AN IMPROVED FORMULATION OF THE OXYGEN-DIFFUSION PROBLEM AND ITS APPLICATION TO ZIRCALOY OXIDATION BY STEAM

Numerical solutions of the oxygen-diffusion problem arising in the oxi dation of metals at high temperatures ale complicated by the change in density as the oxide is formed and the occurrence of moving boundarie s separating the different phases. The former complication is resolved by a transformation of the dependent variable and the coordinate, whi ch reduces the problem to a form identical to one without density chan ge. The latter complication is dealt with by demonstrating an analogy with the Stefan problem in heat transfer with phase change in the enth alpy formation, for which abundant numerical works exist. A finite-dif ference code is written to solve the resulting equations. It is succes sfully applied to simulate an oxidation experiment of Zircaloy by stea m at 1600 degrees C.