A RADIOACTIVE cloud that spread around the world in 2017 was likely caused by an explosion at a Russian nuclear plant, scientists have said.
The highest radiation levels of the toxic fumes were detected in Russia – however Moscow has denied responsibility for the mystery leak.
The Kremlin claimed the cloud was caused by the combination of a satellite burning up and a “rather rare meteorological event”.
But a new study conducted by radiation expert Georg Steinhauser, of University of Hanover, and his team has ruled out Moscow’s explanation.
Their findings, based on weather patterns, shows the radioactive fumes were “unquestionably” caused by a nuclear accident.
Professor Steinhauser said: “We measured radioactive ruthenium-106.
“The measurements indicate the largest singular release of radioactivity from a civilian reprocessing plant.”
The last time the rare isotope had been seen in the atmosphere worldwide was after the Chernobyl meltdown in 1986.
TOXIC NUKE BLAST
In October 2017, a radiation monitoring site in Italy spotted a huge increase in the ruthenium-106 – an isotope used in chemotherapy to treat eye tumours.
Over the next few days almost every country in Europe registered the same effect as the radioactive cloud spread.
By the time it was detected the level was too low to raise concerns for public health, but officials were still worried.
However, the low levels of the isotope did not pose a threat to human health, the Office for Radiation Protection said at the time.
Professor Steinhauser said that his research, published in Proceedings of the National Academy of Sciences, ruled Russia’s claims, The Times reports.
The isotope’s vertical distribution in the atmosphere pointed to a source on the ground.
There were no reports of satellites going in autumn 2017 and the use of ruthenium for power would be considered an impractical choice.
By using weather data and tracking the cloud back, Steinhauser and his team found that it originated in the Southern Urals, at the Mayak reprocessing facility.
The data also suggested that it was unlikely that the nuclear plant would not have known about the release.
He said: “This must have left a radiation aura all around the facility.”
By looking at the chemistry of the compounds, they established that there had to have been considerable energy produced in the initial release, probably from a “fire or explosion”.
“There is no question about the source,” he said. “The Russians could and should have been more transparent.
“Not because we want to blame them it’s not about pointing and making fun of them, we want to learn the lessons of this release.”
Rosatom, the Russian State Atomic Energy Corporation, rejected Steinhauser’s findings.
In a statement, the organisation said: “We maintain that there have been no reportable events at any Rosatom-operated plants or facilities.
MOSCOW HITS BACK
“Both the national regulator and experts from an independent international inquiry inspected the Mayak facility back in 2017 and found nothing to suggest that the ruthenium-106 isotope originated from this site, nor found any traces of an alleged accident, nor found any evidence of local staff exposure to elevated levels of radioactivity.
“The recent PNAS report does not contain any new data or facts that differ from the data previously used by the national regulator and the independent international inquiry which reviewed all the scenarios, including that of an alleged accidental leak on the Mayak facility.
“The independent international inquiry has found the accidental release scenario to be inconsistent with the established facts.
“Had an accidental release of the alleged magnitude (250 TBq at once, as suggested in the PNAS report) taken place, the facility’s automated control and monitoring systems would have recorded radioactivity thousands of times higher than what was actually recorded.
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“Such levels would have triggered alarms at the plant to evacuate staff and residents from the surrounding area.
“If staff had been exposed to this much radiation, the ruthenium-106 would have been detectable.
“However, 250 of the Mayak site employees, including those working in its radiochemistry plant, were checked by an independent lab and none of them were found to have any traces of excess exposure.
“Contrary to a speculative theory in the PNAS report, the cerium-144 project activities conducted at the Mayak facility from August to November 2017 were related only to rare-earth concentrate which would only contain barely detectable traces of ruthenium-106 isotope.”
The study’s full findings can found in journal PNAS.
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