Three Mile Island will conduct two separate tests of its emergency notification siren system on Thursday.
Exelon spokesman Ralph DeSantis said the first sounding will occur at 12:15 p.m. and will test the original siren system. The second test will take place at 1:15 p.m. and will test the new, upgraded siren system.
The new system has a battery backup capability that allows the sirens to sound during power outages.
The test of the new system is part of the process to gain Federal Emergency Management Agency approval to place the system in service.
During each test, all 96 sirens will sound for three minutes.
Exelon is conducting the tests in cooperation with Cumberland, Dauphin, Lancaster, Lebanon and York Counties and the Pennsylvania Emergency Management Agency.
A full three-minute sounding of the sirens is required on an annual basis. TMI conducts routine electronic testing of the sirens on a weekly basis.
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.