Authorities at Pennsylvania’s Three Mile Island nuclear plant were investigating what caused a weekend radiation leak that resulted in 150 workers being sent home, officials said Sunday. An airborne radiological contamination alarm sounded about 4 p.m. Saturday in the Unit 1 containment building, according to a statement from Exelon Nuclear, which operates the Three Mile Island plant near Middletown, Pennsylvania. The unit had been shut down since October 26 for refueling, maintenance and steam generator replacement, the company said. ‘A monitor at the temporary opening cut into the containment building wall to allow the new steam generators to be moved inside showed a slight increase in a reading and then returned to normal,’ the company said. ‘Two other monitors displayed normal readings.’ Three Mile Island was the scene of the worst U.S. nuclear accident, a partial meltdown in 1979 that resulted in the plant’s second reactor being shut down permanently. Tests showed the contamination in Saturday’s incident was confined to the building itself, and none was found outside, Exelon said. There was no threat to public health and safety, but the workers were sent home because they could not continue until the area was cleaned, Bill […]