Thule-2007 - Investigation of radioactive pollution on land

A survey of radioactive pollution on land in the Thule area from an airplane accident in 1968 was carried out during 2007 and 2008. The results show levels of plutonium in soil at Narsaarsuk ranging from background values around 39 Bq m-2 up to levels of 1.7 MBq m-2. Local sub-areas of sizes ranging from a few hundred to a few thousands of square metres show elevated levels above 10 kBq m-2 of plutonium. Based on geostatistical analysis, the total amount of plutonium in soil at Narsaarsuk is estimated at 270 GBq (100 g). Investigations were carried out at Narsaarsuk to determine the occurrence of radioactive particles in air. This involved collection of airborne particles with an air sampler, collection of airborne particles on sticky foils, collection of rain samples and collection of particles that could be resuspended by wind from the soil surface to the air. Small amounts of plutonium were found in air and rain samples, but the derived concentrations in air were very low corresponding to typical back-ground levels in Europe in the range 1-10 nBq m-3. A few small particles were found on the soil surface with activities up to 1000 Bq plutonium but the air and rain samples showed no sign of resuspension of such particles from the soil. Local areas with elevated levels of radioactive pollution in soil were found at Kap Atholl and Groennedal 15-20 km south of Narsaarsuk. Here the levels were lower than those in the Narsaarsuk area but clearly above background. It was not possible within this project to carry out a systematic survey of the entire region. Hence, it cannot be excluded that there may be more local sub-areas than those identified with elevated levels of radioactive pollution in soil. Screening surveys were carried out at Thule Air Base, Moriusaq, Saunders Island and Wolstenholme Island. The results showed background levels in soil at these locations which means that no sign of radioactive pollution from the accident was found at these locations. (Author)