The distribution of 137Cs in the Meråker and Grong/Snåsavatnet Areas

Abstract

Helicopter radiometric data collected over parts of Nord-Trøndelag between 1988 and 1991 have been reprocessed to produce maps of 137Cs fallout resulting from the reactor accident in Chernobyl. Backcalculated data indicate that some parts of Nord-Trøndelag received 137Cs levels in 1986 were one sixth of levels publi- shed for certain areas in the 30 mile exclusion zone around Chernobyl. Four maps at 1:100.000 scale have been produced. Two cover the municipality of Meråker and 2 cover the map sheets Grong and parts of Harran, Overhalla, Snåsa and Snåsavatnet. Each area is covered by a map of cesium counts at helicopter level and a map showing apparent ground concentrations back calculated to 1986. The Meråker cesium map is compared to topographic and quaternary geological maps. The distributions of radio-cesium are found to be consistent with the behaviour as documented in the literature. We demonstrate that airborne mapping is a rapid and cost effective technique for mapping contaminated areas, and that it has potential for monitoring the movement of cesium in the environment following a nuclear accident.