ASSESSMENT OF THE RELAP5-3D SUBCOOLED BOILING MODELS FOR LOW-PRESSURE CONDITIONS

Two different low-pressure subcooled flow boiling experiments have been simulated using the thermal-hydraulic computer program RELAP5-3D. After carrying out the simulation of the cases with the original subcooled boiling model adapted in RELAP5-3D, the Savannah River subcooled boiling model (SRL) option in the code was selected and the simulations were repeated. The results of these simulations are compared against the experimental data. It is found that the axial void fraction predictions obtained using the SRL model compare better to the experimental data than the original model in RELAP5-3D. The annulus case using the SRL model gave reasonable results, however, refinements are required to reasonably predict the tube case experimental results. RELAP5-3D1 is the latest version of the RELAP series of computer programs that are used for the thermal-hydraulic safety analysis of water-moderated nuclear reactors. In this version of the code, a three-dimensional simulation of thermal-hydraulic and neutronic phenomena occuring in a reactor can be simulated