ltgbrown wrote: The fission of 235U results in a large amount of missing mass so is exothermic.
Yes, but fusion of two lighter elements to make U235 in endothermic and fission of light elements (like Boron) is endothermic.
Right, exactly the opposite of the reaction I showed. The equation I provided in the earlier quote would still pertain since the total mass in the nucleii/free nucleons AFTER the reaction would weigh
more than the sum of the starting parts.
ltgbrown wrote: While U235 may have greater total binding energy, the binding energy between individual nucleons in a very large atom is less than the binding energy between individual nucleons in a small atom. So, the total amount of energy available from fission of a very large atom is much greater (large total binding energy) and easier (small binding energy between nucleons), while the total amount of energy available from fission of a small atom is much smaller (small total of binding energy) and difficult (large binding energy between nucleons).
I think this is what Dan is trying to say.
If so, he is doing a confusing job of it. But his main contention was that Ni+p would be endothermic which is just plain wrong.
If you fuse two (or more) atoms that are LARGER than Fe together to make U, you will need to add energy. But if you could add free nucleons, one by one, from Ni to U, you would release energy with each and every nucleon added. True, the more you added, the less the next one would release, but it would still release energy, still be exothermal. The key to this is that free nucleons have
ZERO (
even negative(?)) binding energy so adding one to a nucleus with ~8MeV PER NUCLEON, will release about 8MeV. The math is simple. There should be no confusion.