Feds: Nebraska Nuke Plant Fire Was Serious Threat Federal regulators say a fire that briefly knocked out the cooling system for used fuel at a Nebraska nuclear plant last June represented a serious safety threat. The Nuclear Regulatory Commission says in a preliminary report Monday that the Fort Calhoun plant north of Omaha was shut down at the time and temperatures never exceeded safe levels during the fire. But the commission says the fire remains a major concern because it could have happened any time and because workers didn't fully investigate an unusual smell in the area three days earlier. The Associated Press obtained the preliminary report from the NRC hours before its official release. Regulators already have imposed strict oversight at Fort Calhoun because of several other reported problems and the prolonged shutdown that began last spring.