Assessment of RELAP5/TRACE against VEFITA Thermal-Hydraulic Level Swell Tests

摘要

Filtered Containment Venting System (FCVS) is a safety system equipped in nuclear power plants to release steam and non-condensable gases from the containment during a severe accident scenario, in order to avoid over-pressurizing the containment, while retaining most radioactive fission products inside the plant. This paper presents the RELAP5/Mod3.3-p3 and TRACE/V5.0-p2 simulations of the experiments performed in the VEFITA (Venting Filter Assessment) test facility at Paul Scherrer Institut (PSI). This experimental program is designed to investigate thermal-hydraulic phenomena in the FCVS such as internal recirculation, water inventory, and level swell. The water level swell during the gas injection is particularly interesting since it would affect the design and operation of the venting filtration system. Test section is a vessel with a 0.58 m diameter and 12 m total height. The lower wet scrubber section is filled with water to a certain level above the gas injection nozzle. Non-condensable gas at various mass flow rates are fed through the injection nozzle into the test section. RELAP5 and TRACE code models are developed for the test facility and several series of experiments are simulated. The system code simulation results, as well as a previous physical model based on homogeneous-heterogeneous regimes transition in bubble columns, are compared with the experimental data.