Reactor cavity cooling systems (RCCSs) ensure the physical integrity of the containment structures in a high-temperature gas-cooled test reactor (HTR-10) and a high-temperature gas-cooled pebble-bed module reactor (HTR-PM). HTR-10 is a graphite-moderated and helium-cooled pebble-bed reactor prototype designed to demonstrate the technical feasibility and safety of the pebble-bed reactor design concept under normal and accident conditions. This prototype served as a proof of concept for the HTR-PM that shares several design similarities with the HTR-10, including a reactor cavity that requires cooling owing to the high core outlet temperature. The RCCS conceived in the design of both the reactors increases the inherent safety of the system by dissipating heat through passive heat removal processes. This paper proposes an RCCS model for system-scale analysis. The conventional scale method is adopted to determine the conditions necessary for complete similarity between two RCCSs in the steady-state flow regime. In addition, a scaling evaluation between the RCCSs of both the HTR-10 (model) and HTR-PM (prototype) is performed using the proposed RCCS model based on data from two benchmark problems: pressurized and depressurized loss of forced cooling. This evaluation shows that the RCCSs of the HTR-10 (model) and HTR-PM (prototype) show similarity to a specific operational condition in each of the problems analyzed.
