A tourist at the Bradbury Science Museum in Los Alamos, New Mexico, in February examines a full-size replica of the "Fat Man" atomic bomb which was dropped on Nagasaki, Japan, on Aug. 9, 1945. Los Alamos is home to the Los Alamos National Laboratory which was established in 1943 as part of the Manhattan Project. Robert Alexander/Getty Images hide caption

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Members of the 320th Missile Squadron missile combat crew work through a scenario in the 90th Operations Support Squadron's Missile Procedure Trainer on F.E. Warren Air Force Base, Wyo., in June 2014. The MPT is a simulator that allows missile crews to practice contingencies they might face while on alert. R.J. Oriez/U.S. Air Force hide caption

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President Obama, speaking in Prague in 2009, said: "I state clearly and with conviction America's commitment to seek the peace and security of a world without nuclear weapons." While Obama has pushed for a reduction in nuclear arms throughout his presidency, he has also agreed to an expensive upgrade of America's aging nuclear arsenal. Charles Dharapak/AP hide caption

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A North Korean man reads a local newspaper on Sunday with an image of leader Kim Jong Un. Kim said during a critical ruling party congress that his country will not use its nuclear weapons first unless its sovereignty is invaded, state media reported. Kim Kwan Hyon/AP hide caption

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N. Korea Wants Economic And Nuclear Expansion, But One Undercuts The Other

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North Korean leader Kim Jong-Un reporting works of North Korean Workers Party Central Committee during the second-day of the 7th Workers Party Congress in Pyongyang. KCNA/AFP/Getty Images hide caption

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A ballistic surface-to-surface missile is fired by Iran's Revolutionary Guard, during a maneuver, in an undisclosed location in Iran on Wednesday. Omid Vahabzadeh/AP via Fars News Agency hide caption

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People watch a news report at a railway station in Seoul on Feb. 3. North Korea launched a long-range rocket Sunday local time, defying international criticism. Jung Yeon-Je/AFP/Getty Images hide caption

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Sumiteru Taniguchi, 86, a survivor of the 1945 atomic bombing of Nagasaki, walks up to deliver his speech at the 70th anniversary of the atomic bombing in Nagasaki, southern Japan, on Sunday. Eugene Hoshiko/AP hide caption

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NPR's Morning Edition host Steve Inskeep interviews President Obama at the White House on Monday. Maggie Starbard/NPR hide caption

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Obama Compares Iran Deal To A House Under Contract, Awaiting Appraisal

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A Minuteman III missile engine is loaded into a truck for transport to another building for X-raying before being torn down and rebuilt. The Air Force's missile command-and-control structure has been the subject of several recent scandals. Douglas C. Pizac/AP hide caption

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