According to a report released by the French Radioprotection and Nuclear Safety Institute (IRSN) on Thursday, a cloud of radioactive pollution over Europe detected in recent weeks indicates that there has likely been an accident in a nuclear facility somewhere in Russia or Kazakhstan.  According to their estimation, the incident must have occurred at some point during the last week of September.

Based on the nature of the nuclear pollutants, the IRSN has ruled out the possibility of a reactor meltdown like the Chernobyl disaster that occurred in Soviet controlled Ukraine in 1986.  Instead, their analysis indicates a high likelihood that some sort of accident occurred at either a nuclear fuel treatment site, or potentially at a center for radioactive medicine.  The pollutants are not considered to be in sufficient abundance over Europe to cause a health hazard, however, based on the levels of ruthenium-106 identified, IRSN experts believe it would have required the evacuation of an area kilometers-wide surrounding the accident site.

The IRSN was unable to pinpoint the exact location of the nuclear incident by analyzing the radioactive pollutants, but based on weather patterns they were able to extrapolate that it most likely occurred somewhere south of the Ural Mountains but north of the Volga River, indicating that it must have occurred in Russia or potentially in Kazakhstan.

This map shows the northern and southern limits of where the IRSN believes the incident must have occurred. | Map courtesy of Google

“Russian authorities have said they are not aware of an accident on their territory,” IRSN director Jean-Marc Peres told Reuters.  At the time, he had not yet been in contact with the Kazakh government.

According to the IRSN report, the group coordinated with several other nuclear safety groups throughout Europe in identifying and measuring high levels of ruthenium-106 in the air.  That particular radioactive nuclide does not occur naturally and can only be the result of splitting atoms inside a nuclear reactor.

Ruthenium-106 has a short half-life of about a year and is commonly used in nuclear medicine.  IRSN was able to rule out the possibility of an incident with an actual nuclear reactor because of the absence of other radionuclides that would have been released in such an incident as well.  They were also able to rule out the possibility of a nuclear powered satellite crashing by coordinating an investigation with the International Atomic Energy Agency to confirm that no ruthenium-containing satellites have reentered earth’s atmosphere within the half-life of the nuclides that were measured.

The number of ruthenium-106 nuclides measured in the air over a number of European nations has risen steadily since October 6, allowing experts to backtrack using weather patterns to establish the general time frame and location of the incident.