Patent Number: 043303684
Section: summary

The present invention relates generally to cable handling systems and more particularly to a system for use in a specific type of nuclear reactor, for example one which utilizes an assembly of rotatable plugs such as a liquid metal fast breeder reactor (LMFBR). A typical reactor of the type just recited has many operating components located within a sealed vessel. These components include an inner core, and, with respect to the present invention, an upper internal structure or instrument tree as it is also called and an internal fuel hoist for carrying fuel assemblies into and out of the core. The vessel itself includes an assembly of rotatably mounted, horizontal plugs serving to perform certain position related functions within the vessel including moving the hoist between various operating points therein. The reactor also requires power, instrumentation and service connections between an internal location within the vessel, specifically the instrument tree, and an external location, whereby to interconnect certain components within the vessel to certain remote, external components. In an actual reactor of the type to which the present invention is especially suitable, specifically the LMFBR referred to above, the assembly of plugs, also referred to above, includes three horizontally extending, circular plugs mounted for rotation about their respective vertical axes. These plugs include an outermost plug which is the largest of the three, an intermediate plug mounted eccentrically within the outer plug and an inner plug mounted eccentrically within the intermediate plug. The internal fuel hoist is mounted to and extends down from the underside of the inner circular plug. In this way, by rotating the three plugs alone or in different combinations with one another, either clockwise or counterclockwise, the hoist can be moved both rectilinearly and/or curvilinearly between various points within the reactor vessel. However, at the same time it must be remembered that the reactor also includes power, instrumentation and service connections between components within the vessel, specifically the instrument tree and external components, as stated previously, and this has heretofore been greatly complicated by plug rotation. A common way of alleviating the complication just recited has been to actually disconnect the various connections (actually electrical and/or tubular fluid carrying cables) between the internal and external components during rotation of the plugs. In order to do this in a reliable manner, it is absolutely necessary to make sure that all cables are completely connected or unconnected, whichever the case may be, and this is quite time consuming and hence costly. Accordingly, there have been proposals in the past to maintain the connections between the internal and external components during rotation of the plugs, thereby eliminating this latter time consuming and hence costly drawback. One proposal has been to use a cable support system that sits on the rotatable plugs and spans the annulus between adjacent plugs. This system uses commercially available hardware including a cable containing a rolling chain belt mechanism which rests on the plugs and spans the annulus between the plugs, thereby greatly congesting the area over the reactor vessel and complicating the rotating plug seal replacement. As will be seen hereinafter, the present invention eliminates the time consuming and costly problem of connecting and disconnecting cables between internal and external reactor components by providing a cable handling system which allows the cables to remain connected during rotation of the various plugs. However, the cable handling system of the present invention is one which does not congest the area over the rotatable plugs or cause problems related to seal replacement. In addition, as will be seen hereinafter, this system is relatively uncomplicated in design, reliable in use, and, in a preferred embodiment, uses commercially available cable containing rotating belt equipment as part of the main support. Aero-trak by Aero-Motive Manufacturing Company and Powertrak by Gleason, division of Maysteel Corporation are two commercially available rolling belt devices useable in the present invention. In view of the foregoing, one object of the present invention is to provide a cable handling system for use in a nuclear reactor of the general type described above and specifically a system which does not require disconnecting the otherwise connected internal and external components of the reactor during rotation of its plug assembly. Another object of the present invention is to provide a cable handling system which does not greatly congest the area of the reactor directly above its plug assembly and which does not complicate seal replacement to any significant degree. Still another object of the present invention is to provide a cable handling system which is relatively uncomplicated in design and reliable in use. As will be seen hereinafter, the cable handling system disclosed herein includes a vertically extending drum tower fixedly mounted to and extending up from the topside of one of the rotating plugs, specifically from the center point on the previously recited intermediate plug in a preferred embodiment and carrying a cylindrical drum at its top. In this system, a first section of power, instrumentation and service cables (including electric and fluid cables) extend between certain components within the vessel, for example, the previously recited instrument tree, and a fixed terminal box at the base of the drum or tower. This section then passes up the tower to a fixed drum point at the top of the tower. A second section of the cables (and a section of the aforementioned rolling belt) is between the point on the drum and a remote, external point such that the distance between the two points varies, depending upon the way in which the plug and drum move. In this regard, the second cable section must be of sufficient configuration to compensate for this change in distance as the plugs rotate. Moreover, in order to compensate for plug rotation, the overall cable handling system includes cable support means (the rolling belt mechanism described) for supporting it for movement with the drum and for causing a segment to wrap around or unwrap from the drum, depending upon the way in which the latter and its supporting plug rotate. As will be seen hereinafter, for the majority (normally about 5/6th) of the fuel handling operations within the reactor core, the remote end of the rolling belt mechanism stays in one location. Rotation and relative movement is compensated by rolling on and off the drum and/or by axial movement of the radial loop. For the remaining portion, (about 1/6th) of the operation within the core, the fuel hoist tower will hit the rolling belt mechanism unless the latter is moved. For these operations a carriage is provided to move tangentially to one side or another of a center line moving the mechanism with it to allow the fuel hoist to reach the center line from either side, i.e., as a result of clockwise or counter-clockwise rotation of the plugs.