Phase-field simulation of the stability of reaction phases at UO2/β-Zr interface

The stability of reaction phases at the UO2/Zr (beta-Zr) interface in the O-U-Zr system was simulated by a newly constructed multi-phase-field model. At the UO2/Zr (beta-Zr) interface, we assumed a liquid phase and an alpha-Zr (Hcp) phase. The phase growths and atomic diffusions of the constituent elements were simultaneously calculated in one-dimensional simulations. During isothermal aging at 1500 degrees C and 1600 degrees C, the thicknesses of both reaction phases increased. As O diffused much faster than U, O concentration increased immediately in the alpha-Zr (Hcp) phase. On account of its high 0 concentration, the alpha-Zr (Hcp) phase rapidly expanded toward the beta-Zr (Bcc) side, blocking the diffusion of U from the liquid phase to the beta-Zr (Bcc) phase. The stability of the liquid phase was influenced by the U concentration in the liquid phase and was correlated to the growth of the alpha-Zr (Hcp) phase that was accelerated by the diffusion of O from UO2 to the alpha-Zr (Hcp) phase. (C) 2015 Elsevier B.V. All rights reserved.