In another messageboard some time ago, that question came up: how feasible it is to power a locomotive with a nuclear reactor. Yes, that kind of railroad vehicle. It would work much like a diesel-electric locomotive. That kind of locomotive works by a diesel engine turning a generator, which in turn powers motors which turn the wheels. In effect, an electric transmission. A nuclear-powered locomotive would have a nuclear reactor instead of the diesel engine. A typical diesel-electric locomotive is EMD SD40-2 - Wikipedia Length: 68 ft 10 in / 21.0 m Width: 10 ft 3 in / 3.1 m Height: 15 ft 7 in / 4.8 m Weight: 184 US tons / 170 metric tons Engine power: 3000 hp / 2240 kW Engine weight: 18.2 US tons / 16.5 metric tons Would it be possible to have a nuclear-powered locomotive that (1) fits in the above size and has less than double the above weight or (2) has tolerably low ionizing-radiation emissions, or (3) both?