Optimized flower tubes and optimized advanced grid configurations

Abstract

A support grid for a nuclear fuel assembly, the fuel rod assembly having a generally cylindrical fuel rod with a diameter, wherein the support grid includes a frame assembly having a plurality of outer straps and a plurality tubular members and/or helical frame members. The tubular members/helical frame members have a contact portion structured to contact an adjacent helical frame member and at least one helical fuel rod contact portion with a lesser diameter. The lesser diameter is generally equivalent to the fuel rod diameter such that a fuel rod disposed in the helical frame member would engage the inner helical frame member at helical fuel rod contact portion. The helical fuel rod contact portion may have a variable pitch.

1 . A fuel rod support structured to support an elongated, generally cylindrical fuel rod in a support grid for a nuclear fuel assembly, said support grid for a nuclear fuel assembly having a frame assembly and a plurality of other fuel rod supports, said fuel rod support comprising:
 a tubular member having a contact portion, a transition portion, and at least one helical fuel rod contact portion;   said contact portion and said fuel rod contact portion joined by said transition portion;   said contact portion having a greater diameter structured to contact one of an adjacent fuel rod support or said frame assembly; and   said at least one helical fuel rod contact portion having a lesser diameter, said lesser diameter being generally equivalent to said fuel rod diameter such that, if a fuel rod is disposed in said tubular member, said helical fuel rod contact portion would engage said fuel rod.   
     
     
         2 . The fuel rod support of  claim 1  wherein said at least one helical fuel rod contact portion has a variable pitch. 
     
     
         3 . The fuel rod support of  claim 1  wherein said at least one helical fuel rod contact portion has a constant pitch. 
     
     
         4 . The fuel rod support of  claim 1  wherein:
 said tubular member has a cylinder axis and at least a first axial portion and a second axial portion; 
 said at least one helical fuel rod contact portion extending over both said first axial portion and said second axial portion; and 
 wherein said at least one helical fuel rod contact portion on said first axial portion has a first pitch and said at least one helical fuel rod contact portion on said second axial portion has a second pitch. 
 
     
     
         5 . The fuel rod support of  claim 1  wherein:
 said at least one helical fuel rod contact portion is a plurality of helical fuel rod contact portions; and 
 each said helical fuel rod contact portion in said plurality of helical fuel rod contact portions is disposed equally angularly about said tubular member. 
 
     
     
         6 . The fuel rod support of  claim 1  wherein the number and spacing of the plurality of helical fuel rod contact portions are selected from the group consisting of the following: two helical fuel rod contact portions spaced 180 degrees apart, three helical fuel rod contact portions spaced 120 degrees apart, four helical fuel rod contact portions spaced 90 degrees apart, five helical fuel rod contact portions spaced 72 degrees apart, six helical fuel rod contact portions spaced 60 degrees apart, and eight helical fuel rod contact portions spaced 45 degrees apart. 
     
     
         7 . The fuel rod support of  claim 1  wherein said frame assembly includes a plurality of generally flat members having a height and wherein said tubular member has a height that is different than said frame assembly member height. 
     
     
         8 . The fuel rod support of  claim 7  wherein said tubular member height is less than said frame assembly member height. 
     
     
         9 . A support grid for a nuclear fuel assembly, said fuel rod assembly structured to support a generally cylindrical fuel rod having a diameter, said support grid comprising:
 a frame assembly and a plurality of tubular members;   wherein each said tubular member has a contact portion, a transition portion, and at least one helical fuel rod contact portion, said contact portion and said fuel rod contact portion joined by said transition portion, said contact portion having a greater diameter structured to contact one of an adjacent tubular member or said frame assembly said at least one helical fuel rod contact portion having a lesser diameter, said lesser diameter being generally equivalent to said fuel rod diameter such that when a fuel rod is disposed in said tubular member said helical fuel rod contact portion would engage said fuel rod; and   said a plurality of tubular members disposed within the perimeter of said frame assembly.   
     
     
         10 . The support grid for a nuclear fuel assembly of  claim 9  wherein:
 said plurality of tubular members includes a plurality of helical frame members disposed in a matrix pattern; 
 said frame assembly includes a plurality of outer straps; 
 said outer straps extending about the perimeter of said helical frame members; and 
 wherein each said helical frame member contact portion is structured to contact one of an adjacent helical frame member or at least one said outer strap. 
 
     
     
         11 . The support grid for a nuclear fuel assembly of  claim 10  wherein at least one of said helical frame members has at least one helical fuel rod contact portion with a variable pitch. 
     
     
         12 . The support grid for a nuclear fuel assembly of  claim 10  wherein at least one of said helical frame members has at least one helical fuel rod contact portion with a constant pitch. 
     
     
         13 . The support grid for a nuclear fuel assembly of  claim 10  wherein:
 at least one of said plurality of helical frame members has a cylinder axis and at least a first axial portion and a second axial portion; 
 on said at least one of said helical frame members having at least a first axial portion and a second axial portion, said at least one helical fuel rod contact portion extending over both said first axial portion and said second axial portion; and 
 wherein said at least one helical fuel rod contact portion on said first axial portion has a first pitch and said at least one helical fuel rod contact portion on said second axial portion has a second pitch. 
 
     
     
         14 . The support grid for a nuclear fuel assembly of  claim 10  wherein:
 at least one of said helical frame members has a plurality of helical fuel rod contact portions; and 
 each said helical fuel rod contact portion in said plurality of helical fuel rod contact portions is disposed equally angularly about said at least one of said helical frame members. 
 
     
     
         15 . The support grid for a nuclear fuel assembly of  claim 10  wherein:
 said frame assembly includes a plurality of generally flat strap members having a height; and 
 wherein at least one of said helical frame members has a height that is different than said frame assembly member height. 
 
     
     
         16 . The support grid for a nuclear fuel assembly of  claim 15  wherein:
 said frame assembly has a top side; 
 said at least one of said helical frame members having a height that is different than said frame assembly member has a height that is less than said frame assembly member height; 
 said at least one of said helical frame member having a height that is different than said strap member further having an upper edge; and 
 wherein said at least one of said helical frame member having a height that is different than said strap member upper edge is generally parallel with said frame assembly top side. 
 
     
     
         17 . The support grid for a nuclear fuel assembly of  claim 10  wherein:
 each said helical frame member may have a clockwise twist or a counterclockwise twist; 
 at least one helical frame member having a clockwise twist; and 
 at least one helical frame member having a counterclockwise twist. 
 
     
     
         18 . The support grid for a nuclear fuel assembly of  claim 9  wherein:
 said frame assembly includes a plurality of substantially flat, elongated strap members disposed in two interlocked sets, a vertical set and a horizontal set, said vertical and horizontal sets of strap members being generally perpendicular to each other and wherein the strap members in each set are generally evenly spaced so that said strap members form generally square cells; 
 each tubular member contact portion being a cell contact portion; 
 each said tubular member disposed in a frame assembly cell; and 
 wherein at least one of said tubular members has at least one helical fuel rod contact portion with a variable pitch. 
 
     
     
         19 . The support grid for a nuclear fuel assembly of  claim 18  wherein:
 at least one of said tubular members has a cylinder axis and at least a first axial portion and a second axial portion; 
 one said at least one of said tubular members having at least a first axial portion and a second axial portion, said at least one helical fuel rod contact portion extending over both said first axial portion and said second axial portion; and 
 wherein said at least one helical fuel rod contact portion on said first axial portion has a first pitch and said at least one helical fuel rod contact portion on said second axial portion has a second pitch. 
 
     
     
         20 . The support grid for a nuclear fuel assembly of  claim 18  wherein:
 at least one of said tubular members has a plurality of helical fuel rod contact portions; and 
 each said helical fuel rod contact portion in said plurality of helical fuel rod contact portions is disposed equally angularly about said tubular member. 
 
     
     
         21 . The support grid for a nuclear fuel assembly of  claim 20  wherein the number and spacing of the plurality of helical fuel rod contact portions are selected from the group consisting of the following: two helical fuel rod contact portions spaced 180 degrees apart, three helical fuel rod contact portions spaced 120 degrees apart, four helical fuel rod contact portions spaced 90 degrees apart, five helical fuel rod contact portions spaced 72 degrees apart, six helical fuel rod contact portions spaced 60 degrees apart, and eight helical fuel rod contact portions spaced 45 degrees apart. 
     
     
         22 . The support grid for a nuclear fuel assembly of  claim 18  wherein:
 said frame assembly includes a plurality of generally flat strap members having a height; and 
 wherein at least one of said tubular members has a height that is different than said frame assembly member height. 
 
     
     
         23 . The support grid for a nuclear fuel assembly of  claim 18  wherein:
 said frame assembly has a top side; 
 said at least one of said tubular members having a height that is different than said frame assembly member has a height that is less than said frame assembly member height; 
 said at least one of said tubular member having a height that is different than said strap member further having an upper edge; and 
 wherein said at least one of said tubular member having a height that is different than said strap member upper edge is generally parallel with said frame assembly top side. 
 
     
     
         24 . The support grid for a nuclear fuel assembly of  claim 18  wherein:
 each said tubular member may have a clockwise twist or a counterclockwise twist; 
 at least one tubular member having a clockwise twist; and 
 at least one tubular member having a counterclockwise twist.