Assessment of MARS-GCR Code for a New Reactor Cavity Cooling System Design

Seoul National University (SNU) proposed a new concept of a reactor cavity cooling system (RCCS), which is a critical safety feature in high-temperature gas-cooled reactors. To provide reasonable experimental data for the code assessment and evaluate the feasibility of the proposed system, performance and integrity were tested by separate-effects test apparatuses and a reduced-scale mockup facility named RCCS-SNU. Calculations were performed using the MARS-GCR code for the validation of its capability to simulate multidimensional behavior, natural convective heat transfer, radiative heat transfer, etc. This assessment showed that the MARS-GCR code reasonably predicts the characteristics of the radiative heat transfer in the cavity and the forced convective heat transfer through the air-cooling pipes. However, the study showed deviation in the simulation of heat transfers that occur inside the cavity and water pool, especially the thermal stratification phenomenon. As a result, it was concluded that applying the system code with coarse node, MARS-GCR had certain limitations in the simulation of local phenomena.