The measurement flights of the exercise ARM12 were performed between June 25^th and 29^th. The exercise was organized by the National Emergency Operations Centre (NEOC) under coordination from the Expert Group for Aeroradiometrics (FAR). According to the alternating schedule of the annual ARM exercises, the environs of the nuclear power plants Leibstadt (KKL) and Beznau (KKB) were inspected together with the premises of the Paul Scherrer Institut (PSI) and the interim storage facility Zwischenlager Würenlingen AG (ZWILAG). As in previous years, the distinction between pressurised and boiling water reactor is clearly identified from the photon spectra. The intermediate storage facility ZWILAG could not be detected with airborne gamma-spectrometry. Due to the intersection of the flight line with air discharged from the stack of the accelerators located at the western part of the Paul Scherrer Institut (PSI) a clear signal is observed over PSI. The detected radionuclides are a controllled and permitted release from the stack of PSI West.
Measurement flights over Zurich city continued the series of baseline measurements over Swiss towns and cities. Both the results over Zurich and over the freight yard near Spreitenbach showed homogeneous results at background level. The results of further measurements near Lac d’Emosson and Limmerensee reflect the alpine topography and local geological features.
A profile from Weinfelden to the Great St. Bernhard was measured to supplement the data base of Swiss aeroradiometric measurements. The results reflect changes in ground radiation and are characterised by the attenuation of photons from natural radionuclides in water bodies, glaciers and snow fields.