(Reuters) - Nebraska Public Power District (NPPD) said its Cooper nuclear plant in Nebraska continued to operate safely at full power on Monday as the Missouri River floodwater around the plant receded following a late winter storm last week.
The plant was cut off from road access, however, and the company is ferrying workers and supplies in and out via helicopter.
"We are operating at full power and the water is receding ... and we expect the water level to continue dropping," NPPD spokesman Mark Becker said, noting there was no danger to the plant employees or the public.
Becker said the water was receding because some levees up river from the plant had collapsed, flooding low-lying plains, mostly in Iowa, rather than flowing down the river.
Becker said NPPD and the U.S. Army Corps of Engineers have checked the levees at Cooper and they are "in good shape." He also noted the Army Corps was reducing water releases from the Gavins Point Dam on the Missouri River between Nebraska and South Dakota to help reduce flooding downriver.
The storm last week spawned blizzards and left floods in its wake after hitting the U.S. Mountain and Plains states before pushing east into the Midwest and the Great Lakes Region.
The biggest danger to a nuclear plant from flooding is the loss of power, which can make it difficult to circulate the water needed to cool the uranium fuel in the reactor core and the fuel stored in the spent-fuel pool.
That caused the fuel in some reactor cores at the Fukushima Daiichi plant in Japan to partially melt down in 2011 after a giant earthquake and tsunami cut power to the plant.
Since Fukushima, all U.S. reactors have been upgraded with additional safety equipment, including portable pumps and generators to keep cooling water circulating through the reactor in case the plant loses offsite power.
Becker said the water at the plant was 899.75 feet above sea level Monday morning and declining. If it reaches 901.5 feet, NPPD said it would take the station offline as a protective measure.
The 770-megawatt (MW) Cooper plant, near Brownville, Nebraska, was built at 903 feet above sea level, which is 13 feet above natural grade, NPPD said.
Separately, Becker said NPPD's 215-MW Sheldon and 1,365-MW Gerald Gentleman coal plants were "chugging along" at or near full power and access by rail was "just fine."
(Reporting by Scott DiSavino; Editing by Steve Orlofsky)