Radiolysis influence on the tritium content in irradiated lithium nitrate for fluorine-18 production using a nuclear reactor

Natural non pre-treated polycrystalline lithium nitrate suffered radiolysis by cobalt gamma-rays, 2.65 and 3.37 MeV protons, β-particles from 3 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 F 2 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 NO 2 , NO 3 , NO 2- 3 , NO 2- 2 radicals and NO 1- 2 . 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.