I think that heavy Rydberg matter dipole shielding of the nickel nuclei allow protons to penetrate the nuclear coulomb barrier of nickel atoms.
In Rydberg matter, this dipole shielding goes as the 7th power of the number of atoms in the Rydberg matter assemblages. This polarization of Rydberg matter is clearly huge and can easily overcome the coulomb potential in the nickel atoms. In Rydberg matter, all the dipole moments of all the constituent atoms are coordinated and identical. Furthermore, the coherent nature of Rydberg matter range from just a single atom to large numbers in excess of 100 based upon the temperature and pressure of the hydrogen envelope; the higher the pressure and temperature, the greater on the average is the number of member atoms in the Rydberg matter assemblages. In other words, the higher the temperature of this hydrogen envelope, the greater is the number of coherent atoms that join the Rydberg matter assemblages. You may have not considered how nuclear reactions affect atoms in a large assemblage of coherent and entangled atoms. In such a collection, what happens to one member of such a coherent collection happens to them all. It may well be that an averaging effect takes place where the nuclear energy output of one atom is averaged over a hundred or more atoms in the coherent collection. Nuclear reactions inside a quantum condensate have yet to be studied. Look at this reference: http://cold-atoms.physics.lsa.umich.edu/projects/dipoleblockade/blockade.html >From this reference, the dipole blockade of the 80 atom Rydberg matter assemblages is .3 microns. Any nickel atom within this blockade distance is subject to intense dipole masking in addition to being forced into coherence with the Rydberg assemblages. Rydberg matter sits on top of the nano-powder and completely negates coulomb repulsion of the nuclei of these nickel atoms that they cover. However, when Rydberg coherence is not yet fully established or is breaking down, gamma radiation production will occur, not being completely negated by atomic coherence. This happens when the temperature and/or the pressure of the hydrogen envelope is lowering or low. This is where the gamma radiation bursts from the Rossi reactor sometimes come from.