It's intentionally a hybrid of D-D and D-He3. The output of D-D is half He3, and half tritium which decays to He3 with a 12-year half-life. So the only external

It's intentionally a hybrid of D-D and D-He3. The output of D-D is half He3, and half tritium which decays to He3 with a 12-year half-life. So the only external input is actually deuterium. I've seen Helion and other say that the combined reaction will release 6% of its energy as neutron radiation. That's low enough to skip a heat cycle, which is the real benefit since it substantially lowers your capital cost. That's why Helion estimates a cost starting at $0.01/kWh, and less as they get into mass production.