Thule-2003 - Investigation of radioactive contamination

Analyses of marine and terrestrial samples collected in August 2003 from Bylot Sound at Thule, Northwest Greenland, show that plutonium from nuclear weapons in the American B52 plane, which crashed on the sea ice in January 1968, persists in the environment. The highest concentrations of plutonium are found in the marine sediments under the location where the plane crashed.

The distribution of plutonium in the marine sediment is very inhomogeneous and associated with hot particles with activities found up to 1500 Bq 239,240Pu. Sediment samples collected in Wolstenholme Fjord north of the accident site show plutonium concentrations, which illustrates the redistribution of plutonium after the accident.

The total plutonium inventory in the sediments has been assessed based on systematic analyses considering hot particles. The inventory of 239,240Pu in the sediments within a distance of 17 km from the point of impact of the B52 plane is estimated at 2.9 TBq (1 kg). Earlier estimates of the inventory were approximately 1.4 TBq 239,240Pu.

Seawater and seaweed samples show increased concentrations of plutonium in Bylot Sound. The increased concentrations are due to resuspension of plutoniumcontaining particles from the seabed and transport further away from the area. Plutonium concentrations in seawater, seaweed and benthic animals in Bylot Sound are low but clearly above background levels.

All soil samples collected from Narssarssuk show accident plutonium with levels above background. Plutonium is very inhomogeneously distributed and associated with particles in the surface layers. Hot particles were found in soil with activities up to 150 Bq 239,240Pu. Plutonium in the marine environment at Thule presents an insignificant risk to man.

Most plutonium remains in the seabed under Bylot Sound far from man under relatively stable conditions and concentrations of plutonium in seawater and animals are low. However, the plutonium contamination of surface soil at Narssarssuk could constitute a small risk to humans visiting the location if radioactive particles are resuspended in the air so that they might be inhaled.