Supercritical CO₂ (sCO₂) power cycles are promising next generation power technologies offering improved efficiency, lower electricity costs, lower customer costs, and less water usage. They hold great potential in fossil fuel power plants, nuclear power production, solar power, geothermal power, and ship propulsion. To unlock the potential of sCO₂ power cycles, technology readiness must be demonstrated on the scale of 10 – 600 MWe and at sCO₂ temperatures and pressures of 350 – 700 °C and 20 – 30 MPa for nuclear industries. Amongst many challenges at the component level, the lack of suitable shaft seals for sCO₂ operating conditions needs to be addressed for the next generation nuclear turbine and compressor development. In this study, we propose a novel Elasto-Hydrodynamic (EHD) high-pressure, high temperature, and scalable shaft seal for sCO₂ turbomachinery that offers low leakage, minimal wear, low cost, and no stress concentration. The focus in this paper was to conduct a proof-of-concept study for the proposed technology. To this end, a fully coupled Fluid-Structure Interaction (FSI) modeling approach was adopted, and the simulations were carried out in COMSOL Multiphysics software. The modeling approach was presented thoroughly, the results were discussed, and the next research steps were highlighted. For testing purposes, a test rig was developed with a 2” shaft diameter, 1" seal length, 0.5" seal thickness, and 2 mil seal clearance. The seal and shaft material were made from stainless steel, and the working gas was chosen to be nitrogen for the proof-of-concept purposes. The simulation results were validated with experimental data, and a good correlation was observed between the two. The future work was discussed to incorporate the temperature effects, real-gas effects, surface roughness, and the rotor dynamics. This research was supported by a DOE STTR Phase II grant.