An air-cooled helical coil reactor cavity cooling system (RCCS) unit immersed in the water pool was proposed to overcome the disadvantages of the weak cooling ability of an air-cooled RCCS and the complex structure of a water-cooled RCCS for the high-temperature gas-cooled reactor (HTGR). An experimental apparatus was constructed to investigate the various heat transfer phenomena in the water pool-type RCCS, such as the natural convection of air inside the cavity, radiation in the cavity, the natural convection of water in the water pool, and the forced convection of air in the cooling pipe.

The RCCS experimental results were compared with published correlations. The CFX code was validated using data from the air-cooled portion of the RCCS. The RELAP5 code was validated using measured temperatures from the reactor vessel and cavity walls.