The bombarded with neutrons bismuth is transferred from Mayak to the Avangard Electromechanical Plant in the closed city of Sarov.

The isotope used in killing of Litvinenko has been traced by a British theoretical physics professor Norman Dombey:

"The Po-210 used to poison Mr Litvinenko was made at the Avangard facility in Sarov, Russia. One of the isotope-producing reactors at the Mayak facility in Ozersk, Russia, was used for the initial irradiation of bismuth. In my opinion, the Russian state or its agents were responsible for the poisoning." — Norman Dombey, Supplementary Report

This of course does not exclude the possibility that the polonium that killed Litvinenko was imported by a licensed commercial distributor, but no one—including the Russian government—has proposed that this is likely, particularly in regard to the radiation detected on the British Airways passenger jets travelling between Moscow and London. Russian investigators have said they could not identify the source of polonium.