VIPRE-02 Subchannel Validation Against NUPEC BWR Void Fraction Data

A void fraction validation study is undertaken for the VIPRE-02 code due to the importance of void feedback when the code is coupled to the neutronic code ARROTTA in the new code package CORETRAN. This first stage is based on the steady-state boiling water reactor void fraction data obtained from the Nuclear Power Energy Corporation (Japan) experimental program.

The code bundle-averaged void prediction is found to be adequate for the different assembly types studied, but at the subassembly level, the code underpredicts substantially the void for regions with low power-to-flow ratios. This is believed to be due to the lack of a lateral void drift model. The importance of these regional void underpredictions is negligible for the standard 8 x 8 assembly, but their impact on neutronics still needs assessing for the newer assembly types.