Experimental Investigation of a Scaled Water-Cooled Reactor Cavity Cooling System

The Very High Temperature Gas-Cooled Reactor (VHTR) is one of the next-generation nuclear reactors designed to achieve high temperatures to support industrial applications and power generation. Because of the high temperature reached during normal operation, new safety features were added to its design. The reactor cavity cooling system (RCCS) is a passive safety system that will be incorporated in the VTHR. The system was designed to remove the heat from the reactor cavity and maintain the temperature of structures and concrete walls under desired limits during normal operation (steady state) and accident scenarios. A small-scale (1:23) water-cooled experimental facility was scaled, designed, and constructed in order to study the thermal-hydraulic phenomena taking place in the RCCS during steady-state and transient conditions. The facility represents a portion of the reactor vessel with nine stainless steel coolant risers and utilizes water as coolant. The facility was equipped with instrumentation to measure temperatures and flow rates. A steady-state experimental run was conducted to study the behavior of the coolant under this condition. The experimental results obtained confirmed the capabilities of the system in removing the heat from the cavity and helped in identifying phenomena that may occur in this type of passive system.