A Russian nuclear reprocessing plant is the likely source of the mysterious cloud of radioactive ruthenium-106 that spread across Europe in 2017, experts said.
At its most intense, the cloud’s radiation levels reached 176 millibecquerels per cubic meter of air — 100 times higher than noted in Europe after the Fukushima meltdown.
The exact source of the cloud had been uncertain — although the highest radiation levels were detected in Russia, the Federation has denied responsibility for the leak.
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A Russian nuclear reprocessing plant is the likely source of the mysterious cloud of radioactive ruthenium-106 that spread across Europe in 2017, experts said
Ruthenium is part of the platinum group of metals.
It is a hard, silvery-white metal with a shiny surface.
Its melting point is about 2,300 to 2,450°C (4,200 to 4,400°F)
Its discovery is credited to Polish chemist Jedrzej Sniadecki, who announced the announced the discovery of the element in 1808.
Chemists were unable to confirm Sniadecki’s work and, as a result, the element was rediscovered twice more in later years.
The primary uses of ruthenium are in alloys and as catalysts for industrial processes.
Ruthenium-106 is an isotope, or variant with a different number of neutrons in its nucleus, used for radiation therapy to treat eye tumours.
It is sometimes as a source of energy, known as radioisotope thermoelectric generators, used to power satellites.
The radioactive isotope has a half-life of 374 days.
In order to pin down the origins of the incident, radiation expert Georg Steinhauser of the University of Hanover, Germany and colleagues analysed more than 1,300 measurements of the cloud taken from across Europe and beyond.
These recordings were taken across 176 measuring stations in 29 different countries, reflecting the vast geographic spread of the cloud, which not only covered large parts of Europe but reached as far as the Arabian Peninsula, Asia and the Caribbean.
‘We measured radioactive ruthenium-106,’ said Professor Steinhauser.
‘The measurements indicate the largest singular release of radioactivity from a civilian reprocessing plant.’
The team reached this conclusion based on the fact that — unusually — the only radioactive substance measured from the release was ruthenium.
‘We were able to show that the accident occurred in the reprocessing of spent fuel elements, at a very advanced stage, shortly before the end of the process chain,’ said Professor Steinhauser.
‘Even though there is currently no official statement, we have a very good idea of what might have happened.’
By combining the distribution pattern of the radioactive material with atmospheric modelling, the team have concluded that the cloud was released from within the Southern Urals — where the Russian Mayak nuclear processing facility is located.
To date, no nation has claimed responsibility for the release of radioactive material — with Russia having repeatedly denied having had any involvement in the emission.
The Mayak facility is no stranger to nuclear release, having previously emitted one of the largest historical radiation leaks in the September of 1957 — bigger that the release from the Fukushima meltdown and second only to the Chernobyl disaster.
By combining the distribution pattern of the radioactive material with atmospheric modelling, the team have concluded that the cloud was released from within the Southern Urals — where the Russian Mayak nuclear processing facility, pictured, is located
The root of the 1957 incident was the explosion of a tank full of liquid waste generated as a byproduct of plutonium production.
At that time, a tank containing liquid waste from plutonium production had exploded, causing massive contamination of the area.
The researchers have dated the time of the 2017 release to between 18:00 on September 25 and 12:00 on September, 26 — almost 60 years exactly after the 1957 accident.
According to Professor Steinhauser, the incident ‘was a pulsed release that was over very quickly.’
In contrast, the leaks from Chernobyl and Fukushima went on for days.
Even though the release was unusual, the radioactive material did reach a high enough concentration anywhere in Europe to be detrimental to human health.
The full findings of the study were published in the journal PNAS.