"In the end," Jaczko said, "this challenge is yours."

"What's keeping me up at night is making sure that we're going to have electricity for everybody," says Gates. "Electricity is so important to... the mitigation efforts of our whole community. Fort Calhoun's safe. It'll continue to be safe."

Gates and his colleagues say the water has not breached the buildings housing the reactor core and the spent fuel rods, and they're confident it won't. Those buildings and the barriers protecting them are designed to withstand flooding extending 1,014 feet above sea level. The water is now at about 1,006 feet, and they say they do not expect it to exceed 1,008 feet.

Officials did not allow journalists directly into the rooms housing the reactor core and the spent fuel rods, but did allow them to view those rooms via closed-circuit cameras. The rooms did not appear to be damaged by floodwater.

Gates says the Nuclear Regulatory Commission cited the Fort Calhoun plant in 2009 for not being adequately prepared for a flooding event. Since that time, he says, they've taken steps to upgrade safeguards for the facility, and he says NRC officials were satisfied with the handling of the current flooding. Still, NRC Chairman Gregory Jaczko had solemn words for the staff of Fort Calhoun after touring the plant on Monday.

"In the end," Jaczko said, "this challenge is yours."

Fort Calhoun Nuke Plant SNAFU: Borated Water in Reactor, Spent Fuel Pool, Normal Procedure, Says Plant CEO & now a 10 Mile evacuation zone. Shades of Fukushima

Nuke Plants + Fault Lines + Tsunami Hazard Zones = Fukushimas... Any Questions?