kg(−1) as well as (90)Sr up to 5.6 Bq kg(−1). This is one of the first reports on radiostrontium in sea sediments from the Fukushima exclusion zone. Seawater exhibited contamination levels up to 5.3 Bq kg(−1) radiocesium. Tap water from Tokyo from weeks after the accident exhibited detectable but harmless activities of radiocesium (well below the regulatory limit). Analysis of the Unit 5 reactor coolant (finding only (3)H and even low (129)I) leads to the conclusion that the purification techniques for reactor coolant employed at Fukushima Daiichi are very effective.