From Climate Central:
On July 8, 2010, as the temperature in downtown Decatur, Alabama climbed to a sweltering 98°F, operators at the Browns Ferry nuclear power plant a few miles outside of town realized they had only one option to avoid violating their environmental permit: turn down the reactors. For days, the Tennessee Valley Authority (TVA), which owns the nuclear plant, had kept a watchful eye on the rising mercury, knowing that more heat outside could spell trouble inside the facility. When the Tennessee River, whose adjacent waters are used to cool the reactors, finally hit 90°F and forced Browns Ferry to run at only half of their regular power output, the TVA hoped the hot spell would last just a few days. Eight weeks of unrelenting heat later, the plant was still running at half its capacity, robbing the grid of power it desperately needed when electicity demand from air conditions and fans was at its peak. The total cost of the lost power over that time? More than $50 million dollars, all of which was paid for by TVA’s customers in Tennessee.