Patent Number: 
Section: claims

1. A flow diverter for diverting flow between cells of a spacer in a nuclear fuel bundle into the diverter and in a first downstream flow direction relative to the spacer, the spacer having a rectilinear array of cells, comprising: a cylindrical tube for overlying a spacer cell and having an axis extending in first and second opposite axial directions, a plurality of tabs projecting laterally from said cylindrical tube adjacent a first end portion thereof and at perpendicular locations relative to one another about said axis for disposition in the spacer between diagonally adjacent cells of the rectilinear array thereof;  said tabs forming with said axis acute angles opening in the second axial direction for diverting flow through the spacer into said cylindrical tube in the first axial direction and toward the axis; and  a vortex generator carried by said cylindrical tube adjacent a second end portion of said tube opposite said first end portion, said vortex generator including vanes extending from said tube in said first axial direction and spaced from said tabs for swirling the flow diverted through the cylindrical tube by said tabs. 2. A flow diverter according to  claim 1  wherein said tabs are integral with the cylindrical tube. claim 1 3. A flow diverter according to  claim 1  wherein said tabs have tips and arcuate side edges terminating in said tips, said side edges being arcuate for substantial conformance with arcuate side edges of diagonally adjacent spacer cells. claim 1 4. A flow diverter for diverting flow between cells of a spacer in a nuclear fuel bundle into the diverter and in a downstream flow direction relative to the spacer, the spacer having a rectilinear array of cells, comprising: a cylindrical tube for overlying a spacer cell and having an axis, a plurality of tabs projecting laterally from said cylindrical tube at perpendicular locations relative to one another about said axis for disposition in the spacer between diagonally adjacent cells of the rectilinear array thereof;  said tabs forming with said axis acute angles for diverting flow through the spacer into said cylindrical tube;  a vortex generator carried by said cylindrical tube and including vanes for swirling the flow diverted through the cylindrical tube, said vortex generator comprising a cylindrical tube portion having an axis generally coincident with the axis of said flow diverter, said vanes extending integrally from said cylindrical tube portion in an axial direction and extending inwardly from walls of said tube portion such that an edge of each vane lies adjacent the axis of the cylindrical tube portion. 5. A flow diverter according to  claim 4  wherein the tips of said vanes are welded to one another. claim 4 6. A flow diverter according to  claim 5  wherein said vortex generator is removably mounted on said flow diverter. claim 5 7. A flow diverter according to  claim 5  wherein said vortex generator comprises a second cylindrical tube having a plurality of locking projections, the first mentioned cylindrical tube having a plurality of slots therethrough for receiving said locking projections to releasably secure said second cylindrical tube and said first cylindrical tube to one another. claim 5 8. A flow diverter according to  claim 7  wherein said projections comprise spring-biased tabs of the vortex generator. claim 7 9. A flow diverter according to  claim 4  wherein said cylindrical tube portion includes a second cylindrical tube, said first and second tubes having complementary threads for releasably securing the first and second tubes to one another, said vanes extending inwardly in a direction tending to tighten the threads of said second cylinder on the threads of said first cylinder in response to flow through said vortex generator. claim 4 10. A flow diverter according to  claim 1  wherein said vanes are twisted, said vanes lying within peripheral confines of said vortex generator tube. claim 1 11. A flow diverter according to  claim 1  wherein said tabs are twisted to impart a swirl to the flow-diverted for flow through said tube. claim 1 12. A flow diverter according to  claim 11  wherein said tabs have opposite edges, one edge being longer than an opposite edge. claim 11 13. A nuclear fuel bundle comprising: a plurality of full-length nuclear fuel rods and at least one part-length rod, said fuel rods extending generally axially along the fuel bundle;  a plurality of spacers axially spaced from one another along the bundle, each said spacer having generally cylindrical side-by-side cells in cell positions arranged in parallel rows and parallel columns forming a generally rectilinear array of cells having parallel axes, certain of the cells of each spacer receiving the full-length fuel rods, one of said spacers spaced from an end of the part-length rod having an open cell in axial registration with the part-length rod;  a flow diverter including a cylindrical tube overlying said open cell and connected to said one spacer, said tube having an axis generally coincident with the axis of said open cell, a plurality of tabs projecting laterally from said cylindrical tube at perpendicular locations relative to one another about said axis, each tab extending diagonally relative to said rectilinear array of columns and rows of said cells into spaces between diagonally adjacent cells;  said tabs forming with said axis acute angles opening in an upstream direction for diverting flow through openings between the cells of the spacer into said cylindrical tube; and  a vortex generator carried by said cylindrical tube downstream of said tabs for swirling the flow diverted through the cylindrical tube. 14. A nuclear fuel bundle according to  claim 13  wherein each of said tabs terminates in a tip extending beyond a straight line interconnecting centers of diagonally adjacent cells between which the tab projects. claim 13 15. A nuclear fuel bundle according to  claim 13  wherein said tabs are integral with the cylindrical tube. claim 13 16. A nuclear fuel bundle according to  claim 13  wherein said tabs have tips and arcuate side edges terminating in said tips, said side edges being arcuate and in substantial conformance with the arcuate side edges of said diagonally adjacent cells. claim 13 17. A nuclear fuel bundle according to  claim 13  including four tabs perpendicular to one another about said cylindrical tube, each tab extending diagonally relative to said rectilinear array of columns and rows of said cells into spaces between diagonally pairs of cells, a cell of each pair of diagonally adjacent cells being common to an adjacent pair of diagonally adjacent cells between which a tab extends. claim 13 18. A flow diverter/spacer combination for diverting flow between cells of a spacer in a nuclear fuel bundle for flow within the diverter and in a downstream flow direction relative to the spacer, comprising: a spacer having generally cylindrical side-by-side cells in cell positions arranged in parallel rows and parallel columns forming a generally rectilinear array of cells, the cells having parallel axes;  a cylindrical tube overlying a cell of and connected to the spacer and having an axis generally coincident with the axis of the cell, a plurality of tabs projecting laterally from said cylindrical tube at perpendicular locations relative to one another about said axis, each tab extending diagonally relative to said rectilinear array of columns and rows of said cells into spaces between diagonally adjacent cells;  said tabs forming with said axis acute angles opening in an upstream direction for diverting flow through openings between the cells of the spacer into said cylindrical tube; and  a vortex generator carried by said cylindrical tube downstream of said tabs for swirling the flow diverted through the cylindrical tube;  said vortex generator including a cylindrical tube portion having integral vanes extending axially in a downstream direction and curved inwardly from walls of said cylindrical tube portion such that an edge of each vane lies adjacent the axis of the cylindrical tube portion. 19. A flow diverter/spacer combination according to  claim 18  wherein the tips of said vanes are welded to one another. claim 18 20. A flow diverter/spacer combination according to  claim 13  wherein said vortex generator is removably mounted on said flow diverter. claim 13 21. A flow diverter/spacer combination according to  claim 20  wherein said vortex generator comprises a second cylindrical tube having a plurality of locking projections, the first mentioned cylindrical tube having a plurality of slots therethrough for receiving said locking projections to releasably secure said second cylindrical tube and said first cylindrical tube to one another. claim 20 22. A flow diverter/spacer combination according to  claim 21  wherein said projections comprise spring-biased tabs of the vortex generator. claim 21 23. A flow diverter/spacer combination according to  claim 18  wherein said cylindrical tube portion includes a second cylindrical tube, said first and second tubes having complementary threads for releasably securing the first and second tubes to one another, said vanes being curved inwardly in a direction tending to tighten the threads of said second cylinder on the threads of said first cylinder in response to flow through said vortex generator. claim 18 24. A flow diverter/spacer combination according to  claim 13  wherein said vortex generator includes vanes extending axially in a downstream direction and twisted inwardly so that an edge of each vane lies adjacent the axis of said cell, said tabs and said vanes being formed integrally with said first cylindrical tube. claim 13 25. A flow diverter/spacer combination according to  claim 13  wherein said tabs are twisted to afford a swirl to the flow diverted by the diverter and into the cylindrical tube. claim 13 26. A nuclear fuel bundle according to  claim 13  wherein said vortex generator includes vanes integral with said cylindrical tube portion and extends axially in a downstream direction, said vanes being curved inwardly from walls of said cylindrical tube portion such that an edge of each vane lies adjacent the axis of the cylindrical tube portion. claim 13 27. A flow diverter according to  claim 1  wherein said vanes extend generally in said first axial direction and are twisted such that one edge of each vane lies inboard of said tube and another edge of each vane lies generally along the circumference of the tube. claim 1 28. A flow diverter according to  claim 1  wherein said cylindrical tube has apertures in lateral registration with said tabs, respectively, for receiving the diverted flow. claim 1 29. A nuclear fuel bundle according to  claim 13  wherein said cylindrical tube has apertures in lateral registration with said tabs, respectively, for receiving the diverted flow for flow in a downstream direction within the cylindrical tube. claim 13 30. A nuclear fuel bundle according to  claim 29  wherein said vanes extend generally in said first axial direction and are twisted such that one edge of each vane lies inboard of said tube and another edge of each vane lies generally along the circumference of the tube. claim 29