QuantumPion said:
I'm not familiar with (λ,α) reactions.
Yep I guess that this is the general problem when answering to this question :-( It is not easy to find empirical data, and it is not easy to be sure about how some gamma pressure should enhance, if it does, the tunneling rate. But it is important,imo, to stress that the usual answer "It needs to much energy" is wrong; with a positive Q-Value, one can not tell that it is about energy.
Of course, for the particular formulation of the question here, there is a trivial answer, as the OP asks about "fission" and not "nuclear reactions". In this case, it is OK to tell that the fission products are very scattered in the periodic table and unmanageable.
For nuclear reaction, I think the answer is more subtle.
- First, there is only a few suitable reactions (plus few data on them, plus few researchers who could be interested... but in any case, only a few suitable)
- Second, suitable reactions are going to be across elements with nearby masses, this is different from fission. And elements with similar mass have, in first order of approximation, similar production rates in stellar process and then, barring chemical opportunities, similar abundance. Most Hg, for instance, comes from two or three extraction sites.
- Third, the ambiental risk of some of the suitable reactions goes even worse. Take Hg; its extraction and chemical separation is even forbidden in some parts of the world. Put some excess in water and kill yourself in the long run. Add the costs and risk of preparation, with isotope separation and all that, and the cost of late purification. Join all of it to the second point, and break-even becomes unfeasible