I think that it is trying to make the fission and fusion mutually reinforce each other. As I said in my post, I just skimmed the technical details and will double check this tomorrow. But they are using a fusion reaction that produces neutrons (Deuterium-Tritium) and the neutrons will break apart Uranium atoms they hit and enhance the fission reaction and the extra heat and energy put out by the uranium atoms will keep the plasma hot to maintain the fusion.