The transient heat transfer and Larson-Miller creep failure analysis of severe accident relief pipeline

Abstract

During postulated severe reactor accidents, severe accident relief valves are activated, and products, including water vapor and hydrogen gas, are released to prevent high-pressure core melting. The severe accident relief pipeline is specified with functional requirements based on typical severe accident scenarios, creating the risk of high-temperature creep failure. A numerical simulation of the transient heat transfer characteristics using RELAP/SCDAPSIM and CFX was performed, and the Larson-Miller model was applied. The results indicate that the relief pipeline temperature is much lower than the core melting point 1200°C, and to avoid high-temperature creep failure, the design pressure and temperature of the entering fluid products should not be high values simultaneously. Moreover, the Cr content of the pipe’s austenitic stainless steel is critical, and content with no less than 12% Cr is advised. The investigation thus elucidates the inherent characteristics of the severe accident relief pipeline during postulated severe reactor accidents.