A Multiple-Node Real-Time Pressurizer Model

Abstract

The pressurizer module of the Point Lepreau real-time full scope simulator is modified by using a multiple-node model. In the new model, the pressurizer is divided into a number of control volumes. The vapor node consists of the control volumes where the vapor phase is continuous and liquid phase is dispersed, while each liquid node is a control volume where the liquid phase is continuous and vapor phase is dispersed. In the vapor node, the fluid is homogeneous and equilibrium, however, in any liquid node, the fluid is assumed to be in thermal equilibrium only. Liquid and vapor bubbles in the liquid node may have different velocity, and non-equilibrium exists among the liquid nodes and between the top liquid node and the vapor node. The mass, momentum and energy equations for the vapor-liquid mixture are applied to the vapor node and each of the liquid nodes. To take into account the velocity difference between the vapor bubbles and the liquid in the liquid nodes, the slip ratio is modeled. The new pressurizer module is integrated in the simulator. Some of the predictions from a number of transients are presented. The simulations are compared against available plant data and that of the previous two-node model. The comparisons show good agreement between the simulation by using the multiple-node model and the plant data. They also show significant improvements of the multiple-node model upon the two-node model.