MIDDLETOWN, Pa. - AmerGen, the owner of Three Mile Island, has announced plans to add 14 sirens to the emergency warning system as part of a $730,000 upgrade to the nuclear plant. The upgrade follows an acoustic test indicating that the plant's warning system was not loud enough in some areas. The sirens must be audible at a minimum rate of 60 decibels throughout the 10-mile radius, AmerGen spokesman Ralph DeSantis said. The added sirens will bring to 93 the total number within a 10-mile radius of Three Mile Island. Six of the sirens will be replaced by louder ones,...