U.S. to announce scientific breakthrough on fusion energy -sources

The U.S. Department of Energy will announce on Tuesday that scientists at a national lab have made a breakthrough on fusion energy, the process that powers the sun and stars that one day could provide a cheap source of electricity, two sources with knowledge of the matter said.

The scientists at Lawrence Livermore National Laboratory in California have achieved a net energy gain for the first time, in a fusion experiment using lasers, one of the people said. The FT first reported the experiment.

Fusion works when nuclei of two...