How is polonium-210 made?
Polonium-210 could be extracted from uranium bearing rocks e.g. granite. It can however be made in larger quantities by bombarding the element bismuth with neutrons. The isotope bismuth-209 captures a neutron and becomes bismuth-210m. This unstable form undergoes radioactive beta decay with a half life of 5 days to become polonium-210. Some of the bismuth is also converted to thallium. Specialist research reactors, used to make radioactive isotopes for medical applications, also produce polonium-210. The amount of polonium likely to cause the symptoms seen in this incident can only have been produced in a large industrial scale facility.
