Patent Number: 041526023
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 there is shown a plurality of nuclear fuel racks 10 positioned within a spent fuel storage pit 12. The racks are arranged within the pit or pool in a rectangular array, and each rack includes a plurality of cells 14 sized to receive a fuel assembly 16. Adjacent racks 10 are joined by lateral supports 18 so as to form a structure which moves essentially as a single mass under high loading conditions. The racks are also typically affixed to the bottom of the spent fuel pit by a bolted or welded structure (not shown). The spent fuel pit typically includes a concrete or other structural support 20 with a metallic sealed lining 22. The racks have sides 24, typically comprised of a plurality of metallic beams affixed in an open fashion to allow the flow of borated water therethrough. Between the sides 24 and the substantially parallel lining 22 are positioned a plurality of lateral support and restraint devices 26. The devices can be positioned at varying elevations along the sides of the fuel racks, although preferably positioned near the top of the racks. One embodiment of a lateral support and restraint device in accordance with this invention is shown in FIGS. 2 and 3. It includes one or more preferably ball jointed swivel pads 28 having a flat surface 30 that will seat against any surface substantially perpendicular to the axis of the arms 32 to which the pads 28 are affixed. The arms 32 can be affixed directly to a piston 34 or joined thereto by additional components as shown. The additional components can include a leveling foot 36 affixed to a piston extension 38 by a pinned connection 40. The piston 34 is slidably disposed within a cylinder 42 for reciprocating motion therein, and preferably extends through an open end 35 of the cylinder. Between the piston and the fuel rack, preferably contained within the cylinder, is an elastic compressible member such as the compression spring 44. The spring 44 is specifically sized to continuously apply a positioning force to the piston. Means are also provided for affixing the cylinder 42 to the fuel rack 10, such as the cylinder being welded to the rack support 46 by welds 48. Alternatively, as shown in FIG. 4, the pads 28 can be joined to the cylinder 42a which slides, through a predetermined clearance 56a, on stationary piston 34a. Piston 34a is affixed to the side 24 of the fuel rack, and spring 44a continuously acts upon cylinder 42a. Referring again to FIGS. 2 and 3, structure is also provided for selectively restraining the piston 34 in a retained position while the spring is compressed. This can include the opening 50 in the wall of the cylinder, a mating aperture 52 partially through the piston, and a ringed pin 54 insertable through the opening 50 into the aperture 52 upon alignment of the opening and aperture. The opening 50 is preferably positioned so that a portion of the piston is always aligned with the opening, thereby preventing undesirable flow paths into or out of the cylinder. Means are also provided for controlling the flow of fluid into or out of the portion of the cylinder between the piston and the fuel rack. This can include a preselected clearance 56 between the piston 34 and cylinder 42 or alternatively, one or more small openings through the cylinder wall or the end 58 adjacent the spring 44. As will be readily apparent, the device 26 can be easily installed. The piston can be loaded into the cylinder so as to compress the spring and locked into position by the ringed pin. The cylinder can then be affixed to the fuel rack side. The leveling foot and affixed components can than be attached to the piston or its extension, readying the device for final positioning. With properly sized components, the device can then be positioned merely by removing the ringed pin, allowing the spring to act on the piston, thereby forcing the piston laterally out of the cylinder and the joined pads against the spent fuel pool wall. The water in the pit flows, in a controlled fashion, into the area 60 within the cylinder and about the spring. For non-rapid relative motions, such as those brought about by differential thermal expansion between the pit wall and the rack, the piston will slide in the appropriate direction within the cylinder restrained or assisted as the case may be by the compression spring for rapid relative movements, such as seismic loading conditions, however, the hydraulic fluid within the cylinder cannot be rapidly discharged, and the support will accordingly react as a substantially rigid restraint or damper of the loading. The magnitude of the restraining force can be adjusted to any desired level by incorporating variously sized piston to cylinder clearances and/or variously sized and oriented flow relief openings 62. The device shown in FIG. 4 will operate similarly. It will be apparent that many modifications and additions are possible in view of the above teachings. It therefore is to be understood that within the scope of the appended claims, the invention can be practiced other than as specifically described.