Thermomechanics challenges in new nuclear reactor technologies

The extreme operation conditions, such as higher temperature and pressure, higher neutronic flow, higher levels of burn-up, swelling, and irradiation in the cladding in the new technologies of nuclear reactors, generate more advanced thermomechanics analysis and new methodologies to study the heterogenic of the core and the porous media in fuel pellets. Further, the long operation and extended operation licenses of Nuclear Power Plants (NPP) generate a necessity to consider thermomechanics phenomena in the analysis and design of nuclear reactors. This paper reviews some of the fuels and structural materials used in advanced nuclear reactors, also some techniques to ensure fuel safety for accident conditions, such as a coated fuel cladding Accident Tolerant Fuel (Atf). These methodologies include the Volume Average Method (VAM), which considers the porosity and contact surface between different phases in the fuel rod in the core of the nuclear reactor. Also, an analytical module to analyze the fuel pellet with and without gap has been developed to evaluate the mechanical behaviors of the Atf cladding, and the main results are presented, using values of Young Modulus and Poisson ratio in function of temperature. (author)