Development of Fuel Rod Thermal-Hydraulic Model for the Thermal-Hydraulic Feedback in Condor Code

Abstract

The fuel at high burnup has a complex behavior due to the resonance absorptions of the U238 and the Pu239 production especially at the rim zone of the fuel pin. For that reason, the radial dependence of the generated power and the corresponding burnup needs to be carefully studied. The resonance effects has a high dependence with temperature that depends on the generated power, hence, it needs to be properly evaluated. At the rim zone, the resonance effects dependence with fuel temperature becomes more significant than the inner zones. This fact requires a thermal-hydraulic model to take this effect into consideration as a function of burnup. Cladding temperature will be also evaluated to take care of the resonance cross section of the cladding material. In this work, a one dimensional steady state heat equation is used to formulate a set of finite difference equations to evaluate temperature distribution in fuel pin for a non-uniform power generation. Material properties such as thermal conductivity are considered to be a function of temperature and burnup. The model would solve pin by pin temperature distribution in a fuel assembly array for a non-uniform radial and potential azimuthal discretization. Verification against analytical solution and simple test cases are demonstrated. The application of this work would be for BWR, PWR, CANDU, ATUCHA and TRIGA fuel pin. Upon a successful implementation of this model, it would be in future integrated with CONDOR code.