Abstract
Efforts to improve the economics and safety of commercial nuclear reactors have led to the creation of many new cladding forms, including the M5® alloy invented by Framatome. M5 is a niobium-based zirconium alloy designed to have lower rates of corrosion under normal operating conditions, enabling the fuel to be used to higher burnups. Additionally, the application of a chromium coating to the material has been shown to reduce oxidation in high-temperature steam – theoretically improving performance under accident scenarios. However, additional data on the mechanical properties of M5 and the adhesion of such coatings under neutron irradiation is critical in order to support its use in industry. To this end, two capsule designs have been developed to irradiate coated and uncoated M5 specimens of various geometries in the High Flux Isotope Reactor (HFIR). These geometries include standard pressurized water reactor (PWR) cladding and specimens for both axial tension and plane strain testing. The capsules achieve a time-averaged specimen temperature of 350°C, where the specimen temperature notably increases ~10°C per cycle due to the axial growth of zirconium cladding in neutron fields. This analysis shows that the capsules provide an effective and flexible vehicle for gathering needed cladding data.
