APPLICABILITY OF REFLA TRAC CODE TO A SMALL-BREAK LOCA OF PWR/

The applicability of the REFLA/TRAC code, which is one of best-estimat e codes based on two-fluid model, was assessed for a typical small-bre ak loss-of-coolant accident (SBLOCA) transient of PWR. The main assess ment subject was to investigate whether the physical models in REFLA/T RAC can apply to the transient under SBLOCA condition (high pressure/l ow flow rate) or not. The applicability had been verified under low pr essure/low flow rate condition during reflood phase in large-break LOC A transients of PWR. The assessment calculation was performed for Run SB-CL-05 (5% cold leg break SBLOCA test) in the ROSA-TV large-scale te st facility. The REFLA/TRAC almost predicted the thermal-hydraulics in primary loops while the hydraulic models should be improved for regio ns at the pump side of loop seal and at the up-flow side of steam gene rator tube under CCFL condition. The core thermal-hydraulic models in REFLA/TRAC give better prediction for core full-height differential pr essure and the peak clad temperature (PCT) than those in original TRAC code. The PCT by the models in TRAC was lower about 100 K than the me asured one but the PCT by those REFLA/TRAC was lower only about 40 K.