On Tue, Dec 8, 2015 at 6:18 PM, <[email protected]> wrote: Note that with alpha fusion some extra energy is available, so I suppose > that in > theory that means you could start a little lower, however that would also > not be > spontaneous fission, but rather triggered fission. >
Agreed. The reference to spontaneous fission in the appendix was an interesting detail, but the fragmentation would be induced, presumably, by the additional energy in the compound nucleus resulting from the capture of an alpha particle. This is not to say that spontaneous fission might not also be a possibility if something is increasing the tunneling probability for fission. If you add a neutron to U238 it doesn't fission, despite the addition of 4.8 > MeV. So unless the alpha fusion releases quite a bit more than this, I > don't > think you are going to get much fission for lower isotopes. > Agreed. Added to this picture is the assumption that something is simultaneously increasing the rate of alpha decay, the alpha capture cross section and the probability of fragmentation. Note that addition of 2 D's or 4 H's yields some 20+MeV more than addition > of an > alpha, making such a combination much more likely to be able to trigger > fission. > That would also create daughters with much higher energies. A nice thing about the lower energies involved in alpha captures is that the daughters end up having ~ 300 keV/nucleon, which is not that much. Also, 2 D's and 4 H's require 3-body and 5-body reactions, which seem improbable to me. About the matter of the Coulomb barrier -- I like your and Dave's argument that the Coulomb barrier should be expected to work in one direction (and this would also seem to be implied by the shell theorem). But Krane on three or so occasions has written things that imply that the Coulomb barrier works in two directions, suggesting that it's not just a misinterpretation on my part. One possibility here is that a side effect of decreasing the Coulomb barrier surrounding the nucleus is that this somehow alters the nuclear potential in a way that makes it seem as though the Coulomb barrier works in two directions. Eric
