 Emergency officials will be testing the alert system of the Salem-Hope Creek nuclear power plants tonight. DEMA set to set off the 37 sirens within 10 miles of the plants, which includes Delaware City, Middletown, Odessa, and Townsend. Residents will hear the siren for about three to five minutes, then advise to tune to WDEL for a message in case of an emergency. The sirens are tested four times a year.