Light water, in the terminology of nuclear reactors, is ordinary water. Its chemical formula is H_{2O. While ordinary water has some heavy water molecules in it, it is not enough to be important in most applications. Light water reactors are simpler and cheaper than heavy water reactors, and although they have the same power-generating capabilities, it is far more difficult to use them to produce weapons-grade plutonium, as the reactor must be shut down and the fuel rods replaced every four months because if they stay in any longer, the plutonium-240 concentration will become too high and poison the plutonium-239. A disadvantage of light water reactors is that they must use enriched uranium, while heavy water reactors can use natural uranium.}

Nuclear materials

Eau légère | 軽水