 Mark Fouser, WDEL, Delaware's News Radio. Residents in parts of Delaware can expect to hear an 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 will blare for about three to five minutes for those within 10 miles of the reactors. The radius includes parts of Delaware City, Middletown, Odessa, and Townsend. The tests are held four times a year.