Thermal Hydraulic Analysis of the AP1000 Passive Containment Cooling System following LBLOCA using ANSYS FLUENT

Abstract

The AP1000 power plant is a generation III+ design that uses a simplified, innovative, and effective approach to enhance its safety. Among these systems is the Passive Containment Cooling System (PCCS) in which natural recirculation and steam condensation, water film evaporation, conduction, and radiation are the key heat transfer mechanisms. These phenomena are capable of removing decay heat from the containment during the postulated design basis accidents (DBAs) such as large break loss of coolant accident (LBLOCA) and main steam line break (MSLB). As a matter of fact, during LBLOCA blowdown phase and MSLB, hot steam jet is discharged from the break and flows upward due to buoyancy-induced natural circulation, then condensates on the inner wall of the steel containment vessel, which in turn acts as a heat sink to prevent the containment from exceeding design limits for pressure and temperature. Therefore, it is crucial to investigate the containment response following abnormal condition to ensure its safety and integrity. In this paper, a CFD-based model was developed using ANSYS FLUENT to study the containment response following the vapor generated by the jet effect. Moreover, the model simulates the steam jet under LOCA conditions, and corresponding thermal-hydraulic phenomena such as natural circulation and wall film condensation during the blowdown phase. The results were compared with the available data reported in the AP1000 WGOTHIC containment evaluation code.