Investigation of thermal margin in an advanced pwr core loaded with hexagonal fuel assembly

An evaluation study has been performed on currently available CHF prediction models, including empirical correlations and phenomenological models, and experimental data base to determine their applicability to the analysis of thermal-hydraulic performance for triangular lattice assembly, It turns out, as the result of study, that the KfK-3 CHF correlation with the limit CHFR of 1,24 is the best prediction model. The thermal margin of hexagonal fuel assembly, which have been optimized in the aspect of maximizing the thermal margin, in 600MWe class PWR core have been evaluated and compared with those of square lattice fuel assemblies such as V ANTAGE-SH and KOFA, COBRA-VI with KIlO correlation and TORC with KRB-l correlation have been used for VANTAGE-5H and KOFA respectively. The analysis result shows that hexagonal fuel assembly is generally superior to square fuel assemblies with normal grids(KOFA), and comparable to those with turbulence promoters(V ANT AGE- 5H), in terms of steady-state overpower margin