Patent Number: 048881520
Section: claims

1. A grid for assembling a plurality of nuclear fuel rods, comprising a plurality of cylinder portions and means for joining said cylinder portions in a parallel array, wherein each of said cylinder portions has a substantially polygonal cross section comprising a plurality of sides connected by a corresponding plurality of flat portions, each one of said fuel rods being encompassed by a corresponding one of said cylinder portions, each cylinder portion having a plurality of cut-outs, each cut-out extending over a corresponding part of the height of said cylinder portion and having a flat portion of a different cylinder portion inserted therein, whereby each of said nuclear fuel rods not arranged on the periphery of said grid bears against a flat portion of each of a predetermined number of said cylinder portions, but does not bear against any portion of the cylinder portion encompassing the respective fuel rod. 2. The grid as defined in claim 1, wherein said predetermined number is four, said substantially polygonal cross section is a square and said flat portions are truncated corners. 3. The grid as defined in claim 1, wherein said predetermined number is three, said substantially polygonal cross section is a triangle and said flat portions are truncated vertices. 4. The grid as defined in claim 2, wherein each of said cut-outs comprises a recess extending from a top edge of said cylinder portion. 5. The grid as defined in claim 3, wherein each of said cut-outs comprises a window formed in said cylinder portion. 6. The grid as defined in claim 1, further comprising an edging arranged to peripherally surround said plurality of cylinder portions, said edging comprising a plurality of projecting portions, each of said projecting portions being inserted in a cut-out of a corresponding one of said cylinder portions, the nuclear fuel rod encompassed by said corresponding one of said cylinder portions bearing on said corresponding projecting portion. 7. The grid as defined in claim 1, further comprising fin means extending from the top edge of at least one of said cylinder portions for disturbing the fluid flowing through said grid. 8. The grid as defined in claim 1, wherein each of said cut-outs is formed in a portion of said cylinder portion comprising one of said flat portions.