Nuclear fusion: more energy produced than consumed

Nuclear fusion is the process that powers the Sun: light atoms, generally deuterium and tritium, fuse at extreme temperatures to form heavier atoms and release enormous amounts of energy. Unlike nuclear fission, it produces no long-lived radioactive waste and its fuels are abundant on the planet. The promise of fusion as a clean and inexhaustible energy source has been around for decades, but concrete advances were slow in coming.

The milestone achieved at the ITER reactor in France, and independently by the National Ignition Facility in California, consisted of surpassing for the first time the "ignition" barrier: the energy produced by the fusion reaction exceeding the energy delivered to the plasma to sustain it. That does not mean fusion is yet a commercially viable energy source, but it closes a technical debate that lasted decades about whether the process was physically possible at a controlled scale.

The remaining challenges are of engineering and economics. Sustaining the plasma at 150 million degrees for timescales useful for continuous generation, capturing the heat efficiently to convert it into electricity, and building reactors at a cost competitive with other energy sources. The most optimistic estimates place fusion energy connected to the grid between 2040 and 2060. What the recent advance changed is the certainty that the path is achievable.