Void Fraction and Critical Power Assessment of CORETRAN-01/VIPRE-02

Abstract

CORETRAN-01 is the Electric Power Research Institute core analysis computer program that couples the neutronic code ARROTTA to the thermal-hydraulic code VIPRE-02 to achieve an integrated three-dimensional representation of the core for both steady-state and transient applications. The thermal-hydraulic module VIPRE-02, the two-fluid version of the one-fluid code VIPRE-01, has been the object of relatively few assessment studies, and the work presented seeks to reduce this lacuna. The priority has been given to the assessment of the void fraction prediction due to the importance of the void feedback on the core power generation. The assessment data are experimental void fractions obtained from X- and gamma-ray attenuation techniques applied at assembly-averaged as well as subchannel level for both steady-state and transient conditions. These experiments are part of the NUPEC (Japan) program where full-scale boiling water reactor (BWR) assemblies of different types, including assemblies with part-length rods, and pressurized water reactor subassemblies were tested at nominal reactor operating conditions, as well as for a range of flow rates and pressures. Generally, the code performance ranged from adequate to good, except for configurations exhibiting a strong gradient in power-to-flow ratio. Critical power predictions have also been assessed and code limitations identified, based on measurements on full-scale BWR 8 × 8 and high-burnup assemblies operated over a range of thermal-hydraulic conditions.