To develop a cycle operation strategy for a supercritical carbon dioxide (S-CO2) Brayton cycle, a series of MARS code simulation results were compared to experimental data from an SCIEL compressor test, which was collected at both component and whole-loop level. The simulation results show reasonable agreement with the experimental results. The MARS code was used to simulate behavioral responses at varying scenarios, the valve control for cycle operation, a power swing to simulate load following behavior, and an effect of the heat sink reduction to simulate failure. The electric power output of the turbine decreased to 50% of that during normal operation through valve control. After power swing, the system reverted to the initial steady-state conditions. The fluid behavior in precooler and the eventual change in the system were identified through the scenario of the heat sink reduction. The simulations provide a notable insight into the responsiveness of an SCIEL to these variable scenarios. Even though the MARS code was specifically developed for analysis of water reactor transients, its field of application may be extended to analyze the S-CO2 Brayton cycle, and may thus assist with the development of control strategies for SCIEL and the S-CO2 Brayton cycle. (C) 2017 Elsevier Ltd. All rights reserved.