Pellet-clad interaction (PCI) failures of zirconium alloy fuel cladding - a review

This review summarizes the history of the appearance and cure of pellet-cladding interaction (PCI) failures during the operation of Zircaloy clad UO2 fuel in a number of reactors. The work carried out to permit unrestricted operation of reactors without causing PCI failures has led to the universal adoption of the CANLUB-graphite coated cladding in CANDU reactors, and to the wide adoption of Zr-liner cladding in BWRs. There has only been a low incidence of PCI failures in PWR cladding, and the problem has not loomed large enough to require the adoption of either of the above protective methods in these reactors, although experimental liner cladding has been tested. The extensive work on the mechanism of PCI failures (leading to the conclusion that an SCC process induced by fission product iodine is the most probable cause) is summarised. (orig.)