This April 2, 2014 file image provided by the U.S. Department of Energy shows workers underground inside the Waste Isolation Pilot Plant facility in Carlsbad, N.M., for the first time since the Feb. 14 radiological release. Workers at a West Texas nuclear waste disposal site are closely monitoring containers from Los Alamos National Lab, Tuesday, May 20, 2014, a day after New Mexico officials announced a type of kitty litter is believed to have caused a radiation leak at the federal government's troubled nuclear waste dump. (AP Photo/U.S. Department of Energy, File)
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