Joshua PollackGuest Post: the Odds of Simultaneous Multiple Independent Detector Failures

Not long after the August 8 explosion at Nyonoksa in northern Russia–and the initial report of a spike in radioactivity in the nearby city of Severodvinsk–something else unexpected happened. Multiple radionuclide (RN) detectors inside Russia, part of the International Monitoring System of the CTBTO, stopped relaying their data to the CTBTO in Vienna. The Russian authorities explained this development vaguely, referring to network problems.

Now, the IMS is meant to detect and deter clandestine nuclear explosive testing. That’s not what happened at Nyonoksa, which a group of CNS researchers quickly identified as having been (in all likelihood) an accident involving a nuclear-propelled cruise missile. In other words, it looks very much like an engine based on a small nuclear reactor blew up. And RN detectors have a way of sniffing out the radioactive particles and gases from a broken reactor as they drift around the landscape.

That is apparently what’s at issue. Russian officials haven’t directly acknowledged any nuclear accident, preferring to describe what was involved with an ambiguous circumlocution (“isotopic power source”). Perhaps by silencing the RN stations, the Russians are trying to avoid embarrassment and alarm at home.

Or perhaps they hope to deny the outside world enough information to understand the design of the engine. Somewhat surprisingly after all this, a recent report from the Russian government’s own hydro-meteorological service, Roshydromet, listed the following radioisotopes as having been detected on August 8 in Severodvinsk: Sr-91, Ba-139, Ba-140, and La-140. That confirms that the accident involved nuclear fission, the process that takes place in a nuclear reactor (or in a nuclear explosion). But it’s not enough to say much else.

Does the appearance of the relatively forthcoming Roshydromet report mean that the silencing of the IMS RN stations in Russia might indeed have been a big coincidence? CNS scientist-in-residence Ferenc Dalnoki-Veress has crunched the numbers, and he has an answer: it’s extraordinarily unlikely that five stations would independently go quiet within days of each other. It’s still less likely that they would do so within days of a nearby radiological accident.

Ferenc’s paper with all of the numbers can be found here.


  1. William Moon (History)

    Excellent points. Deputy Foreign Minister Sergei Ryabkov response to the Interfax news agency was also quite telling. He said that it is Russia’s choice, not an obligation, to share radiation monitoring data under the treaty. He also noted that the international nuclear watchdog’s mission is to monitor the global nuclear test ban, not missile tests like the one conducted in Nyonoksa. The responses further erode Russia’s credibility in terms of supporting international agreements.

    • Ferenc Dalnoki-Veress (History)

      The important point to remember is that because the CTBT is not in force they are not violating any agreement. In spirit absolutely, but not legally. Therefore, yet another reason to not delay and get the CTBT treaty in force. Looking at you United States, but also the other Annex 2 states! If the treaty was in force then the Russians would have had to continue transmission which clearly was stopped deliberately.