Containment pressure analysis methodology during a LBLOCA with COCOSYS code

Abstract

During a nuclear power plant basic design accident, the containment integrity is a determining factor for the accident severity. The pressure and temperature conditions inside the containment in case of a Large Break Loss of Coolant Accident (LBLOCA) must be verified. This paper presents a containment pressure and temperature analysis methodology of a Brazilian PWR, Angra 2, using a code that simulates guillotine rupture - RELAP5 - and the COCOSYS code, which analyzes the containment pressure from the accident conditions. The Angra 2 containment behavior results during the design basis accidents studied - primary cooling system cold and hot legs guillotine ruptures - were satisfactory when compared to those presented in the Final Safety Analysis Report (FSAR / A2) and the pressure distributions were below the containment design pressure value (6.3bar).