March 18 (Reuters) - Nebraska Public Power District's (NPPD) Cooper nuclear plant in Nebraska was still operating at full power early Monday after the company said on Friday it was preparing for possible flooding, according to a report from the U.S. Nuclear Regulatory Commission (NRC).
Officials at NPPD were not immediately available for comment Monday morning.
The company said on Friday that the plant continued to operate safely and "there is no threat to plant employees or to the public."
On Friday, NPPD declared an "unusual event" at Cooper because of the possibility of flooding along the Missouri River following a powerful winter storm last week.
The late winter storm, dubbed a "bomb cyclone" by meteorologists, spawned blizzards and tornados and left floods in its wake after hitting the U.S. Mountain and Plains states last week, before pushing east into the Midwest and the Great Lakes Region early Friday.
NPPD said its workers have filled sandbags along a river levee and procured other materials and supplies for flood protection.
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.
NPPD said its procedures require it to declare an unusual event to the NRC when the Missouri River tops 899 feet above sea level. It reached 899.05 feet Friday morning, the company said.
Should the river rise to 900 feet above sea level, NPPD said plant workers will "barricade internal doorways as another layer of protection for facility equipment."
If the river reaches 901.5 feet, NPPD said it would take the station offline as a protective measure.
The plant was built at 903 feet above sea level, which is 13 feet above natural grade, NPPD said.
The 770-megawatt Cooper station is three miles (4.8 km) southeast of Brownville, Nebraska, near the Missouri River. One megawatt can power about 1,000 U.S. homes.
(Reporting by Scott DiSavino; Editing by Steve Orlofsky)
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