The Tennessee Valley Authority has lost nearly $50 million in power generation from its biggest nuclear plant because the Tennessee River in Alabama is too hot.

Unless the summer cools down, TVA could lose millions of dollars more, pushing up fuel costs and consumer electric bills even after seven consecutive monthly increases.

The Browns Ferry Nuclear Power Plant near Athens, Ala., has operated at only about half power for most of the past month and could remain at reduced power through September, TVA officials said. The three-reactor plant - TVA's biggest nuclear facility - has been the hardest hit of any of the nation's 104 nuclear plants by thermal concerns over river water, according to the Nuclear Energy Institute and TVA.

"All the radiant heat gets in the river when you have a summer as hot as this has been," TVA President Tom Kilgore said.

Today is expected to be the 40th day since July 8 that TVA has reduced power production at Browns Ferry because of hot water in the river. Last week, TVA violated its permit with the Alabama Department of Environmental Management when the river temperature topped 90 degrees.

The cutback means TVA is losing 1,500 megawatts of power generation just when it's needed most. For each day of 50 percent power at Browns Ferry, the utility spends more than $1 million extra to pay for replacement power, officials said.

The extra cost is added to ratepayer bills in the monthly fuel cost adjustment, which is up by more than 25 percent since March.

heat is on

When the Tennessee River flows into the Guntersville Reservoir around Browns Ferry, the river widens, slows and gets shallower. TVA uses mechanical draft cooling towers to help pull heat out of the cooling water.

Most U.S. nuclear plants are on an ocean or one of the Great Lakes or have closed-loop cooling systems that don't rely as much upon water from nearby rivers or lakes.

TVA's Watts Bar Nuclear Plant in Spring City, Tenn., has a closed-loop system. The Sequoyah plant near Soddy-Daisy uses less river water than Browns Ferry and has two cooling towers.

TVA also plans a closed-loop system with twin cooling towers at the Bellefonte plant planned in Hollywood, Ala.

Two coal-fired TVA plants - Cumberland, west of Nashville, and Colbert, near Muscle Shoals, Ala. - also are thermal-limited and have had to cut production this summer, although not as much as Browns Ferry.

But during a public hearing before the TVA board last week, anti-nuclear activist Margaret Klein, of Knoxville, said nuclear plants are bound to encounter more thermal problems on the Tennessee River as global warming raises river temperatures.

"This is a serious problem and will only get worse if we add more reactors," she said.

Looking for a fix

Ashok Bhatnagar, a TVA senior vice president, said the utility considered adding more cooling towers or a closed-loop cooling system when Browns Ferry was refurbished in the 1990s. At the time, TVA estimated that the chance of exceeding the 90-degree temperature limit in the Tennessee River was very rare, he said.

Browns Ferry did get some added cooling capacity in the last decade but still has had to cut production in two of the last five years because of water temperatures.

The utility now is looking at new options to cool Browns Ferry without heating the river.

"Our study just got started, and there are multiple options," Bhatnagar said. "They really are looking at different ways we can address this issue."

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