RELAP5/MOD3 Assessment for Calculation of Safety and Relief Valve Discharge Piping Hydrodynamic Loads. International Agreement Report

摘要

The report presents an assessment study for the use of the code RELAP5/MOD3/5M5 in the calculation of transient hydrodynamic loads on safety and relief discharge pipes. Its predecessor, RELAP5/MOD1, was found adequate for this kind of calculation by Electric Power Research Institute (EPRI). The hydrodynamic loads are very important for the discharge piping design because of the fast opening of the valves and the presence of liquid in the upstream loop seals. The code results are compared to experimental load measurements performed at the Combustion Engineering Laboratory in Windsor (U.S.A.). This particular kind of transients challenges the applicability of the following code models: Two-phase choked discharge; Interphase drag in conditions with large density gradients; Heat transfer to metallic structures in fast changing conditions; and Two-phase flow at abrupt expansions. The code applicability to this kind of transients is investigated. Some sensitivity analyses to different code and method options are performed. Finally, the suitability of the code and some modeling guidelines are discussed.