Answer to Question #13056 Submitted to "Ask the Experts"

Regarding the Russian radiological missile incident, is it possible to determine, based on radiological sampling data, whether this was a nuclear warhead destruction, nuclear detonation, propulsion system malfunction, or propulsion systems emissions?

We have two responses as shown below.

First Response:

Decoding this Russian explosion is difficult because of the lack of information coming from Russia. The short answer to your question is that current analyses based on the mix of radionuclides detected has concluded that the accident involved a nuclear reactor. Certain radionuclides associated with nuclear fission, e.g., strontium-91 (⁹¹Sr), barium-139 (¹³⁹Ba), ¹⁴⁰Ba, and lanthanum-140 (¹⁴⁰La), were detected in rain and air samples leading scientists to believe that there was damage to a reactor core. At this point in time it is not clear whether this was a propulsion system or other nuclear-powered device such as an underwater nuclear reactor or a small reactor for space applications. As more information becomes available, scientists may be able to pinpoint the type of device involved in the accident based on nuclides detected.

Jan Johnson, PhD, CHP

Second Response:

This is a tough question to answer because there is so very little information available. That means that this answer is going to be a little long because there are a lot of bases to cover. What I'd like to do is start with what we might see from a couple of different scenarios and then we'll compare what we know with these possibilities. And, for the record, the possibilities that occur to me are:

• Nuclear weapon—does not explode
• Nuclear weapon—explodes with a nuclear yield
• Nuclear propulsion reactor on missile
• Radioisotope thermal generator (RTG) on missile

So . . .

• Nuclear weapons are made of uranium-235 (²³⁵U) or plutonium-239 (²³⁹Pu). If they explode (fission) then they produce a bright flash, make a huge explosion, and produce a lot of radioactivity. The radioactive fission products are distinctive—they include isotopes of iodine, cesium, krypton, xenon, ruthenium, and many more; as well as unfissioned ²³⁵U and ²³⁹Pu. If a nuclear weapon explodes with a nuclear yield, the radioactivity will be detectable all over Europe, the blast will be detected by monitoring stations around the world, and the flash can be detected by orbiting satellites.
  • To the best of my knowledge there has been no detection of shock waves, no wide distribution of radioactivity, and no detected flash—this suggests that whatever happened did not involve a nuclear detonation.
  • I have heard of no reports of ²³⁵U or ²³⁹Pu detected outside of Russia. This might indicate that there was not a nuclear warhead involved at all. On the other hand, this is not definitive because these elements don't necessarily travel far and could have settled out entirely within Russia.
  • It seems safe to say that there was not a nuclear explosion. But I don't think that we can necessarily rule out the possibility that the missile was carrying a nuclear weapon.

• Nuclear reactors can be made of highly enriched uranium, but it's in a configuration that will not explode. An operating nuclear reactor will produce fission products similar to those produced by nuclear weapons—an accident involving an operating reactor will have many of the same signatures as a nuclear detonation, but without the boom. The detection of radioactive iodine, cesium, ruthenium, and so forth, but without a boom or flash, could indicate that an operating nuclear reactor was involved in an accident of some sort. And it might also release uranium into the environment (but likely not plutonium).
  • The United States experimented with this sort of thing in the 1950s and 1960s. Among other things, the reactor tended to spew a lot of radioactivity into the environment along with chunks of its core. But an operating reactor—even one emitting radionuclides—does not release as much radioactivity as a reactor accident.

• RTGs use the heat generated by radioactive decay to produce energy-using devices called thermocouples. These are typically used in deep-space probes, such as those that the United Sates has sent to Jupiter, Saturn, and the rest of the outer solar system. In addition, the Soviet Union used RTGs as power sources for meteorological stations and lighthouses in very remote locations. The United States tends to use ²³⁸Pu while the Soviet Union was more partial to ⁹⁰Sr. Stronium-90 is produced in fairly large quantities as a fission product, but it doesn't spread as readily as more volatile elements such as iodine, cesium, or noble gases such as krypton and xenon.
  • If an RTG was involved in an accident, we would likely not pick up any volatile fission products and might (or might not) see the ⁹⁰Sr or ²³⁸Pu since neither of these spread widely.

Okay, so now let's see what's been reported! We’ll start with a BBC story.

• Russia noted that radiation levels had "spiked to 16 times above normal" in a city 47 km away from the naval test site. This is hard to evaluate—normal background radiation levels are typically quite low, so this is not dangerous—but at the same time, it's nearly 50 km away. This suggests that a fairly large amount of radioactivity was released—but not what the source was.
• This story also notes that several Russian atmospheric monitoring stations were taken off-line (possibly by the Russians), so there still is no information on isotopes.
• But—no flash and no seismic signal!

Then there's an article in the New York Times. This article states that Russia acknowledged that five people died in an accident involving a "nuclear" accident while at the same time claiming that the missile using an "isotope power source." Technically, ²³⁵U is an isotope, just one that happens to fission. But this wording makes it sound as though Russia is talking about an RTG rather than a nuclear reactor.

• The only problem with using an RTG is that they are not very efficient—they're good at powering weather stations, but don't tend to put out enough power to drive a missile at high speeds.

And then there's an interesting tidbit from a Russian source. Letting Google Translate do its work, this article recommends that those living nearby "to close the windows and drink iodine," presumably to protect the thyroid from radioactive iodine. In mid-August, Norwegian monitoring stations detected radioactive iodine in the air. However, this is circumstantial evidence as the station detects iodine from radiopharmaceutical manufactures a few times annually—this detection could be coincidental rather than linked to the accident.

• Both of these articles suggest a nuclear reactor accident since iodine isotopes are not used for RTGs and (again) there was no flash and no seismic signal that would indicate a nuclear explosion.

All of this seems to suggest that whatever happened involved a nuclear reactor—given the noted increases in radiation dose rates, likely one that was destroyed while it was operating.

This is a guess, an educated guess, but a guess nevertheless—and it can be proven wrong if more information becomes available. But at the moment, it seems more likely than the other possibilities mentioned.

Andy Karam, PhD, CHP