Feb 7 - Knight Ridder/Tribune Business News - Tim Huber Pioneer Press, St. Paul, Minn.

 

One of two reactors at Xcel Energy's Prairie Island nuclear power plant was shut down Sunday because planned repairs to a backup generator are more extensive than expected, the plant's operator said Monday.

Nuclear Management Co., which operates the plant for Minneapolis-based Xcel, would not say when the reactor would return to service.

Nuclear Management said it shut down the unit when it determined that generator repairs would not be completed by Sunday night. Each reactor has two backup diesel generators that provide power to run cooling systems if electricity to the plant is cut off.

"We were doing partial repairs and we're going to go in and do some additional repairs," said Pam Gorman, a spokeswoman for Nuclear Management.

Nuclear Management had replaced cylinder liners, rings and pistons in an engine of one twin-engine generator and was testing the repairs when it discovered high oil pressure in the other engine, according to the Nuclear Regulatory Commission.

Nuclear Management now must fix that problem. Work on the generator startedand Nuclear Management had seven days to finish without shutting down the reactor, but determined that would not happen.

Nuclear Management shut down the same reactor to fix the same problem with its other diesel generator last April. Those repairs took about two weeks.

Problems with the reactor's backup generators date back to early 2001, when Nuclear Management found high crankcase pressure due to incompatible fuel and lubricating oils had damaged the diesel engines, according to the NRC. All the cylinders and pistons were replaced at that time, along with the lubricating and fuel oils.

Prairie Island's other reactor, Unit 1, remains in operation. Prairie Island, located near Red Wing, is capable of generating 1,076 megawatts of electricity -- about 20 percent of the power used in the Upper Midwest.

Generally, Xcel either buys electricity to replace power lost when one of its facilities is out of service, or it ramps up one of its own units, spokeswoman Mary Sandok said.

The temporary shutdown of Prairie Island comes at a time of lower demand; typically Xcel sees demand spike during the summer when air conditioners are in use. If the company must buy power, the cost is passed along to customers, but Sandok said the amount isn't likely to be large enough to notice.

Tim Huber can be reached at thuber@pioneerpress.com or 651-228-5580.