In an average year, about 85 grams of the substance is made at the Avangard facility, a former nuclear weapons plant, and then sold under strict controls to Russian and foreign companies that prize it for its abilities to reduce static electricity.
Last fall, a microscopic quantity of polonium-210, from somewhere, found its way into the body of Alexander Litvinenko. He died an agonizing death in a hospital 22 days later.
Now an international investigation is trying to track that dose back to its source. Detectives from Scotland Yard have said little about where the trail of evidence may be leading; Russian officials have been more willing to talk, saying Avangard is tightly audited and that illicit production of polonium-210 is technically possible at many of the world's reactors.
Still, Russia's near total domination of the world's legal trade in the substance has focused new international attention on the country's production system and controls. Russia is the main source of polonium in part because it offers high quality and the best price for commercial users, said Nick Priest, professor of radiation toxicology at Middlesex University and a former head of biomedical research at the United Kingdom Atomic Energy Authority. No polonium is produced in Britain, and officials in Russia said none had been exported commercially to Britain for at least five years.
Polonium-210 is produced in reactors by irradiating bismuth-209. Specialists say that around the world, reactors capable of this operation belong either to state agencies or universities and so are highly regulated. "Everything connected with polonium production and application is controlled by governments," said Boris Zhuikov, head of the radioisotope laboratory in the Nuclear Studies Institute of the Russian Academy of Sciences. "You cannot just put any target inside a reactor. It is regulated and checked by many, many people. It would be discovered."
The Avangard plant operates under close government scrutiny. Officials said four organizations were licensed to handle the material made there: the chemistry faculty of Moscow State University; the Federal Nuclear Center in Samara, also on the Volga; Tenex, the state-controlled uranium supplier; and one private company, Nuclon, which uses it for medical devices and transports isotopes to customers.
The controls have proved effective, officials contend. "I can say with complete certainty that no deviations from the rules of storage and transportation of nuclear materials, including polonium, have been discovered at any structures of our fuel and nuclear complex," said Konstantin Pulikovsky, head of the Federal Service for Ecological, Technological and Atomic Inspection, RIA-Novosti reported.
Worldwide, polonium has been lost or stolen in at least 15 known incidents before 2006, most of them in the United States, according to the International Atomic Energy Agency, or IAEA.
Priest said he believed that in Russia, audit safeguards could be circumvented if there was demand for polonium from officials with strong influence. Audits could also be an unreliable gauge of pilfering because during production, much more polonium is made than is actually needed, with the surplus never entering the officially recognized supply.
Other theories suggest that the polonium that killed Litvinenko may have been obtained from an officially tracked commercial supply after it reached its final customer.
The substance's great giveaway is that once discovered, its telltale traces are easily tracked. Out of its box, polonium smears everything. After Litvinenko's death, it was discovered in planes, cars, hotels and offices -- all places that the victim and people he met had visited around the time of the poisoning.
If it enters the body in tiny amounts, death is certain. The devastating effects were studied in the 1960s at a Moscow institute where the isotope was administered to dogs, rabbits and rats, Zhuikov said. He said scientists wanted to understand polonium's potential in case humans were exposed to it, because the isotope was used in various applications in Soviet nuclear and space programs.
The IAEA is considering tighter controls on polonium. An IAEA diplomat, who was not authorized to speak on the record, said that in the wake of the Litvinenko case, concerns have risen at the agency about a mass poisoning through the introduction of polonium into the food chain or drinking water.
Polonium-210 and Its Dangers
Polonium-210 is a silvery-gray metal that eludes normal radiation detection because it emits alpha rays rather than the gamma rays that devices look for.
Alpha particles do not travel far -- only a few centimeters in the air. They are stopped by a sheet of paper or by human skin.
Polonium-210 becomes dangerous when it enters the body by ingestion of food or water or inhalation of particles. Other radioactive materials are absorbed through the skin.
One-millionth of a gram can be fatal, and one gram could theoretically kill tens of millions of people.
Polonium-210 is produced in nuclear reactors by irradiating bismuth-209.
Russia dominates polonium production. Only one facility, the Avangard plant, produces it, making about 85 grams per year, some of which is exported.
Polonium is commonly used in static eliminators in printing plants, photography labs and textile mills. In these applications, it is bound in extremely small quantities with other metals.