Brownville, Nebraska (CNN) -- A top manager at one of Nebraska's two nuclear power plants says he's "100 percent confident" the facility's countermeasures will keep the overflowing Missouri River from damaging critical gear and causing a hazard to the public.
The Cooper Nuclear Power Station, about 80 miles south of Omaha, is still in operation and several feet above the swollen waterway. Nuclear Regulatory Commission Chairman Gregory Jaczko toured the plant Monday, along with a plant north of Omaha that is already surrounded by floodwaters.
"I am not going to predict what is going to happen with the water level," Jaczko said. "Our job is to make sure the licensee does their job to make sure the plant stays safe. Right now, it appears they are taking proactive steps to do that."
The NRC says both Cooper and the Fort Calhoun plant, about 20 miles north of Omaha, have taken precautions against this summer's flooding. And Brian Hasselbring, a reactor operator at Cooper, said even high water won't cause a radiation leak.
"I am 100 percent confident that we are not going to have an issue here," Hasselbring said. "If river levels continue to rise, we will follow our procedures, we will shut down the plant, do whatever is required to maintain our safety."
At Fort Calhoun, as much as two feet of water has forced plant workers to navigate a catwalk from the parking lot, and a water-filled berm that surrounded the reactor containment structure and auxiliary buildings was punctured by a worker early Sunday. A representative of the manufacturer is at the plant helping assess whether the berm can be repaired, the plant's owner, the Omaha Public Power District, said.
But the plant has been shut down for refueling since April, and authorities have put floodgates, sandbags and other barriers in place to help protect the facility.
Despite the flooding, Fort Calhoun is designed to withstand water up to 1,014 feet above mean sea level, according to the Omaha Public Power District. The river is not expected to exceed 1,008 feet, the OPPD said.
Plant managers also have brought in additional diesel fuel for generators should the site lose electricity. Workers switched to those generators briefly to keep the plant's spent fuel cool after water came too close to electrical transformers, but the plant was again drawing power from the electrical grid, utility spokesman Jeff Hanson said Monday.
"The plant is designed, when they get to these higher flood levels, to use their diesel generators when necessary," Jaczko said.
It was catastrophic flooding from Japan's March 11 tsunami that knocked out cooling systems at the Fukushima Daiichi nuclear power plant, resulting in three reactors melting down and producing the worst nuclear disaster since Chernobyl. This year's Midwestern flooding has also led to a spate of rumors about the Fort Calhoun plant that OPPD and the NRC have been trying to knock down.
The utility has set up a "flood rumor control" page to reassure the public that there has been no release of radioactivity from the plant. An electrical fire June 7 did knock out cooling to its spent fuel storage pool for about 90 minutes, but the coolant water did not reach a boiling point before backup pumps went into service, it has said.
Heavy rainfall in Montana and North Dakota, combined with melting snow from the Rocky Mountains, have sent the Missouri surging downstream this summer. The river washed over and punched through levees in northwestern Missouri, spurring authorities to urge about 250 nearby residents to leave their homes.
The 6 to 12 inches of rainfall in the upper Missouri basin in the past few weeks is nearly a normal year's worth, and runoff from the mountain snowpack is 140% of normal, according to forecasters.
The Missouri River is forecast to remain at record or near-record levels from south of Omaha all the way to Atchison, Kansas, into next week. The flooding is affecting communities in Nebraska, Kansas and Missouri.
CNN's Patrick Oppmann and Ed Payne contributed to this report.