Zefeng Yu¹, Kory D Linton², Lingfeng He³, Mukesh N Bachhav³, Xiang Liu³, Adrien Couet¹; ¹University of Wisconsin, ²Oak Ridge National Laboratory, ³Idaho National Laboratory

ZrNb alloys have significant advantages over Zircaloys due to the reduced irradiation induced growth and corrosion kinetics. Such enhancements have been hypothesized to be related to the precipitation of irradiation induced platelets (IIP) / nanoclusters in the Zr matrix. However, there are only a few reports giving detailed characterizations on IIP in the Zr metal of neutron irradiated industrial samples. The stability (dissolution, amorphization, oxidation) of IIP/nanoclusters in the oxide has not been reported yet. To understand the neutron irradiation induced microstructure and microchemistry, neutron irradiated M5® and X2® have been studied using (S)TEM/EDS to investigate the size, density, and crystallography of IIP in both metal and ZrO2. APT analysis on the Nb concentration in the Zr solid solution has been performed on X2®, in an effort to support the hypothesis that irradiation induced Nb reduction in solid solution is responsible for the lowered in-reactor corrosion kinetics of ZrNb alloys.