MOSCOW, April 21 Russia said on Monday it had closed a weapons-grade plutonium reactor as part of a deal with the United States to reduce the risk of proliferation from Cold War-era nuclear bomb plants.
The reactor, at a secret Siberian plant founded by Soviet leader Josef Stalin, was turned off on Sunday, 45 years after it was started up to create plutonium for the Soviet weapons programme.
"The industrial reactor ADE-4 was finally stopped on Sunday at 11 in the morning. That is the final closure of the reactor," said a spokesman for the Siberian Chemical Combine, in the closed city of Seversk, formerly known as Tomsk-7.
After the end of the Cold War, weapons-grade plutonium was no longer needed for Russia's nuclear weapons programme.
But the reactors at the plant were kept running to provide heat and electricity for the local community, and the U.S. Department of Energy has estimated the plant produced enough plutonium for several nuclear bombs a week.
The unwanted plutonium was stored at the plant, prompting environmental groups to raise questions about its security. Russia says its nuclear plants are properly guarded.
Aid from the United States was used to help refurbish a 1950s coal-fired power plant, reducing the community's dependence on the reactors for power.
Another reactor at the plant, known as ADE-5 and started in 1965, will continue to produce heat and power until the summer.
The United States and Russia agreed in March 2003 to shut down Russia's three remaining plutonium-producing reactors.
The U.S is funding an electricity and heat plant to replace a plutonium plant near the closed city of Zheleznogorsk, formerly Krasnoyarsk-26. The plant at Zheleznogorsk, which would be Russia's last, is scheduled to be shut down by late 2010.
Plants that supplied material for nuclear weapons were among the best-kept secrets in the Soviet Union. Known only by code names, they were closely guarded and not even shown on maps. (Reporting by Guy Faulconbridge, editing by Tim Pearce)