Natural non pre-treated polycrystalline lithium nitrate suffered radiolysis by cobalt gamma-rays, 2.65 and 3.37 MeV protons, P-particles from 'H and nuclear reactor irradiation at room temperature. The sample irradiated in the nuclear reactor was a deep reddish-orange, and contrary to what was expected, this colour was stable, disappearing only after annealing or dissolution. These colour centres, seemingly F2 centres, are produced by neutrons, tritons and alfa-particles and are diamagnetic since the paramagnetic Electron Spin Resonance (ESR) signal centred at 2.009 did not change after annealing. This study suggests that radiolytical products might be NO2, NO3, NO:-, NO:-radicals and NO:-. The high content of tritium in the lithium nitrate irradiated in the nuclear reactor is promoted by these radicals and defects which act as trapping centres for tritons.