The state corporation in charge of Russia's nuclear energy industry, Rosatom, says that a spike in radioactivity over Europe earlier this autumn could have come from a falling satellite.
At a news conference on December 8, nuclear scientist Rafael Arutyunyan said a probe by a commission led by Rosatom found no leaks of the radioactive isotope ruthenium-106 at the Mayak fuel plant or any other facility on the ground.
Suspicions had focused on Mayak, near the city of Chelyabinsk in the southern Urals Mountains, after European institutions raised alarms about a cloud of radioactive pollution detected drifting over the continent in late September and early October.
The French nuclear-safety institute, IRSN, said on November 9 that the ruthenium-106 probably came from a facility such as a nuclear-fuel-treatment site or radioactive medicine center in that part of Russia or to the south in Kazakhstan.
It said the pollution did not pose health or environmental risk, but the lack or a warning from Moscow raised concerns -- in Russia and abroad -- that the government could be withholding information about accidents involving radioactivity.
Arutyunyan said the commission concluded that the contamination could have resulted from a satellite with ruthenium-106 aboard burning up upon entry into the Earth's atmosphere.
France's IRSN initially believed the radioactive material might have come from a satellite equipped with a generator containing ruthenium.
But IRSN health director Jean-Christophe Gariel, said in November that the institute no longer believed that was the case.
He cited an investigation by the UN's International Atomic Energy Agency, which found that no satellites powered by ruthenium had reentered the atmosphere during the time period in question.
Mayak has denied responsibility, saying it has not produced ruthenium-106 in 2017 and that its emissions into the atmosphere had been normal throughout.
With reporting by TASS, Interfax, and The Telegraph