Passive nuclear power plant containment system

A closed passive nuclear reactor pressure suppression containment system comprising a low leakage reactor compartment housing a reactor vessel and its associated primary coolant system, at least one vent line extending from the reactor compartment, a plurality of suppression tanks elevated above the reactor compartment and partially filled with water, a downcomer line from said vent line directed into each suppression tank at a point above the water level in said tanks and terminating below the water level in said suppression tanks, and at least one return line from each suppression tank, located below the water level in said suppression tank, to return water to the reactor vessel through a check valve in said return line, wherein during a loss of coolant accident causing an increased pressure in the reactor compartment steam and gases are directed through said vent line and said downcomer lines, the gases being filtered and steam condensed by said water in said suppression tanks and noncondensable gases vented into the gaseous space in said suppression tanks, and the heat from said condensed steam is transferred from said suppression tanks to the surrounding environment.