Modelagem da pressurização da contenção de um PWR com resfriamento passivo de material de mudança de fase

Abstract

Pressurization of the containment building of a pressurized water reactor (PWR) nuclear power plant can occur in a short time if a loss of coolant accident (LOCA) occurs due to a break in the primary circuit piping. Recently, phase change materials (PCM) have been considered as a method of passive cooling in the containment building by storing thermal energy in case of accidents. In this study, we propose a coupled model for the pressurization of the PWR containment during a hypothetical LOCA. The proposed model consists of a conservative single-cell thermodynamic model for the mass and energy balance in the containment, and an improved lumped parameter model for one-dimensional heat conduction with melting of a PCM plate, based on Hermite approximations for integrals. The nonlinear system of ordinary differential equations is solved numerically using the symbolic-numerical software Wolfram Mathematica 11.0. The containment model is verified by comparing the final containment pressure and temperature with data available in the literature, and the model for conduction in the PCM is validated by comparing the melting interface and the liquid phase average temperature of the PCM with an approximate analytical solution. Temperature and pressure variations in the containment were evaluated for different types and heat transfer areas of the PCM. The analysis results demonstrated that the PCM could successfully cool the containment and lower the maximum pressure significantly.