1 Fission product activity measurements in air particulate filters collected after Fukushima accident at Palermo, Italy Salvatore Rizzo, Elio Tomarchio * Palermo University, Energy Department, Nuclear Engineering Section, Viale delle Scienze, Building No. 6, 90128 Palermo (Italy) Abstract. In the framework of routine operation of AGN-201 COSTANZA Nuclear research reactor, measurements of radionuclide air concentration are periodically performed by filtering an high volume of air through paper filters and by using HPGe gamma-ray spectrometry. After Fukushima accident, a series of samplings was carried out with a daily frequency so to detect the possible arrival of air radioactive contamination and to follow its evolution. Particulate collection was performed by suction of atmospheric air through 45cm × 45cm Sofiltra-Poelman HYN-75 (Bleu type) cellulose filter paper using a high-volume air sampler located on the roof of our department 20 m above ground-level. The sampling time was generally set to 14 h from 6 p.m. to 8 a.m. the next day; the filtered air volume is typically 10,000-13,000 m 3 . After particulate sampling, the filters were sprayed with a suitable fixer, cut into strips, folded and pressed into 6 cm side and 0.7 cm thickness packets by a 15-t press. These samples are then measured by HPGe gamma spectrometric systems. The analysis of the spectrometric measurements highlights the presence of 131 I, 134 Cs, 136 Cs , 137 Cs and, only for a sample, traces of 132 Te- 132 I. The trend of air concentration values shows a rapid initial increase, related to the most significant release from Fukushima plant, followed by a steady decrease in the values caused by air masses dilution and, only for 131 I and 136 Cs, radioactive decay. From a dose to population point of view, no significant values are obtained. Compared with the values determined immediately after the Chernobyl accident, the concentration values are from 1,000 to 100,000 times lower while, for only 137 Cs, are comparable with the ones highlighted after the Algeciras (Spain) accident. . KEYWORDS: Air Particulate, Fukushima accident, radionuclide concentration. 1. Introduction A research activity on environmental radioactivity monitoring was held for many years at Energy Department of Palermo University. The analysis started with the detection of radioactive contamination produced by atmospheric nuclear tests in the early sixties of the last century and continued with measurements oriented to determine natural or artificial radioactive compounds in air particulate as a way of transport of various pollutants [1-14]. Particularly interesting are measurements and monitoring activities conducted in the aftermath of the Chernobyl accident [2-5]. For these activities, since 1979 until a few years ago, a sampling station equipped with an high volume sampler (about 15000 m 3 /day) was extensively used. Following the notices on the accident in Fukushima and on a possible contamination in the air, the frequency of sampling was intensified (up to become at least daily) and the samples were analyzed with at least two spectrometric systems. In the following it will show the results of measurements of fission products concentration in the air of Palermo related to Fukushima plant accidental release. The results of the monitoring activity confirm that air concentration values have no significance from a dose point of view, being very far from the limits of concentration in the air provided by rules with reference to population dose. * Presenting author, E-mail: elio.tomarchio@unipa.it