Boiling water reactor fuel bundle

A fuel bundle for a boiling water nuclear reactor, said fuel bundle containing a plurality of elongated first cladding tubes vertically oriented therein, said fuel bundle being in the active core of the reactor and being cooled by water pressurized such that boiling thereof occurs, comprising:

• a casing;
• a plurality of thin elongated first cladding tubes vertically oriented in said casing which defines a perimeter of a plurality of fuel rods, first predetermined ones of said first cladding tubes containing nuclear fuel and a solid moderator material of zirconium hydride, both of which are axially distributed therein in an asymmetrical manner relative to a plane through the axial midpoint of each rod and perpendicular to the axis of the rod, an upper half of said first predetermined ones of said cladding tubes containing less fuel than an upper half of second predetermined ones of said cladding tubes, said upper half of said first predetermined ones of said cladding tubes containing more moderator material than a lower half thereof, amounts of said fuel and said moderator material in said upper half of said first predetermined ones of said cladding tubes and locations of said first predetermined ones of said cladding tubes within said fuel bundle being determined to enhance neutron moderation achieved and power produced in an uppermost section of said fuel bundle to compensate, without the use of control rods or burnable poisons for power shaping, for reduced moderation of said neutrons by said water due to said boiling thereof in an uppermost section of the active core of said boiling water nuclear reactor;
• a sealed internal second cladding tube located within each of said first predetermined ones of said first cladding tubes, said moderator material in each of said first predetermined ones of said first cladding tubes being contained in a respective said sealed internal second cladding tube to prevent interaction between said moderator material and said first predetermined ones of said first cladding tubes;
• and
• wherein the number of said first predetermined ones of said first cladding tubes is at least thirty, the upper quarter of each of said at least thirty cladding tubes contains only said moderator material, and the adjacent lower quarter of at least sixteen of said at least thirty cladding tubes contains only said moderator material.