Complications as Cooper nuclear station refuels

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May 2nd, 2011

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Lincoln, NE – A problem with emergency equipment at Nebraska’s Cooper Nuclear Station is adding to the cost of a refueling shutdown there. The trouble comes just a few weeks after three workers were exposed to radiation at the nuclear plant, after workers failed to follow proper procedure in early April.

A problem with emergency equipment at Nebraska’s Cooper Nuclear Station is adding to the cost of a refueling shutdown there. (Photo credit Cooper Nuclear Plant)

Cooper Nuclear Station, owned by the Nebraska Public Power District, is located on the Missouri River just outside the southeast Nebraska town of Brownville. The plant was taken offline March 13 for a routine refueling operation. Nuclear Regulatory Commission spokeswoman Lara Uselding said last week, a problem was discovered during an equipment test. NPPD spokeswoman Jeanne Schieffer explains.

“We discovered there was an issue with a voltage regulator,” she said. “So we started looking further into what might be causing the problem with that voltage regulator. And it’s on one of two emergency diesel generators that we have.”

Uselding said the generators are in place to operate in emergency conditions. “They aren’t needed for the regular operations, but they’re certainly part of our design and our emergency system that’s in place.”
In fact, those generators can be critically important. Alan Dostal, NPPD’s corporate nuclear business manager, said that in the Fukushima disaster in Japan, first the plant lost its connection to the grid that supplied power from off-site.

“So before the tsunami hit, the plants went into automatic shutdown and their diesel generators automatically started as we would expect ours to,” Dostal said. “And they were providing electricity to pump cooling water into the plants. But when the tsunami hit, the fuel tanks for their diesel generators were actually swept out to sea, so they lost all sources of off-site power at that point.”

That led to numerous problems that have been reported, including a loss of cooling water and release of radiation requiring evacuation of the area around the plant. No one’s predicting a tsunami or a similar sequence of events on the Missouri. And Dostal said it’s unclear whether the emergency generators at Cooper have ever been used. Still, he said, NPPD is working to minimize risks.

“We have two of these main station emergency generators,” he said. “But just to add some additional redundancy to our … emergency systems at Cooper, we added a third diesel generator that we just installed during this outage. So now we have three of these generators to provide that defense in depth, which you want to have in a nuclear plant.”

After the problem with the one generator is fixed, Dostal said NPPD will examine the second one. The third generator is of a different design.

Dostal said it’s hard to say how much more ratepayers will have to pay for electricity from other sources while Cooper remains off-line. He said the direct costs of the shutdown, originally budgeted at $31 million, have increased by $5 million as a result of fixing the generator and other problems. And he said the handling of the problem reflects the nuclear industry’s general approach.

“This is a routine problem in a business that has very high expectations for high reliability … post-Fukushima,” he said. “And we went into our refueling right on the heels of that event. It does make people stop and think and be a little bit more deliberate about what they do. But the industry has that fundamental belief and understanding that this is serious business and we’re going to do everything we can to do it as close to perfect as we can.”

Dostal said NPPD hopes to have Cooper back online, generating power, toward the end of this week.

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