Dear PF Forum, I'd like to know more about fusion power. Perhaps someone can give me idea. 1. Is Q is inefficient, take ITER for example? Supposed Q < 1, can't the produced heat boils water and recycled back to the system to produce fusion again? After all, fusion power plant (if it can be built after all) is just a very sophisticated James Watt kettle. 2. Can tritium be produced from deuterium? 3. If yes, what's more difficult, to produce tritium from deuterium or lithium? 4. Is fusion power plant really clean? If it could be build, does it really produce no radioactive material? If yes, what radioactive material that it generate?