Russia has shut down its last weapons-grade plutonium reactor, in line with a pledge made at a nuclear security summit in Washington this week. Yelena Golovinkina, spokeswoman for the Mining-Chemical Complex in the Siberian city of Zheleznogorsk, which houses the reactor, said it was shut down today. Russian president Dmitry Medvedev had pledged to close the reactor earlier this week at the 47-nation summit hosted by US president Barack Obama dedicated to keeping nuclear arms away from extremists. A statement on the Mining-Chemical Complex website said the closure of the ADE-2 reactor has major international significance as it is the last active military plutonium producer in the world. Located about 4,000 kilometers east of Moscow, the production complex was founded in 1950 on the orders of Soviet dictator Joseph Stalin.