Thule-2007 - Investigation of radioactive pollution on land

• Main Authors: Nielsen, Sven Poul, Roos, Per
• Format: Book
• Language: English
• Published: Danmarks Tekniske Universitet, Risø Nationallaboratoriet for Bæredygtig Energi 2011
• Subjects: Risø-R-1781; Risø-R-1781(EN); Kap; Saunders; Thule Air Base; Saunders Island; Grønnedal; Atholl; Kap Atholl; Wolstenholme Island; Thule Air
• Online Access: https://orbit.dtu.dk/en/publications/c3b7244a-5c9d-49a1-84aa-4397903103ec; https://backend.orbit.dtu.dk/ws/files/6305377/ris-r-1781.pdf

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 me-tres show elevated levels above 10 kBq m-2 of plutonium. Based on geostatistical analysis, the total amount of pluto-nium 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 col-lection 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 concentra-tions 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 Grønnedal 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 system-atic 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, Mo-riusaq, Saunders Island and Wolstenholme Island. The re-sults showed background levels in soil at these locations which means that no sign of radioactive pollution from the accident was found at these locations.