Undeclared Russian nuclear accident to blame for 2017 radiation cloud: Study

It was a scene eerily reminiscent of the Chernobyl nuclear accident of 1984, when the news of a suppressed nuclear disaster in Ukraine became evident in Europe only after a Swedish nuclear scientist raised an alarm over an abnormally-high reading of radiation coming from his shoes.

In January, 2017, radiation monitoring institutions detected high levels of Iodine 131 across Europe. In October of 2017, multiple European countries reported abnormally-high levels of ruthenium-106 in the air. Both are radioactive isotopes, with Ruthenium-106 only occuring as a result of nuclear fission, ie, atoms being split. It is an isotope that has not been detected in the earth’s atmosphere since the Chernobyl nuclear disaster.

For it to reach so many European nations suggests a fission-related incident. An international radiation monitoring group, the Ring of Five, sounded an alarm.

Russia confirmed the presence of radiation a month later, but did not identify its source. The country’s meteorological agencies did, however, identify the highest concentrations of radiation at a town 30km from the Mayak nuclear power plant, the site of the third-deadliest nuclear accident in human history in 1957. Later that year, Russian state sources, comprising a commission from Rosatom, the Nuclear Safety Institute of the Russian Academy of Science and other groups, later said that they found no abnormal concentrations of ruthenium-106 at Mayak, and that the radiation in the air could be attributed, “among other things, to the burning in the atmosphere of an artificial satellite or its fragment.”

Now, on July 26, the largest study yet conducted on the incident has confirmed that the source of the radiation came from the Southern Urals region of Russia — which comprises Mayak — and that it was no satellite.

A team of 70 scientists led by research engineer Olivier Masson looked at 1,100 atmospheric and 200 deposition data points from Eurasia. They reconstructed the spread of the radiation as well as the age of the radioactive material. Two points stand out from their findings: One, that the radioactive material was less than two years old and that it was released from somewhere in the Southern Ural region. Two, that it was probably released during an ‘advanced stage’ of nuclear fuel reprocessing, sometime around the end of September, 2017.

Luckily, the concentrations found were not enough to cause public harm, and Ruthenium-106 has a half life of just short of 374 days, which means that half of its atoms radioactive material would decay in little over a year, with the entire quantity gone by two.

The study traced the chronology of ruthenium-106 detections across Europe, identifying only Russia and most likely the Mayak nuclear facility as the possible source for the radioactive plumes (the highest concentrations were found in Romania but the width of the plume suggested it came from outside the country).

During the Cold War, Mayak was among the largest nuclear facilities of the Soviet Union. A chemical explosion at the plant in 1957 released 2,700 trillion becquerels (units of radiation), creating the 100-km long ‘East Ural Radioactive Trace’. For comparison, the 2017 radioactive cloud registered levels close to just 150 micro-becquerels.

The study discussed a likely explanation for the release — a botched job at reprocessing spent nuclear fuel. In this hypothesis, the Mayak plant was attempting to produce Cerium-144 in order to participate in neutrino research experiments at the Gran Sasso lab in Italy (the world’s largets underground research centre. A hitch during this process could have led to a series of events that would have produced ruthenium-106 in the detected concentrations.

A brief history of the Ring of Five: A global radiation monitoring network

In the early 1980s, despite the end of atmospheric nuclear bomb testing by China, scientists in Europe continued to find radioactive particles in the atmosphere. In 1983, a group of North European countries decided to share data with one another whenever even the most-minute levels of radioisotopes were detected in the air. This informal grouping became known as the 'Ring of Five' (RoF): Their first big test came in 1986 with the hushed-up Chernobyl nuclear disaster.

Decades since, the RoF has expanded to 22 members (though it has kept its old name), with the criteria for joining being that member-states have the ability to detect particles to within a tenth of a micro-becquerels per cubic meter (µBq/m3) — a sub-atomic level of precision for measuring radioactive emissions.