Abstract:
A device is provided for repairing a damaged location in an underwater region of a wall of a vessel or pool, in particular in the region of a wall of a pool of a nuclear reactor plant. The device includes a guiding system, which can be attached along a side wall at a distance therefrom and can be fixed thereto, for guiding a carriage which can be made to move in a longitudinal direction of the guiding system. Arranged on the carriage is a displaceably mounted holder for a repair support, which can be placed with an adhesive surface against the wall region containing the damaged location. With such a device, wall regions that are at a great depth and can only be accessed through narrow gaps can be repaired quickly and reliably.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application, under 35 U.S.C. §120, of copending international application PCT/EP2009/052715, filed Mar. 9, 2009, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application DE 10 2008 014 544.0, filed Mar. 15, 2008; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to an apparatus for repairing a damaged area in an underwater wall region of a vessel or pool, in particular in a wall region of a pool in a nuclear reactor plant. 
         [0003]    The wall surfaces (side walls and bottom surface) of water-flooded pools in a nuclear reactor plant, for example the reactor pit or the fuel assembly storage pool, are provided with a liner of steel plates which are welded together. The welds by which the steel plates are welded to one another or to a substructure are vulnerable to chlorine-induced stress corrosion cracking owing to mechanical stresses inevitably occurring during welding. In order to prevent pool water from escaping through such cracks into the concrete wall, they need to be sealed. In order to ensure sufficient shielding of the maintenance staff against radioactive radiation during such a repair, the water cannot be drained, in particular in a fuel assembly storage pool which is loaded with fuel assemblies, and therefore the repairs must take place under water. The side wall regions in such a fuel assembly storage pool, however, are not easily accessible since only a small gap is available between the fuel assembly storage rack, located in the fuel assembly storage pool, and the side walls. 
         [0004]    In principle it is known, for example from published, non-prosecuted German patent application DE 100 26 649 A1, to seal such cracks by applying an adhesive or by adhesively bonding repair overlays onto them. To this end, the repair overlay was affixed either manually by a diver or using a linkage system on the wall which is operated from the pool edge. However, it is not possible to repair, in this fashion, damaged areas which are not easily accessible and are located at great depth under the water surface. 
       SUMMARY OF THE INVENTION 
       [0005]    It is accordingly an object of the invention to provide an apparatus for repairing a damaged area in an underwater wall region of a vessel or a pool, in particular in the wall region of a pool in a nuclear reactor plant, which overcomes the above-mentioned disadvantages of the prior art devices of this general type, by which it is possible to repair even areas which are not easily accessible. 
         [0006]    The problem stated is achieved according to the invention by way of an apparatus which contains a guidance system, which can be attached along a side wall at a distance therefrom and fixed thereto, for guiding a carriage which is displaceable in a longitudinal direction of the guidance system. Arranged on the guidance system is a displaceably mounted holder for a repair overlay which can be placed, by way of an adhesive surface, against the wall region containing the damaged area. 
         [0007]    Such an apparatus can be used to reach side wall regions and edge regions of the bottom surface which adjoin the side wall regions, both of which, wall regions and edge regions, are accessible only via a narrow gap due to fixtures located inside the pool, such as the fuel assembly storage racks in a fuel assembly storage pool. 
         [0008]    The use of a carriage, which can be placed on rails on the guidance system, which is fixed to the side wall, and is displaceable in the longitudinal direction of the guidance rail, for transporting the repair overlay to the damaged area can make it possible to bring a repair overlay, which is provided with a viscous flowable adhesive, into the correct work position very quickly since the position was previously locationally fixed by way of the attachment of the guidance rail. In other words, the guidance rail can be attached and positioned very precisely without any time pressure, since the repair overlay, which is provided with the adhesive, is not transported to the damaged area until the guidance rail has been installed. 
         [0009]    If the carriage is not motorized and displaceable into an end position exclusively by the action of gravity, the configuration of the apparatus is simplified considerably. 
         [0010]    Installing the guidance system in situ is simplified if it is assembled from sections which are releasably connected to one another. 
         [0011]    The guidance system is preferably composed of two parallel guidance rails. In this manner it is possible to better absorb the forces and torques acting on the guidance system via the carriage when the repair overlay is pressed against the wall. 
         [0012]    A particularly simple way of fastening the guidance system to the side wall is possible if suction cups, which are connected to a suction line, are arranged on the guidance system. 
         [0013]    Positioning of the guidance rails in narrow gaps is simplified if at least one suction cup is mounted on the guidance system such that it is displaceable transversely to the longitudinal direction thereof. 
         [0014]    Safe transport of the repair overlay to the repair area is permitted if the repair overlay can be fixed in the holder by producing a negative pressure on a rear side which is applied to the adhesive surface. Owing to this measure it is also possible to simply remove or release the repair overlay when the latter is permanently fixed to the wall once the adhesive has cured. 
         [0015]    High pressure forces for a secure adhesive bond are achieved in particular when the holder is pneumatically displaceable. 
         [0016]    In a particularly advantageous embodiment of the invention, the apparatus contains a frame which surrounds the holder and is mounted displaceably in the advancement direction of the holder with a bias relative thereto, the frame having a lip which extends into the interior space surrounded by the frame and the inner edge of which is aligned with the outer edge of the repair overlay in the advancement direction and protrudes beyond the repair overlay in a starting position. This measure prevents the adhesive, which seeps out laterally when the repair overlay is pressed against the wall region to be repaired, from spreading on the wall outside the repair overlay or from dripping off. 
         [0017]    If there is also a collection space located between the frame and the holder and surrounding them, the adhesive which is wiped off by the lip is reliably captured and does not reach the pool interior. 
         [0018]    The lip preferably consists of a spring plate with the result that the lip bears against the wall as uniformly and tightly as possible. 
         [0019]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0020]    Although the invention is illustrated and described herein as embodied in an apparatus for repairing a damaged area in an underwater wall region of a vessel or a pool, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0021]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a diagrammatic, side view of an apparatus in a work position in a fuel assembly storage pool according to the invention; 
           [0023]      FIG. 2  is a diagrammatic, plan view of the apparatus; 
           [0024]      FIG. 3  is a diagrammatic, perspective view of a lower part of the apparatus with a carriage, which holds a repair overlay, in an end position; 
           [0025]      FIG. 4  is a diagrammatic, cross-sectional view through the carriage with the repair overlay located thereon; and 
           [0026]      FIG. 5  is a diagrammatic, perspective view of an alternative embodiment of the apparatus according to the invention, which is suitable for repairs in the region of an inner edge. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    Referring now to the figures of the drawing in detail and first, particularly, to  FIGS. 1 and 2  thereof, there is shown an apparatus according to the invention in a work position in a water-flooded fuel assembly storage pool  2  of a nuclear reactor plant. The apparatus contains a supporting frame  4 , held in a rack  3  which is placed at a pool edge, for a guidance system  6 , which extends in a longitudinal direction, is composed of two mutually parallel guidance rails  6   a ,  6   b  and is assembled from a plurality of sections  8 . Arranged on the guidance system  6 , or on the guidance rails  6   a ,  6   b , is a plurality of suction cups  10  which can be supplied with negative pressure via a non-illustrated suction line and can in this manner fix the guidance system  6  to a side wall  12 , which extends vertically in the example, at a distance therefrom. 
         [0028]    In the exemplary embodiment, the guidance system  6  is linear in an upper region and inclined with respect to the side wall  12  in order to thus bridge fixtures  14  which are located in the upper region of the fuel assembly storage pool  2  and shown schematically in  FIG. 1 . The inclined region merges at the free end of the guidance system  6  into an end section  80  which is parallel to the wall surface  12  and is connected in an articulated manner to the neighboring section  8  with limited clearance. 
         [0029]    The suction cups  10  are arranged in each case in pairs at a free end of the limbs of U-shaped retaining brackets  16 , which grip around the guidance rails  6   a ,  6   b , with the length of the limbs decreasing according to the necessary inclination as the distance from the supporting frame  4  increases. 
         [0030]    The free end of the guidance system  6  is inserted into a gap between the side wall  12  and a fuel assembly storage rack  18  (illustrated schematically) and fixed to the wall likewise via the plurality of suction cups  10 .  FIG. 1  shows a situation in which a carriage  20 , which is placed onto the guidance rails  6   a ,  6   b  of the guidance system  6  and support a repair overlay  22  which is provided with an adhesive surface, is in the work position at a damaged area  21  in the side wall  12 . The work position is locationally fixed by way of the position of end stops for the carriage  20  on the guidance system  6 . The damaged area  21  and the exact position thereof was found in a prior examination and measured, such that the guidance system  6  can be positioned accurately—position at the pool edge and depth position. The carriage  20  is not motorized and is lowered into the work position using a cable winch located on the supporting frame  4  into its end position exclusively under the action of gravity. 
         [0031]    It can be seen from the plan view according to  FIG. 2  that the suction cups  10  are arranged on both sides of the guidance rails  6   a ,  6   b  such that they are at a distance therefrom in order to permit the carriage  20  to pass between them.  FIG. 2  also shows that the number of suction cups  10  is higher in the region of the free end of the guidance system  6  in order to absorb the opposing forces resulting from pressing the repair overlay  22 , which is transported by the carriage  20 , against the wall and to ensure that the guidance system  6  remains in its fixed location on the side wall  12 . 
         [0032]    The enlarged perspective illustration of the end section  80  according to  FIG. 3  shows that the carriage  20 , which is moved into its end position up to a stop, supports a holder  30  which is mounted on the carriage  20  such that it can be displaced transversely to the longitudinal direction of the guidance system  6  into an advancement direction  31  (indicated by an arrow) and holds the repair overlay  22 . Seven suction cups  10 , which can be deployed preferably pneumatically in each case using pneumatic cylinders, of which only pneumatic cylinder  33  of the suction cup pair shown on the left can be seen, in pairs (the upper four suction cups  10 ) or in a group of three (the lower three suction cups  10 ) in the direction of the double-headed arrow  32  transversely to the longitudinal direction of the guidance system  6 , are provided in the exemplary embodiment in order to fix the end section  80  in the region of the repair area. This has the advantage that the suction cups  10  located in the region of the free end can, when the guidance system  6  is inserted into the narrow gap, be moved back into a position which makes the insertion into the narrow gap, which is located at a depth of about 10 m under the water, easier. Once the apparatus has been positioned on the side wall  12 , the suction cups  10  can be placed against the side wall  12  and fixed to it by the application of negative pressure. The distance available to the carriage  20  from the side wall  12  can be increased by further extending the suction cups  10 . 
         [0033]    The suction cups  10  are spring-mounted relative to the guidance system  6  in the longitudinal direction with limited clearance S in both directions (toward the free end and away therefrom), with the result that once the suction cups  10  have been fixed to the side wall  12 , later adjustments to the carriage in the longitudinal direction are still possible by way of displacing the guidance system  6  in this direction. 
         [0034]    In order to facilitate the guidance of the apparatus along the side wall  12  and the insertion of the end section  80  into the gap, the gap has, at the distal end, rollers or bearing balls  34  which can roll along the wall. 
         [0035]    According to  FIG. 4 , the guidance rails  6   a ,  6   b  have, in the exemplary embodiment, a profile which is square in cross section. The carriage  20  has U-shaped runners  40   a ,  40   b , the bases of which are inclined with respect to each other—90° in the example—and by which the carriage  20  is placed onto the guidance rails  6   a ,  6   b . One limb of the U-shaped runner  40   a ,  40   b  is here formed in each case by a conical roller  42   a ,  42   b  which bears against a side surface of the guidance rail  6   a  or  6   b  in each case by way of its conical surface. Owing to the mutually inclined arrangement of the bases of the U-shaped runners  40   a ,  40   b , the carriage  20  is secured transversely to the longitudinal direction of the guidance system  6  (vertically with respect to the plane of the drawing in the figure) on the guidance rails  6   a ,  6   b.    
         [0036]    The holder  30  arranged on the carriage  20  contains a punch  50  which is displaceable, using a pneumatic unit  52 , transversely to the longitudinal direction of the guidance system  6  in the direction of the double-headed arrow  31 . The punch  50  is surrounded by a supporting frame  54  which is mounted axially such that it is displaceable relative to it and on which the repair overlay  22 , which is provided with adhesive (not shown in the figure for reasons of clarity) on the flat side which is remote from the punch, is placed by way of its edge. 
         [0037]    A plurality of suction cups  51 , by which the repair overlay  22  is fixed in the holder  30  for transport, is likewise axially spring-mounted in the punch  50 . In order to enhance the stability, guidance studs  56 , which guide the punch  50  during operation of the pneumatic unit  52 , are additionally provided. 
         [0038]    The holder  30  is additionally surrounded by a frame  60 , which is mounted such that it is axially displaceable to it and which contains a lip  62 , consisting for example of an angled-away spring plate, which extends into the interior space surrounded by the frame  60  and an inner edge  64  of which is aligned with an outer edge  65  of the repair overlay  22  in the advancement direction  31 . In a starting position, the inner edge  64  protrudes beyond the repair overlay  22  by a distance a and is biased with respect to the holder  30  with the aid of pneumatic cylinders having a specified force. 
         [0039]    Advancing the holder  30  with the aid of the pneumatic unit  52  causes the lip  62  to first touch the side wall  12 , before the latter comes into contact with the adhesive surface of the repair overlay  22  which is provided with the adhesive. As the holder  30  is advanced further, the bias of the frame  60  is overcome and the adhesive surface of the repair overlay  22  comes into contact with the wall surface of the side wall  12 , wherein a gap between the rear side of the repair overlay  22  and a contact pressure surface  58  of the holder  30  is closed when the contact pressure force is increased by way of the spring-mounted suction cups  51 , with the result that an areal contact pressure force occurs. While the repair overlay  22  is pressed against the wall surface, the excess adhesive which seeps out laterally is wiped off by the lip  62  into a collection space  66  which is located between the frame  60  and the holder  30  and surrounds it. The contact pressure force is maintained until the adhesive is cured. When the adhesive is cured, the suction cups  51  are aerated, the punch  50  is withdrawn and the carriage  20  is pulled up with the aid of the cable winch. 
         [0040]    In principle it is also possible to modify the apparatus which is explained in more detail in  FIGS. 1 to 4  in a manner such that it is made possible to repair the edge regions of the bottom surface which adjoin the side walls, for example by arranging the holder for the repair overlay such that it can pivot relative to the carriage, with the result that the repair overlay can even be placed or pressed against surfaces, which are inclined or oriented at right angles to the longitudinal direction of the guidance system, by way of advancing the holder. 
         [0041]    The apparatus according to the invention is also not only suitable for adhesively bonding planar wall surfaces, but can also correspondingly be fitted to differently shaped wall surfaces by repair overlays which are matched to the respective contour of the wall.  FIG. 5  shows such an exemplary embodiment. For the purpose of repairing a damaged area in the region of a side edge of a pool, an angle profile as the repair overlay  22  with a holder, which has been correspondingly modified in terms of its configuration, and the guidance system  6  with the suction cups  10 , which are correspondingly aligned with respect to one another at 90° and can be used to fix the guidance system to two adjoining side walls, are provided in this case. The holder is mounted on the carriage  20  such that it is displaceable transversely to the longitudinal direction of the guidance system  6  in this exemplary embodiment, too. Accordingly, cylindrical vessels or tubes can also be repaired using holders, guidance systems and repair overlays which are adapted correspondingly in terms of design.