Watts Bar nuclear plant shuts down for second time in three weeks

By Dave Flessner, Chattanooga Times Free Press, Tenn.

America's first new nuclear power plant to be added to the grid in the 21st century shut down Monday afternoon for the second time in three weeks when an auxiliary feedwater system tripped the reactor.

TVA said today that the Unit 2 reactor at the Watts Bar Nuclear Power Plant shut down around 3:40 p.m. Monday after the nuclear unit had achieved its highest power production so far, generating more than 390 megawatts, or about one third of its rated capacity.

TVA spokesman
Jim Hopson said the equipment performed as designed when sensors detected the irregularity on the non-nuclear side of the plant. The incident presented no danger to the public or plant employees and is is often part of an initial power ascension testing of a new nuclear reactor.

TVA still expects to bring
Watts Bar Unit 2 to full power generation by this summer, making the unit the first commercial reactor in the United States in 20 years.

In an incident report, the Nuclear Regulatory Commission said the reactor shutdown was "due to reaching the automatic Lo-Lo steam generator trip set point on the No. 4 steam generator. Concurrent with the reactor trip the auxiliary feedwater system actuated as designed."

"All safety systems responded as designed," the NRC said in its report.

TVA hopes to have the unit back on line generating power by the end of the week following an investigation of the cause of the problem.

The unit also tripped just two days after it began power generation on June 5. That shutdown was caused by problems in the plant's turbine system on the nonnuclear part of the plant.

The trips are the latest setback for a nuclear plant that has taken 43 years of starts and stops to finish and ended up costing nearly twice as much as what was forecast when the project was resumed in 2007.

TVA officials said adding a second reactor at the Spring City, Tenn., facility is still cost effective because it cost only about half the expense of other new nuclear plants and can operate along with the Unit 1 reactor for a fraction of the operating costs for most fossil fuel power plants.

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