The Three Mile Island nuclear power plant, where the U.S. suffered its most serious nuclear accident in 1979, is pictured through a dormant corn field in Middletown, Pennsylvania March 15, 2011. U.S. regulators should press ahead with approving construction licenses for new nuclear power plants despite Japan's nuclear crisis, President Barack Obama's top energy official Energy Secretary Steven Chu said on Tuesday. REUTERS/Jonathan Ernst (UNITED STATES - Tags: ENERGY ENVIRONMENT POLITICS BUSINESS)