Analysis of Steam Generator Blowdown System Flash Tank Liquid Level Instability and Study on Blowdown System Modification

Abstract

Due to the complexity of its control system, the steam generator blowdown system often experiences issues with unstable of control parameters. The present study investigates the impact of different parameters on the liquid level of the flash tank by RELAP5. When the two blowdown flash tanks operate in parallel, only one of the flash tanks' liquid level is used as the control signal for the liquid level control system. When the operating parameters of blowdown system fluctuate, the liquid level of flash tanks may rise above or fall below the permitted water liquid level. Based on actual system operational data and computational results, this article proposes a modification plan to combine two blowdown flash tanks into one and the liquid level of the combined flash tank provides the control signal for the liquid level control system. The modification plan addresses the issue of unstable liquid level problem.

Keywords: Steam generator blowdown system, thermal hydraulic characteristics, liquid level instability, blowdown flash tank, RELAP5