Solving the six-field governing equations for a system code

The coolant systems of nuclear power plants are modeled with system codes. The results of the system code calculations are necessary not only to develop new power plants, but also in the licensing and analysis of existing power plants. Therefore, it is essential that system codes produce realistic results. Simple models using a single fluid field have been used in initial versions of many system codes. In recent years, more fluid fields have been used for best-estimate code results to improve two-phase flow predictions of the system codes. This paper introduces the numerical equations and solution methods for a next-generation system code that uses 6 fluid fields. It demonstrates the discretization of the mass, momentum, and energy governing equations and the application of matrix solutions that are necessary to implement the 6-field model in a software code.