With the supposed need for vast new electricity generation to fuel the artificial intelligence (AI) boom, AI companies are pushing nuclear power as one solution to provide that power for the many data centers they plan to build. (Count me skeptical of the boom and therefore of the need for vast new electricity generation capacity. See here, here, here, here and here.) AI boosters usually talk about expanding existing nuclear power technologies, that is, fission reactors that run on uranium and (more dangerously) on plutonium.
But it is well to keep in mind that there are two kinds of nuclear power: fission and fusion. For now, there are no commercial fusion reactors since with current technology it takes far more than the equivalent of a kilowatt of energy to produce a kilowatt of electricity. This is because it takes a lot of energy just to get a fusion reaction going. The current state of affairs in fusion reminds me of the old joke about the manufacturer who admits he loses a nickel on every sale, but claims he makes it up in volume.
Fortunately, fusion researchers are smarter than this and await the day when fusion technology can produce more energy than it consumes. That waiting has spawned another well-worn joke about the coming of clean, limitless fusion energy, namely, that it's only 25 years away and always will be. (Whether fusion energy will be clean, that is, non-radioactive, is debatable.)