In late September 2017, meteorology and monitoring stations across Europe detected a spike of radiation in the air, suggesting an undeclared atmospheric release of radioactive substances. Till these days, no individual or organization has come forward to claim responsibility for this serious incident.
According to the latest report composed by a group of 70 scientists from around the world, this accidental release of ruthenium-106—the main radioisotope of the radioactive cloud —very likely originated in Russia's southern Ural mountain.
Ruthenium-106 (Ru-106) is a radioactive, beta particle-emitting nuclide that can be produced from uranium-235 fission. In its pure form, Ru-106 is useful in radiotherapy for cancer patients. It can also be used as fuel material to power small spacecraft via thermoelectric effect.
It was estimated that approximately 100 to 300 trillion becquerels (TBq) of radiation was spread across a vast region during the incidence, but there was no reporting on any harmful effects to humans thanks to its quick dilution in the air. (In comparison, between March 11 and April 5, 2011, Fukushima nuclear disaster released about 130 PBq for iodine-131 and 11 PBq for cesium-137, which was 1,000 times bigger in scale).
With a physical half-life about 374 days, the radioactive particulate can linger on surfaces for quite a while when they drop out from the air. The isotope's unique decay time-span and its intense beta energy provided scientists clues to help identify the nuclide.
By combing through the atmospheric data of Ru-106 collected at 176 measuring stations in 30 countries from the affected region, the group of nuclear scientists, led by Olivier Masson from the Institut de radioprotection et de sûreté nucléaire (IRSN) in France, concluded with high confidence that the release originated from a nuclear reprocessing facility located in the Southern Urals, possibly from the Russia's Mayak nuclear complex.
Another point from their report is that the plume of Ru-106 was unlikely the result of a crashed satellite, which the Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE, the operating body of the Mayak facility) suggested as a source of the release according to their own investigation back in 2017.
In communication with ScienceAlert, Russia's nuclear authority disputed the findings in the report and denied that the Mayak facility was related to the release.
This report is published in the journal PNAS.
Russia confirms radioactivity spike around the Ural Mountains (AP)
Source: Science Alert