The world's biggest experimental reactor for nuclear fusion, a technology in its infancy but billed by some as the answer to humanity's future energy needs, was inaugurated in Japan on Friday.

Fusion differs from fission, the technique currently used in nuclear power plants, by fusing two atomic nuclei instead of splitting one.

The goal of the JT-60SA reactor is to investigate the feasibility of fusion as a safe, large-scale and carbon-free source of net energy — with more energy generated than is put into producing it.