Study: Fukushima plutonium in Pacific Ocean from ‘liquid direct releases’?

Much less information is available in the case of plutonium isotopes. Trace amounts of Pu isotopes originating from the accident have been identified in soil samples. While it is known that atmospheric releases of Pu were several orders of magnitude lower than that from Chernobyl accident, no information on Pu isotopes in the liquid direct releases to the sea is available. Pu isotopes have been measured in marine sediments outside a 30 km radius circle around Fukushima. Results do not show any contamination due to the accident. Instead Pu isotopes here detected are attributed to global fallout. However, the situation inside the 30 km zone remains unknown. It could be possible that Pu isotopes entered this coastal area from the direct release of contaminated water in early April 2011. The objective for this work consists of showing, by means of numerical modelling, that, if Pu contamination originating from the accident would be present in sediments of the close area to Fukushima, contamination would not reach areas far from the plant. Contamination would be restricted to the close area because of the low mobility of Pu. Thus, it would not be detected if samples are not collected there. Consequently, further studies on the determination of Pu isotopes in seawater and sediments within the 30 km zone would be required.

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