A radioactive cloud that engulfed Europe earlier this year originated in Russia, researchers say.
The exact origin of the cloud has not been verified but the most likely source is a Russian nuclear reprocessing plant. No authority has come forward to confirm any connection with the cloud.
At its point of origin the cloud had had a radioactivity level around 1,000 times higher than recommended levels.
Austria was the first European country to detect unusually high levels of radiation on October 3. They were swiftly followed by Germany, who confirmed their readings were unusually high the very next day.
Radiation levels in the area fluctuated over the following two weeks until the radioactivity tapered away.
The Institute for Radiological Protection and Nuclear Safety reported the cloud of radioactive isotopes had posed no health hazards but that if a similar spike in radiation occurred in Europe, the responsible government would likely have ordered a local evacuation. Their research suggested the cloud originated from Russia.
Their findings suggest the radiation could have come from a medical research plant, a fallen satellite or a nuclear fuel reprocessing site. There have been no reports of a fallen satellite.
Russian authorities have denied that there had been a leak from Mayak, the state-owned plant under scrutiny. The plant has been involved in several incidents in the past, including contaminating a river in 2004 and in 1957 when the plant triggered what has been called the world's “second biggest nuclear disaster in history” after a storage tank exploded and tens of thousands of people were contaminated.
However, on Tuesday, Russia’s Meteorological Service confirmed that it recorded “extremely high contamination” with radioactive isotopes in the southern Urals region at the end of September.
Rosatom, the state-controlled group who own the plant, continue to deny responsibility.