Air radioactivity levels following the Fukushima reactor accident measured at the Laboratoire Souterrain de Modane, France

The radioactivity levels in the air of the radionuclides released by the Fukushima accident were measured at the Laboratoire Souterrain de Modane, in the South-East of France, during the period 25 March–18 April 2011. Air-filters from the ventilation system exposed for one or two days were measured using low-background gamma-ray spectrometry. In this paper we present the activity concentrations obtained for the radionuclides 131I, 132Te, 134Cs, 137Cs, 95Nb, 95Zr, 106Ru, 140Ba/La and 103Ru. The activity concentration of 131I was of the order of 100 μBq/m3, more than 100 times higher than the activities of other fission products. The highest activities of 131I were measured as a first peak on 30 March and a second peak on 3–4 April. The activity concentrations of 134Cs and 137Cs varied from 5 to 30 μBq/m3. The highest activity concentration recorded for Cs corresponded to the same period as for 131I, with a peak on 2–3 April. The results of the radioactivity concentration levels in grass and mushrooms exposed to the air in the Modane region were also measured. Activity concentrations of 131I of about 100 mBq/m2 were found in grass. ► Air activity concentration following Fukushima accident were measured in Modane, France. ► 131I level in the air was of the order 100 μBq/m3 and 134Cs and 137Cs levels were between 5 and 30 μBq/m3. ► The highest 131I, 134Cs and 137Cs levels were on 30 March and 2–4 April 2011. ► Peak activity levels explained by meteorological conditions and consistent with simulation models.