VIPRE-01 is a subchannel analysis tool designed for general-purpose thermal-hydraulic analysis under normal operating conditions, operational transients, and events of moderate severity. VIPRE was developed on the strengths of the various COBRA codes and has been tailored to the analytic needs of nuclear utilities. It has improved flexibility of use, upgraded capabilities, and improved numerical solution schemes. Some of the more important improvements are an expanded choice of correlations for critical heat flux, critical power ratio, two-phase flow and heat transfer for reload and safety analysis, one-pass hot-channel analysis capability, automatic iteration for set point analysis, subcooled voiding capability, and the ability to compute bypass channel flow for boiling water reactor (BWR) applications.

VIPRE-01 predicts the three-dimensional velocity, pressure, thermal energy fields, and fuel rod temperatures for single- and two-phase flow in pressurized water reactor (PWR) and boiling water reactor (BWR) cores. It solves the finite-difference equations for mass, energy, and momentum conservation for an interconnected array of channels, assuming incompressible thermally expandable homogeneous flow. The equations are solved with no time-step or channel size restrictions for stability. Although the formulation is homogeneous, nonmechanistic models are included for subcooled boiling and vapor/liquid slip in two-phase flow. VIPRE is a safety related code and complies with the requirements of 10CFR50 Appendix B. It has been approved by the United States Nuclear Regulatory Commission for use in performing licensing calculations and is used by a number of domestic and foreign utilities and fuel vendors.