Water from the Missouri River that normally aids in cooling the Fort Calhoun Nuclear Station has now become its worst enemy, as a levee helping to protect electrical transformers at the Nebraska facility has collapsed, forcing workers to switch to emergency generators.
Flood waters reached containment buildings and transformers Sunday, forcing the shutdown of electrical power at the plant.
Although the plant has been shut down since April, Gregory Jaczsko, the head of the Nuclear Regulatory Commission, is now Nebraska to see for himself but insisting that there is no danger.
"Mother nature takes care of the floods, so we have to do the best we can to make sure we're prepared, and all the plants in the U.S. have been designed to deal with historically the largest possible floods," Jaczsko said.
Still, some nuclear watchdog groups are not convinced. They point out that nuclear regulators said in October that Fort Calhoun failed "to maintain procedures for combating a significant flood," earning a "yellow" safety violation. New documents show that workers were still plugging holes 11 days ago where water could come flooding in.
"If there are radioactive areas of that plant internally, they could get washed out," Paul Gunter of advocacy group Beyond Nuclear said. "There's also the fact that if water does penetrate into the reactor itself that it could encroach upon electrical circuits, junction boxes on safety related equipment."
Downstream from Fort Calhoun, workers at a second nuclear plant near Brownville, Neb., have put up a 10-foot wall to keep water out. The plant is operating normally and officials say flooding is not a major threat.
In Minot, N.D., where the Souris River peaked two feet lower than expected, the destruction is extensive, and will be long-lasting.
The flooding has now caused damage to more than 4,000 homes, including resident Leslie Dull's.
"When you actually see your house … and you know it's not just your basement, it's your whole house, it's -- I'm sorry," Dull said, as she broke down crying.
Few households in the area -- approximately 375 homes -- have flood insurance, according to the Federal Emergency Management Agency.
There is some good news, however: the river in Minot peaked two feet lower than expected, although it is nearly 13 feet above flood stage and it is expected to stay near that level for days.
"It could be two to four to six weeks, or more, before the water actually goes back into its banks ... [and] before [residents] get to come and see their houses," Brig. Gen. Bill Seekins of the North Dakota National Guard told ABC News during a tour through the flooded areas.