Abstract: In a nuclear reactor fuel bundle packaging apparatus including a hollow cylindrical cask (22) and a basket liner assembly (23) receivable within the cask, the basket liner assembly including a plurality of laterally spaced disks (26) rigidly held by a plurality of tie rods (28), and a plurality of elongated hollow basket liners (33) extending through and fixed to the plurality of disks, each hollow basket liner (33) holding a nuclear fuel bundle assembly (10) having an upper tie plate (14), a lower tie plate (16) and a plurality of fuel rods (12) arranged in a substantially square array, extending between the upper and lower tie plates, the improvement comprising an oversized hollow fuel bundle channel (68) received over the fuel bundle assembly, the channel (68) having the same cross sectional shape as the basket liner (33) but sized to fit within the basket liner, the basket liner having at least one slot (74) formed in at least one side thereof at each disk, and at least one spring (72) mounted on the bask

Abstract: In a boiling water reactor fuel bundle, a three dimensional debris catching grid construction is placed within the flow volume defined by the lower tie plate assembly between the inlet nozzle and upper fuel rod supporting grid. A perforated plate is utilized having round holes as small consistent with the prevention of inadvertent closure due crudding and a hole pitch consistent with mechanical integrity requirements. The perforated plate is placed in a three dimensional construction such as a dome, cylinder, pyramid, inverted pyramid or corrugated construction spanning the flow volume of the lower tie plate assembly. As a consequence of this three dimensional grid construction, the total flow through area of the perforations in the metal plate does not introduce appreciable pressure drop in the lower tie plate assembly between the inlet nozzle and the rod supporting grid.

Abstract: In a boiling water reactor fuel bundle, a three dimensional debris catching grid construction is placed within the flow volume defined by the lower tie plate assembly between the inlet nozzle and upper fuel rod supporting grid. A perforated plate is utilized having round holes as small consistent with the prevention of inadvertent closure due crudding and a hole pitch consistent with mechanical integrity requirements. The perforated plate is placed in a three dimensional construction such as a dome, cylinder, pyramid, inverted pyramid or corrugated construction spanning the flow volume of the lower tie plate assembly. As a consequence of this three dimensional grid construction, the total flow through area of the perforations in the metal plate does not introduce appreciable pressure drop in the lower tie plate assembly between the inlet nozzle and the rod supporting grid.

Abstract: In combination with a boiling water nuclear reactor core undergoing a reload, an improved core reload and process of reloading is disclosed. The core reload consists of fuel bundles having differing design margins to critical power and linear heat generation rate. Specifically, a first part of the core reload is selected from fuel bundles having relatively high critical power margin and relatively lower linear heat generation margin. A second part of the core reload is selected from fuel bundles having relatively high linear heat generation margin and relatively low critical power margin. Distribution of the reload fuel bundles throughout the reactor core occurs as a function of critical power margin and linear heat generation rate margin. Specifically, fuel bundles having the high critical power margin are placed in selected intervals to the central portion of the cylindrical core. Fuel bundles having high linear heat generation margin are placed in the peripheral region of the core.

Abstract: In a fuel bundle for use in the core of a boiling water nuclear reactor, part length rods having a tendency to reduce pressure drop are used in combination with spacers and spacer attached devices tending to restore pressure drop to improve critical power. The addition of the part length rods has the advantage of lowering the pressure drop. Attached devices substantially recapture the pressure drop. Exemplary spacer attached mechanisms for the recapture of pressure drop are set forth including vanes--preferably swirl vanes on the spacers, decreasing the spacer pitch to increase the total number of spacers in the upper two phase region of the fuel bundle, increasing the vertical height of the spacers, and increasing the thickness of the metal from which the spacers are constructed. Two classes of separation devices are disclosed for placement in the volume overlying the end of the partial length fuel rods.

Abstract: In a boiling water reactor (BWR) of the D-lattice type an improved apparatus and method for the mounting of a nuclear fuel assembly is disclosed. Specifically, a D-lattice nuclear fuel assembly is diagonally displaced at the top and diagonally displaced at the bottom to and toward the cruciform shaped control rod interstices. Displacement at the bottom end of the nuclear fuel assembly occurs by an eccentrically centered lower tie plate and fluid inlet for fitting to the core plate at the bottom end of the assembly. Displacement at the top end of the nuclear fuel assembly occurs by shims in the vicinity of the upper end of the channel at the top guides. The disclosed channel assembly is capable of installation during refueling cycles, with a displaced channel being substituted for prior art conventional D-lattice channels. Substitution of one displaced channel occurs with each refueling cycle in a group of four channels.

Abstract: Advantage is taken of the non-uniform axial neutron flux density distribution in a nuclear reactor core by using fuel rod spacers of low neutron absorption in high neutron flux density regions and fuel rod spacers of low coolant flow resistance in the lower neutron flux density regions of the core, this spacer combination also providing higher fuel bundle thermal limits.