ASEA-ATOM results on pci experiments on fuel rods; a review

Abstract

ASEA-ATOM results on PCI-behaviour of LWR fuel generated since 1970 are reviewed and discussed. It is shown that standard LWR fuel is sensitive to PCI failures and that minor design changes such as variation in cladding thickness, pellet density etc. have a negligible effect on this sensitivity. PCI failures have been observed without excessive release of fission products from the UO 2 pellets. Further results generated are that the PCI failure probability can be strongly influenced by certain operating restrictions. The ramp rate dependence clearly dominates over effects from minor design modifications. This fact is utilized in ASEA-ATOM constructed reactors, thus avoiding PCI failures at a very low penalty (0.4% loss in capacity factor). The current ASEA-ATOM development work in the PCI area is directed towards PCI immune designs. One promising remedy design is internally copper-plated cladding tubes. Lead test assemblies are in the 2nd cycle of irradiation in a power reactor.