Maybe I am misreading this, but Aldo Rosa tells me in “Fundamentals of Renewable Energy Processes” (P.33) that D-D fusion is aneutronic. According to Rosa, the result of D-D fusion results in stable Helium 4 that must shed its energy by emitting gamma rays. As gamma are far more energetic than the x-rays emitted from p-B fusions, I was wondering if, theoretically of course, a pure deuterium plasma might be a better fuel for a theoretical over-unity DPF device?
Unless I’m profoundly mistaken, the D-D reaction has two equally-likely paths: an H3 nucleus and a proton, or a He3 nucleus and a neutron. As far as I know, D-D -> He4 is not a reaction that occurs with D-D; the secondary reaction of D with the H3 produced can generate He4, but it will also produce another neutron.
So in general, D-D fusion is not at all aneutronic.
D-D fusion can be aneutronic when a third body is present like another atom. Momentum conservation requires two products so He-3 and n or p+H-3. There is a very rare reaction <1E-12% of the time that can lead to He-4+ gamma but it is not worth mentioning. The aneutronic D-D is one of the hopes of cold fusion folks. Evidence does not support that this reaction can favor the aneutronic branch in the presence of current materials or conditions that can be reproduced.