Volume 2, Issue 5 (May 2005)
In-Core Tests of Effects of BWR Water Chemistry Impurities on Zircaloy Corrosion
There have been several cases of fuel failures resulting from localized corrosion acceleration of the Zircaloy-2 cladding in BWRs over the last 25 years [1–3]. Some of the failures resulted from localized crud deposition, but others appear to be related to accelerated corrosion of the cladding, possibly due to certain chemical attacks of the cladding. The corrosion variability of Zircaloy-2 in BWRs has been attributed to a synergistic effect of Zircaloy-2 material variability, water chemistry impurities, and in-core service duty. Through extensive research efforts, the susceptibility of Zircaloy-2 cladding to nodular corrosion has been mitigated through improvements in the thermo-mechanical processing and surface finish since the mid-1980s. However, isolated cases of enhanced nodular corrosion have been reported recently in US BWRs . Since such corrosion variability of Zircaloy-2 is undesirable, particularly for high burnup fuel components, candidate new Zr-alloys that are expected to have better nodular corrosion resistance than Zircaloy-2 have been developed [4–6].