Russia will shut down on Thursday its last plutonium reactor, which has been producing weapon-grade plutonium at a formerly closed town in Siberia for more than 46 years.

President Dmitry Medvedev announced the imminent shutdown of the reactor at the Nuclear Security Summit in Washington on Tuesday.

Plutonium production ended at the facility in the Krasnoyarsk Region town of Zheleznogorsk in June 2009, but the dual-purpose ADE-2 reactor continued to generate heat and electricity for local businesses and residents.

In the heyday of the Cold War, the Soviet Union operated 13 plutonium reactors, but in the 1990s the Russian Defense Ministry stopped purchasing the plutonium they produced and most of them were shut down by 2008.

The United States has shut down all 14 reactors it used to produce weapons-grade plutonium.

Both Moscow and Washington pledged on Tuesday to each dispose of 34 metric tons of excess weapons-grade plutonium.

Russia and the United States, which possess about 90% of global arsenals of nuclear weapons, signed an agreement in Prague last week to reduce the number of nuclear warheads to 1,550 on each side and the number of deployed and non-deployed delivery vehicles to 800 each.