In an information notice published in French on November 15 2011, IRSN reported that it had detected traces of iodine-131 in the form of airborne particles. The traces were detected in a number of samples taken by aerosol monitoring stations in the IRSN OPERA-Air network. The results of sampling measurements taken over the first ten days of November were around a few microbecquerels per cubic meter of air (µBq/m3). These values are close to the detection limits of the most effective measuring methods. Although iodine-131 is not normally found in the air throughout the country, its presence did not give any cause for concern for the population's health or the environment.
It was detected in France following similar detection reports in various countries in central and northern Europe. As the reasons for this radioactive pollution were unknown, IRSN performed trajectory calculations to try to locate the origin of the air masses transporting the iodine-131. Meanwhile, the International Atomic Energy Agency (IAEA) issued a press release on November 17, indicating that it had received information from the Hungarian Atomic Energy Authority (HAEA) that «… the source of the iodine-131 detected in Europe was most probably a release to the atmosphere from the Institute of Isotopes Ltd., Budapest ». The institute produces radioisotopes for healthcare, industrial, and research applications. According to the HAEA, the release is thought to have begun on September 8, 2011, with a period of increased intensity on October 12-14. The authority stated, however, that the quantity of iodine-131 released over the period was below the institute's authorized annual radioactive release limit. The cause of the release has yet to be determined and is still under investigation.
The information notice of November 30 2011 provides an update of measurement results in France, together with IRSN's trajectory analysis of the air masses that explain the iodine-131 traces observed in Europe. Based on currently available technical data, IRSN also estimated the radiological impact of this radioactive release in the near field, in other words in the Budapest region.
Download the information notice of November 30, 2011 « No health risk related to airborne traces of iodine-131 from Hungary »
Download the information notice of November 15, 2011 « Detection in France of traces of iodine-131 in the air coming from radioactive releases in a foreign country »