VIPRE-02 is a thermal-hydraulic analysis code designed to model steady-state conditions and operational transients in LWR cores and vessels. It uses a two-fluid representation of two-phase flow, solving conservation equations for mass, momentum and energy for each phase. This six-equation model is solved implicitly, using a modified Gauss-Seidel iteration procedure, and has no time-step size limitation for stability. Models for phase interaction based on flow regime mapping are provided, using semi-empirical interfacial correlations for heat and mass transfer, and vapor generation.

For core analysis, VIPRE-02 uses a subchannel formulation of the conservation equations; for PWR vessel models, it contains options for a fully three-dimensional representation of the lower plenum. For core analysis, boundary conditions can be specified using the inlet flow or the overall core pressure drop. For vessel models, the hot and cold leg boundaries can be represented using mass sources or pressure sinks in appropriate modes, with local flow blockages to model vessel internal structures and the lower plenum and upper head domes. The input specification is designed to be as flexible as possible, and still remain user friendly.