Detective Work in the Nuclear Era: Investigating a Mysterious Radioactive Event

Above: Nuclear experts at the Fukushima nuclear facility. Source: Wikipedia.

Article: Masson, O., et al. “Airborne concentrations and chemical considerations of radioactive ruthenium from an undeclared major nuclear release in 2017.” Proceedings of the National Academy of Sciences 116.34 (2019): 16750-16759.


Three Mile Island.



Chances are you immediately knew what at least one of these were, and it’s likely that you’ve heard of them all. These are all notable nuclear accidents that occurred in the last forty years. Nuclear (or radioactive) materials can be very dangerous to humans and other life forms. The destructive powers of nuclear materials aren’t limited to people, animals, or buildings in the immediate area. They can remain deadly in the soil, water, and air for decades or even centuries – and can cause birth defects and other illnesses in future generations of humans and other organisms.

Because of all these dangers, effective nuclear safeguards like the International Atomic Energy Agency (IAEA) have a crucial role to play. Other lesser-known and informal organizations like Ring of 5 (Ro5) also are important monitoring bodies. Ro5 was the central player in a recent scenario that seems almost unthinkable in today’s hyper nuclear-aware world: a mystery source of radiation, with no claims of responsibility, and with its location unknown.

The process of detecting, analyzing, and finally determining the location of the radiation is detailed in a paper recently published in the Proceedings of the National Academy of Sciences (PNAS).

First Signs of Trouble

Ro5 is a European organization set up originally by five countries to quickly exchange information about airborne radiation. Today, it spans 22 countries and directly (but informally) connects scientists across borders.

Maximum concentrations of ruthenium-106 measured during the October 2017 time period. Source: PNAS.

In October 2017, a laboratory in Italy detected higher-than-normal concentration of ruthenium-106 (a radioactive isotope) in the atmosphere. The concentration was not high enough to be harmful, but was still unusual as ruthenium-106 is generally not present in the atmosphere. The last time ruthenium-106 had been detected was after the 1986 Chernobyl disaster. This lab raised the alarm through Ro5. Facilities and scientists in other countries also reported similarly high ruthenium concentrations, shown below.

Deepening Mystery and Denials

Following the widespread detection of high ruthenium concentrations, the IAEA sought recent data from all European member states about all known sources of radioactive ruthenium to try and determine the source of the recently-detected amounts. Authorities in Russia denied that their area in general and the Mayak facility specifically was the source. Mayak had been involved with another nuclear disaster 60 years ago. Other possible sources of ruthenium, including a satellite unintentionally entering the atmosphere and burning up, were considered and ruled out due to lack of direct evidence.

A Timely Breakthrough

Most of the Ro5 facilities tested the air for radioactive materials weekly or daily. This wasn’t enough to pinpoint the source of the ruthenium, given that winds and other weather events change much more frequently. Romania, in southwestern Europe had several dozen Ro5 facilities that tested the air several times a day, and some tested the air every hour.

The data from the Romanian facilities yielded a much more thorough and frequent estimate of ruthenium in the air.

Average 7-day concentrations of ruthenium-106 at various Ro5 stations. Source: PNAS.

Crucially, this data also allowed researchers to track the spread of ruthenium hour by hour.

Using known weather conditions like wind speed and direction in the time leading up to each reading of the various Romanian facilities, scientists were able to re-construct the path that the ruthenium took to reach those facilities from its original source.

And all signs pointed to Mayak.


While this may seem like a techno-thriller fiction, this is indeed a real-life true story, with real implications on nuclear detection and safety.

First, some thing or things happened that should not have. And radioactive material was released into the air. Thankfully, the concentration released was too low to cause harm. But harmful amounts could be similarly released.

Secondly, the Ro5 detection and reporting network worked as intended – particularly the Romanian facilities, as did the IAEA. International cooperation and sharing of resources and data allowed for relatively rapid determination of the likely source of the release.

Third, no specific actions have been taken to ensure this (the ruthenium release) doesn’t happen again.

Fourth, no one connected to Mayak or regional authorities have admitted that the ruthenium was, in fact, released from there. Relevant parties continue to insist that there is not enough evidence to verify the source of the release. In fact, the PNAS paper was written to show the full weight of evidence.

It seems that while the current detection and cooperation mechanisms are working as intended, there is still a long way to go to ensure safety compliance and responsibility.

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Munim Deen

Munim is an epidemiologist and cartographer. His primary interests are infectious disease outbreaks and their intersection with the environment, public policy, and society at large. A geographic information system (GIS) devotee, he incorporates mapping and spatial analysis into his work whenever possible. A former newspaper columnist, he holds a bachelor's degree in microbiology and a master's degree in epidemiology.

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