A Fully Implicit Hybrid Solution Method for a Two-Phase Thermal-Hydraulic Model

This paper will present a hybrid solution algorithm for the two-phase flow equations coupled to wall heat conduction. The partial differential equations in the physical model are the same as in RELAP5. The hybrid solution algorithm couples two solution methods, the solution method currently employed by RELAP5 and an implicitly balanced solution method. The resulting hybrid solution method is both fast and accurate. Results will be presented that show when accuracy and CPU time are considered simultaneously that there are ranges when the hybrid solution algorithm is preferred over the RELAP5 solution method.