Small nuclear reactor can use existing power-transmission lines without overloading them. mPower and other small reactors can act as a “drop-in replacement” for ageing coal furnaces without the need for costly refurbishment. The Tennessee Valley Authority (TVA), America’s biggest public utility, hopes to put two of the firm’s reactors into an old coal plant. Five other American utilities are also considering replacing coal furnaces with nuclear reactors, according to Philip Moor of the American Nuclear Society, an industry group. He estimates that in America alone perhaps 100 old coal plants could be converted to nuclear within a decade—a trice by the industry’s standards.