Flow twister for a nuclear reactor

Claim 2

A grid structure for a nuclear reactor fuel assembly containing a plurality of elongated fuel elements each having a longitudinal axis and arranged in a generally parallel array with provision for a coolant flow along said elements, said grid structure comprising intersecting cross members intersecting at, and defining, cross member intersections and forming openings through which the fuel elements are adapted to extend and through which coolant flow in the reactor may pass, flow twisters integral with said grid structure at said intersections of said intersecting cross members and extending outwardly therefrom to a free end in a direction generally parallel to the longitudinal axis of said fuel elements, each twister comprising at least one tab having four outwardly extending arms with surfaces substantially extending from said cross member intersection to said free end, said tab having a cruciform cross section with a longitudinal centerline substantially parallel with the longitudinal axis of said fuel elements and being twisted about said longitudinal centerline to provide a plurality of spiral flow directing surfaces.

Claim 3

A grid as claimed in claim 1 in which said arms of said tab match the grid cross members of said cross member intersections with said arms connected at one end along said grid cross members to provide rigid support and the other end of the twister is free.

Claim 4

A grid as claimed in claim 1 in which the twister comprises a plurality of flow guiding surfaces spiraling along and around said twister centerline with one edge of said surfaces located at said centerline and forming an inner edge and with said surfaces extending radially outward from said centerline and terminating at a surface outer edge and extending transversely of adjacent twister surfaces.

Claim 5

A grid as claimed in claim 1 in which the twister is formed of two intersecting tabs with one tab integral with one cross member and the other tab integral with the other cross member.

Claim 6

A fuel assembly for a nuclear reactor comprising a plurality of elongated fuel elements disposed in a generally parallel spaced array and forming a plurality of longitudinal coolant flow channels between adjacent fuel elements, a plurality of spaced grids disposed in longitudinally spaced relationship along the said fuel elements and extending laterally thereof, each grid comprising intersecting cross members forming passageways through the grid through which passageways said fuel elements extend, said cross members intersecting, and defining cross member intersections, in said flow channels, means for supporting said fuel elements and said grid structures, flow directing tabs of cruciform cross section positioned at said intersections with each tab having a longitudinal central axis extending outwardly from, and in alignment with, a respective cross member intersection and parallel to said elements, said tabs each having four outwardly extending arms with longitudinal surfaces substantially extending along the longitudinal length of said tabs, said tabs each spiraling along and around said axis, each tab including a helical flow directing portion and each of said tabs having one end integral with at least one grid cross member at a respective cross member intersection and a free end spaced from each adjacent fuel element.

Claim 7

A fuel assembly for a nuclear reactor comprising a plurality of elongated fuel elements disposed in a generally parallel spaced array and forming a plurality of longitudinal coolant flow channels between adjacent fuel elements, a plurality of spaced grids disposed in longitudinally spaced relationship along the said fuel elements and extending laterally thereof, each grid comprising intersecting cross members forming passageways through the grid through which passageways said fuel elements extend, said cross members intersecting, and defining cross member intersections, in said flow channels, means for supporting said fuel elements and said grid structures, flow directing tabs of cruciform cross section positioned at said intersections with each tab having a longitudinal central axis extending outwardly from, and in alignment with, a respective cross member intersection and parallel to said elements, said tabs each having four outwardly extending arms with longitudinal surfaces substantially extending along the longitudinal length of said tabs, said tabs each spiraling along and around said axis, each tab including a helical flow directing portion and each of said tabs having one end integral with at least one grid cross member at a respective cross member intersection and a free end spaced from each adjacent fuel element.

Claim 8

The fuel assembly as claimed in claim 5 in which said tab is made of two intersecting helical members intersecting along said axis with one helical member secured to one said cross member and the other helical member secured to the other cross member.

Claim 9

The fuel assembly as claimed in claim 6 in which one helical member is integral with one cross member and the other helical member is integral with the other cross member.

Claim 10

A grid for spacing fuel elements in a nuclear reactor comprising one set of spaced parallel cross members arranged on edge and having fuel element spacing means, a second set of spaced parallel cross members arranged on edge also having fuel element spacing means and arranged transversely of, intersecting, and defining cross member intersections with, said one set of members, tabs integral with said cross members and extending outwardly from said grid at respective cross member intersections, the tabs of one set slotted to receive the cross members and tabs of the second set, each tab having a longitudinal central axis and spiraling along and around said axis, said axis concentric with the respective cross member intersection.

Claim 11

A grid for spacing fuel elements in a nuclear reactor comprising one set of spaced parallel cross members arranged on edge and having fuel element spacing means, a second set of spaced parallel cross members arranged on edge also having fuel element spacing means and arranged transversely of, intersecting, and defining cross member intersections with, said one set of members, tabs integral with said cross members and extending outwardly from said grid at respective cross member intersections, the tabs of one set slotted to receive the cross members and tabs of the second set, each tab having a longitudinal central axis and spiraling along and around said axis, said axis concentric with the respective cross member intersection.

Claim 12

A grid for spacing parallel fuel elements each having a longitudinal axis in a nuclear reactor comprising one set of spaced parallel cross members arranged on edge and including fuel element spacing means, a second set of spaced parallel cross members including fuel element spacing means and arranged on edge transversely of and intersecting, and defining cross member intersections with, said one set of members; a longitudinally extending tab of cruciform cross section having four outwardly extending arms with longitudinal surfaces substantially extending along the longitudinal length of said tab, having a longitudinal central axis and connected at one end to said members at a respective cross member intersection with said arms of said tab aligned with the intersecting members at the respective intersection and connected along the edges of said members, said tab extending outwardly from said grid in a direction generally parallel to the longitudinal axis of the fuel elements, said tab spiraling along and around said central axis of said tab, said axis aligned with said respective intersection, said arms and the connection to both said members providing a rigid self-supporting spiral tab.

Claim 13

A grid for spacing parallel fuel elements each having a longitudinal axis in a nuclear reactor comprising one set of spaced parallel cross members arranged on edge and including fuel element spacing means, a second set of spaced parallel cross members including fuel element spacing means and arranged on edge transversely of and intersecting, and defining cross member intersections with, said one set of members; a longitudinally extending tab of cruciform cross section having four outwardly extending arms with longitudinal surfaces substantially extending along the longitudinal length of said tab, having a longitudinal central axis and connected at one end to said members at a respective cross member intersection with said arms of said tab aligned with the intersecting members at the respective intersection and connected along the edges of said members, said tab extending outwardly from said grid in a direction generally parallel to the longitudinal axis of the fuel elements, said tab spiraling along and around said central axis of said tab, said axis aligned with said respective intersection, said arms and the connection to both said members providing a rigid self-supporting spiral tab.