All 96 emergency notification sirens in the 10-mile radius around Three Mile Island Generating Station in Londonderry Township will be sounded for three minutes at 12:15 p.m. Thursday. A full three-minute sounding of the sirens is required on an annual basis. TMI conducts routine electronic testing of the sirens weekly.

Exelon Nuclear is conducting the test in cooperation with Cumberland, Dauphin, Lancaster, Lebanon and York Counties and the Pennsylvania Emergency Management Agency.

The purpose of the sirens is to notify residents to tune into an Emergency Alert System radio or television station in case of an emergency at TMI or tornadoes, floods, or other events requiring notification to residents.