Helium fusion reaction is an alternative to uranium nuclear reaction source of energy.

Nuclear reactions release immense amounts of energy. Uranium undergoing fission – the type of reaction that drives today’s nuclear power plants – releases about 2.7 million times more energy per gram than coal. But fission reactors come with dangerous baggage: radioactive waste and the small but serious risk of nuclear meltdown.

In contrast, fusion reactions are safe and produce virtually no radioactive waste. Their main waste product, helium, is a non-toxic gas used in everything from party balloons to the Large Hadron Collider. And fusion fuels are easy to find: deuterium is abundant in seawater and tritium can be made from lithium. In a fusion reaction, these fuels produce about four times as much energy per gram as uranium fission, or 11.3 million times as much as burning coal.

A single gram would produce enough heat to boil the water in a swimming pool.
The trouble is, we still can’t get fusion to work for us. Fusion reactions require sustained temperatures of millions of degrees Celsius. Research has been ongoing for decades but, as of 2017, it takes more energy to get the reaction going – and keeps it going – than you get out the other end. This means it’s not a viable way of generating electricity yet. There’s an old joke that fusion power is only 30 years away – and always will be.

But this could change. Important technical challenges have been solved in the last 20 years and investment continues to pour in to fusion technology, lured by the tantalising prospect of a virtually inexhaustible clean energy supply. Thirty-five countries are collaborating to build the world’s largest tokamak (magnetic fusion device) in Southern France, which will aim to produce positive net energy for experimental purposes by the end of 2025. But it will be several years longer until this energy can be harnessed to power our homes, cars and offices.