Washington DC (Platts)--27Jun2011/539 am EDT/939 GMT

Floodwater from the Missouri River was 2 feet deep around the auxiliary and containment buildings at the Fort Calhoun nuclear power plant in the state of Nebraska Sunday after a temporary berm surrounding the plant sprung a leak early morning, US Nuclear Regulatory Commission spokesman Victor Dricks said.

The water is not expected to penetrate the buildings, which are water proof, Dricks said late Sunday. There is no danger to the plant's vital systems, he added.

The Omaha Public Power District or OPPD shut Fort Calhoun for a refueling and maintenance outage April 7 and later decided not to resume operations till the floodwaters recede.

NRC has been closely watching Fort Calhoun and the Nebraska Public Power District's Cooper nuclear power plant, both of which are on the Missouri River, for weeks as the floodwaters rose, according to a statement on its website. Cooper, which is downriver from Fort Calhoun, is operating at 100% power.

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NRC, which assigned additional resident inspectors to Fort Calhoun, has verified that the plant's shutdown cooling system and spent fuel pool cooling are operational, Dricks said.

OPPD crews are trying to repair the aqua berm that had been placed around the plant. The berm, which is about 8 feet tall and about 16 feet wide at the base, is filled with water to form a protective barrier.

The berm collapsed after it sprung a leak about 1:25 am Sunday, Central time (0625 GMT), Dricks said. Omaha-based KETV reported that a piece of equipment punctured the berm.

Fort Calhoun never lost off-site power, but the plant used emergency diesel generators to supply power to plant systems for a few hours Sunday, Dricks said. After safety checks, OPPD reconnected to external power, KETV reported.

NRC Chairman Gregory Jaczko plans to visit Fort Calhoun on Monday.

--Christine Forster, christine_forster@platts.com
--Elaine Hiruo, elaine_hiruo@platts.com