More Oversight at SC Nuke

Monday, October 15, 2012 @ 05:10 PM gHale


Duke Energy’s two-unit, 2,258 MW Catawba nuclear power plant near York, SC, about 18 miles south of Charlotte, NC, will get increased oversight, said officials at the Nuclear Regulatory Commission (NRC).

The increased oversight from the NRC is because of violations linked to an event in April where the plant temporarily lost offsite power.

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The NRC said the two violations involved an incorrect modification to a Unit 1 generator protective relay that resulted in the loss of offsite power event.

The NRC found the violation for Unit 1 was a “white,” which means it has low to moderate safety significance.

Meanwhile, the violation for Unit 2 was “green,” or had very low safety significance.

The chain of events started April 4, when the plant lost power coming into the plant. Backup generators kicked in and the one operating reactor shut down safely. Catawba’s second reactor was already down for refueling.

Catawba officials declared an “unusual event,” the lowest of four emergency levels and one not experienced at the plant since 2006.

Nuclear plants have multiple backup systems to keep them safe if there is some type of malfunction. But losing off-site power removes the primary energy source needed to operate the plant and keep vital cooling water in circulation.

The NRC investigation traced the April incident to a programming error when electrical modifications occurred on the plant’s Unit 1 last July and November, and to Unit 2 in February. The error meant off-site power could inadvertently be lost anytime if the units’ generator shut down due to a power fluctuation.

That’s what happened April 4. A ground fault on a reactor coolant pump triggered the reactor, turbine and generator to stop. Because of the programming error, the unit also lost off-site power.

Duke corrected the problem and both Catawba reactors are now operating at full power.



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