Analysis of TRAC-PF1 calculated core heat transfer for a CCTF test

TRAC-PF1 posttest calculation for CCTF test C1-5 (Run 14) was performed to assess the core thermal-hydraulic models in the TRAC-PF1 code during the reflood phase of a PWR LOCA. TRAC showed good agreement with data for heater rods turnaround temperatures and turnaround times in the lower half of the core. However, TRAC overpredicted turnaround times and underpredicted quench times in the upper part of the core. Even though heat transfer correlations have a strong dependency on the local void fraction in TRAC, TRAC-predicted void fraction profiles showed poor agreement with CCTF data that have been inferred from differential pressure measurements. From these comparisons with CCTF data, the following areas for future improvements of TRAC-PF1 should be considered: (1) the core hydraulic modeling used to calculate the void fraction profile in the core. (2) the method for evaluating heat transfer within the core.