SC Nuke Back Online

Wednesday, October 30, 2013 @ 05:10 PM gHale

One of Oconee Nuclear Station’s three atomic reactors is back online after a system malfunction caused a four-day shutdown.

The reactor — Unit 3, the youngest reactor online since the 1970s — “is at 100 percent this morning,” said Duke Energy spokeswoman B.J. Gatten Monday.

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The shutdown occurred early last Thursday morning after plant engineers became concerned over how the system was using water to operate.

The plant could operate safely because the malfunction happened on the non-nuclear side of the plant, said U.S. Nuclear Regulatory Commission (NRC) spokesman Roger Hannah.

The NRC issued an event notice about the shutdown. The shutdown began just before 6 a.m., 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, 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 workers lowered system pressure, according to the notice.

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

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