Aeroradiometric measurements in the framework of the ARM05 experiment

The air borne gamma spectrometry (AGS) equipment was employed during the annual exercise of the Swiss national emergency operations centre (NAZ) during June 20th to 23rd, 2005. Following the measurements over the towns of Davos and Lausanne in 2004, the town of Bellinzona was surveyed during this years exercise. Elevated 137 Cs-activity was observed at the slopes of the surrounding mountains compared to the activity values measured in the valley of Bellinzona. In the vicinity of the villages of Coglio and Monte Laura, also located in canton Ticino, 137Cs- hot spots were observed. With a high probability, this Cesium was deposited during the Fallout after the Chernobyl accident. Measurements over a waste disposal site in the Magadino plateau and an industrial area near Bodio showed no indication of artificial radionuclides. The localisation and recovery of radioactive sources was trained together with emergency response teams of canton Ticino. Intercomparison measurements with ground-Ievel in-situ gamma spectrometry and dose rate measurements at the airport of Locarno confirmed the calibration of the AGS equipment. A measuring flight was performed on a profile from the Ajoie to the Mattmark reservoir, supplementing profiles of the previous years. The measurement results mirrored clearly geological and topographical variations along the profile. Lowest dose rates were found over the Bieler lake, the Schwarz glacier near the Balmhorn and the Mattmark reservoir. Measurements in connection with the large scale emergency exercise Kronos II showed a 37 Cs hot-spot northwest of the town Winterthur. The vicinity of the nuclear power plants Goesgen (KKG) and Muehleberg (KKM) was surveyed on behalf of the Swiss federal nuclear safety inspectorate (HSK). As found in previous years, KKG was not detectable from the air, whereas KKM showed a significant signal due to 16N activity. No elevated signals were measured outside of the plant premises. (author)