Shifting winds placed a former nuclear reactor and rocket testing site in the path of the growing Sandy Fire. The region’s first major blaze of the season raised alarm from families aware of the site’s history and spotty cleanup.By Steven Rodas, Nina DietzWEST HILLS, Calif.—Her gray SUV packed and a fire-proof bag ready, Melissa Bumstead didn’t waste any time Monday as plumes of smoke engulfed the sky near her suburb.