A supercritical carbon dioxide power cycle has been focused as a promising power cycle because of its compactness, a high efficiency, and a wide applicability. A 10-kWe-class simple unrecuperated supercritical carbon dioxide Brayton experimental loop including a turbo-alternator-compressor unit using a centrifugal compressor and a radial turbine was developed. A shrouded type of a compressor impeller and a turbine wheel with labyrinth seals were designed to overcome thrust balancing problems of the high-pressure fluid turbomachinery. In addition, this type has no issues on the thermal growth collision failure and clearance loss between a shroud and a wheel. Preliminary operation at 30,000rpm, turbine inlet temperature of 83 degrees C, and pressure of 8500kPa was successful. It is founded that all states of the cycle existed in the supercritical region. Copyright (c) 2015 John Wiley & Sons, Ltd.