THERMAL ANNEALING OF IRRADIATED PREHYDRIDED ZIRCALOY-4 MATERIALS

摘要

Hydrogen-assisted irradiation growth is animportant issue for reliability and performance of nuclearmaterials in nuclear fuel cladding and fuel assemblycomponents. The mechanisms of irradiation growth arenot entirely clear and the role of hydrogen and hydridesare less so. There is evidence that breakaway irradiationgrowth is strongly influenced by the formation anddynamics of dislocation loops that vary with alloycomposition, heat treatment and hydrogen content. Tostudy this phenomenon, thermal annealing of eightZircaloy-4 specimens irradiated in the Advanced TestReactor (ATR) at Idaho National Laboratory wasperformed using various techniques. Transmissionelectron microscopy (TEM) with a hot stage was used forthe quantification of and dislocation looppopulation densities and size distributions at a range oftemperatures from 25 to 800oC. Differential scanningcalorimetry (DSC) and dilatometry were performed bydynamically heating and cooling from 30 to 750°C atrates of 5, 10, and 20 K per minute (Kpm) to determinethe behavior of dislocation loop annealing. The resultsare discussed in the context of the larger AsTeR programthat will include higher exposure (～20 dpa) and differentalloys when they become available in 2021.