With the heat index predicted to top 100 degrees today and Wednesday, electricity users in the Tennessee Valley are expected to push power consumption this week to the highest levels of the year.
The Tennessee Valley Authority doesn't anticipate any problems keeping the juice flowing to cool homes and offices this week. But the federal utility must make some costly reductions at some of its biggest power plants to avoid overheating the Tennessee and Cumberland rivers.
On Monday, TVA cut in half the production at its biggest nuclear power plant - the three-reactor Browns Ferry plant in Alabama - when the temperature of the Tennessee River neared the 90-degree maximum, TVA spokesman Terry Johnson said.
"With the hot temperatures we are expecting this week, it is anticipated that Browns Ferry will continue to be 'de-rated' (to cut power output and water use) through this week," Mr. Johnson said. "We will lower power as necessary to stay within the thermal limit of our (water discharge) permits."
State regulators in Tennessee, Alabama and Kentucky set acceptable water temperatures for the Tennessee River and its tributaries to limit the threat to aquatic life and water quality.
Over the past two weeks, TVA has reduced power production to limit the amount of river water used to cool condensers at the Browns Ferry nuclear plant as well as the Cumberland, Gallatin and John Sevier coal plants in Tennessee and the Widows Creek and Colbert coal plants in Alabama.
The power reductions are being made only during selected periods of the day. But to replace the lost power generation from the plants that provide most of TVA's baseload power, especially during peak demand periods, TVA must spend millions of dollars for extra fuel costs, which ultimately flow to consumer bills in higher monthly fuel cost adjustments.
A nuclear reactor generates more than $1 million worth of electricity a day when in full production. But each of the three units at Browns Ferry are producing only about one-half to two-thirds of their capacity this week, potentially costing TVA more than $10 million in lost power last week and this week due to the sweltering air and water temperatures.
TVA is replacing the lost power from its nuclear and coal units with more expensive gas-generated or purchased power from other utilities.
Dick Urban, director of water quality for the Tennessee Department of Environment and Conservation in Chattanooga, said the agency will be closely monitoring water temperatures in Lake Chickamauga this week. But so far, neither the twin-reactor Sequoyah Nuclear Plant near Soddy-Daisy, which uses cooling towers, and the single-unit Watts Bar Nuclear Plant, which uses a closed-loop cooling system to limit river water use, have pushed lake temperatures above acceptable limits, he said.
"If the water gets too hot, the dynamics of the aquatic food web change and there is more stress for the entire ecosystem," Urban said. "Temperatures have been hotter than normal this summer, but fortunately for TVA, there was plenty of rain in the past year for cold water storage reservoirs like those at Lake Norris and Lake Fontana."
During the drought and heat of 2007, when water temperatures rose in the Cumberland River near TVA's Cumberland coal plant, many fish died when river temperatures got too hot, Urban said.
Browns Ferry appears to be the hardest hit nuclear plant in the country this summer for power reductions due to thermal pollution, Nuclear Energy Institute spokesman Mitch Singer said.
Although there is still plenty of power to buy from other producers, the cutbacks at Browns Ferry this week couldn't come at a worse time. TVA expects the reach new power peaks for the summer today and Wednesday, although the peaks will remain below the all-time high reached three years ago.