Nuclear Friday: Polonium

I’ve written before about the strengths and weaknesses of radioactive materials as a terrorist weapon, but what about using radioactive materials as a tool of assassination? Turns out there aren’t very many good options. Any material that would be deadly in a single dose would be difficult to acquire and most would present a serious risk to the handler. Isotopes of Iodine and Cobalt that might be easy to obtain from hospitals would require multiple doses over extended periods of time, and can easily be detected by the simplest radiation detectors. Your plot might be discovered before your task is complete. Americium extracted from smoke detectors would be even easier to obtain, and also harder to detect with standard medical equipment, but this element would still require multiple doses over periods of months. So what is a would-be radiological assassin to do? Fortunately, nature provides a near perfect option, Polonium 210. It is difficult to detect, deadly in minute doses, and can be delivered in a form that is not very dangerous to the assassin. As you might guess, it’s difficult to acquire, unless you know the right people and they’re OK with what you might do with it. And someone wanted Alexander Litvinenko dead and had access to Polonium. Litvinenko died 22 days after consuming an amount of Polonium that weighed less than the ink to make a period on a printed  page. It was an almost perfect murder.

The Discovery of Polonium:

Polonium was first extracted from uranium ore by Marie and Pierre Curie in 1898. This is part of the work for which they were jointly awarded the Nobel Prize in Chemistry in 1911. They at first called it “Radium F” but Marie was able to determine that it had a unique radiation signature and was thus probably a distinct chemical element. This technique of distinguishing substances by their radioactivity was what won her the 1903 Physics Nobel. Marie Curie named this element Polonium in an effort to draw attention to the Polish Nationalist cause. Pierre and Marie didn’t know it, but they had found Polonium 210, the only naturally occurring isotope of Polonium.

An Element from Hell:

The Curies were fortunate they were only able to extract miniscule amounts of Polonium, just enough to make the barest investigation into its chemical and radioactive properties. Polonium is an element from hell. Large amounts were never extracted until the UK, Germany, and the US began large scale Uranium processing as a prelude to investigating nuclear weapons. Some Polonium did make its way into early atomic bombs as a type of “sparkplug” but it was almost useless even for such terrible purposes. Polonium 210 decays rapidly with a half-life of 138 days. That means that in a year, you have less than a quarter what you started with. Early nukes required disassembly and frequent maintenance to replace these parts that contained Polonium.

Polonium is so highly radioactive that even small samples will become warm from their own radioactivity. But almost all the radiation is alpha particles, so in principle, you could have a sheet of Polonium foil sitting next to you and you would be perfectly safe as alpha particles travel only a few inches in the air and can be stopped the layers of dead cells on the surface of your skin. As much as I’d like sit in a darkened room and watch a sheet of polonium foil glow dimly as its alpha radiation ripped apart molecules of air around it, I think I’ll pass. While Polonium has a melting point around as hot as a standard oven gets, and having the metal in a foil would allow heat to dissipate, Polonium kicks off little bits of itself by alpha particle recoil. I think I’ll pass.

An Almost Undetected Assassination:

The November 2006 assassination of former KGB and later FSB agent Alexander Litvinenko brought public attention to the lethality and gruesomeness of Polonium as a means of murder. The Board believes that he was quite a shady character, but generally agrees that his murder was orchestrated at the highest levels of the Russian government and agrees with the broad consensus that his independent activism against the Russian government let to his murder more than anything else. I will post some links to some good documentaries at the end of this post if you want to learn more about the spy/activist angle.

As with all things nuclear, there are many misconceptions about the physics and chemistry of the Litvinenko murder. One of the most important can be found in this picture:

podetect

See that little radiation detector next to the bottle? Most folks think that because Po-210 is so intensely radioactive, the detector would be set off by the bottle. Incorrect. You could dissolve a hundred or more lethal doses in a bottle like that and there would be no detectable radiation. All the radiation would absorbed by the water and glass. It might be possible to detect a Polonium signature if you put the detector over the mouth of the open bottle and counted events over a few days, but I’m sure that’s not what people think of when they see this picture.

I think this misconception comes from the fact that most discussion of radiation involves shielding from deeply penetrating effects. This is true of gamma and X rays, but alpha particles can’t get to you, and they can’t get through you. But if you ingest a substance that emits alpha particles, this is potentially very serious. Alpha particles are a cluster of two protons, and two neutrons, basically the same a Helium nucleus. They don’t move fast, but with their large mass and +2 electric charge they rip apart chemical  bonds. The chemical machinery of the cell, including DNA. The DNA damage isn’t part of the initial symptoms, but it’s part of what kills you in the end. Normal cell function ceases as the DNA becomes stuck in a continuous self-repair cycle from the ongoing damage.

Yet none of this is detectable even by the standard equipment in hospitals that handle radioactive materials. Airport security scanners can’t detect it either, even though people who have had radiation treatment for thyroid disease sometimes get pulled out of line as potential terrorists.

Litvinenko began showing symptoms. He vomited and felt dizzy just hours after being dosed. These symptoms are classic signs of ingesting radioactive material. They are caused by the direct effects of radiation on the digestive tract and slight impairment of nerve function from exposure. Nerve cells are able to recover and even adapt to exposure, but that just means that radiation sickness is a horrible way to die. Your brain is the last thing to go. The digestive system is unable to recover. Its cells divide and slough off constantly. These cells keep their DNA coiled tightly and thus have poor repair capability. Cancer cells are like this too, which is why radiation is useful in treating cancer. Alpha emitters also damage the blood cell producing stem cells in bone marrow, and tend to become concentrated in liver and kidneys, causing more damage there than elsewhere.

Litvinenko checked into a local hospital two days after first showing symptoms and identified two suspects. He was transferred under armed guard to University Hospital in London the next night and kept under guard. MI-6 likes to protect their informants. The toxicology lab could find nothing wrong, but Litvinenko insisted he had been poisoned. Accounts vary as to when he was screened for radiation exposure, and I think he had been early on, but it was only three days before he died that a cancer specialist became convinced that Litvinenko had been exposed to radioactive material and insisted that a blood sample be sent to a government lab. All they found was a very weak gamma signature, but an old nuclear weapons scientist recognized that it might be Polonium. When they adjusted the equipment, they found the characteristic alpha emission profile of Polonium.

Litvinenko would die just two days after this discovery.

Did the Russians Do It?

Almost certainly. Once it was determined that Polonium was the cause of death, it was simple to follow the radioactive trail of the two killers. Once you know what to look for and have the right equipment, tiny trace amounts of Polonium are easy to find and the two suspects left many traces. In 2006 all the world’s Polonium was artificially manufactured in Russia rather than laboriously extracted from natural sources. The Russian government pointed out that there are commercial sources of Polonium, but provided no evidence that the suspects bought any. And extracting Polonium from commercial products would be difficult and risky.

I think there’s only one source of Polonium in a specially prepared safe and easy to administer form. The only question is who knew and who decided. I think it went all the way to the top.

The Last Words of a Dead Man While he Still Lived:

I will close with the last statement of Alexander Litvinenko, someone who knew Putin much better than Trump, Flynn, or Bannon ever will.

…this may be the time to say one or two things to the person responsible for my present condition. You may succeed in silencing me but that silence comes at a price. You have shown yourself to be as barbaric and ruthless as your most hostile critics have claimed. You have shown yourself to have no respect for life, liberty or any civilised value. You have shown yourself to be unworthy of your office, to be unworthy of the trust of civilised men and women. You may succeed in silencing one man but the howl of protest from around the world will reverberate, Mr Putin, in your ears for the rest of your life. May God forgive you for what you have done, not only to me but to beloved Russia and its people.

politvinenko

Documentary Videos:

BBC Newsnight documentary. Good interviews with nuclear scientists but leaves out info about how alpha particles do damage.

More recent CBC documentary. Interview with Litvinenko’s son and others.

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