Will we ever … have reliable nuclear fusion power?
In the era of global climate change, and concerns about humanity's long-term reliance on fossil fuels, many think the solution lies in alternative sources of energy, including nuclear power. All our nuclear power plants are based on fission: splitting heavy atoms into lighter components in a controlled fashion. Though fission is safe when all goes well, the fuel is radioactive, waste disposal can be problematic, and as the Fukushima disaster showed there is a high cost to accidents.
Nuclear fusion is in principle cleaner and comes from a cheaper, more abundant fuel source: an isotope of hydrogen called deuterium can be extracted from water and only helium is produced as waste. From The Matrix to SimCity 2000 to political dreamers, fusion has often been seen as an inevitability for society. However, despite decades of work nuclear fusion remains a dream. As the joke goes fusion is the power of the future – and always will be.
That's not because creating a sustained fusion reaction – in which more energy is produced than is required to start and maintain the process – is impossible or even terribly hard to achieve (at least by high-energy particle physics standards). The most infamous example of a fusion reaction is the hydrogen bomb, which sacrificed control and safety for the sake of violence and death. Fusion reactors obviously need to have more stringent requirements.
Cosmic collider
To see what's needed to create a sustained reaction, let's look to the best-known fusion reactors of all: stars. In the core of a star like the Sun, strong gravitational pressure forces together hydrogen plasma – an equal mixture of protons and electrons. Extreme conditions of 15 million-degree-temperatures and high pressures mean that protons have enough energy to overcome their mutual repulsion for each other, allowing the attractive forces to kick in. When protons fuse