INVESTIGATION OF THERMAL MARGIN IN AN ADVANCED PWR CORE LOADED WITH HEXAGONAL FUEL ASSEMBLY

An evaluation study has been performed on currently available CHF pred iction models, including empirical correlations and phenomenological m odels, and experimental data base to determine their applicability to the analysis of thermal-hydraulic performance for triangular lattice a ssembly. It turns out, as the result of study, that the KfK-3 CHF corr elation with the limit CHFR of 1.24 is the best prediction model. The thermal margin of hexagonal fuel assembly, which have been optimized i n the aspect of maximizing the thermal margin, in 600MWe class PWR cor e have been evaluated and compared with those of square lattice fuel a ssemblies such as VANTAGE-SH and KOFA. COBRA-VI with K110 correlation and TORC with KRB-1 correlation have been used far 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(VANTAGE-5H), in t erms of steady-state overpower margin. (C) 1997 Elsevier Science Ltd.