> France’s rivers might not be such key freight arteries, but they do serve to cool the nuclear plants that produce 70% of the country’s electricity. As prices hit all-time highs, power giant EDF has been forced to reduce output because of the drought.<p>> Strict rules regulate how far nuclear plants can raise river temperatures when they discharge cooling water – and if record low water levels and high air temperatures mean the river is already overheated, they have no option but to cut output. With Europe’s looming energy crisis mounting and the Garonne, Rhône and Loire rivers already too warm to allow cooling water to be discharged, the French nuclear regulator last week allowed five plants to temporarily break the rules.