Massive flooding along the Missouri River has put two nuclear plants in Nebraska on alert. On Sunday, the Cooper Nuclear Station declared a low-level emergency as the Missouri River threatened to flood the nuclear power facility. Authorities say the plant, which is about 70 miles south of Omaha, will have to close down if the river rises another three inches. Meanwhile, the Fort Calhoun nuclear power plant, located about 20 miles north of Omaha, has been shut down since April 9, in part due to flooding.