Could nuclear power be rapidly expanded on a global scale? There are a number of practical limiting factors, including site availability and acceptability, nuclear waste disposal issues, and the risks of accidents and proliferation. But there are also a variety of resource limitations. One particular resource limitation that has not been clearly articulated in the nuclear debate thus far is the availability of the relatively scarce metals used in the construction of the reactor vessel and core. While this scarcity is not of immediate concern, it would present a hard limit to the ultimate expansion of nuclear power. This limit appears to be a harder one than the supply of uranium fuel. An increased demand for rare metals—such as hafnium, beryllium, zirconium, and niobium, for example—would also increase their price volatility and limit their rate of uptake in nuclear power stations. Metals used in the nuclear vessel eventually become radioactive and, on decommissioning, those with long half-lives cannot be recycled on timescales useful to human civilization. Thus, a large-scale expansion of nuclear power would reduce “elemental diversity” by depleting the world’s supply of some elements and making them unavailable to future generations.