Study of optical (laser or spontaneous) radiation of nuclear-excited plasma is of interest for development of the way to extract energy from nuclear reactor and control and adjustment of the nuclear reactors' parameters as well. Interest to the researches in this field is also connected with sufficient difference of the levels' population mechanisms at nuclear pumping from the processes of population in the common gas-discharge lasers. Excitation transfer to the neon atoms from metastable atoms of helium and direct excitation of neon by nuclear particles and secondary electrons are assumed  to be the most probable channel of the Ne(3p) population. In neon 3d and 4s, 5s levels are excited by secondary electrons, in cascade transitions from these levels the Ne(3p) population takes place. The 3d and 4s, 5s levels radiatively bound with the basic state shall be effectively excited by electron impact. The 5s-4p, 4p-4s, 4s-3p cascade transitions may also contribute in populating the 3p-levels of NeI. In helium-neon mixtures the 3p-levels' populating also occurs in the processes of non-resonant transfer of excitation from the He(23S 1), He(21S0) metastable atoms to the 4s, 5s levels of neon and in subsequent cascade transitions.