| > The idea for future designs is to breed Tritium in the blanket surrounding the vessel. This obviates the need for external sources. The problem is that, at best, you can create as much Tritium in the blanket as you put in as fuel (since every emitted neutron is coming from a Tritium atom). So, to be self-sustaining, every emitted neutron would have to be caught by the blanket to form a Tritium atom, and you would have to be able to extract every single atom of Tritium from the blanket back as usable fuel - and this is assuming 100% of the tritium you put in actually fuses, which is unlikely given how hard tritium is to contain (essentially every material is porous to Tritium). So, since there are losses at each of these levels, you need to inject new tritium into the cycle. Also note that this entire blanket design is entirely theoretical at the moment: no fusion experiment has ever attempted to do anything with the fusion products other then measure the amount of heat generated. > I'm no expert on solid state physics, but that seems a little short? JET is more than ten times as old, and as we speak it's in its second run of D-T experiments. I'm no expert either, but these are the estimates I have read everywhere. JET is not in any way representative, as they do a handful of fusion events per year, for a few seconds - while a DEMO plant would be running continuously, 24/7. The amount of irradiation is incomparable. > To be clear these are limitations of a specific kinds of fusion reaction and/or reactor design, primarily that of Deuterium-Tritium in a solid-walled tokamak. These are all limitations of the only fusion electrical power-producing technology that is anywhere close to realistic. All other fusion reactions require much, much higher temperatures and pressures to ignite, so they are many more decades away (regardless of what some snake oil start-ups are claiming). All other magnetic confinement D-T fusion reactions have the same problems I discussed. And inertial-confinement fusion approaches are much less likely to ever be economical given the huge costs of the actual fuel. |