The Long-Term Environmental Degradation of Zirconium Alloys in Contact With Spent Nuclear Fuel: A Review

Zirconium (Zr) alloys were mostly developed for nuclear power applications. The most common commercial alloys are Zircaloy, which are used as cladding for fuel pellets in water-cooled reactors. These alloys have adequate corrosion resistance in service under irradiation in presence of high-purity water at approximately 300–350°C but in a few cases they may suffer environmental degradation. The most common types of degradation are hydriding, shadow corrosion and nodular corrosion. After the fuel rod bundles are removed from the reactors they are temporarily stored in water pools until their permanent disposition nuclear waste repositories. Simulated laboratory testing and modeling show that the long-term storage in the sealed containers would not cause further damage to the cladding material until the waste containers are breached by corrosion many thousands of years later. And even after water incursion, since the temperature will be low, it is predicted that the cladding material would survive for many thousands of years more, thus delaying the release of the radionuclides to the atmosphere.