TRANOX: Model for non-isothermal steam oxidation of zircaloy cladding

[摘要] TRANOX-1.0 (TRANsient OXidation), a mechanistic model that calculates oxygen distribution for isother-mal and non-isothermal transients (10 0 0-1250 degrees C) has been developed. TRANOX solves radial transient diffusion equation using Finite Difference Method (FDM) with spatial phase changes for each time step. Diffusion coefficients of each resulting phase were obtained by searching a combination that best guar-antees Equivalent Cladding Reacted (ECR) and alpha-Zr(O) thickness simultaneously. The model has been extensively validated by overarching experimental campaigns including isothermal and non-isothermal high temperature steam oxidation, and post-metallurgical characterization. Accounting for alpha+ beta equilib-rium phase, TRANOX gives accurate predictions for ECR, spatially averaged radial oxygen distribution, and thicknesses of each phase. Mechanistically solving the diffusion equation, TRANOX exhibits unbiased predictability for isothermal and non-isothermal transients. TRANOX was used to understand the oxygen distribution of pre-hydrided high burnup fuel cladding. The diffusion resistance behavior of alpha-Zr(O) and alpha+beta with respect to hydrogen content counteract, neutralizing the overall hydrogen effect on oxygen distribution. The limited hydrogen effect on diffusion resistance during the early stage of steam oxidation further reduces the hydrogen-sensitivity of oxygen profiles. This finding provides a cogent explanation for the effect of hydrogen on oxygen distribution and oxidation kinetics observed by a number of past studies. (C) 2021 The Author(s). Published by Elsevier B.V.

[发布日期] 2021-12-01

[关键词] Zircaloy;Steam oxidation;Oxygen diffusion;Highburnup;Non-isothermal;Equivalent cladding reacted