Nuclear fusion

Nuclear fusion occurs when two atoms of a light element (such as hydrogen) combine to create a single atom of a heavier element (such as helium). Fusion of elements lighter than iron can theoretically release energy, while fusion of elements heavier than iron will always consume energy. Efficient production of energy using nuclear fusion requires light hydrogen isotopes (such as deuterium) that will fuse relatively easily to liberate a relatively large amount of energy.

SciFi Clichés

Nuclear fusion reactors are prone to exploding in science fiction stories, but in real life, the conditions of high-temperature and high-pressure needed to initiate and maintain a nuclear fusion reaction mean that any problem with a fusion reactor will almost certainly cause the reaction to die instead of running out of control.