Passively-cooled spent nuclear fuel pool system and method therefor

Abstract

A passively-cooled spent nuclear fuel pool system and method therefor. In one embodiment, the invention can be a passively-cooled spent nuclear fuel pool system comprising: a spent nuclear fuel pool comprising a body of liquid water having a surface level, at least one spent nuclear fuel rod submerged in the body of liquid water that heats the body of liquid water; a lid covering the spent nuclear fuel pool to create a hermetically sealed vapor space between the surface level of the body of liquid water and the lid; and a passive heat exchange sub-system fluidly coupled to the vapor space, the passive heat exchange sub-system configured to: (1) receive water vapor from the vapor space; (2) remove thermal energy from the received water vapor, thereby condensing the water vapor to form a condensed water vapor; and (3) return the condensed water vapor to the body of liquid water.

What is claimed is: 
     
         1 . A passively-cooled spent nuclear fuel pool system comprising:
 a spent nuclear fuel pool comprising:
 a body of liquid water having a surface level, at least one spent nuclear fuel rod submerged in the body of liquid water which heats the body of liquid water and produces water vapor; 
 a lid covering the spent nuclear fuel pool to form a hermetically sealed vapor space between the surface level of the body of liquid water and the lid, the water vapor accumulating within the vapor space; 
   a passive heat exchange sub-system fluidly coupled to the vapor space, the passive heat exchange sub-system configured to: (1) receive water vapor from the vapor space; (2) remove thermal energy from the received water vapor, thereby condensing the water vapor to form a condensed water vapor; and (3) return the condensed water vapor to the body of liquid water.   
     
     
         2 . The system according to  claim 1 , wherein the passive heat exchange sub-system further comprises:
 at least one riser conduit having an inlet located within the vapor space and receiving water vapor from the vapor space;   at least one downcomer conduit fluidly coupled to the riser conduit and receiving the water vapor from the riser conduit, the water vapor condensing within the downcomer conduit to form a condensed water vapor; and   at least one return conduit fluidly coupled to the at least one downcomer conduit, the return conduit having an outlet arranged within the spent nuclear fuel pool and returning the condensed water vapor to the body of liquid water.   
     
     
         3 . The system according to  claim 1 , further comprising a containment vessel comprising a thermally conductive shell having an inner surface defining an interior cavity, the spent nuclear fuel pool and passive heat exchange sub-system disposed within the interior cavity of the containment vessel. 
     
     
         4 . The system according to  claim 3 , further comprising a containment enclosure structure surrounding the containment vessel, and a heat sink comprising water formed between the containment vessel and the containment enclosure. 
     
     
         5 . The system according to  claim 4 , wherein the heat sink is annular in configuration and surrounds the containment vessel, and wherein the at least one downcomer is directly attached to the inner surface of the containment vessel such that thermal energy from the water vapor is transferred to the water in the heat sink through the at least one downcomer conduit and the containment vessel. 
     
     
         6 . The system according to  claim 4 , further comprising a plurality of the downcomer conduits arranged vertically and in a circumferentially spaced apart manner about the inner surface of the containment vessel, and wherein each of the plurality of downcomer conduits is in intimate surface contact with the inner surface of the containment vessel to transfer thermal energy to the heat sink. 
     
     
         7 . The system according to  claim 2 , wherein the at least one riser conduit comprises a thermal insulating layer. 
     
     
         8 . The system according to  claim 1 , wherein the condensed water vapor is discharged by the at least one return beneath the surface level of the body of liquid water within the spent nuclear fuel pool to mix with the body of liquid water. 
     
     
         9 . The system according to  claim 1 , wherein the vapor space is divided into a first vapor space and a second vapor space by a divider which extends downwards from the lid into the body of liquid water, the first and second vapor spaced fluidly coupled to the at least one riser conduit. 
     
     
         10 . The system according to  claim 9 , wherein the divider extends into the body of liquid water between approximately one-third and one-fifth of a depth of the body of liquid water. 
     
     
         11 . The system according to  claim 9 , wherein the first and second vapor space sections are hermetically isolated from one another by the divider so that the water vapor in the first vapor space section cannot flow into the second vapor space section and the water vapor in the second vapor space section cannot flow into the first vapor space section. 
     
     
         12 . The system according to  claim 11 , wherein each of the first and second vapor space sections is a separate hermetically sealed space. 
     
     
         13 . The system according to  claim 9 , wherein the lid comprises a first lid section associated with the first vapor space and a second lid section associated with the second vapor space, and further comprising a gasket coupled between the first and second lid sections and the divider to fluidly isolate the first vapor space from the second vapor space. 
     
     
         14 . The system according to  claim 1 , wherein a peripheral wall of the spent nuclear fuel pool is formed of concrete, and the at least one riser and return conduits extend inwards through the concrete into the spend nuclear fuel pool. 
     
     
         15 . The system according to  claim 3 , wherein the passive heat exchange sub-system further comprises: (1) an inlet manifold attached to the inner surface of the thermally conductive shell of the containment vessel, the inlet manifold fluidly coupling the at least one riser conduit to the at least one downcomer conduit; and (2) an outlet manifold attached to the inner surface of the thermally conductive shell of the containment vessel below the inlet manifold, the outlet manifold fluidly coupling the at least one downcomer conduit to the at least one return conduit. 
     
     
         16 . The system according to  claim 1 , wherein the passive heat exchange sub-system is a closed-loop fluid circuit. 
     
     
         17 . The system according to  claim 1 , further comprising:
 a nuclear reactor; and   the nuclear reactor, the spent nuclear fuel pool, and the passive heat exchange sub-system housed within a thermally conductive cylindrical containment vessel in thermal contact with an annular reservoir comprising water surrounding the containment vessel and providing a heat sink for condensing the water vapor.   
     
     
         18 . A passively-cooled spent nuclear fuel pool system comprising:
 a thermally conductive containment vessel disposed inside the containment enclosure structure, the containment vessel including an interior surface defining an interior space;   a heat sink comprising water in contact with an exterior surface of the containment vessel;   a spent nuclear fuel pool disposed in the interior space of the containment vessel, the spent nuclear fuel pool comprising:
 a body of liquid water having a surface level, at least one spent nuclear fuel rod submerged in the body of liquid water which heats the body of liquid water and produces water vapor; 
 a lid covering the spent nuclear fuel pool to form a hermetically sealed vapor space between the surface level of the body of liquid water and the lid, the water vapor accumulating within the vapor space; 
   a passive heat exchange sub-system disposed in the interior space and comprising:
 at least one riser conduit having an inlet located within the vapor space for receiving water vapor from the vapor space; 
 a plurality of downcomer conduits in thermal conductive contact with the interior space of the containment vessel, the downcomer conduits fluidly coupled to the riser conduit for receiving the water vapor from the riser conduit, the water vapor condensing within the downcomer conduit to form a condensed water vapor; and 
 at least one return conduit fluidly coupled to the at least one downcomer conduit, the return conduit having an outlet located within the body of liquid water for returning the condensed water vapor to the body of liquid water. 
   wherein water vapor within the downcomer conduits transfers thermal energy to the water in the heat sink to condense the water vapor and induces gravity-driven thermosiphon flow through the heat exchange sub-system.   
     
     
         19 . The system according to  claim 18 , wherein the passive heat exchange sub-system further comprises:
 an inlet manifold attached to the inner surface of the containment vessel and fluidly coupling the at least one riser conduit to the downcomer conduits; and   an outlet manifold attached to the inner surface of the containment vessel and fluidly coupling the downcomer conduits to the return conduit.   
     
     
         20 . The system according to  claim 19 , wherein the inlet and outlet manifolds are horizontally oriented and the downcomer conduits are vertically oriented, the downcomer conduits each having a top end fluidly coupled to the inlet manifold and a bottom end fluidly coupled to the outlet manifold.