Facing hot weather, some Midwestern power plants are facing some challenges.

The twin-unit Braidwood plant in northeastern Illinois had to receive special dispensation to stay online after the temperature of its cooling pond reached 102 degrees Fahrenheit. Typically, the plant is allowed to run only when the temperature in its 2,500-acre cooling pond, located in a former strip mine, stays below 100 degrees.

Craig Nesbit, a spokesman for plant owner Exelon Corp., said lower nighttime temperatures usually help regulate the ponds, but lately the low temperatures in the area have remained in the 90s.

When asked whether he thought the problems the plant faces were linked to global warming, he refused to speculate.

"I'm not a climatologist," Nesbit said. "But clearly the calculations when the plant was first operated in 1986 are not what is sufficient today, not all the time."

A spokeswoman for the Midwest Independent System Operator, which controls the region's energy grid, said other plants are having trouble dealing with the record heat as well. All nuclear and coal plants, as well as many natural gas plants, use water for cooling. Such plants are supposed to run at reduced power levels during the hot summer months as the water used for cooling is warmer and therefore cannot absorb as much heat (Matthew L. Wald, New York Times, July 17). -- WW