SAC-PREARS is a special code for analyzing the steady and transient safety characteristics of the passive residual heat removal system. The calculation for steady state performed by SAC-PREARS code is compared with the results obtained by MISAP code which is developed for safety analysis of the passive residual heat removal system AC600,and checked by experiments. SAC-PREARS is used for analyzing the steady and transient themal-hydraulic characteristics of the passive res...