Comparison of a DNB Calculation in a Single Channel Model Using System Codes TRACE5 and RELAP5

Abstract

System codes TRACE5 and RELAP5 are used for predicting and analyzing the thermohydraulic behaviour of nuclear reactors. Although being used for the same purposes, they differ in their calculation methodologies, numerical methods, algebraic correlations, hydraulic components and user options. In some applications, these codes calculate the Departure from Nucleate Boiling (DNB), which is one of the most important phenomena which may occur in a nuclear reactor and it is highly relevant for nuclear safety. In this work, both codes are used to calculate the DNB Ratio and the pressure and temperature profiles of the same PHWR single channel model. In both cases, the same geometry and boundary conditions were used so the differences in the results are attributed to the numerical methodologies, user functions and, most important, the numerical methods of each code. This work aims to compare the consistency of the results obtained, analyze the capability of each code to reproduce the thermohydraulic methodology and analyze the impact of user options in the results.