[nbanks]

The Joint European Torus had a 67% efficient reaction back in 1997. The torus wasn't designed for it, so they never tried again. It seams that ITER could achieve break-even quite realistically simply because tokamak reactors are more efficient when they're bigger. Yes, it has to be hotter than the sun and use a deuterium/tritium fuel, but it's all doable with known physics.

I'm not sure when or if a sustained reaction can be done economically.