Slate.com is running an article by Edward Jay Epstein this week, which argues that much more important than the results of the Litvinenko murder investigation is the story of how the Polonium-210 got into the wrong hands:
If a rogue nation (or terrorist group) obtained access to any quantity of polonium—even, say, a half gram—it could use it as an initiator for setting off the chain reaction in a crude nuclear bomb. With a fissile fuel, such as U-235, and beryllium (which is mixed in layers with the polonium-210), someone could make a “poor man’s” nuke. Even lacking these other ingredients, the polonium-210, which aerosolizes at about 130 degrees Fahrenheit, could be used with a conventional explosive, like dynamite, to make a dirty bomb. … The diversion could have come from only a limited number of places. Just four facilities are licensed to handle polonium-210 in Russia: Moscow State University; Techsnabexport, the state-controlled uranium-export agency; the Federal Nuclear Center in Samara; and Nuclon, a private company. Although these licensees are monitored by the Russian government, it would not necessarily require an intelligence service to divert part of the supply into private hands. A single employee who was bribed, blackmailed, or otherwise motivated conceivably could filch a pinhead quantity of polonium-210 and smuggle it out in a glass vial (in which its alpha particles would be undetectable). Such corruption is not unknown in Russia. Or the diversion could have come from outside Russia. A number of other countries with nuclear reactors have been suspected of clandestinely producing or buying polonium-210, including Iran (where it was detected by IAEA inspectors in 2000), North Korea (where it was detected by U.S. airborne sampling), Israel (where several scientists died from accidental leaks of it in the 1950s and 1960s), Pakistan, and China. But whatever its source, the polonium diversion has serious implications. The real problem is not its toxicity, since its alpha particles can’t penetrate the surface of the skin and therefore have to be ingested or breathed in to cause any damage. (That can happen if you have polonium-210 on your person or clothes.) The more serious danger is that it could be sold to a country that wanted to set off a nuclear device, clean or dirty.
UPDATE: MT/AP reports that the timing of the Litvinenko attack now in doubt.