Transient Two-Phase Blowdown Predictions of an Initially Stagnant Saturated Liquid Steam in a Vessel Using TRAC-PF1

Comparisons of the predictions of the best-estimate pressurized water reactor TRAC-PF1/MOD1 computer code to data of the General Electric level swell tests were performed. Various time-step sizes and nodalization schemes were employed. With appropriate time-step size, void fraction distributions predicted by TRAC compared favorably with the void fractions inferred from the measured data. Nonphysical oscillations in spatial void profiles were observed when a large time step was used. Comparisons of TRAC predictions with results obtained using three codes of the RELAP family were performed.