Patent Number: 043449158
Section: summary

BACKGROUND OF THE INVENTION The present invention relates generally to nuclear reactor fuel rod attachment devices and more particularly to a reusable system for removably attaching a nuclear fuel rod to a support member. The core of a typical nuclear reactor includes many fuel assemblies, with each fuel assembly having many closely-spaced, elongated, cladded fuel rods (also called fuel pins), and with each fuel rod generally containing many fuel pellets. Coolant usually flows in through the bottom of the fuel assembly, up through the spaces between the fuel rods and out through the top of the fuel assembly. The fuel assembly usually contains a support member, and means must be supplied to attach one end of the fuel rod (usually the bottom end) to this support member. Firm attachment is necessary as the fuel rods can be subjected to any number of disturbances, such as: irradiation-induced swelling, fluid flow, thermal variations, and the like. At the same time, the need arises to remove the fuel rods for various reasons, such as: inspection, testing, maintenance and/or replacement. U.S. Pat. Nos. 3,150,057; 3,743,578; 3,755,077; 3,890,197; 3,951,739; 3,996,101; and 4,003,787 disclose fuel rod attaching mechanisms which engage strips having circular, widened portions. In these patents, fuel rods are slid sideways onto the strips and secured for in-reactor operation. Total, or at least considerable, fuel assembly dismantling must take place prior to removing even one fuel rod. In U.S. Pat. No. 3,945,885 (Cocker et al, Mar. 23, 1976), attachment is accomplished by a spigot/socket arrangement. The socket has a lead-in taper and may also have a lead-out taper. The spigot has a lead-in taper but does not have a lead-out taper. Attachment is by a push fit in which the two lead-in tapers allow the socket to expand to accept the spigot into the socket cavity. Removal is accomplished by pulling apart with sufficient force to distort the spigot and/or socket. There may even be fracturing of these parts. This distortion of materials is a desired goal of that patent. The onetime removability does not allow that attachment/removal system to be reused. The spigot is also purposely designed not to fill the entire socket cavity so that there is no rigid attachment, and limited lateral and longitudinal movement under such forces as coolant flow and gravity is allowed. SUMMARY OF THE INVENTION It is an object of the invention to quickly, inexpensively and rigidly attach a nuclear reactor fuel rod to a support member. It is another object of the invention to quickly, inexpensively and nondestructively remove an attached nuclear reactor fuel rod from a support member. It is a further object of the invention to allow repeated attachment and removal of a nuclear reactor fuel rod and a support member. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the nuclear reactor fuel rod and support member attachment and removal system may comprise a locking cap fastened to the nuclear reactor fuel rod and a locking strip fastened to the support member. Both the locking cap and the locking strip can be used repeatedly. The locking cap has two or more opposing fingers shaped to form a socket having a body portion with a narrowing lead-out chamfered section from the body portion to a throat portion and a narrowing lead-in chamfered section from a mouth portion to the throat portion. The fingers spring back when moved apart and released. The locking strip has an extension shaped to rigidly attach to the socket's body portion. The top part of the extension is capable of being pushed against the socket's lead-in chamfered section to move the fingers apart to widen the socket's throat portion to allow attachment. The bottom portion of the extension is capable of being pulled against the socket's lead-out chamfered section to move the fingers apart to widen the socket' s throat to allow removal. In a further aspect of the present invention, in accordance with its objects and purposes, the system hereof may also comprise the above-mentioned locking cap fastened to the support member with the above-mentioned locking strip fastened to the nuclear reactor fuel rod. In another aspect of the present invention, the system hereof may also comprise a locking cap whose chamfered sections would flatten a resiliently transversely compressible locking strip extension to allow the extension to squeeze through the socket's throat portion for attachment and removal. In an additional aspect of the invention, the above-mentioned compressible locking strip is fastened to the nuclear reactor fuel rod and the locking cap is fastened to the support member. Several benefits and advantages are derived from the invention. The invention's rapid attachment and removal feature allows easy removal of a fuel rod from within the fuel assembly for inspection, testing, maintenance and the like. The invention's reusability feature allows the removed fuel rod to be reinserted or replaced with a different fuel rod. This is to be contrasted with that prior art patent which provided for a destructive, one-time removal system. The invention's reusability feature and rapid attachment and removal feature provide an economic benefit for test and/or commercial reactors. Use of the invention in the U.S. Department of Energy's Fast Flux Test Facility reactor in Richland, Wash., would be expected to save over $1,000,000 a year.