Supercritical CO2 (sCO2) power cycles are promising next generation power technologies, holding a 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 with the help of physics-based computer simulations. The results showed that the proof-of-concept study was successfully demonstrated, warranting further investigation. Particularly, it was interesting to note the quadratic form of the leakage rate, making its peak of = 0.075 kg/s at Pin = 15 MPa and then decaying to less than = 0.040 kg/s at Pin = 30 MPa, suggesting that the proposed seal design could be tailored further to become a potential candidate for the shaft seal problems in sCO2 turbomachinery.