MECHANICAL-BEHAVIOR MODELING OF FRACTURED NUCLEAR-FUEL PELLETS

The mechanical behaviour of fractured nuclear fuel pellets is far from simple. In order to take correctly into account this behaviour and model it in the frame of a computer code, a lot of phenomena must be examined. Most of them can hardly be assessed physically and so only empirical models are available. This paper deals with some mechanical and physical phenomena which participate in the total radial deformation of a fuel rod during its in-reactor lifetime and which are mainly relevant to pellet fracturing and pellet-cladding mechanical interaction (PCMI) in normal (steady state) and off-normal (transient) operating situations. Based on qualitative considerations and comparison with experimental results, empirical models for pellet fracturing and PCMI have been established, introduced into the TRANSURANUS code and calibrated against various experimental results, so that the evolution of fuel radial deformation can be correctly simulated.