Water Woes Force Down SC Reactor

Monday, October 28, 2013 @ 05:10 PM gHale

After plant engineers became concerned over how the system was using water to operate one of Oconee Nuclear Station’s three atomic reactors, they decided to manually shut it down.

“The unit is shut down and they’re working now to identify and repair any issues they might find,” said Duke Energy spokeswoman B.J. Gatten of the nuclear plant near Seneca, SC.

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Gatten said the station is operating safely and there will be no interruption in energy production as power will come from alternate sources until the unit restarts.

The U.S. Nuclear Regulatory Commission issued an event notice about the shutdown. The shutdown began just before 6 a.m. Thursday, and the NRC received notification a few hours later at 9:45 a.m., according to the notice.

The problem stemmed from the unit’s “feedwater system,” which governs how water ends up used to generate steam for power.

The malfunction didn’t present a meltdown threat, because the system governs only water between the steam generator and turbine and isn’t part of cooling the reactor core, said NRC spokesman Roger Hannah.

“There’s not a big safety issue because it’s on the non-nuclear side of the plant,” Hannah said.

The system showed variations in how water was flowing, the NRC notice said.

“The feedwater control system was placed in manual in an attempt to stabilize feedwater flows,” the notice said. “Feedwater oscillations continued to grow in magnitude and … a manual trip was directed to prevent an automatic reactor trip.”

Following the reactor trip, four valves that relieve steam failed to “reseat” and ended up reseated after system pressure lowered, according to the notice.

“Operations have been stabilized on Unit 3,” the notice said. “A post-trip investigation is in progress, per site procedures and directives.”

All backup systems designed to protect the reactor worked as they should, Gatten said.

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