Alloy M5 in action

摘要

Increases in fuel assembly burnup are limited by the irradiation behaviour of its materials. Corrosion, hydriding, growth and creep performance of current zirconium alloys does not permit the more aggressive operating and environmental conditions required to achieve higher duty and longer cycles. Alloy M5, developed by Framatome ANP, for fuel rod cladding, guide tubes and spacer grids, exhibits superior performance in high burnup, high duty PWR applications and in a wide variety of PWRs worldwide. M5 is a fully recrys-tallised, ternary Zr-Nb-O alloy with the composition shown in Table 1. Four advanced lead assemblies with M5 fuel rod cladding and guide tubes recently completed three cycles in Dominion Generation's North Anna 1 reactor. A post irradiation inspection (PIE) campaign, funded by EPRI as part of the Robust Fuel Programme and performed by Framatome ANP during and after the cycle 15 refuelling outage, served two purposes. The first was to assess the performance of the advanced lead assemblies at normal discharge burnups for three representative cycles of irradiation. The second was to verify that the assemblies had sufficient margin so that one could be safely irradiated for a fourth cycle to a peak rod burnup greater than 70MWd/kgU.