The source of a gigantic, mysterious leak of radioactive material that swept across Europe in 2017 has been traced to a Russian nuclear facility, which appears to have been preparing materials for experiments in Italy. From a report: The leak released up to 100 times the amount of radiation into the atmosphere that the Fukushima disaster did. Italian scientists were the first to raise the alarm on 2 October, when they noticed a burst of the radioactive ruthenium-106 in the atmosphere. This was quickly corroborated by other monitoring laboratories across Europe. Georg Steinhauser at Leibniz University Hannover in Germany says he was “stunned” when he first noticed the event. Routine surveillance detects several radiation leaks each year, mostly of extremely low levels of radionuclides used in medicine. But this event was different. “The ruthenium-106 was one of a kind. We had never measured anything like this before,” says Steinhauser. Even so, the radiation level wasn’t high enough to impact human health in Europe, although exposure closer to the site of release would have been far greater.