 Mark Fouser, WDEL, Delaware's News Radio. Residents in parts of Delaware can expect to hear a three- to five-minute emergency siren test tonight. DEMA will be testing the alert system for the Salem and Hope Creek nuclear power plants around 7.20 p.m. The siren warns those living within 10 miles of the reactors to listen to WDEL for an emergency alert message. The radius includes parts of Delaware City, Middletown, Odessa, and Townsend. The tests are held four times a year.