Russian officials have openly acknowledged the country's August 8 nuclear blast. Why did they turn off four nuclear monitoring stations anyway?

After the August 8 nuclear explosion in Russia’s Arkhangelsk region, four nearby radiation detection stations suddenly shut down. The stations are operated by Russia’s Defense Ministry, which also conducted the nuclear-powered missile test that caused the explosion. Meduza set out to explain why having the four monitoring stations turned off would have been to the Russian government’s advantage even though Russian officials have publicly acknowledged both the explosion and the cloud of radioactive particles it released.

The monitoring stations

According to the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) website, there are seven radionuclide detection stations in operation in Russia with one more under construction in Norilsk. After August 8, two stations in the European section of Russia (one in Kirov and one in Dubna) stopped transferring data to the CTBTO, and after August 13, two more stations in Siberia (one in the Altai region and one in Yakutia) did the same. The latter two stations were back online by August 20, but the Kirov and Dubna monitoring posts remain disconnected.

What are these stations?

Around the world, there are more than 300 facilities set aside for equipment that collects primary data about possible nuclear tests. About 80 radionuclide detection stations collect air samples and test them for radioactive materials and other signs of nuclear fallout. The rest collect information on seismic waves in the Earth’s crust and on fluctuations in the air or in water.

The sensors installed in radionuclide stations detect gamma rays emitted by radioactive aerosols and noble gases. By analyzing gamma ray spectra, sensors can identify various radioactive isotopes. On a daily basis, every radionuclide station sends its spectroscopy data to the CTBTO. Here’s an example of what those spectra look like. The precision of the sensors depends on their distance from the source of the radionuclides detected and on the wind trajectory that brought them to the station.

If a spectrum that reaches the CTBTO appears to be the result of a nuclear explosion, that data is transferred to two radionuclide laboratories (there are 14 of these labs in all, and one of them is in Moscow). There, scientists produce a wind map that allows them to locate the source of the radioactive particles detected. They also use the spectra to determine what the source of the particles may have been.

At first, Russian officials claimed that the stations had simply experienced a signal failure. Then, Foreign Affairs Ministry representatives argued that they were not obligated to share information from the detectors even though they had opted into the CTBTO’s data sharing system as a whole. Data from the monitoring stations are typically transferred to the CTBTO automatically.

Lassina Zerbo, the Executive Secretary of the CTBTO, explicitly tied the data outages to the August 8 nuclear explosion, which took place near the village of Nyonoksa in Russia’s northwestern Arkhangelsk region. Seven people died as a result of the blast, and sensors detected a short-term release of radioactive particles. The Russian Defense Ministry, which controls the country’s CTBTO monitoring stations, also conducted the missile test in Nyonoksa that caused the explosion. U.S. officials have suggested that the missile in question was a Burevestnik (known in NATO terminology as Skyfall), which is both nuclear-powered and capable of transporting nuclear weapons.

According to Zerbo, the timing of the data outages at Russia’s nuclear monitoring stations coincided with the spread of airborne particles from the Arkhangelsk region through northern Eurasia.

Those particles, including radioactive substances from the explosion, were initially carried over the European section of Russia before turning toward Siberia. From there, some of the airborne cloud moved north toward the Krasnoyarsk region and then eastward while another portion of the cloud traveled toward Mongolia and northern Asia. Two Russian radionuclide detection stations in Ussurysk and Kamchatka that were not located near the traveling particle cloud continued to operate throughout the aftermath of the explosion.

Apart from Russia’s detection stations, the monitoring sites with the best chance of analyzing the airborne particles from Nyonoksa are located in Mongolia and northern China. The CTBTO did not report on spectra detected by those two stations. Only CTBT signatories have a right to receive nuclear detection data from other member countries.

Another monitoring station in northern Norway that is not a part of the CTBTO’s network also detected heightened radiation levels. However, the wind in Nyonoksa was blowing away from Norway at the time of the incident, leaving the station unable to gather precise data about the blast.

Why would the Russian government turn off its nuclear monitoring stations if it had already admitted that the Nyonoksa blast released radiation?

The purpose of radionuclide monitoring stations is to determine the isotopic composition of airborne radioactive substances. That means the stations can typically identify the processes and materials that caused the radioactive emissions they detect. The isotopic profiles of underground nuclear explosions, missile explosions above ground, medical devices, nuclear reactors, and atomic batteries are all very different from one another.

The sensitivity of the stations is such that they can even allow scientists to develop a model of the specific device that exploded in a given nuclear test. That was how a group of scientists argued in 2010 that the North Korean government had conducted tests aimed at adding fusion boosts to fission-based nuclear weapons. Some nuclear scientists disagreed with their colleagues’ conclusions, however.

There have been similar disagreements about what exactly blew up on August 8. Immediately after the incident, Russian scientists gave a remarkably vague description of the device in question, but a contradictory set of semi-official claims emerged in the following days. Those arguments held that the device was a liquid rocket engine containing atomic batteries, which release energy using natural nuclear decay, not a chain reaction.

U.S. officials, as echoed in a tweet from President Donald Trump, have expressed certainty that it was a Burevestnik missile that exploded in Nyonoksa. The Burevestnik, which has a practically unlimited range, does require a power source that runs on a nuclear chain reaction.

Data from nuclear monitoring stations could likely determine which country’s claims about the origin of the explosion is correct. It appears that the Russian government has made an attempt to keep that data out of other governments’ hands because it could also have been used to reveal the construction of one of the country’s newest and most powerful weapons.

Analysis by Dmitry Kuznets

Translation by Hilah Kohen