Advanced techniques for real time simulation of reactor coolant system two-phase transients

Current nuclear power plant training simulators have limited capability for the simulation of two-phase flow in the reactor coolant system following significant losses of primary coolant system (RCS). Increased attention to operation sequences or accidents leading to two-phase conditions in the RCS indicated a need to enhance this capability in plant simulators. This paper represents the major features of Westinghouse simulator technology by describing the hardware and software used in current Westinghouse-designed simulators, and the software under development for the advanced simulator. The advanced simulator is an all digital solution method and permits Westinghouse simulators to compute the two-phase fluid conditions in a reactor coolant system following significant losses of primary coolant, and other similar related transients. Simulator model requirements address both single- and two-phase flow, forced and natural circulation, phase separation, reliability, and real-time capability. The Westinghouse advanced simulator reactor coolant system model meets these requirements through non-equilibrium stratified fluid nodes, drift flux flow links, and global compressibility