Patent Number: 046831100
Section: summary

BACKGROUND OF THE INVENTION The present invention relates, in general, to nuclear power plants. More particularly, the present invention pertains to an apparatus in which spent fuel rods from spent fuel assemblies may be consolidated for storage and to a method for consolidating spent fuel rods. In a nuclear power reactor, fuel rods are typically held in a fuel assembly by a grid structure, which positions the fuel rods so that they are spaced from one another. Once a fuel assembly has been sufficiently used in the nuclear reactor, it is removed from the nuclear reactor and usually stored in a fuel pool in the nuclear power plant. The spent fuel assembly is radioactive, emitting alpha, beta, and gamma radiation; consequently, it generates decay heat. The water in the fuel pool removes some decay heat through free circulation. The water in the fuel pool also provides some shielding from the radiation emitted by the spent fuel assemblies in the pool. The spent fuel assemblies are located with sufficient spacing between them to preclude criticality. Fuel pools in existing nuclear power plants were typically designed to accommodate spent fuel assemblies for interim storage only. The expectation was that reprocessing plants would be in service and that the spent fuel assemblies would be sent to such plants. However, such plants have not yet become operational. Furthermore, facilities for long-term storage of spent fuel assemblies on a large-scale basis are presently nonexistent. Accordingly, spent fuel assemblies are being stored in the fuel pools of nuclear power plants, and the available storage space in such pools is rapidly being consumed. In order to provide more storage space in their fuel pools, many nuclear power plants have installed, or intend to install, racks in their fuel pools that will permit the fuel assemblies to be stored closer together. These racks are typically equipped with sheets of shielding material located between the fuel assemblies. The sheets of shielding material enable the fuel assemblies to be stored closer together without becoming critical. Conventional fuel pool racks, however, generally have insufficient storage capacity to accommodate the spent fuel assemblies and rods that will accumulate during the lifetime of a nuclear power plant. Accordingly, a need exists for an uncomplicated, inexpensive apparatus in which spent fuel rods from spent fuel assemblies may be consolidated for storage after they have decayed sufficiently. Moreover, a need exists for a simple, efficient method for consolidating spent fuel rods. SUMMARY OF THE INVENTION The present invention satisfies the need for an uncomplicated, inexpensive apparatus in which spent fuel rods may be consolidated for storage and the need for a simple, efficient method for consolidating spent fuel rods. The present invention solves the problems associated with known devices and methods by providing an apparatus with a container having a front wall, a back wall, side walls connected between the front and back walls, and a bottom connected to the front, back, and side walls. The container also has a plurality of flutes positioned adjacent to the front wall. The plurality of flutes defines a plurality of channels. Springs bear against the flutes and channels when no fuel rods have been inserted into the container and the springs are located proximate the front wall. The springs are capable of maintaining a fuel rod in a preselected location in the container. The springs are mounted to a support, which is positioned within the container and which is movable between the front and back walls. Preferably, the springs are arranged in two or more rows, with the rows running between the side walls of the container. Each spring may be a resilient finger that extends outwardly from the support toward the front wall. The support may include a movable installation sheet, or it may include two or more plates. If the support includes two or more plates, the springs are advantageously arranged in two or more rows mounted on each of the plates. The flutes may be formed in the front wall; alternatively, the flutes may be formed in a stationary installation sheet that is positioned adjacent to the front wall. An apparatus according to the present invention may include a device for moving the support. Such a device may have two plates and a plurality of resilient elements connected between the two plates. One of the plates abuts the support, while the other of the plates is connected to a mechanism for adjusting its position. Such a mechanism may include a pantograph extension device. Furthermore, such a mechanism advantageously includes a control system for automatically adjusting the position of the second plate, and therefore the position of the support, in response to a control signal. An apparatus according to the present invention may include a plurality of resilient elements positioned between the support and the back wall instead of the device for moving the support. The resilient elements urge the support toward the front wall. The resilient elements may be wave-shaped springs, leaf springs, conical coil springs, or torsional springs. A further alternative to the device for moving the support is a device for producing a substantially constant force against the support means and urging the support means toward the front wall. An apparatus according to the present invention desirably includes a frame that is capable of holding the container and at least one fuel assembly. In addition, holes are advantageously formed in the bottom of the container and in the walls of the container at a level above the level of an inserted fuel rod. The holes permit inserted rods to be convectively cooled. Preferably, the holes in the bottom of the container are aligned with the interstitial channels defined by fuel rods inserted into the container. The container optionally includes a removable cover. The flutes and the channels of the container define a first row of locations along the front wall of the container. Accordingly, the container is packed by installing a first row of fuel rods in the first row of locations. The springs then bear against the first row of fuel rods and the flutes; the springs maintain the first row of fuel rods in position after the first row of fuel rods has been installed. The first row of fuel rods and the flutes define a second row of locations. Next, a second row of fuel rods is installed in the second row of locations. The springs then bear against the first row of fuel rods and the second row of fuel rods; the springs maintain the first and second rows of fuel rods in position after the second row of fuel rods has been installed. Preferably, fuel rods in the first row of fuel rods are in contact with the front wall, and fuel rods in the second row of fuel rods are in contact with fuel rods in the first row of fuel rods. Each row of fuel rods may be installed by inserting one fuel rod at a time into the container. In this manner, spent fuel rods from spent fuel assemblies may simply and efficiently be consolidated for storage.