When subjected to a temperature ramp, irradiated nuclear fuel undergoes fragmentation, which increases with increasing temperature ramp. This intuitive result cannot, however, be described by the fuel behavior codes existing at the CEA, because the latter calculate the stress state of the fuel pellet statically, that is to say with equations, which do not depend on the time. The aim of the thesis is to go beyond this limitation by proposing a modeling, in elastic mechanics, which can account for the effect of the speed of temperature rise. To do this, we will adopt a thermodynamic approach, using the Onsager formalism. The thesis work will consist of writing a theoretical model of mechanical thermal coupling based on time-dependent equations, then applying it to a simplified simulation of the fuel pellet. The candidate must have knowledge of mechanics and thermodynamics, ideally in the thermodynamics of irreversible processes. He will benefit from a high-level scientific environment with skills on thermomechanical codes and the behavior of the fuel pellet during a thermal transient at the Fuel Research Department (IRESNE Institute, CEA Cadarache) and skills on the Onsager formalism with his thesis director.