Effect of iron on hydrogen absorption properties of zirconium alloys

Higher hydrogen absorption at high burn-up strongly affects the embrittlement of BWR fuel cladding. HiFi (High corrosion resistance and high Fe (iron) zirconium alloy) alloy, higher iron content compared with Zry-2, showed the lower hydrogen pickup according to the previous Post irradiation examination (PIE) results. In order to clarify the mechanism, contact potential difference (CPD) for the oxide film in Zry-2 and HiFi alloy was measured in high temperature atmosphere. The results showed that CPD value increased during initial oxidation and the electrical potential of the oxide surface tended to increase with higher iron concentration due to higher anion vacancy concentration. This larger electrical potential of the oxide surface might reduce the electrical potential gradient over the oxide film, thus the amount of protons transport through the oxide film into the metal decrease. Therefore, hydrogen absorption of HiFi alloy will be suppressed.