WELL begun; half done. That proverb—or, rather, its obverse—encapsulates the problems which have dogged civil nuclear power since its inception. Atomic energy is seen by many, and with reason, as the misbegotten stepchild of the world’s atom-bomb programmes: ill begun and badly done. But a clean slate is a wonderful thing. And that might soon be provided by two of the world’s rising industrial powers, India and China, whose demand for energy is leading them to look at the idea of building reactors that run on thorium.

Existing reactors use uranium or plutonium—the stuff of bombs. Uranium reactors need the same fuel-enrichment technology that bomb-makers employ, and can thus give cover for clandestine weapons programmes. Plutonium is made from unenriched uranium in reactors whose purpose can easily be switched to bomb-making. Thorium, though, is hard to turn into a bomb; not impossible, but sufficiently uninviting a prospect that America axed thorium research in the 1970s. It is also three or four times as abundant as uranium. In a world where nuclear energy was a primary goal of research, rather than a military spin-off, it would certainly look worthy of investigation. And it is, indeed, being investigated.