The TREAT facility, located at the Idaho NationalLaboratory, is an air-cooled test facility designed tosimulate rapid reactor transient conditions up to 600 °C.Zirconium and its alloys are known to undergo atransition from parabolic to linear oxidation kinetics,termed “breakaway.” After breakaway, the oxide formedis porous and non-protective which significantly decreasesits mechanical stability as a cladding material. In thiswork, the oxidation behavior of Zircaloy-3, Zircaloy-4,and Zr-1Nb is evaluated in isothermal and rapid transientconditions (air at ≤ 820 °C). Separate effects studies weredone on plate samples in air (80% N2+O2) and oxygen(80% Ar+O2) to characterize the effect of nitrogen on theoxidation behavior during isothermal oxidation usingthermogravimetric analysis. It was observed that the threealloys exhibit decreased resistance to breakaway in air. Inaddition, the effects of chamfering and welding on theoxidation behavior were investigated during isothermaland rapid transient oxidation. All alloys were affected bywelding, however only the Fe/Sn containing alloys wereaffected by plastic deformation. Advancedcharacterization techniques (scanning Kelvin probe forcemicroscopy and Raman spectroscopy) were performed oncross sections of oxidized specimens to further investigatethe effects of oxide phase and composition on breakaway.
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