29 September, 2007 is the 50th anniversary of the Mayak explosion in Russia, which caused the second largest radiation catastrophe in the world. Mayak, in the Southern Urals 1,400 km east of Moscow, is the biggest nuclear complex in the world. Although its five plutonium production reactors were closed in 1991, the plant RT-1 is still reprocessing spent nuclear fuel2. In addition, Mayak has a nuclear waste treatment plant with interim storage and pilot facilities for the production of plutonium-based Mixed Oxide (MOX) fuel and a facility for the vitrification3 of liquid radioactive wastes.