Analysis of pressurizer level control system using MAAP4 code

The code initialization effort has been troubling code users for decades for system transient and severe accident analyses using codes such as RETRAN, MAAP4, MAAP5 and MELCOR. The purpose of this work is to demonstrate an approach that could be considered a generic method to address the code initialization problem. This was demonstrated by developing a pressurizer level control model and temperature dependent level control logic in MAAP4 without re-compiling with the source code. The method would enhance the simulation capability and accuracy of a severe accident analysis by transient and severe accident analyses codes. The demonstration case used MAAP4 to show that the adopted proportional–integral controller with the temperature dependent level control logic would reduce its code steady state errors to zero. The subsequent transient response would become more realistic. The proposed method provides a convenient and exemplified approach for code initialization which is applicable to the next generation of codes that couple with the balance of plant models. These codes include the MAAP5 code and others future codes that could simulate the whole plant by a single and elaborate plant model with exhausting component and phenomenological models.