Detection of traces of ruthenium 106 in the ambient air in France and in several European countries in October: no risk identified for the population in France

As part of its duty of radioactivity monitoring nationwide, the French Institute for Radiation Protection and Nuclear Safety (IRSN) measured the presence of ruthenium 106 in south-eastern France, between the end of September and the beginning of October 2017, albeit at very low levels, representing a few microbecquerels per cubic metre (µBq/m³). This detection led to the distribution by IRSN of several information notices on its website www.irsn.fr.

ASN and IRSN contacts with their European counterparts confirmed the detection of ruthenium 106 in the ambient air during the same period in at least fourteen European countries. Once informed of this situation, the International Atomic Energy Agency (IAEA) asked all member states to communicate their measurement results for this radionuclide. The highest value reported by IAEA, from among about 400 results collected, stood at 0.15 Bq/m³ and was measured in Romania on 30 September 2017. The falling activity levels measured, which are currently below the detection threshold, show that this episode is now over.

As ruthenium 106 is not normally detected in the air, its presence can only be linked to an uncontrolled release. The absence of any other artificial radionuclide rules out the possibility of a release from a nuclear reactor. However, a release such as this could come from a spent nuclear fuel reprocessing activity or the production of radioactive sources.

However, as yet, no country has informed IAEA that it is the origin of this release, as required by the 1986 convention on the early notification of a nuclear accident.

IRSN carried out simulations to recreate the release from the observed measurement results. It compared its results with those of other Technical support organisations (TSO) in Europe, working with different methods and models. All of these simulations show that the most probable origin of this release is the southern Urals, without it being possible to be any more precise. The event which lead to this release most probably occurred during the last few days of September and the quantity of ruthenium 106 dispersed indicates that this release could be the result of an accident.

The levels of atmospheric contamination by ruthenium 106 which were observed in France and the other European countries have no consequences for health and the environment and thus required no measures to protect the populations from the risk of inhalation. ASN also examined the risk linked to the consumption of imported foodstuffs.

According to IRSN, the maximum allowable radioactive contamination levels for foodstuffs as stipulated by the European regulations could have been exceeded within a radius of a few tens of kilometres around the point of origin of the release. However, ruthenium transfer through the food chain is very slight. Therefore the estimated radiological doses linked to the consumption of goods from the environs of the site of the accident, mushrooms in particular, show that there is no identified health risk for consumers in France.

On the basis of this information, ASN therefore considered that there was no justification for implementing systematic checks on the radioactivity levels of foodstuffs imported into France and which could come from the southern Urals.