Numerical Investigation of Chemical and Volume Control System Behavior in Normal Operation and Incident Situation

The Chemical and Volume Control System (CVCS) in nuclear pressurized power plant are in charge of coolant pump seal injection, primary loop volume control and plant safety or security. The characteristics of the system in normal operation and incident situation will leave a remarkable impact on the power plant safe operation and security. The numerical verification of CVCS behavior in normal operation shows that the model established in this paper can predict the thermal hydraulic characteristics of the system accurately. CVCS and SIS are numerical investigated with the Computational Software, Flowmaster V7.5, and the models are validated with design data. If SGTR takes place, the flow limits of letdown, charging and coolant pump seal injection will significantly influence the reactor safety. In this accident situation, the safety injection mode of the Reactor Safety Injection System will be switched into the charging mode of the Chemical and Volume Control System, the charging and seal injection maximum flowrates variations with Reactor Coolant System pressure are predicted, and different charging modes are simulated and compared in detail. The comparison results show that one low head safety injection pump of SIS will increase the charging and coolant pump seal injection flow significantly, but two low head safety injection pumps of SIS will not increase these two flows more greatly than the one low head safety injection pump mode.