Russia's nuclear chief Sergei Kiriyenko has estimated the country's program on the disposal of weapons-grade plutonium at between $2.5 billion and $3 billion.

At the nuclear summit in Washington on April 12-13, Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State Hillary Clinton signed the Plutonium Disposition Protocol, which stipulates that Russia and the United States would each dispose of 34 metric tons of excess weapons-grade plutonium.

"The final cost of the [disposal] program will become known only when it is completed...We estimate it at between $2.5 billion and $3 billion," Kiriyenko said, adding that the United States will contribute $400 million to the Russian program.

Kiriyenko, who heads the Russian state nuclear corporation, Rosatom, said the protocol meets Russia's interests as it retains the goals of a framework agreement on disposing plutonium, which was signed in 2000.

Russia's nuclear chief said the agreement will help in "resolving the most important disarmament goal." He said Moscow and Washington have pledged to dispose of their weapons-grade plutonium symmetrically and under joint control.

"This is at least 17,000 warheads if not more. At the same time, we will get the possibility under this additional agreement to dispose of this plutonium not at light-water reactors but at fast reactors," Kiriyenko said.

The U.S. State Department said the protocol "marks a further major step in U.S. and Russian efforts to eliminate nuclear-weapon-grade materials, thereby making nuclear arms reductions irreversible and reducing nuclear dangers."

Russia shut down on Thursday its last plutonium reactor, which has been producing weapons-grade plutonium for more than 46 years in the formerly closed city of Zheleznogorsk in Siberia.

In the height 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.