Abstract:
An integrated reactor missile shield and crane assembly (IRMSCA) is disclosed and claimed. The IRMSCA replaces the existing concrete missile shields and reactor services crane. The IRMSCA is moveable such that the missile shield can be moved away from the reactor head, allowing the integral crane to lift the control rod drive mechanism components and other routine loads at the refueling cavity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit of U.S. Provisional Patent Application No. 61/369,583 filed on Jul. 30, 2010, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an integrated reactor missile shield and crane assembly. 
         [0004]    2. Description of the Related Art 
         [0005]    Pressure vessels containing fuel assemblies in commercial nuclear reactor facilities, such as pressurized water reactors (PWRs), have control rods which are operated by control rod drive mechanism assemblies (CRDMs). The CRDMs are mechanically supported on a removable closure head bolted to the pressure vessel and laterally supported by a seismic support platform and vertically restrained by a missile shield. Missile shields are generally relatively large heavy concrete or metal structures designed to absorb kinetic energy from dislocated CRDMs or other objects originally attached to the reactor pressure vessel. 
         [0006]    Each of these components is typically designed and installed as a permanent fixture to perform designated functions during plant operation. However, during refueling of the reactor, the closure head, CRDM assemblies and their supporting subsystems, missile shield and other devices located over the closure head must be disassembled and moved in order to remove the reactor vessel closure head from the reactor vessel. 
         [0007]    Typically, as the missile shields and other components are heavy loads, their rigging and handling is a time consuming process and requires use of the reactor building polar crane. Disassembling and moving the missile shields is a complex and potentially dangerous undertaking; many industry events (mishaps) have occurred during missile shield handling. 
         [0008]    Numerous missile shield designs have been installed to improve efficiencies and accommodate the various nuclear power plant configurations. One such design provides a missile shield that is a hinged steel structure, and which is rotated clear of the reactor. In another such design, the missile shield rolls along the rails used by the fuel handling bridge (FHB). 
         [0009]    At some nuclear power plants, a rolling missile shield would not be practical on the FHB rails, which are crossed by many CRDM cables, head vents, and component cooling water (CCW) piping. At the FHB elevation, a rolling missile shield would interfere with extensive CRDM activities that are routine for such a nuclear power plant. 
       SUMMARY OF THE INVENTION 
       [0010]    The integrated reactor missile shield and crane assembly (IRMSCA) of the present invention will traverse the rails atop the D-ring (bio-shield) walls, and it replaces the existing concrete missile shields and reactor services crane. Alternatively, the IRMSCA can be configured to traverse the D-ring walls themselves, such that the IRMSCA can be used in plants that do not have rails atop the D-ring wall. The IRMSCA fully integrates their functions, and the new assembly has improved capabilities that will facilitate refueling outage (RFO) activities. By eliminating the rigging, handling, and storage of the huge missile shields, IRMSCA improves personnel safety, frees the polar crane, and reduces RFO durations. Further RFO flexibility and schedule improvements are gained by the extended capabilities of the integral reactor services crane, which can be used to lift the CRDM components and the other routine loads at the refueling cavity. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention is described with reference to the accompanying drawings, in which like reference characters reference like elements, and wherein: 
           [0012]      FIG. 1  shows an isometric view (top) of an IRMSCA of the present invention. 
           [0013]      FIG. 2  shows an elevation view (operating plant configuration) of the IRMSCA of 
           [0014]      FIG. 1 . 
           [0015]      FIG. 3  shows an isometric view (operating plant configuration) of the IRMSCA of  FIG. 1 . 
           [0016]      FIG. 4  shows an isometric view (operating plant configuration - near) of the IRMSCA of  FIG. 1 . 
           [0017]      FIG. 5  shows an anchorage detail (operating plant configuration) of the IRMSCA of  FIG. 1 . 
           [0018]      FIG. 6  shows the IRMSCA of  FIG. 1  disengaged from its support brackets. 
           [0019]      FIG. 7  shows a plan view (operating plant configuration - hoist north) of the IRMSCA of  FIG. 1 . 
           [0020]      FIG. 8  shows a plan view (operating plant configuration - hoist south) of the IRMSCA of  FIG. 1 . 
           [0021]      FIG. 9  shows a plan view (refueling configuration - hoist south) of the IRMSCA of  FIG. 1 . 
           [0022]      FIG. 10  shows a suspension crane of the IRMSCA of  FIG. 1 . 
           [0023]      FIG. 11  shows a catwalk of the IRMSCA of  FIG. 1 . 
           [0024]      FIG. 12  shows an isometric view (bottom) of the IRMSCA of  FIG. 1 . 
           [0025]      FIG. 13  shows a rolling missile shield assembly. 
           [0026]      FIG. 14  shows a missile shield support bracket assembly. 
           [0027]      FIGS. 15 through 39  illustrate exemplary operations that can be achieved using the IRMSCA of  FIG. 1 . 
           [0028]      FIG. 40  shows an isometric view of an IRMSCA of the present invention in plant operation configuration. 
           [0029]      FIG. 41  shows a front elevation view of the IRMSCA of  FIG. 40 . 
           [0030]      FIG. 42  shows a detailed view of the anchorage of the IRMSCA of  FIG. 40 . 
           [0031]      FIG. 43  shows a side elevation view of the IRMSCA of  FIG. 40 . 
           [0032]      FIG. 44  shows a side elevation view of the IRMSCA of  FIG. 40  in refueling configuration. 
           [0033]      FIG. 45  shows the IRMSCA of  FIG. 40  disengaged from its support brackets. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The present invention relates to an integrated reactor missile shield and crane assembly.  FIG. 1  shows an isometric view (top) of an IRMSCA  100  of the present invention, and  FIG. 12  shows an isometric view (bottom) of the IRMSCA  100 . The IRMSCA  100  includes a number of components, including a support frame  1 , a handrail  2 , a plurality of clevises  4 , a motor  8 , a catwalk  12 , a monorail  14 , a rail extension  15 , a hoist  16 , and a suspension crane  17 . During plant operation, the IRMSCA devises  4  are anchored to the D-rings that form a part of the containment building structure. Atop the support frame  1  is a floor plate, and the missile shield  20  plate is attached to its lower surface as illustrated in  FIG. 12 . The floor plate provides access to the IRMSCA  100  and both D-rings. For ease of illustration, the catwalk  12  is not shown in the view illustrated in  FIG. 12 ;  FIG. 11  shows a detailed view of the catwalk  12 , which is used to access the suspension crane  17 . Handrails  2  are included for personnel safety. 
         [0035]    During a refueling outage, the IRMSCA  100  is disengaged from the anchorage and it can function as a crane. Preferably, the IRMSCA  100  rolls along rails  24  atop the D-ring  25  using the drive motor  8 . Alternatively, the IRMSCA  100  can be configured to traverse the D-ring walls themselves, such that the IRMSCA  100  can be used in plants that do not have rails  24  atop the D-ring wall  25 . A minimum working load limit (WLL) of  7 . 5  tons ensures it can handle most of the reactor services routine lifts. Rails  15  extend beyond either end of the support frame  1  to permit material handling between both ends of the cavity and refuel floor. The extended reach of the IRMSCA  100  will speed material handling at the cavity, and use of the polar crane is eliminated for these typical RFO activities. 
         [0036]    As shown most clearly in  FIGS. 10 and 12 , the hoist  16  is connected to a hoist rail  14 . The hoist  16  is moveable along the rail  14  by a hoist motor that is operatively coupled to the hoist  16  and the hoist rail  14  to translate the hoist  16  along the hoist rail  14  in a first direction. The hoist rail  14  is elongate having a first end and a second end. The hoist rail ends are respectively coupled to a first transverse rail  15   a  and a second transverse rail  15   b,  which are coupled to the support frame  1  and positioned substantially transverse to the hoist rail  14 . The hoist rail  14  is moveable along the transverse rails  15  in a second direction, transverse to the first direction, by one or more motors that operative connect the transverse rails  15  and the support frame  1 . Preferably, the transverse rails  15  extend outward away from the IRMSCA  100 . This extension increases the reach of the hoist  16 , allowing it to be used to lift equipment from a greater range of storage locations. In this manner, the IRMSCA  100  can be used to access and move equipment that is outside of the D-ring wall  25 . 
         [0037]      FIG. 2  shows an elevation view (operating plant configuration) of the IRMSCA  100 . The IRMSCA  100  is anchored to the D-rings  25  towards the top of the illustration, corresponding to their location near the top of the inner containment building wall. The refueling floor RF is shown near the upper portion of the reactor vessel and associated integrated head assembly (IHA), which contains the control rods, CRDMs, and related equipment, and the cavity floor CF is shown at the bottom portion of the reactor vessel.  FIG. 3  shows an isometric view (operating plant configuration) of the IRMSCA  100 , similarly illustrating the vertical layout of these components. 
         [0038]      FIG. 4  shows an isometric view (operating plant configuration—near) of the IRMSCA  100 . During plant operation, the clevises  4  are pinned to the support brackets  26 , a preferred embodiment of which is illustrated in more detail in  FIG. 14 . (For ease of illustration, only one instance of the support brackets  26  is referenced in  FIG. 4 .) Thus, as illustrated more clearly in  FIG. 5 , the IRMSCA  100  through clevises  4 , clevis pins  41 , and support brackets  26 , is secured to the D-rings  25  and, thus, the containment building structure. As illustrated, an anchor bolt  42  embedded with the D-ring  25  may be used to securely retain the IRMSCA  100  in place. The anchor bolts  42  should be positioned such that when the IRMSCA  100  is retained in place, the missile shield  20  is located directly above the IHA to protect against any control rods or CRDMs that may become dislodged from the IHA (the typical function of missile shields). As shown in, for example,  FIG. 12 , the missile shield  20  of the present invention can be much smaller than traditional missile shields. This reduction in size facilitates their movement, further facilitating RFO operations. When the pins  41  are removed, as illustrated in  FIG. 6 , the clevises  4  can be raised clear of the support brackets  26 , rendering the IRMSCA  100  free to roll along the rails  24  atop the D-ring  25 . The IRMSCA  100  is still supported by the D-ring  25 , but not rigidly so. With clevises  4  so disengaged, the IRMSCA  100  can function as an enhanced reactor services crane. 
         [0039]    Alternatively, the IRMSCA  100  can be configured to traverse the D-ring walls themselves, such that the IRMSCA  100  can be used in plants that do not have rails  24  atop the D-ring wall  25 . This embodiment of the IRMSCA  100  is illustrated in  FIGS. 40-45 .  FIG. 40  shows an isometric view of the IRMSCA  100  in the plant operation configuration. It is seen that there are no rails atop the D-ring wall  25 . To accommodate this plant configuration, the IRMSCA  100  includes vertical wheels  30  that are in direct contact with the floor of the D-ring wall  25 . Additional wheels  31  may be provided on the side of the IRMSCA  100  for horizontal stability between the walls  25 .  FIG. 41  shows a front elevation view of the IRMSCA  100  affixed to the D-ring wall  25  in the plant operation configuration.  FIG. 42  shows a detailed view of the IRMSCA  100  anchorage, which is substantially the same as that of  FIG. 5  but with the IRMSCA  100  resting on wheels  30  instead of rails  24 .  FIG. 43  shows a side elevation view of the IRMSCA  100  affixed to the D-ring wall  25  in the plant operation configuration. The wheels  30 ,  31  are seen to be in contact with the D-ring wall  25 . 
         [0040]      FIGS. 44-45  show the wheeled IRMSCA  100  in refueling configuration.  FIG. 44  shows a view similar to that of  FIG. 43 , but clevises  4  retracted from the support brackets  26 .  FIG. 45  shows a detailed view similar to that of  FIG. 6 . It is seen that the IRMSCA  100  is free to roll atop the D-ring  25  along its wheels  30 . 
         [0041]    For ease of description, the IRMSCA  100  may be described herein as rolling on the D-ring rails  24 . However, it should be understood that such discussion includes the wheeled mode wherein the IRMSCA  100  rolls atop the D-ring wall  25  itself with no rails  24  present. 
         [0042]      FIGS. 7 and 8  show plan views of the IRMSCA  100 .  FIG. 7  shows the IRMSCA with the hoist  16  positioned in a first, north side of the containment building. In  FIG. 8 , the IRMSCA is shown with the hoist  16  positioned in a second, south side of the containment building. The hoist  16  can be repositioned by translation along the rails  24 .  FIG. 12  shows a bottom isometric view of the IRMSCA  100 , including the hoist  16 , hoist rail  14 , rail extensions  15 , and associated machinery to translate the hoist  16 .  FIG. 10  shows a suspension crane of the IRMSCA  100 . At a minimum, the suspension crane and supporting IRMSCA  100  structure shall be load tested as an assembly at 300% of the 7.5 ton WLL. 
         [0043]      FIG. 9  shows a plan view of the IRMSCA  100 . Here, the IRMSCA  100  is in the refueling configuration with the hoist  16  positioned in the second, south location of  FIG. 8 . The IRMSCA  100  has been moved along the rails  24  atop of the D-Ring  25  and positioned so that it is offset from the reactor vessel. This allows the vessel head to be removed. The IRMSCA&#39;s integral crane rail extensions  15  and crane  16  expands its benefits; it can be used for equipment transfer to and from the refuel cavity, fuel transfer, tube blank flange installation and removal, internal indexing fixture (IIF) installation and removal from the reactor vessel, any CRDM component (for example, lead screw, stator, and motor tube) handling, and other reactor services activities. 
         [0044]      FIG. 13  shows a preferred rolling missile shield assembly  20  for the IRMSCA  100  of the present invention. The IRMSCA  100  contains a number of components and/or subassemblies, including: a missile shield support frame assembly  1 , a plurality of long missile shield handrail assemblies  2 , a plurality of movable drive frame assemblies  3 , a plurality of missile shield support clevis assemblies  4 , a plurality of missile shield support nuts  5 , a plurality of side missile shield handrail assemblies  6 , a plurality of safety gates  7 , a motor  8 , a plurality of gear boxes  9 , a gear shaft  10 , a plurality of missile shield lower ladder assemblies  11 , a hoist rail access catwalk assembly  12 , and a plurality of short missile shield handrail assemblies  13 . 
         [0045]      FIGS. 15 through 39  illustrate exemplary operations that can be achieved using the IRMSCA  100 . These figures show the IRMSCA  100  in an exemplary nuclear power plant. These figures are shown in the perspective of looking down at the plant equipment from above, at the D-ring  25  location. In  FIGS. 15 and 16 , the IRMSCA  100  is positioned above the IHA. This is the fixed position of the IRMSCA  100 , in which the missile shield  20  is in its operational position. The hoist  16  is positioned in the first, north side of the containment building as in  FIG. 7 . 
         [0046]    In  FIG. 17 , the IRMSCA  100  is being used to remove hardware that retains the IHA and/or other equipment in place during plant operation. 
         [0047]    In  FIGS. 18-20 , the IRMSCA  100  is being used to move equipment to and from the reactor cavity. Movement of the hoist  16  can be accomplished by moving the entire IRMSCA  100  along the D-ring rails  24  or building support surface, by retaining the IRMSCA in place and moving the hoist rail  14  along the transverse rails  15 , or by a combination thereof. The hoist  16  is then used to lower a hook or other coupling device in known manner to the equipment to be moved. The equipment is secured to the coupling device, and the hoist  16  is used to lift the equipment to the desired location, where it is lowered and disconnected from the coupling device. In  FIGS. 18 and 20 , the hoist  16  is positioned over the reactor cavity.  FIG. 19  illustrates the position of the IRMSCA  100  intermediate the steps illustrated in  FIGS. 18 and 20 . Here, the IRMSCA  100  has been translated toward the left side of the page (the north side of the exemplary power plant) along the building support surface, and the IHA is visible. 
         [0048]    In  FIG. 21 , the CRDM lead screws have been raised, lifted by the hoist  16  as a prerequisite to IHA removal and storage during the RFO. 
         [0049]      FIG. 22  shows the IRMSCA  100  at the southernmost location in the exemplary plant, adjacent the end of the building support surface rails  24 / 25 . In this position, the IRMSCA  100  is out of the way so that the polar crane can be used to lift the IHA and move it to a suitable storage position. 
         [0050]      FIGS. 23-31  show the IRMSCA  100  as used to work with the IIF. In  FIG. 23 , the IRMSCA  100  is positioned with the hoist above the IIF. The hoist  16  is used to lift the IIF, and the IRMSCA  100  moves the IIF for installation to the reactor vessel flange, as shown in  FIG. 24 .  FIG. 25  shows the IRMSCA  100  towards the north end of the exemplary power plant, allowing the polar crane to access and move the core support assembly and plenum from the reactor vessel to their storage location. In  FIG. 26 , the IRMSCA  100  is in position to remove the IIF from the reactor vessel and move it to its storage position, as shown in  FIG. 27 . Fuel rods can now be transferred to and from the reactor vessel. After the fuel transfer is complete, the IRMSCA  100  reinstalls the IIF on the vessel flange, as shown in  FIG. 28 . In  FIG. 29 , similar to  FIG. 25 , the IRMSCA  100  is positioned towards the north end of the exemplary power plant so the plenum can be repositioned. Finally, in  FIGS. 30 and 31 , the IIF is removed from the vessel flange and positioned in its storage location. 
         [0051]      FIG. 32 , similar to  FIG. 22 , the IRMSCA  100  is in its southernmost location in the exemplary plant, adjacent the end of the building support surface rails  24 / 25 . In this position, the IRMSCA  100  is out of the way so that the IHA can be repositioned on the reactor vessel. 
         [0052]    In  FIG. 33 , the CRDM lead screws are lowered from their parked position in the IHA. 
         [0053]    In  FIGS. 34-37 , the IRMSCA  100  is being used to move equipment to and from the reactor cavity similarly as done in  FIGS. 18-20 . 
         [0054]    Finally, in  FIG. 38  the IRMSCA  100  is used to reinstall hardware that retains the IHA and/or other equipment in place during plant operation, and in  FIG. 39  the IRMSCA  100  is positioned above the IHA. This is the fixed position of the IRMSCA  100 , in which the missile shield  20  is in its operational position. The hoist is positioned in the first, north side of the containment building away from the IHA so that it is not between the IHA and the missile shield. 
         [0055]    The reactor building polar crane is typically used in many RFO operations. Such operations frequently are delayed due to the reactor building polar crane being used for other tasks. Thus, the use of the hoist  16  of the IRMSCA  100  of the present invention to perform the functions discussed above, in lieu of the reactor building polar crane, frees the polar crane to be used in other RFO operations. The time saved increases efficiency and could reduce the overall duration of the RFO, allowing the plant to be brought back on-line more quickly, which reduces the monetary costs associated with such outages. 
         [0056]    While the preferred embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Furthermore, while certain advantages of the invention have been described herein, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.