General Electric Company

Richard A Wolters

Bruce Matzner

Eric B Johansson

Robert B Elkins

Thomas G Dunlap

Harold B King

Anthony P Reese

Paul W Sick

Roy C Challberg

Gary E Dix

Kevin L Ledford

David L Faulstich

Roland Otto Jackson

Mark J Colby

Bishara E Kakunda

Donald Keith George

James Everett Boyden

Robert H Jones

Donald K Henrie

John D Wilford

Karim-Panahi Khosrow

Bernt R Gaertner

William J Knowles

Tommy C Lee

Michael G McBride

Methods and apparatus for moving fuel bundles in a reactor pressure vessel (RPV) of a nuclear reactor are described. In one embodiment of the apparatus, a support tube facilitates the positioning of a multiple channeled magazine within the RPV, especially at locations adjacent fuel bundles. In the one embodiment, the support tube extends in the reactor pressure vessel into the area above the top guide. A magazine assembly is coupled to the support tube, and includes a magazine having a plurality of fuel bundle receiving channels. The magazine extends from the support tube so that it is adjacent the fuel bundles and the top guide. Grapples extend through the magazine channels, engage the fuel bundles, and retract the bundles into the magazine channels. The magazine and support tube, and thus the bundles, are then moved.

Methods and apparatus for moving fuel bundles in a nuclear reactor

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 basket liner (33) spanning the slot (74) with one surface of the spring engaging the disk (26) and another surface of the spring engaging an adjacent surface of the oversized hollow fuel bundle channel (68).

Nuclear fuel bundle packaging apparatus

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. Fluid movement at the debris restraining holes of the grid construction has a low flow velocity and a change in flow direction before passing through the holes to discourage debris from finding its way through the grid holes. Finally, it is possible to incorporate debris traps within the flow volume of the lower tie plate assembly that can cause trapping and subsequent removal of trapped debris upon fuel bundle replacement. A double corrugated plate having large holes in the lower plate and smaller holes in the upper plate is utilized to trap debris.

Lower tie plate strainers including double corrugated strainers for

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. Fluid movement at the debris restraining holes of the grid construction has a low flow velocity and a change in flow direction before passing through the holes to discourage debris from finding its way through the grid holes. Finally, it is possible to incorporate debris traps within the flow volume of the lower tie plate assembly that can cause trapping and subsequent removal of trapped debris upon fuel bundle replacement.

Lower tie plate strainers for boiling water reactors

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. Preferably and on a diameter basis, the middle third of the core is interspersed with fuel bundle loading including the high critical power margin fuel bundles. The outer third of the core is interspersed with fuel bundle loading including the high linear heat generation rate margin. There results an overall core loading having overall power exceeding that power attainable by the prior art practice of utilizing one margin design uniformly distributed throughout the core.

Core loading strategy for reload of a plurality of different fuel bundle

A fuel bundle for a boiling water nuclear reactor having an improved water rod is disclosed, this water rod having two discrete compartments upper and lower for containing water. The bottom compartment flows moderator from the bottom of the fuel bundle through the water rod compartment to discharge points located through the water rod side walls between the upper most spacers; the top compartment opens upwardly and is naturally filled with liquid moderator settling out of the upwardly flowing moderator during reactor operation. There results the requisite presence of liquid moderator within the water rod for supplying the upper two phase region of the fuel rod with nearly full moderator density. At the same time, water flow through of the water rod from the bottom of the fuel bundle to the upper two phase region of the fuel bundle improves the thermal hydraulic performance. Specifically, water is discharged in the upper two phase region of the fuel bundle at the center of the fuel bundle where the density of the upwardly flowing moderator has the largest vapor fraction. As a result, liquid moderator is injected where it has the maximum beneficial effect on moderator density and the beneficial formation of a liquid film immediately upstream of the spacers. Improved thermal hydraulic performance of the fuel bundle results.

Two compartment water rod for boiling water reactors

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. A first type of device fits to the end of the part length rods and is primarily intended for preventing water passing along the surface of the part length rod adjacent the end of the part length rod from entering the volume overlying the part length fuel rod. A second type of device resides in the volume overlying the part length rod. In either case, critical power is improved.

Optimized critical power in a fuel bundle with part length rods

A fuel bundle having spacers optimally deployed is disclosed wherein the distance between the spacers varies along the length of the fuel bundle. The fuel bundle has a dense fuel rod array (preferably in the range of 10.times.10). It includes at least one part length rod extending from the lower tie plate toward but not to the upper tie plate, which part length rod terminates at a spacer and defines under the upper tie plate overlying the end of the spacer a vent volume for the preferential venting of vapor moderator (steam) from the fuel bundle. A vertical spatial distribution of the spacers is disclosed in which the bottom spacers in the single phase region of the fuel bundle are relatively closely vertically spaced and the upper spacers are relatively more distantly vertically spaced one from another. The design enables optimum resistance to flow induce vibration and rod bow, minimum interference of the spacers with pressure drop in the sensitive upper two phase region of the fuel bundle, and the required bracing of part length rods adjacent their ends.

Fuel bundle with short and intermediate part length rods minimized for

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. Consequently, there results at the end a maximum of four refueling cycles, complete installation of the displaced channels. As substitution occurs, there results an improved worth of each fuel channel assembly enabling an eventual aggregate 2% increase in life with resultant savings.

Repositioned fuel assembly

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.

Growing community of inventors

San Jose, CA, United States of America

Richard A Wolters