[en] Zircaloy cladding has been modeled as a series of infinitely long, concentric, hollow thin cylinders, each having orthotropic elastic and heat-conduction properties, as functions of temperature and oxygen content. The same finite-element model is used to perform both heat-transfer and stress-analysis calculations for the thermal-shock loading. At every time step, a transient heat-transfer analysis is followed by stress analysis and crack-growth analysis. A computer program is written to perform all calculations. Important parameters that control fracture of the oxidized tube during a thermal shock are discussed, and recommendations are made for future improvements of the proposed model