Uranium is a heavy, silvery-white metal, and it is one of the chemical elements — symbol U, number 92. What makes it famous is that it is radioactive: its atoms slowly break apart on their own, giving off energy and invisible rays that are dangerous to living things. Some kinds of uranium atom can be made to split in a chain reaction, releasing an enormous amount of heat. That single fact gives the word both its uses: uranium fuels nuclear power stations, and it is also the material of nuclear weapons. So in the news it almost never appears as a neutral scientific word — it appears in stories about power plants, about mining, about countries enriching uranium, about safety and about war. 'Enriched uranium' means uranium that has been treated so that more of it is the kind that splits easily; this is the step that worries other governments. It is an uncountable noun: uranium, never 'a uranium' or 'uraniums'. In its natural state, dug out of rock, it is not especially dangerous to hold briefly, but the dust and the processed forms very much are. Australia, Kazakhstan and Canada mine most of the world's supply.