BWR Zircaloy cladding corrosion behavior - effect of microstructure

Corrosion behavior of three types of cladding tubes used in commercial boiling water reactors was evaluated in terms of its correlation to their original second phase particle (SPP) sizes. The mean particle sizes ranged from about 0.07 to 0.4 μm and the maximum fuel burnup was about 46 GW d/t. The results showed that nodular corrosion tended to disappear and the maximum oxide thickness decreased with decreasing particle size. The results also suggested that the SPP size of the current Zircaloy-2 cladding tube used in Japan was in the most preferable range. The effect of temperature on the dissolution of the particles was discussed, and it was pointed out that the variation of temperature experienced by cladding tubes in light water reactors had a significant effect on the dissolution phenomenon. (orig.)