A chemical explosion at the Y-12 nuclear weapons plant in Oak Ridge, Tenn., injured 10 workers. The workers were cleaning a welding area that had been shut down since 1994.
The building where the explosion occurred houses a portion of the plant's enriched uranium operation, which was shut down for five days in November because of safety problems. The explosion, however, was in a different section of the building and no nuclear materials were affected, officials said.
Three workers were hospitalized for burns or smoke inhalation. One man suffered second-degree burns over his face and chest. The others were treated and released.
The workers were removing an old crucible used in casting nuclear weapons parts. The explosion occurred when they were attempting to mop up a sodium hydroxide alloy that had spilled.
The alloy might have reacted with moisture, but the exact cause of the explosion was unclear, said David Page, a spokesman for the Department of Energy (DOE).
Y-12, created as part of the top-secret Manhattan Project in World War II to build the first atomic bomb. Today the plant makes warhead components for the MX missile system and is the primary uranium storage site for the nation's nuclear arsenal.
The entire 5,300-employee plant underwent a site-wide standdown in 1994 for safety deficiencies.
The DOE and managing contractor Lockheed Martin have been slowly restarting the plant, section by section.