Effects of rare earth oxides and UO 2 + x on the structure and the mechanical properties of Zircaloy

Abstract

Tension test specimens of Zircaloy have been annealed with simulated fission products, as CeO 2, La 2O 3, Nd 2O 3, Y 2O 3 or mixtures of these rare earth oxides and UO 2 + x at 350°C up to 10 000 hours and at 500 or 700°C up to 2000 hours. The long term effects have been studied by tension tests, scanning electron microscopy, X-ray diffraction and metallography. Annealing of Zircaloy at 700°C with rare earth oxides generally leads to total embrittlement. There exists a gradation of efficacy which becomes obvious when the results of the annealing series at 500°C are compared. Rare earth oxides in mixtures with UO 2 + x cause improportional intense reductions of ductility. The structural characteristics of specimens lead to thermodynamic considerations of the probable reaction mechanism.