Multi-Physics Simulation of Inadvertent Opening of a Steam Generator Atmospheric Dump Valve for APR1400 Power Plant

Deterministic safety analysis is essential for evaluating the safety of nuclear power plants to demonstrate the reliability of their designs. Multi-Physics models consider the three-dimensional nature of the reactor core, offering a detailed representation of its behavior and incorporating complex interactions through real-time updates of key feedback mechanisms due to the fuel temperature coefficient (FTC), moderator temperature coefficient (MTC) and moderator density coefficient (MDC). This paper provides a comprehensive analysis of the inadvertent opening of a steam generator atmospheric dump valve (IOSGADV) in the APR1400 reactor. Initially, a thermal hydraulic model was developed using the stand alone RELAP5/SCDAPSIM/MOD3.4 code with point kinetics. The analysis was then refined by integrating the RELAP5/SCDAPSIM/MOD3.4 code with 3DKIN, resulting in a high-fidelity representation of core dynamics during the incident. The results revealed radial power distribution asymmetry between the affected and unaffected sides, with a maximum deviation of 4.62%. The asymmetry emerged immediately after the opening of the ADV. In the final stage, uncertainty quantification was performed to systematically evaluate the impact of variations in system parameters, ensuring reliable predictions of the reactor's response.