This paper presents an experimental investigation of rotor passage loss in an S-CO2 radial turbine. It addresses the need to adapt existing design methodologies for S-CO2 turbomachinery due to its distinct physical behavior compared to ideal gas turbomachinery. This study involves selecting and calibrating existing rotor passage loss models, crucial for determining the pressure ratio and efficiency of a radial turbine. An S-CO2 Turbine-Alternator-Compressor (TAC) in KAIST is utilized for empirical measurements, leading to the calibration of existing Balje's rotor passage loss model. The paper highlights the uniqueness of S-CO2 turbomachinery and contributes to the understanding and improvement of their design and operation.