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New Russian government data on August 8 explosion reveals that a nuclear reactor was definitely involved


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Russia’s National Weather Service (Roshydromet) released a report on August 26 that detailed the radioactive substances found in the atmosphere following a testing accident near Severodvinsk on August 8. Roshydromet’s data indicates at the very least that there was a nuclear reactor at the site of the explosion, though state officials have insisted otherwise. Below, we explain what other conclusions can be drawn from the Russian government’s meteorological report on the blast.

What happened near Severodvinsk and what Roshydromet reported

According to official Russian government data, an explosion took place during August 8 tests for an unnamed device at the Russian Navy’s Central Missile Polygon. The facility is located near the village of Nyonoksa, about 30 kilometers (18.6 miles) from the city of Severodvinsk. Seven people died in the accident, including five employees of Russia’s state nuclear energy corporation Rosatom and two military servicemembers.

At first, military officials said that the device involved was a standard liquid rocket engine. However, that position changed after local government officials began reporting heightened radiation levels and journalists found that those injured in the blast had been checked into hospitals capable of treating radiation-related injuries. Russia’s Defense Ministry as well as Rosatom began reporting that the engine of the missile in question contained an atomic battery.


A few days later, Donald Trump announced on Twitter that U.S. officials believed the explosion took place on a Burevestnik missile, known in NATO terminology as Skyfall. The Burevestnik is one of the superweapon models Vladimir Putin announced in the spring of 2018. Putin said that the missile uses new nuclear designs to achieve an “unlimited range.” Nuclear experts surmised that the model’s engine contains a compact nuclear reactor. An atomic battery would be insufficient to provide a missile with an “unlimited range,” assuming that term indicates a capacity to stay in the air for days or even weeks.

American officials did not provide direct evidence that it was a Burevestnik missile that had exploded in Nyonoksa. The indirect evidence they publicized included a satellite image of the Nyonoksa base that included what appeared to be a Burevestnik launching device.

It later came to light that Russia had cut off four radionuclide detection stations from the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) monitoring system. CTBTO leaders indicated that the four stations in question would have been capable of recording identifying data about the isotopes released in the August 8 explosion. That data, in turn, would have enabled scientists to determine whether the device that exploded in Nyonoksa was a nuclear reactor or an atomic battery and whether any dangerous substances were emitted into the atmosphere as a result of the blast.

On August 26, Roshydromet published a report on the isotopic composition of the chemicals emitted in the explosion. The report indicated that the emissions included the radioactive isotopes strontium-91, barium-139, barium-140, and lanthanum-140.

What we can tell from Roshydromet’s report (in brief)

  • The accident was preceded by a nuclear chain reaction. This means it almost certainly involved a nuclear reactor. Roshydromet’s data is fully compatible with the possibility that a nuclear-powered missile like the Burevestnik caused the explosion.
  • The body of the reactor was not destroyed: Only radioactive noble gases, the products of the nuclear chain reaction, were able to escape it. The half-life of these isotopes is only a few seconds. They decay into the isotopes Roshydromet detected. However, even those resulting isotopes decay relatively quickly over the course of hours or days, and the products of those nuclear reactions are not radioactive.
  • It is difficult to say exactly what happened to the reactor and what killed the explosion’s victims using isotope detection data alone. However, if Roshydromet’s data is accurate, it is fair to suggest that the isotopes emitted in the explosion did not present any danger to individuals located outside the Nyonoksa military facility.
  • Believing Roshydromet’s data would mean believing official reports that the cesium-137 found in one local doctor’s tissues came from some source other than the explosion. After the doctor treated patients who had been injured in the blast, the radioactive isotope was detected in his muscle tissue.

The Russian branch of the environmental organization Greenpeace noted that while Roshydromet’s report was sufficient to conclude that the Nyonoksa explosion originated near a nuclear reactor, refuting the Russian government’s previous claims, the report lacked two kinds of basic information. Without data on the concentration of the isotopes released in the accident as well as an account of the numerous other isotopes that are typically released in similar explosions, Greenpeace argued, it is difficult to assess the risk posed to Russian residents.

What we can tell from Roshydromet’s report (in detail)

Strontium-91, barium-139, barium-140, and lanthanum-140 typically form due to chain reactions of heavy isotopes like uranium-235. Those chain reactions can be controlled, as in a functioning nuclear reactor, or they can be uncontrolled, as in an atomic bomb explosion or an accidental accumulation of a critical mass of reactive materials. Uranium-235 and its oxides were considered as possible fuel sources for a nuclear-powered missile in the 1960s and 1970s in the United States.

Strontium-91, barium-139, barium-140, and lanthanum-140 are not the direct products of nuclear chain reactions. Instead, they follow from the nuclear decay of short-lived noble gases like krypton and xenon that do form immediately in those reactions. Strontium-91, barium-139, barium-140, and lanthanum-140 themselves are highly likely to decay within hours or days. (In terms of human health and safety, this puts strontium-91 ahead of isotopes like the more common strontium-90, which has a half-life of 28.8 years.)

All of the isotopes Roshydromet listed decay into stable — that is, non-radioactive — nuclei. Only strontium-91 passes through one other radioactive state before decaying into a stable isotope. This means the radioactivity of an emissions cloud containing these isotopes decreases rapidly over time.

Barium-140 and lanthanum-140 are not as readily absorbed by living organisms as, for example, cesium-138, which became infamous for its disastrous effects in the Chernobyl disaster. The short half-lives of these isotopes prevent them from causing long-term damage to doctors who treat those injured in the epicenter of an explosion.

Experts believe Roshydromet’s data provides a feasible explanation of the picture they have been able to observe in Severodvinsk: A short-term but high-magnitude jump in radioactivity levels that left some isotopes at up to 16 times their typical concentration. The radioactive isotopes of noble gases can escape a reactor during an accident because they are difficult to contain through filtration, unlike the airborne forms of other isotopes. This means that if Roshydromet’s data is accurate, both the fuel for the reactor in question and most of the products of that fuel’s decay remained within the reactor itself. If the reactor really did remain whole, then the cesium-137 found in the tissue of a local doctor really can be said to have entered his body from a source unrelated to the explosion.

It is difficult to say exactly what happened to the reactor, what the reactor really was, or what killed the explosion’s victims using isotope detection data alone. Boris Zhuykov, who leads a laboratory in the Institute of Nuclear Research of the Russian Academy of Sciences, told Meduza that the victims may have been injured by an explosion that took place outside a nuclear reactor and then been exposed to a dose of short-lived isotopes.

“People may have been killed by radiation if the reactor’s biological defense system was destroyed even if the reactor itself remained whole. The patients may have been exposed to a lot of barium-140, but the doctors would not have been able to experience contamination from their patients in turn,” Zhuykov explained.

There is a well-known historical case that bears a number of similarities to the current situation in Russia as far as isotopic composition is concerned. In 1999, operators at the Tokaimura nuclear facility in Japan accidentally allowed a nuclear chain reaction involving uranium-235 and a uranium salt solution to reach a critical mass. Two of the operators suddenly saw a bright blue burst and felt a wave of extreme heat. Ionizing gamma rays emit blue light in liquid environments. Both of the operators nearest to the blast died. A third who was located in a neighboring room suffered severe radiation damage but survived. Following the explosion strontium-91, barium-140, and lanthanum-140 were detected on the victims’ clothing and in their hair.

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