Nuke Plants Suffer Shutdowns

Thursday, December 29, 2011 @ 02:12 PM gHale


A leaky valve and an issue with a turbine forced two nuclear plants to shut down this week.

In one case, the reactor at the River Bend nuclear plant in Louisiana shut down automatically after an issue in the turbine caused safety systems to trip.

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In the other, the Pilgrim nuclear plant in Plymouth, MA, shut down Monday after workers found a potential leak in a valve meant to release steam in case of a sudden build up of pressure.

Workers at the plant began a gradual, controlled shutdown of the facility at 12:50 p.m. Monday after they detected a temperature change in the valve that could indicate a leak, said Nuclear Regulatory Commission (NRC) spokesman Neil Sheehan. The shutdown did not pose a health or safety risk to the public, he said.

Crews are now treating a containment chamber to make it safe for inspectors to enter it and assess the problem. Sheehan said officials do not know how long the plant will remain off line.

“It’s really dependent on what they find once they get in there,” he said. “It could be a really straight-forward repair or it could be something that’s more complicated.”

The shutdown comes less than two months after a leak in a different valve forced Pilgrim officials to shut down the facility for more than a week to make repairs. Any plant that experiences six unplanned power changes in 7,000 hours of operation is subject to increased oversight by the Nuclear Regulatory Commission.

The River Bend shutdown caused the reactor protection system to activate, and the reactor’s water level briefly dropped. Per the system’s design, containment isolation valves in the boiling water reactor’s suppression pool cooling system closed. Reactor core isolation cooling operated manually for 1 minute.

The shutdown from 100 percent power was uncomplicated, according to the NRC. Plant operators are conducting an investigation into the reactor trip, which the report said came from a loss of a speed sensor in the turbine.

Entergy operates River Bend, near Baton Rouge, La. The plant uses a single General Electric boiling water reactor with Mark III containment at the plant generating 989 megawatts, according to the NRC.



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