Evaluation of applicability of WRB-2/COBRA-IV CHF analysis system

Evaluation of performance of WRB-2 CHF correlation has been performed with COBRA-IV subchannel code. To determine input model of COBRA-IV for CHF test section(TS), preliminary analyses had been performed. The preliminary analyses include the sensitivity study with respect to size(or range) of TS model(1/8 TS, 1/4 TS, full TS), number of axial node(or axial length step, 30, 50, 70, 80, 100) and constitutive relations(such as void model, 2 phase flow model, etc.) with arbitrarily selected test data. The predicted flow parameters are similar for all models, but there is somewhat difference in the number of external iteration model to model, ie., size of model, number of axial node, and constitutive relations. Based on the results, the selected optimized model is that full TS model with 100 axial node and constitutive relations of no subcooled void option. Calculations on data base(DB) of WRB-2 CHF correlation and data of Modified V5H/IFM TS have been done with optimized TS model. The results show that parametric trends and performance (correlation limits) of both WRB-2/COBRA-IV and WRB-2/THINC-IV are similar and there is no inherent differences