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VIPRE (Versatile Internals and Component Program for Reactors)

PWR Fuel Bundle
VIPRE is used for nuclear reactor thermal-hydraulic analysis applications. It was designed to help evaluate nuclear reactor core safety limits including minimum departure from nucleate boiling ratio (MDNBR), critical power ratio (CPR), fuel and clad temperatures, and coolant state in normal operation and assumed accident conditions. The VIPRE code was developed for the United States Electric Power Industry under the sponsorship of EPRI.

Zachry operates the VIPRE User Group (VUG) for member organizations and EPRI. VUG members fund ongoing code maintenance and development activities to ensure the long-term code viability.

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.

Subchannel Noding
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.


VIPRE use licenses can be purchased directly from Zachry. For more information on the VIPRE programs and how they can be obtained, please contact Mike Howard. The entire Analysis Division contact list is here, including phone numbers.