The Nuclear Regulatory Commission (NRC) said the breach in the 2,000-foot inflatable berm around the Fort Calhoun station occurred around 1:25 a.m. local time.
More than 2 feet of water rushed in around containment buildings and electrical transformers at the 478-megawatt facility located 20 miles north of Omaha.
Reactor shutdown cooling and spent-fuel pool cooling were unaffected, the NRC said.
The plant, operated by the Omaha Public Power District, has been off line since April for refueling.
Crews activated emergency diesel generators after the breach, but restored normal electrical power by Sunday afternoon, the NRC said.
Buildings at the Fort Calhoun plant are watertight, the agency said. It noted that the cause of the berm breach is under investigation.
NRC Chairman Gregory Jaczko and other officials planned to visit the site on Monday.
Floodwaters surround nuke plant after breach | Reuters
How will they visit ??? By Canoe ???
Nothing unusual to see here folks.... Keep moving.... No camera's, no pictures.
So what danger are you trying to point out? Want to make a point rather than being facetious?
Hey, at least it is not salt water, right? That little incident is no threat at all to the integrity of the plant, right? That's just a tiny little puddle. There is no threat here what so ever.
For the grown ups, defending this position, do I really need to spell out the concerns???