Patent Number: 045483477
Section: summary

This disclosure relates to the assembly of nuclear fuel assemblies, particularly for use in fast breeder reactors. The present state of the art involves fabrication of fuel assemblies by manual manipulation or by mechanical processes incapable of limiting spread of radioactive contamination to adjoining components and equipment. In such configurations, the fabrication steps are time consuming and create significant radiation contamination control problems. To achieve flexibility of process steps, radiation contamination control, and efficient fabrication in an apparatus having production capability, the present invention has been directed toward development of a self-contained automated loading system. It allows for system variation and contamination control without degrading production capability. More specifically, the present apparatus permits fabrication of fuel assemblies by batch processing methods, using equipment which can be physically and environmentally isolated as required. U.S. Pat. No. 4,167,959 exemplifies an apparatus in which a manual glove box is provided for filling fuel rods. A seal is provided at the entrance of the glove box for engaging the cladding. Contamination is stated to be controlled by differences in pressure between an antechamber, a processing chamber, and the exterior of the glove box. The use of a glove box for processing of nuclear fuel assemblies is carried further in the disclosure of U.S. Pat. No. 4,070,240. The patent discloses an automated transport conveyor for moving fuel elements between successive assembly stations. A common sealing apparatus is stated to prevent external contamination as the fuel elements are advanced between the various manual stations. A large scale system for manufacturing nuclear fuel pellets is disclosed in U.S. Pat. No. 4,174,938. The system includes process components arranged vertically and providing for gravity flow of the product from one component to the next. The various process components are modular and each can be removed without interfering with the others. Physical isolation of the components is provided by appropriate seals and manual access is accomplished through glove ports. Another large scale system for cleaning nuclear fuel elements is shown in U.S. Pat. No. 4,063,962. Batches of fuel elements are suspended vertically and moved through the components of the system. Airlocks and seals are provided to contain contamination. A number of prior patents have been directed specifically to sub-systems for loading fuel pellets into nuclear fuel elements by automated or semi-automated equipment. Representative disclosures are found in U.S. Pat. Nos. 3,746,190, 4,125,577, 3,907,123 and 4,158,601. U.S. Pat. No. 3,711,993 relates to an airlock or cylindrical seal for engagement about the periphery of fuel cladding. U.S. Pat. No. 3,828,518 discloses a welding apparatus for closing the end of a fuel rod by use of a rotating electrode head. SUMMARY OF THE INVENTION It is an object of this invention to provide a novel conveyor and support system for handling a batch of fuel pins during fabrication processes. The system permits batch processing of the fuel pins in combination with individual fabrication steps so as to more efficiently adapt automated fuel pin fabrication processes to a production schedule. More specifically, the system lends itself to batch inerting of the fuel pins in an apparatus interposed between subsystems which individually fill and cap the fuel pins. Another object of this invention is to provide a system in which the various work stations and subsystems are modular. They can be duplicated when required by production quotas, and individual components can be removed or substituted as necessitated by servicing and repair schedules. Another object of the invention is to provide an integrated system for fabricating fuel pins which can be totally automated, thereby removing the necessity of using manual glove boxes during fuel pin fabrication. Another object of the invention is to provide a unique system of handling individual fuel pins by which each fuel pin can be reciprocated axially and rotated about its axis. This eliminates the necessity of rotating work elements used to carry out particular fabrication steps, such as the welding or the cleaning of fuel pin surfaces. Another object of the invention is to provide a unique system of seals so as to assure effective protection against contamination of vulnerable mechanical components and to permit efficient inerting of the fuel pin interiors. 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 purposes of the present invention as embodied and broadly described herein, the apparatus of this invention may comprise conveyor means for moving parallel fuel pin assemblies along a path perpendicular to their lengths, transport means for coaxially positioning a fuel pin assembly along a preselected operational axis, transfer means for shifting individual fuel pin assemblies between the conveyor means and the transport means, powered means for shifting the transport means relative to the conveyor means in a direction parallel to the operational axis, and fuel pin handling means for receiving one end of a fuel pin assembly shifted thereto by the powered means. By this apparatus, fuel pin assemblies can be moved to and from the transport means by the conveyor means and can be shifted axially for operations carried out by the fuel pin handling means. The apparatus provides an effective automated system for moving a plurality of fuel pin assemblies between automated production stations including fuel pin handling means by which the fuel pins can be filled, cleaned, inerted, capped and welded. All of these steps can be effectively accomplished without manual intervention.