Cooling Woes Spike Nuke Temps

Tuesday, May 17, 2011 @ 05:05 PM gHale

One of the Browns Ferry Nuclear Plant’s shutdown reactors lost cooling for about 40 minutes and in that short time, temperatures rose dramatically before workers were able to reset the system.

The new problem was akin to an electrical short that occurred as maintenance employees were working on electrical relays, said Tennessee Valley Authority (TVA) spokesman Ray Golden. TVA owns the Brown Ferry Plant.

The problem caused a Unit 3 cooling pump to lose power. After discovering the problem, workers reset the system, much like you would do when you flip a breaker switch, he said.

The reactor cooling water temperature rose about 10 degrees over the 40 minute period — from 112.5 degrees to 122 degrees, according to the report TVA filed with the Nuclear Regulatory Commission (NRC).

The April 27 tornadoes took out all of TVA’s power grid in Alabama and much of the grid in Mississippi. All three reactors at Browns Ferry in Athens, Ala., went into automatic shutdown.

With transmission lines downed, the nuclear plant was not able to ship its excess power to distributors, and the plant shut down to stop producing electricity.

Because Browns Ferry is self-powered, the plant automatically switched to diesel generator power. TVA was able to supplement the diesel power with an outside electrical line to operate lights in the plant, but diesel generators powered the plant’s shutdown cooling until they restored offsite power supplies to the plant.

NRC spokesman Roger Hannah said an electrical issue “unexpectedly affected additional equipment” at the nearly 40-year-old nuclear plant.

“Our inspectors believe the operators and maintenance staff dealt with the issue effectively, and it has been entered into the plant’s corrective action program for further evaluation. Our resident inspectors will follow that evaluation,” Hannah said.

Earlier this week, the NRC, which regulates all 104 U.S. commercial reactors, red-flagged Browns Ferry for safety problems with a stuck valve last fall and placed the plant on “red” or “high safety significance” status.

The NRC’s finding will result in increased NRC inspection and oversight — something the commission has ordered four other times in the past decade.

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