The expansion of nuclear electricity generation is, however, still held back in many countries by concerns about cost and perceptions about safety, which new nuclear fission reactors must address. The next generation of nuclear reactors (Generation IV) will offer electricity generation with passive safety, as well as high temperature process heat for hydrogen production and desalination. Some designs may also re-use nuclear waste as fuel, closing the nuclear fuel cycle to reduce both the demand on uranium supplies and the volume of waste needing long-term storage. These reactors are likely to be generating significant power by the middle of the 21st century, following prototype development over the coming decades.
In the longer term nuclear fusion, which powers the sun, offers a future of sustainable, low carbon electricity generation. It involves the release of energy by fusing light atomic nuclei, rather than splitting (‘fissioning’) heavy nuclei. Fusion is a very attractive source of energy – almost unlimited in potential, with few of the downsides of nuclear fission – but it is very hard to master.