Environmental Behaviour of Plutonium Accidentally Released at Thule, Greenland

The environmental contamination resulting from the B-52 accident in 1968 at Thule was studied by scientific expeditions in 1968, 1970 and 1974. The contamination was mainly confined to the marine environment, where plutonium was preferentially located in the sediments and the benthic fauna. Plutonium concentrations down through the sediment layers decayed exponentially with a half-depth of 1-2 cm. The horizontal distribution of the plutonium may be described by an exponential expression: mCi 239,240Pn km-2 = 460e-0.28R or by a power function: mCl 239,240Pu km-2 = 370 R-1.2, where R is the distance in km from the point of impact. The inventory of 239,240Pu in the marine environment from the accident was estimated at 25-30 Ci. The amount of 238Pu was about 0.5 Ci. The bottom animals, such as worms and molluscs, showed a horizontal distribution of radioactivity similar to that of the sediments. From 1968 to 1970 the 239,240Pu concentrations in the biota decreased by an order of magnitude, since 1970 the decrease has been less evident. In 1970 and 1974 there were no indications of increased plutonium concentrations in surface seawater or in sea plants or zooplankton. Higher animals such as fish, seabirds and marine mammals have shown no tendency to increasing plutonium levels since the accident. (C)1977Health Physics Society