MODELING OF THE MECHANICAL-BEHAVIOR OF THE METAL-OXIDE SYSTEM DURING ZR ALLOY OXIDATION

During the oxidation of Zircaloy fuel cladding, large stresses develop in the oxide layer. This paper presents two approaches to evaluate th e stresses in the metal, modelled as a viscoplastic material, and the oxide, considered as elastic transverse isotropic. The first approach is a computation of the stresses in the whole cladding on a 1D radial geometry. It evidences large compressive hoop stresses in the oxide an d weak tensile stresses in the metal. The second approach is a 2D fini te elements computation accounting for the undulation of the metal-oxi de interface. This specific geometry is found to have an important inf luence on the local stress state. In particular, radial stresses are e videnced near the metal-oxide interface, whose sign and value depend o n the local curvature of the interface. (C) 1998 Elsevier Science B.V. All rights reserved.