Russia's Medvedev calls Obama's nuclear summit a "complete success," but adds, "I hope we won't just go home feeling happy." What will it take to sustain agreements to "lock down" nuclear materials? Is the threat of nuclear terrorism overblown? Also, a major earthquake strikes the Dalai Lama's hometown. On Reporter's Notebook, will a tax on gasoline persuade Senate Republicans to support legislation on climate change?
Banner image: President Barack Obama (L) talks with President Nursultan Nazarbayev of Kazakhstan (C) and Russian President Dmitry Medvedev during the second plenary session at the Nuclear Security Summit in Washington, April 13, 2010. Official White House photo: Pete Souza