Abstract
In this research, using Fortran programming language, a computational code is presented to investigate the effect of xenon concentration on the thermal conductivity of the gap between the fuel and clad. For this purpose, first the heat transfer model between the fuel and the coolant is simulated in which the coolant temperature is calculated using the enthalpy rise method and then the outer and inner surface temperature of clad, the gap temperature and the radial temperature distribution of fuel are calculated. After modeling the heat transfer, the thermal conductivity is investigated by adding xenon to the helium gas in the gap. The results of this study are highly consistent with FRAPCON 3.1 code.