A passive containment cooling system (PCCS) condenser, for reducing some non-condensable gases in the PCCS, includes a first and a second stage condenser that each include channels in fluid communication between an inlet and an outlet header. The inlet header of the first stage condenser is configured to receive a fluid mixture through a first inlet opening. The channels are configured to condense water from the fluid mixture flowing through the channels from the inlet header to the outlet header, respectively, of the first and second stage condenser. The PCCS condenser includes a catalyst in at least one of the outlet header of the first stage condenser or the inlet header of the second stage condenser. The catalyst catalyzes a reaction for forming water from hydrogen and oxygen in the fluid mixture. The outlet header of the second stage condenser is in fluid communication with a combined vent-and-drain line.

A PCCS condenser may include a first and a second stage condenser. Each of the first and second stage condensers may include channels in fluid communication between an inlet and an outlet header. The inlet header of the first stage condenser may be configured to receive a fluid mixture through a first inlet opening. The channels may be configured to condense water from the fluid mixture flowing through the channels from the inlet header to the outlet header, respectively, of the first and second stage condenser. The PCCS condenser may include a catalyst in at least one of the outlet header of the first stage condenser or the inlet header of the second stage condenser. The catalyst may catalyze a reaction for forming water from hydrogen and oxygen in the fluid mixture. The outlet header of the second stage condenser may be in fluid communication with a combined vent-and-drain line.

An assembly for containing and detecting leaks from a coolant line includes a basin with side and end walls, and at least one U-shaped cavity in an end wall for receiving a coolant line of a liquid cooling system. A bottom of the basin includes at least one sloped interior surface arranged to divert water in the basin to a local low point, where a sensor is positioned and operable to detect liquid in the collection basin. A leak detection system can employ a leak detection assembly to detect and/or locate a leak.