Study of the response of Zircaloy-4 cladding to thermal shock during water quenching after double sided steam oxidation at elevated temperatures

摘要

This study investigates the failure of embrittled Zircaloy-4 cladding in a simulated loss of coolant accident condition and correlates it with the evolved stratified microstructure. Isothermal steam oxidation of Zircaloy-4 cladding at high temperatures (900-1200 degrees C) with soaking periods in the range 60-900 s followed by water quenching was carried out. The combined oxide + oxygen stabilized alpha-Zr layer thickness and the fraction of the load bearing phase (recrystallised alpha-Zr grains + prior beta-Zr or only prior beta-Zr) of clad tube specimens were correlated with the %ECR calculated using Baker-Just equation. Average oxygen concentration of the load bearing phase corresponding to different oxidation conditions was calculated from the average microhardness using an empirical correlation. The results of these experiments are presented in this paper. Thermal shock sustainability of the clad was correlated with the % ECR, combined oxide+alpha-Zr(O) layer thickness, fraction of the load bearing phase and its average oxygen concentration. (C) 2016 Elsevier B.V. All rights reserved.