We point out that numerous experimental facts dealing with the observation of nuclear transformations in a condensed matter at room temperature remain totally unexplained till date. In the present article we open up a principal way to understand such phenomena in the framework of pure bound field theory (PBFT) that we developed earlier (e.g. Kholmetskii AL. et al. Eur. Phys. J. Plus 2011;126:33, Eur. Phys. J. Plus 2011;126:35). In this theory, we explicitly take into account the non-radiating nature of the electromagnetic field of quantum bound particles in stationary states, which leads to the corresponding corrections of basic equations of atomic physics, with further elimination of the available subtle deviations between experimental and theoretical data in precise physics of light hydrogen-like atoms. In the present paper we have once more analysed the principal prediction of PBFT, which allows the existence of the second stationary energy state in the bound system “proton plus electron” (next to the usual hydrogen atoms). This new stationary state is characterised by the unusually small averaged radius of about 2α2rB≈5 fm (where rB is the Bohr radius, and α is the fine structure constant), and a huge (in the atomic scale) value of the binding energy about –255 keV. We named this bound system as the “neutronic hydrogen”, because in many processes of its interaction with matter, it is practically indistinguishable from the neutron. The latter circumstance opens up the principal way to understand numerous puzzling facts of low-temperature nuclear synthesis.