If George Romero had directed "The China Syndrome," you might have wound up with this gore-8 slice of Italian horror. A radiation leak turns a planeload of passengers into blood-seeking atomic zombies, and when they're unleashed on the city, the result is utter carnage. Hugo Stiglitz, Francisco Rabal and Mel Ferrer star; Umberto Lenzi directs. AKA: "City of the Walking Dead," "Nightmare." 92 min. Soundtracks: Italian, English Dolby Digital mono; Subtitles: English. In Italian with English subtitles/Dubbed in English. Region Free