The operational characteristics of passive residual heat removal systems (PRS) under marine conditions are crucial for the thermal and hydraulic safety of offshore floating nuclear power plants.

This study aims to verify the applicability of the re-developed RELAP5 code under inclined conditions.

Based on the small-scaled secondary side of the PRS experimental device, simulation of the experiments were carried out by using the secondary-developed RELAP5 code under the operating conditions of the inclination angle from -24° to +24°. Then, a comparative analysis of experimental data was performed to verify the applicability of this secondary-developed code.

The results show that the length of the condensing section in the C-type heat exchanger is changed under inclination conditions, and the larger the tilt angle, the better the overall heat transfer effect is achieved. Besides, the re-developed RELAP5 code can effectively predict changes in the system operating characteristics under tilt conditions, and the deviation between the calculated results and the experimental values is within ±4%.

The results of this study provides some reference for the design of the secondary side passive heat removal system under marine conditions.