Imagine a nuclear reactor that is small enough to be transported on an aeroplane or inside a shipping container, and loaded with ten years’ worth of fuel. This kind of microreactor, say its proponents, could be shipped straight from factories to remote areas where electricity is expensive, such as rural Alaska and remote mining sites, or even extraterrestrial bases. Their compactness could enable integration into industrial facilities, and the heat they generate could be used to drive chemical production.