NASA Tuesday confirmed a 4-foot in diameter sphere debris as a fuel tank that was part of the space shuttle Columbia\'s electrical power system,according to U.S. news reports.NASA engineers identified the 4-foot piece of spherical debris as one of the18 tanks that held chilled oxygen and hydrogen used by the shuttle\'s electricity-generating fuel cells.Police in the city of Nacogdoches, about 160 miles northeast of Houston, said Monday the low water levels of Lake Nacogdoches during the record drought revealed an unexpected object that could be from space shuttle Columbia. The shuttle broke apart and burned as it re-entered the atmosphere on February 1, 2003.The tank will be moved to the Kennedy Space Center, where the rest of the Columbia is stored. Approximately 40 percent of the spacecraft has been recovered.