Patent Number: 
Section: claims

1. A fuel bundle assembly for a boiling water nuclear reactor comprising a plurality of fuel rods having respective fuel columns therein, and arranged in an ordered array, extending between upper and lower support structures, said plurality of fuel rods enclosed within a hollow, open-ended channel member; at least one water rod supported on the lower support and extending upwardly toward said upper support, said at least one water rod having an upward flow path including at least one inlet at a lower end of said upward flow path but no outlets in said upward flow path, and a downward flow path including at least one outlet located only at a lower end of said downward flow path, said outlet located in a range of 35% to 65% of the height of the fuel column; wherein said upward flow path is defined by at least first and second tube portions of relatively larger and smaller diameters, and said downward flow path is defined by an annular chamber surrounding the tube portion of relatively smaller diameter. 2. The assembly of  claim 1  wherein said fuel rods are supported by a plurality of spacers, and wherein said at least one outlet in said downward path is located above a respective one of said spacers in said range. claim 1 3. A fuel bundle assembly for a boiling water nuclear reactor comprising a plurality of fuel rods having respective fuel columns therein, and arranged in an ordered array, extending between upper and lower support structures, said plurality of fuel rods enclosed within a hollow, open-ended channel member; at least one water rod supported on the lower support and extending upwardly toward said upper support, said at least one water rod having an upward flow path defined by upper and lower relatively narrow portions and a middle relatively wider portion; and a downward flow path surrounding the upper relatively narrow portion of said upward flow path, said downward flow path having at least one outlet located in a range of 35% to 65% of the height of the fuel columns. 4. The assembly of  claim 3  wherein no additional outlets are provided in said water rod. claim 3