The transfer to land of actinide-bearing sediments from the Irish sea by spray

Abstract

Since 1957, British Nuclear Fuels Ltd. have discharged to the Irish Sea about 18000 Ci of plutonium alpha activity, in addition to other actinides and fission products. Experiments are described which demonstrate that seaspray in the area is enriched with actinides relative to their concentration in bulk seawater. It has been shown that the actinides in spray are derived predominantly from sediment suspended in seawater in the surf zone, and enrichment factors of 3 to 50 for plutonium and americium in spray relative to unfiltered seawater have been observed. It has also been shown that the intertidal zone is a relatively insignificant source of airborne actinides. The transport and vertical distribution of actinides and seaspray has been determined at heights of up to 10 m above the beach and as far as 9 km inland. These measurements indicate that, in addition to the surf zone, a small but significant source of less enriched spray is present further out to sea, and possible mechanisms are discussed. It is estimated that about 2 Ci of 239+240Pu may have been transferred from the sea to land by seaspray during the last 15 years. The greatest concentration of 239+240Pu detected in air was 22 fCi m −3 and it is concluded that it is improbable that any member of the public would have been exposed to more than 1% of the ICRP dose limit.