Under different water chemistry conditions, which corrosion rate is the highest

Thread Content

Taking into account the background on the corrosion of highly irradiated nuclear fuel discussed earlier, under the typical water chemistry conditions in nuclear reactors, the corrosion rate of the cladding of highly irradiated nuclear fuel is highest in strongly alkaline water chemistry conditions with high Li⁺ concentrations (excess LiOH) and low boron content. When the Li⁺ concentration in the primary coolant exceeds 350 mg/L, the corrosion rate of zirconium alloy cladding increases rapidly, the onset time of corrosion is significantly advanced, and the corrosion rate after that point rises markedly. When combined with conditions featuring low boron (B³⁺) content, the inhibitory effect of boron on LiOH corrosion is completely lost, which further accelerates the corrosion process; as a result, the corrosion rate becomes much higher than that under normal hydrogenation-reduction conditions or oxygen-passivation conditions. Furthermore, the oxygen-enriched conditions resulting from the generation of large amounts of free oxygen under irradiation also significantly increase the stress corrosion susceptibility of the material, with a corrosion rate that is markedly higher than that in the hydrogenation conditions with strict deoxygenation.