Fuel channel assembly and fuel bundle for a nuclear reactor

Abstract

A fuel assembly for a pressure-tube nuclear reactor includes a fuel channel assembly. The fuel channel assembly has an outer conduit and an inner conduit received within the outer conduit. The conduits define an annular fuel bundle chamber for receiving a flow of a coolant in one direction. The inner conduit includes a central flow passage for receiving a flow of the coolant in an opposite direction. A fuel bundle positioned within the fuel bundle chamber consists of fuel dements arranged to form an inner ring surrounding the inner conduit, and an outer ring surrounding the inner ring. The coolant may be light water, and geometries of the fuel assembly may be selected so moderation by the volume of coolant promotes generally uniform power distribution in the fuel elements.

1 . A fuel assembly for a pressure-tube nuclear reactor, comprising:
 a fuel channel assembly comprising an outer conduit, an inner conduit received within the outer conduit and defining an annular fuel bundle chamber therebetween for receiving a flow of a coolant in one direction, the inner conduit comprising a central flow passage for receiving a flow of the coolant in an opposite direction; and   a fuel bundle positioned within the fuel bundle chamber, the fuel bundle comprising a plurality of fuel elements, and consisting of an inner ring of the fuel elements surrounding the inner conduit, and an outer ring of the fuel elements surrounding the inner ring.   
     
     
         2 . The fuel assembly of  claim 1 , wherein a first ratio of a cross sectional area of the coolant in the fuel bundle chamber and the central flow passage to a cross sectional area of the fuel elements is between approximately 2.6 and 7.5. 
     
     
         3 . The fuel assembly of  claim 1 , wherein a second ratio of a cross sectional area of the coolant in the central flow passage to a cross sectional area of the coolant in the fuel bundle chamber is between approximately 0.8 and 1.3. 
     
     
         4 . The fuel assembly of  claim 1 , wherein the inner and outer conduits have generally circular axial cross sectional shapes. 
     
     
         5 . The fuel assembly of  claim 4 , wherein the central flow passage is laterally surrounded by the fuel bundle. 
     
     
         6 . The fuel assembly of  claim 5 , wherein a central axis of the central flow passage is laterally centered relative to the fuel bundle. 
     
     
         7 . The fuel assembly of  claim 6 , wherein the fuel bundle is rotationally symmetrical about the central axis. 
     
     
         8 . The fuel assembly of  claim 7 , wherein the fuel elements of the inner ring are positioned along a first common circumference about the central axis, and the fuel elements of the outer ring are positioned along a second common circumference about the central axis that is concentric with and laterally outboard of the first common circumference. 
     
     
         9 . The fuel assembly of  claim 8 , wherein a number of the fuel elements in the inner ring is equal to a number of the fuel elements in the outer ring. 
     
     
         10 . The fuel assembly of  claim 9 , wherein a subchannel distance between each of the fuel elements in the inner ring and the corresponding adjacent one of the fuel elements of the outer ring is approximately equal to a subchannel distance between each of the fuel elements in the inner ring. 
     
     
         11 . The fuel assembly of  claim 8 , wherein the fuel elements have generally circular axial cross sections. 
     
     
         12 . The fuel assembly of  claim 8 , wherein axial cross sectional areas of each of the fuel elements in the inner ring are different than axial cross sectional areas of each of the fuel elements in the outer ring. 
     
     
         13 . The fuel assembly of  claim 12 , wherein the fuel elements of the inner ring have a smaller cross sectional area than the fuel elements of the outer ring. 
     
     
         14 . The fuel assembly of  claim 1 , wherein the fuel channel assembly comprises an insulator that is positioned radially intermediate of the fuel bundle chamber and the outer conduit. 
     
     
         15 . The fuel assembly of  claim 14 , wherein the insulator is encapsulated between inner and outer liner tubes, the outer liner tube being arranged along an interior surface of the outer conduit. 
     
     
         16 . The fuel assembly of  claim 15 , wherein the insulator is formed of a solid material. 
     
     
         17 . The fuel assembly of  claim 16 , wherein the inner and outer liner tubes are formed of different materials. 
     
     
         18 . A nuclear reactor comprising a plurality of the fuel assemblies of  claim 1  arranged in a lattice, wherein a moderator region laterally surrounds the outer conduit of each of the fuel assemblies, the moderator region retaining a moderator therein. 
     
     
         19 - 25 . (canceled) 
     
     
         26 . A fuel assembly for a nuclear reactor, comprising:
 a fuel channel assembly comprising an outer conduit, an inner conduit received within the outer conduit and defining an annular fuel bundle chamber therebetween for receiving a flow of coolant in one direction, the inner conduit comprising a central flow passage for receiving a flow of the coolant in an opposite direction; and   a fuel bundle positioned within the fuel bundle chamber, the fuel bundle comprising a plurality of fuel elements,   wherein at least one of the following conditions is satisfied:   (i) a first ratio of a cross sectional area of the coolant in the fuel bundle chamber and the central flow passage to a cross sectional area of the fuel elements is between approximately 2.6 and 7.5; and   (ii) a second ratio of a cross sectional area of the coolant in the central flow passage to a cross sectional area of the coolant in the fuel bundle chamber is between approximately 0.8 and 1.3.   
     
     
         27 . A nuclear reactor, comprising:
 a plurality of fuel assemblies arranged in a lattice, each of the fuel assemblies comprising
 a fuel channel assembly comprising an outer conduit, an inner conduit received within the outer conduit and defining an annular fuel bundle chamber therebetween receiving a flow of a coolant in one direction, the inner conduit comprising a central flow passage receiving a flow of the coolant in an opposite direction, and 
 a fuel bundle positioned within the fuel bundle chamber, the fuel bundle comprising a plurality of fuel elements; and 
   a moderator region laterally surrounding the outer conduit of each of the fuel assemblies, the moderator region retaining a moderator therein,   wherein at least one of the following conditions is satisfied:
 (i) a first ratio of a cross sectional area of the moderator in the moderator region to a cross sectional area of the fuel elements is between approximately 10 and 20; and 
 (ii) a second ratio of a cross sectional area of the moderator in the moderator region to a cross sectional area of the coolant in the fuel bundle chamber and the central flow passage is between approximately 2.7 and 3.7. 
   
     
     
         28 - 37 . (canceled)