The Missouri River is already high enough to flow over the top of some levees, and today’s thunderstorms in South Dakota could add enough water to shut down Cooper Nuclear Station in Nebraska. The nuclear power station has already declared an “unusual event” because of the flooding, and its operating plan calls for the plant to go offline if the river rises 1 meter higher. The flooding so far is just an inconvenience at the power station, which has been surrounded by water on all sides since Saturday night. Flooding is also affecting the Fort Calhoun nuclear power plant in Nebraska, which is offline for scheduled refueling. There the water is being kept out of the plant by a series of temporary barriers.
Most nuclear power plants are built on major rivers, which they use as a source of cooling water. Design engineers generally place the buildings inches above the highest expected water levels.