Patent Number: 047073233
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention Broadly, the present invention provides a closure apparatus for an inclined duct. In a more specific embodiment of the invention there is provided a closure for such a duct which is utilized for the transfer of fuel elements into and out of a nuclear reactor vessel. 2. Description of the Prior Art In a typical liquid metal cooled breeder reactor, two vessels are utilized. One vessel houses the reactor core and associated components. The other vessel is utilized for storage of fuel elements. Generally, each of the two vessels will be interconnected via inclined ducts to a fuel transfer cell which moves the fuel elements between the two vessels via the inclined ducts. The duct leading into the reactor-containing vessel is subject to extreme temperatures and radiation during normal operation of the reactor. Thus, the closure for that duct must provide for both thermal insulation and radiation absorption. To accomplish this result, the plug portion of the closure will generally have substantially the same configuration as the duct in cross-section and have sufficient length to achieve the required degree of thermal insulation and radiation absorption. The removal and insertion of such plugs requires a mechanism capable of tilting a sufficient amount to achieve axial alignment with the open end of the duct and must be sufficiently strong to support the plug while moving it axially in an inclined direction corresponding to that of the duct. Obviously, such a mechanism is necessarily bulky and complex. Accordingly, there is need for a closure for such a duct which could be raised and lowered in a vertical direction by a hoist to simplify its insertion and removal from the duct. SUMMARY OF THE INVENTION The present invention provides a simplified closure apparatus for an inclined duct having an open upper end and defining a downwardly extending passageway. The closure comprises a cap means for sealing engagement with the open upper end of the duct and further includes an array of vertically aligned plug members. Each of the plug members has a cross-sectional area substantially conforming to the cross-sectional area of the passageway at least adjacent and upper end thereof, and are freely moveable therein. Means are provided for interconnecting each of the vertically aligned plug members to provide for free movement of plug members only in the plane in which the duct is inclined. The uppermost plug of the array is connected to the cap means. A hoist is provided directly over the open upper end of the duct and connected to the cap means for moving the closure apparatus between an upper position at which the lowermost plug of the array is above the open end of the duct, and a lower position at which the cap means is in engagement with the open upper end of the duct. In accordance with a preferred embodiment of the invention, the cap means further includes a latch for securing the cap to the open upper end of the duct. In accordance with another embodiment of the invention, each of the plug members comprises a cylinder, each cylinder having a longitudinally extending axle at each end. Axles of adjacent cylinders are interconnected by a plurality of end plates. Advantageously, the cylinders are rotatable to facilitate their movement into and out of the duct. In accordance with a particularly preferred embodiment there also is provided means for guiding at least a lower portion of the array of vertically aligned plug members into the open upper end of the duct. Typically, the guide means will comprise a vertical member in fixed relation to the open end of the duct and the cap includes an alignment member in vertically slideable engagement with the vertical member. It is an object of the invention to provide a simplified closure apparatus for inclined duct. It is another object of the invention to provide a closure system suitable for an inclined fuel transfer duct leading into a nuclear reactor vessel. Still another object of the invention is to provide a closure apparatus with a latch which will automatically secure a cap to a duct upon contact. Another object of the invention is to provide a closure system for a fuel transfer duct which will minimize the release of radiation and thermal energy from the interior of the duct. These and other objects of the invention will be more apparent from the drawings and the following detailed description thereof.