The Irradiation of Gold City
Years ago, there was a cataclysmic event in Gold City. There was a sudden, intense burst of lethal radiation that flooded the city and the surrounding environs. Even now, the radiation levels are high enough that entering the city without proper safety equipment would be fatal.
Exactly what happened in Gold City is unknown. Some people think the nuclear reactor that powered the city malfunctioned, while others believe an exceptionally powerful Shortwave was responsible.