Numerical Analysis of ACME Station Blackout Integral Effect Test with Relap

To study the performance characteristics of AP type passive nuclear power plant under typical station blackout (SBO) condition, numerical analyses are investigated based on the SBO integral tests conducted on the Advanced Core-cooling Mechanism Experiment (ACME) facility. The main parameters, which are obtained by establishing model with Relap5 code, are compared with that of SBO integral tests. The results show that the Relap5 model represents the major accident progress of ACME SBO tests well. The accidents chronology and key thermal hydraulic phenomena of post-calculations are consistent with that of tests. For natural circulation process between core and passive residual heat removal heat exchanger (PRHR HX), the calculated circulation rate is greater than that of tests, which results in a faster natural circulation process. The comparison analysis also shows that the results predicted by Relap5 are conservative for transient pressure of reactor coolant system (RCS) and maximum water level in pressurizer. There is a margin between numerical values and experimental values.