Passive systems are widely used in nuclear power plants, to enhance the inherent safety of the plant. Especially in the accident of station blackout, Passive Residual Heat Removal system (PRHR) which is installed on the secondary side of steam generator (SG), highly resolved the problem of the residual heat removal after reactor trip. The plant safety is improved largely by PRHR, this is the trend of the new plant design. A water tank is commonly mounted on the passive residual heat removal system (PRHR) of steam generator secondary side, which heavily impacts the performance and the startup procedure of PRHR. Moreover, there are many different types of tank layout in various plants design. Therefore it is necessary to study the thermal hydraulic feature of the different type the PRHR tank set. In this paper, the station blackout accident is chosen to verify the performance of the tank set. Then the assessment criteria of PRHR is established from a thermal hydraulic perspective. RELAP5/mod3.2 is adopted to simulate the accident. Based on the performance comparison of different tank sets, the best tank layout is selected, which is selected for the engineering practice. At last, the comparison of the predicted results and the test data is done to verify the performance of selected tank set design.
