An advanced power conversion system incorporating a Supercritical Carbon Dioxide(S-CO2) Brayton Cycle for Liquid Metal-Cooled Fast Reactors, can provide much improved cycle efficiency relative to a traditional Rankine cycle. Because of this, current plans for Generation IV reactor systems-like the Liquid Metal-Cooled Fast Reactor-include the use of the S-CO2 Brayton Cycle in the development of a power conversion system. However, a structural issue is raised with the use of a mini-channel heat exchanger because large temperature and pressure differences occur along the passages of the mini-channels during normal and transient operating conditions. The design parameters of the heat exchanger during normal operating conditions (i.e., steady state) are pressures and temperatures at the inlet and outlet of the hot and cold channels, and the average heat transfer coefficients within the mini-channels. In this paper, results are presented from preliminary uncoupled thermal and stress analyses of the heat exchanger based on very simple finite element models and the heat exchanger design parameters. Temperature distributions along the passage ways of the mini-channels are calculated. The stresses resulting from both the pressure load and the thermal load are compared with the ASME Section VIII design requirement. The structural integrity of the simplified heat exchanger model-during normal operating conditions of the S-CO2 Brayton Cycle-is evaluated.