>>12074313Both fission and fusion reactions produce heat in the form of their reaction product's kinetic energy. That's a huge chunk of their energy output, and unavoidable. And yes, the combined rankine cycle with phase change and reheating is the most efficient way there is to derive mechanical work (and thus electricity) from convective heat transfer.
The only thing that could be improved is the difference between hot and cold thermodynamic reservoirs, and the type of material used as a working fluid. Mad that we use water and not iron to spin a turbine? Blame physics for making chemical bonds so wimpy that better materials can't exist to support white-hot pressure vessels and pipes.
And no, even if you hooked peltier pads up to your coolant loops or ran a reaction hot enough to shine out X-rays or whatever to increase efficiency, you'll only ever shuffle ever so slightly closer to the Carnot limit in your efficiency. That isn't a fault of our technology, it's a simple fact which is baked into our reality like electromagnetism and time.
The only way to improve is to utilize a reaction with charged exhaust products, such that their kinetic energy can be directly converted into current via a magnetic B field and Maxwell's blah blah that I never bothered to memorize. Even with something like aneutronic fusion, there's always going to be a huge amount of uncoordinated kinetic heat energy and again unless you have magic materials then the most efficient answer will be at the most a rankine plant that uses boiling sodium metal or something wimpy to turn a turbine. As it happens, water is an excellent working fluid when compactness isn't an issue (i.e. not a spacecraft)
