Patent Number: 049869566
Section: claims

1. 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. 2. A system as defined in claim 1 further comprising at least one interconnect line connecting the gaseous space in each suppression tank. 3. A system as defined in claim 1 further comprising a suppression structure in which said suppression tanks are housed having openings at both the bottom and top thereof to provide flow of ambient air whereby said ambient air enters the openings at the bottom of the suppression structure, extracts heat from the suppression tanks and said heated air rises out of the suppression structure through the openings at the top of the structure. 4. A system as defined in claim 3 further comprising a plurality of vertical fins on the exterior of each suppression tank to aid in the transfer of heat to the ambient air. 5. A system as defined in claim 3 wherein the openings at the top of the suppression structure are offset to prevent escape of radioactive shine from the suppression tanks. 6. A system as defined in claim 1 wherein the volume of water in the suppression tanks above the elevation of the return lines on the suppression tanks is sufficient that when said check valve opens the water will flood the reactor vessel. 7. A system as defined in claim 6 wherein the downcomer lines terminate in the suppression tank at a point below the water level, even once the check valve opens and the water level falls to the point of elevation of the return line, that the gases emerge the downcomer line at least three feet below the water level. 8. A system as defined in claim 1 wherein the elevation of the return lines on the suppression tanks is high enough over the reactor compartment that the water in the suppression tanks above the return line will flow by gravity into the reactor vessel. 9. A system as defined in claim 1 further comprising one or more vacuum tanks connected to the suppression tanks, said vacuum tanks being of sufficient size to substantially maintain the pressure of the system at subatmospheric conditions during an accident. 10. A system as defined in claim 9 wherein the evacuated environment in the vacuum tank is connected to the suppression tank by a connection pipe which terminates just below the water level in the suppression tank so that flow of water to the reactor compartment through the return lines lowers the water level enough to expose the connection pipe in the suppression tank to the atmosphere of the suppression tank and the atmosphere in the suppression tanks will be drawn into the vacuum tanks thereby lowering the pressure in the system. 11. A system as defined in claim 9 wherein the vacuum tank is connected to the atmosphere of the suppression tank by a connection line which terminates below a water seal in the vacuum tank so that when the pressure in the suppression tank rises sufficiently to overcome the hydraulic head of water in the vacuum tank the atmosphere in the suppression tank will be drawn into the vacuum tank.