Secretary of State John Kerry (left), and Russian Foreign Minister Sergey Lavrov (right) wait for the start of a meeting at the Beau Rivage Palace Hotelin Lausanne, Switzerland, on Sunday to discuss a nuclear deal on Iran. Brendan Smialowski/AP hide caption

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A worker rides a bicycle in front of the Bushehr nuclear power plant in Iran in 2010. Iran and six world powers are meeting in Vienna this week with the goal of reaching a comprehensive deal on Iran's nuclear program before a July 20 deadline. Majid Asgaripour/Mehr News Agency/AP hide caption

itoggle caption Majid Asgaripour/Mehr News Agency/AP

The second atomic bomb test at Bikini Atoll on July 25, 1946. The Marshall Islands, where Bikini is located, is suing the U.S. for what it calls a violation of the Nuclear Non-Proliferation Treaty. Anonymous/AP hide caption

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An Aug. 31 image from DigitalGlobe shows the 5-megawatt reactor at North Korea's Yongbyon facility. South Korean officials say they have confirmed that the nuclear reactor has been restarted. DigitalGlobe/ScapeWare3d/via Getty Images hide caption

itoggle caption DigitalGlobe/ScapeWare3d/via Getty Images

Nuclear bomb tests like this one, conducted at the Nevada Test Site in 1957, are helping scientists understand how the human body works. Photo courtesy of National Nuclear Security Administration / Nevada Site Office hide caption

itoggle caption Photo courtesy of National Nuclear Security Administration / Nevada Site Office