Mystery ruthenium-106 cloud over Europe

ROSATOM, the Russian state nuclear company, has denied that a radioactive cloud of ruthenium-106 detected over Europe in September came from any of its facilities.

High levels of ruthenium-106, which does not exist in nature and is only a product of uncontrolled fission reactions, were detected in a number of countries in Europe, including Slovakia, Romania, Poland, Italy and France, in late September, as well as in Tatarstan, Volgograd and the Southern Urals. The French Institute for Radioprotection and Nuclear Safety concluded that the cloud had originated from an accident in the southern Ural Mountains, but Russian authorities denied that there had been an accident.

On 20 November, the Russian federal meteorological agency Roshydromet reported that it had found levels of ruthenium-106 several hundred times higher than normal in its samples from late September and early October. The levels were highest at its monitoring stations in Argayash and Novogorny. In Argayash, the levels were 986 levels higher than normal.

The Argayash station is around 30 km from Rosatom’s Mayak nuclear reprocessing facility, but the company says that the leak could not have come from Mayak. It said that all emissions to the atmosphere were within regulations and background radiation checks at the side have remained normal. It added that it had not carried out ruthenium-106 separation at the Mayak site for many years.

Rosatom also pointed out that the radiation dose that people could have received from such a cloud is 20,000 times less than the maximum permissible dose, and therefore poses no danger to human health.

Paddy Reagan, a nuclear expert at the University of Surrey, told the Guardian that if there had been a reactor leak or weapon explosion, other radioisotopes would have been present, so the release of ruthenium-106 was most likely from waste reprocessing.