Corrosion Behavior of Pyro-Carbon in Hot Lithium Molten Salt Under an Oxidation Atmosphere

Abstract

The electrolytic reduction of a spent oxide fuel involves liberation of the oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is too crosive for typical structural materials. Therefore, it is essential to choose the optimum material for the process equipment for handling a molten salt. In this study, the corrosion behavior of pyro-carbon made by CVD was investigated in a molten LiCl-<TEX>$Li_2O$</TEX> salt under an oxidation atmosphere at <TEX>$650^{\circ}C$</TEX> and <TEX>$750^{\circ}C$</TEX> for 72 hours. Pyro-carbon showed no chemical reactions with the molten salt because of its low wettability between pyro-carbon and the molten salt. As a result of XRD analysis, pyro-carbon exposed to the molten salt showed pure graphite after corrosion tests. As a result of TGA, whereas the coated layer by CVD showed high anti-oxidation, the non-coated layer showed relatively low anti-oxidation. The stable phases in the reactions were <TEX>$C_{(S)}$</TEX>, <TEX>$Li_2CO_{3(S)}$</TEX>, <TEX>$LiCl_{(l)}$</TEX>, <TEX>$Li_2O$</TEX> at <TEX>$650^{\circ}C$</TEX> and <TEX>$C_{(S)}$</TEX>, <TEX>$LiCl_{(l)}$</TEX>, <TEX>$Li_2O_{(S)}$</TEX> at <TEX>$750^{\circ}C$</TEX>. <TEX>$Li_2CO_{(S)}$</TEX> was decomposed at <TEX>$750^{\circ}C$</TEX> into <TEX>$Li_2O_{(S)}$</TEX> and <TEX>$CO_{2(g)}$</TEX>.