The effects of design parameters on the performance of the reactor vessel auxiliary cooling system (RVACS) of a pool liquid-metal reactor (LMR) are investigated. These parameters include (a) stack height, (b) size of the airflow gap, (c) system pressure loss, (d) fins on the guard vessel or the baffle wall, and (e) repeated ribs on the airflow channel walls. As a measure of performance, the peak sodium pool temperature during the transient following a reactor scram from full power was used. Horizontal ribs with a 0.003-m height and a 0.015-m pitch gave the best performance, i.e., the lowest peak sodium pool temperature during the scram transient. For a 3500-MW(thermal) LMR, they gave peak hot pool and peak cladding temperatures that were 52°C lower than those obtained with a reference RVACS having smooth airflow channel walls.