Aug. 12--The Tennessee Valley Authority is having to cope with the high-energy demand of summer's dog days with one-third of its nuclear power capacity not in production.

TVA's newest nuclear reactor and its most recently restored nuclear unit are both idle this week while plant workers make repairs on the non-nuclear portion of the two units, TVA spokesman Gil Francis said Monday.

The Unit 1 reactor at the Watts Bar Nuclear Plant near Spring City and the Unit 1 reactor at the Browns Ferry Nuclear Plant near Athens, Ala., were shut down last week when workers discovered different equipment problems.

Last week, TVA also had to reduce power production at the other two Browns Ferry reactors because a power problem in the plants' cooling systems threatened to overheat the Tennessee River. But Mr. Francis said those two units were restored to full power Monday.

TVA is buying adequate power from other utilities and independent power producers to make up for the loss of nuclear power generation, officials said. But every day a nuclear reactor doesn't produce power typically costs the federal utility more than $1 million, bringing the production losses in the past week to more than $10 million.

The latest series of problems at TVA's nuclear plants began Aug. 1 when a hydrogen leak inside the main generator at the Watts Bar Nuclear Plant forced TVA to lower power production to about 80 percent of normal. Last Thursday, TVA took the Watts Bar reactor off line to repair the generator problem.

At the same time, all three reactors at the Browns Ferry Nuclear Plant were reduced to 50 percent of their power output to avoid overheating the Tennessee River. TVA said a transformer that supplies electricity to Browns Ferry's cooling tower failed last week.

On Friday, the Unit 1 reactor at Browns Ferry was taken completely off line after a leak was found in the instrumentation used to monitor temperatures in the plant's main steam lines, officials said.

The plant shutdowns and power reductions were conducted in accordance with federal regulations and didn't endanger the public or plant staff, according to the U.S. Nuclear Regulatory Commission.

But Sara Barczak, program director for the Southern Alliance for Clean Energy, said the outage at the Unit 1 reactor at Browns Ferry last week was the sixth unplanned shutdown of the unit since TVA restarted the reactor in May 2007 following a $1.8 billion, 5-year repair program.

"The nuclear power industry was touting the return of Browns Ferry Unit 1 as an example of the success of bringing more nuclear units on line," she said. "But having six unplanned outages in a little over a year seems more like the signs of a lemon to me."

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