Abstract: A pressure suppressing and aerosol scrubbing system configured to be located between low pressure upper containments associated with modular reactor vessels is described. In one embodiment, the pressure suppression and scrubbing system includes a water tank having connected, partially filled water chambers and a vertical baffle having horizontal vent holes positioned near the bottom of the tank. Each water chamber is connected by a vent/relief line to one of the respective rectangular upper containments. The partially filled water tank assures that the respective containments are isolated from each other under normal operating conditions due to the water trap inherent in the system. In the event that an accident occurs in one of the reactors, the affected containment is heated by the sodium spray and/or pool fire and such heat forces its way through the pressure suppressing and scrubbing system to the unaffected reactor containment.