Japan will announce Monday that it will turn over to Washington more than 700 pounds of weapons-grade plutonium and a large quantity of highly enriched uranium, a decades-old research stockpile that is large enough to build dozens of nuclear weapons, according to American and Japanese officials.
The announcement is the biggest single success in President Obama’s five-year-long push to secure the world’s most dangerous materials, and will come as world leaders gather here on Monday for a nuclear security summit meeting.