Abstract:
Provided is an apparatus for inspecting a structure including a heating tube, a tube sheet supporting the heating tube, and a flow distribution baffle, which are installed in a steam generator of a nuclear power plant, and more particularly, an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, in which a detector is inserted into gaps of a bundle of heating tubes of an upper portion of a secondary side of a steam generator so as to inspect sludge or foreign objects, and a foreign object remover removes foreign objects when foreign objects are discovered in the gaps of the heating tubes.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0059646, filed on Jul. 1, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for inspecting a structure including a heating tube, a tube sheet supporting the heating tube, and a flow distribution baffle, which are installed in a steam generator of a nuclear power plant, and for removing a foreign object, and more particularly, to an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, in which a detector is inserted into gaps of a bundle of heating tubes of an upper portion of a secondary side of a steam generator so as to inspect sludge or foreign objects, and a foreign object remover removes foreign objects when foreign objects are discovered in the gaps of the heating tubes. 
     2. Description of the Related Art 
     Generally, a steam generator is one of main facilities required to produce power from a steam turbine and a power generator in a nuclear power plant. 
     In detail, a plurality of heating tubes formed in a bundle are disposed in the steam generator. The heating tube performs as a heat exchanger between primary system water containing radioactivity and secondary system water turning a turbine, and separates the primary system water from the secondary system water. 
     Steam is generated as follows. The primary system water heated while passing through a nuclear reactor flows through a path in the heating tube of the steam generator. The secondary system water provided out of the heating tube contacts an external wall of the heating tube. Thus, heat exchange is performed between the primary system water and the secondary system water. The primary system water flows through the path of the heating tube, and circulates through the nuclear reactor. In addition, the secondary system water is changed to steam. 
     That is, radioactive water (i.e., the primary system water) with high temperature and pressure flows in the heating tube, and nonradioactive water (i.e., the secondary system water) flows out of the heating tube, wherein a wall of the heating tube is disposed between the primary system water and the secondary system water. Thus, if the heating tube is damaged, the radioactive water (i.e., the primary system water) flowing through the heating tube may be mixed with the nonradioactive water (i.e., the secondary system water) to be contaminated while leaking out of the heating tube, and thus radioactive contamination may occur throughout a space to which steam changed from the nonradioactive water (i.e., the secondary system water) is provided. Accordingly, it is most important to ensure reliability of heating tubes in various operations in a nuclear power plant. 
       FIG. 1  is a cross-sectional view of a conventional steam generator  10 .  FIG. 2A  is a front cross-sectional view of the steam generator  10  of  FIG. 1 .  FIG. 2B  is a cross-sectional view for explaining a mechanism of the steam generator  10  of  FIG. 1 . 
     Referring to  FIGS. 1 ,  2 A and  2 B, the steam generator  10  includes an inlet nozzle  1  into which a reactor coolant of a primary system flows, a heating tube  3  where heat exchange is performed, and an outlet nozzle  5  transferring heat from the reactor coolant flowing into the inlet nozzle  1  to a reactor coolant of a secondary system disposed out of the heating tube  3 . The heating tube  3  is mounted on a tube sheet  4 , and is supported by tube support plates  6  that are vertically arranged at predetermined intervals. A flow distribution baffle  8  shaped like a doughnut plate is installed between the lowest tube support plate  6  and the tube sheet  4  so as to support the heating tube  3 . The heating tube  3 , and the tube support plate  6  that are vertically arranged at predetermined intervals so as to support the heating tube  3  are coupled to a wrapper  20  of which a lower portion is opened and of which an upper portion has a steam outlet  21 . Water is provided into the lower portion of the wrapper  20  along an inner wall of an external housing  2 . The provided water generates steam by the heating tube  3 , and then the steam is discharged upwards. 
     The steam generator  10  having the above-described structure generates heat as follows: the reactor coolant of the primary system flows through the inlet nozzle  1  in the heating tubes  3 , passes through the outlet nozzle  5 , and transfers heat to the reactor coolant of the secondary system disposed out of the heating tubes  3 , thereby generating steam. 
     A portion of the steam generator  10  where a reactor coolant flows is referred to as a primary side, and a portion of the steam generator  10  where water is fed and steam flows is referred to as a secondary side. The secondary side of the steam generator  10  includes a main steam system, a turbine system, a condensate water system, and a feed-water system. 
     Thus, steam generated by the secondary side of the steam generator  10  moves through a main steam tube, and turns a turbine. 
     However, conventionally, when the steam generator  10  generates steam, although secondary water is filtered and chemically-treated so as to be provided to the secondary side, the secondary water accompanied with foreign objects and sludge which are generated due to various reasons while circulating in the heating tube  3  flows into the steam generator  10 . Thus, the foreign objects and sludge may be deposited onto the tube sheet  4 , the tube support plate  6 , the flow distribution baffle  8 , etc. or may be stuck to an external wall of the heating tube  3 , thereby reducing heating efficiency of the steam generator  10  or damaging the steam generator  10 . 
     That is, the steam generator  10  has a structure in which several thousands of U-shaped heating tubes  3  are disposed in a bundle type, both ends of the heating tube  3  are fixed to the tube sheet  4 , and the heating tube  3  are supported by the tube support plates  6  that are vertically arranged so as to have seven steps at an interval of about 1 m up to an upper portion of the heating tube  3 , as illustrated in  FIG. 2 . Impurities as scale generated due to various reasons when driving soft water flows are stuck to a surface of the heating tube  3 , thereby reducing heat-exchange efficiencies. The impurities are deposited as sludge and are gradually solidified between the heating tube  3  and the tube support plate  6 , and thus denting occurs between the tube support plate  6  and the heating tube  3 , thereby damaging the heating tube  3 . Accordingly, it is necessary to remove scale stuck to the surface of the heating tube  3  and sludge deposited on the tube support plate  6  in order to ensure efficiencies of the steam generator  10  and reliability of the heating tube  3 . 
     To achieve this, a small-sized endoscope camera has been used to check states of the flow distribution baffle  8 , the heating tube  3  and the tube sheet  4 . 
     However, an operator needs to manually push the endoscope camera into a gap of a heating tube through a guide tube. Since the endoscope camera does not include an element for supporting the endoscope camera, the endoscope camera cannot find out and check a desired position. In addition, since a steam generator is surrounded by high radioactivity, an operator may be exposed to radioactivity, and therefore it is difficult to visually inspect or remove foreign objects. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, in which a detector is inserted into a gap of a bundle of heating tubes of an upper portion of a secondary side of a steam generator so as to inspect sludge or foreign objects, and a foreign object remover removes foreign objects when foreign objects are discovered in the gap of the heating tube. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to an aspect of the present invention, there is provided an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, the apparatus including: a mounting fixture fixed to a flange surface of a hand hole of the steam generator by a bolt; a guide rail of which one side is fixed to the mounting fixture, wherein a first end of the guide rail is coupled to a center stay rod disposed at a central portion of the steam generator, and a second end of the guide rail is coupled to a driver; a detector coupled to a lower end of the guide rail so as to slide on the lower end of the guide rail, inserted into the steam generator by a moving belt, and visually inspecting and removing a foreign object; the driver supplying power to the detector, wherein one side of the driver is coupled to the guide rail, and is simultaneously coupled to a rail supporter of the mounting fixture; and local and remote controllers adjacent to the steam generator and controlling the mounting fixture, the detector and the driver. 
     The mounting fixture may include a flange having four bolts installed therein so as to fix the mounting fixture to the flange surface of the hand hole of the steam generator; a panning plate of which a front surface is coupled to the flange so as to slide in a lateral direction of the flange; a tilting lever hinged to a rear surface of the panning plate so as to optionally tilt; the rail supporter coupled to the tilting lever and supporting the guide rail; and two cable guides disposed on a rear surface of the tilting lever so as to stably accommodate cables from the detector therein and to prevent the cables from being entangled and damaged. 
     The flange may include screw holes formed therein into which the four blots are inserted, respectively, so as to fix the mounting fixture to the flange surface of the steam generator, wherein the screw holes each having a circular shape may be formed in four edges of flange, and the mounting fixture may roll by optionally rotating the flange and then coupling the four bolts to the screw holes, respectively. 
     The flange and the panning plate may include respective connectors, which have corresponding shapes to each other and are formed on surfaces of the flange and the panning plate, which come in contact with each other, the flange and the panning plate may be coupled by sliding the flange and the panning plate on each other, and the panning plate may move right and left by a control pin disposed at both sides of the flange. 
     The tilting lever may include a knuckle joint having a first end in contact with the panning plate, and a second end with a screw thread formed thereon; and a control bolt coupled to the screw thread formed on the second end of the knuckle joint, wherein the tilting lever may tilt by a manner in which the control bolt rotates around the knuckle joint to push the knuckle joint. 
     The rail supporter may include a horizontal and vertical level gage installed thereon, wherein the horizontal and vertical level gage checks a change in an angle of right and left rotation of the mounting fixture, and a change in an angle of horizontal and vertical movement of the mounting fixture. 
     The guide rail may function as a guide of the detector, and may include a plurality of rod-shaped guide rods that are separately coupled to each other. 
     The guide rail may include a first guide rod including a gripper that is disposed at a first end of the first guide rod so as to support and fix the center stay rod of the steam generator to the guide rail by tightening the center stay rod, and a connecting block having a screw hole and formed at a second end of the first guide rod; a second guide rod including a clamping bolt that is disposed at a first end of the second guide rod and is screwed to the screw hole formed in the connecting block so as to be coupled to the first guide rod, and a connecting block disposed at a second end of the second guide rod and having a screw hole formed in the connecting block; and a third guide rod including a clamping bolt that is disposed at a first end of the third guide rod and is screwed to the screw hole formed in the connecting bolt so as to be coupled to the second guide rod, wherein the driver is coupled to a second end of the third guide rod. 
     The apparatus may further include a guiding groove formed in a lower portion of the guide rail, wherein the moving belt is inserted into the guiding groove. 
     The detector may include a detecting portion visually-inspecting and removing sludge or a foreign object in the steam generator, including a photographing sheet and a foreign object remover, and rotating right and left; a detection driving portion supplying power to the detector so as to drive the detecting portion; and a bracket portion connecting the detecting portion to the detection driving portion so as to be coupled to the guide rail. 
     The detecting portion may include a body installed in front of the bracket portion and including a bobbin disposed in the body; a steel belt disposed in the body and having a first end wound on the bobbin; the photographing sheet coupled to a second end of the steel belt and having an end at which a charge-coupled device (CCD) sensor and a light emitting display device (LED) are installed so as to generate a image signal of a visual inspection; and the foreign object remover installed adjacent to the photographing sheet so as to remove a foreign object checked by the photographing sheet. 
     The steel belt may include a plurality of coupling holes formed in a center of the steel belt in a longitudinal direction of the steel belt at predetermined intervals, and the steel belt may be wound into the body according to rotation of the bobbin and an intermittent gear having a plurality of protrusions formed on an outer circumference surface of the intermittent gear, wherein the intermittent gear and the bobbin are disposed in the body. 
     The detection driving portion may include a housing installed at a rear surface of the bracket portion, transferring a driving force to the detecting portion, and coupled to the bracket portion; a tilting motor installed in the housing and supplying power to the detecting portion so as to rotate the detecting portion towards both sides of the detecting portion; and a feeding motor supplying power so that the photographing sheet and the foreign object remover of the detecting portion are extended or reduced out of the body. 
     The driver may include a main housing having an end coupled to the guide rail and simultaneously coupled to the rail supporter of the mounting fixture, and including a bobbin disposed in the main housing and rotated by a plurality of gears; the moving having a first end wound on the bobbin and a second end coupled to the bracket portion of the detector so as to move along the guide rail; and a driving motor rotating the bobbin disposed in the main housing so that the moving belt is wound or loosened and the detector is moved. 
     The main housing may include a pinion gear engaged to an intermittent gear having a plurality of protrusions formed on an outer circumference surface of the intermittent gear, the moving belt may include a plurality of through holes formed therein in a longitudinal direction at predetermined intervals, and the plurality of protrusions of the intermittent gear engaged to the pinion gear may be inserted into the plurality of through holes so that the moving belt is wound or loosened on the bobbin. 
     The apparatus may further include a roller disposed in the main housing and pressurizing the moving belt downwards so that the plurality of protrusions of the intermittent gear engaged to the pinion gear are correctly inserted into the plurality of through holes of the moving belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a cross-sectional view of a conventional steam generator; 
         FIG. 2A  is a front cross-sectional view of the steam generator of  FIG. 1 ; 
         FIG. 2B  is a cross-sectional view for explaining a mechanism of the steam generator of  FIG. 1 ; 
         FIG. 3  is a lateral cross-sectional view for explaining a case where an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator is installed, according to an embodiment of the present invention; 
         FIG. 4  is a cross-sectional view of  FIG. 3 ; 
         FIG. 5  is a schematic perspective view of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention; 
         FIG. 6  is a cross-sectional view of a mounting fixture of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention; 
         FIG. 7  is an exploded perspective view of  FIG. 6 ; 
         FIGS. 8A through 8C  are cross-sectional views for explaining movement of the mounting fixture of  FIG. 6 , according to an embodiment of the present invention; 
         FIG. 9  is a schematic perspective view of a guide rail of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention; 
         FIG. 10  is an exploded perspective view of the guide rail of  FIG. 9 ; 
         FIG. 11  is a perspective view of a detector of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention; 
         FIG. 12  is an exploded perspective view of the detector of  FIG. 11 ; 
         FIG. 13  is a schematic perspective view of a configuration of gears of a detecting portion of a detector of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention; 
         FIG. 14  is a front view for explaining a case where the detecting portion of the detector of  FIG. 11  moves right and left, according to an embodiment of the present invention; 
         FIG. 15  is a perspective view for explaining a case where a foreign object remover is inserted into a guide rail, according to an embodiment of the present invention; 
         FIG. 16  is a reference diagram for explaining a case where the foreign object remover of  FIG. 15  is installed, according to an embodiment of the present invention; 
         FIG. 17  is a perspective view of a driver, according to an embodiment of the present invention; 
         FIG. 18  is an exploded perspective view of the driver of  FIG. 17 ; 
         FIG. 19  is a reference diagram for explaining a case where a moving belt of a driver is inserted into a guide rail, according to an embodiment of the present invention; and 
         FIG. 20  is a diagram for explaining a case where an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator is installed at a steam generator, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator will be described with regard to exemplary embodiments of the invention with reference to the attached drawings. 
       FIG. 3  is a lateral cross-sectional view for explaining a case where an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator is installed, according to an embodiment of the present invention.  FIG. 4  is a cross-sectional view of  FIG. 3 .  FIG. 5  is a schematic perspective view of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention.  FIG. 6  is a cross-sectional view of a mounting fixture  110  of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention.  FIG. 7  is an exploded perspective view of  FIG. 6 .  FIGS. 8A through 8C  are cross-sectional views for explaining movement of the mounting fixture  110  of  FIG. 6 , according to an embodiment of the present invention. 
     Referring to  FIGS. 1 through 8C , the apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator is installed in a hand hole ‘H’ of an upper portion of one side of Westinghouse F-type steam generator disposed in an accommodation room, and includes the mounting fixture  110 , a guide rail  120 , a detector  130 , a driver  140 , a foreign object remover  150 , a local controller  160 , and a remote controller  170 . 
     As illustrated in  FIG. 3 , the mounting fixture  110  is fixed to a flange surface of the hand hole ‘H’ by bolts ‘S’, and is used to stably fix and support the guide rail  120 . As illustrated in  FIGS. 6 and 7 , the mounting fixture  110  includes a flange  111  having four bolts ‘S’ so as to fix the mounting fixture  110  to the flange surface of the hand hole ‘H’, a panning plate  112  whose front surface is coupled to the flange  111  so as to slide in a lateral direction of the flange  111 , a tilting lever  113  hinged to a rear surface of the panning plate  112  so as to optionally tilt, a rail supporter  114  coupled to the tilting lever  113  so as to support the guide rail  120  that will be described, and two cable guides  115  disposed on a rear surface of the tilting lever  113  so as to stably accommodate cables from the detector  130  therein and to prevent the cables from the detector  130  from being entangled and damaged. 
     The mounting fixture  110  having the above-described structure may stably support the guide rail  120  so that the detector  130  may stably move along the guide rail  120 . 
     In detail, the mounting fixture  110  may finely adjust a detection angle of the detector  130  by finely adjusting an angle of the guide rail  120 . With regard to the mounting fixture  10 , four screw holes  110   a  each having a circular shape, to which the bolts ‘S’ are inserted, are formed in four edges of the flange  111 , respectively, so that the mounting fixture  10  is coupled to a steam generator  10 . Thus, the mounting fixture  110  may roll in a direction indicated by an arrow of  FIG. 8A  by optionally rotating the flange  111  and then coupling the bolts ‘S’ to the screw holes  111   a . The flange  111  and the panning plate  112  includes connectors  111   b  and  112   a , respectively, which have corresponding shapes to each other and are formed on surfaces of the flange  111  and the panning plate  112 , which come in contact with each other, as illustrated in  FIG. 7 . In addition, the flange  111  and the panning plate  112  are coupled by sliding them onto each other by the connectors  111   b  and  112   a . The panning plate  112  may be moved in a direction (a horizontal direction) indicated by an arrow of  FIG. 8B  by control pins  116  disposed at both sides of the flange  111 . 
     As illustrated in  FIG. 7 , the tilting lever  113  hinged to the rear surface of the panning plate  112  is coupled to hinge blocks  112   b  screwed to a lower portion of the panning plate  112  by pins  112   c  so as to optionally tilt. In this regard, the tilting lever  113  tilting with respect to the panning plate  112  includes a knuckle joint  117  having a first end in contact with the panning plate  112  and a second end having a screw thread formed thereon so as to optionally tilt with respect to the panning plate  112 , and a control bolt  118  coupled to the screw thread formed on the second end of the knuckle joint  117 . The control bolt  118  rotates around the knuckle joint  117  to push the knuckle joint  117 , and then the tilting lever  113  may tilt in a direction indicated by an arrow of  FIG. 8C . 
     In addition, the tilting lever  113  may include a pair of brackets  113   a  so that lateral surface portions of the rail supporter  114  may be supported by the brackets  113   a . At this time, the rail supporter  114  may be coupled to the flange  111 , the panning plate  112  and the tilting lever  113  so as to pass through the flange  111 , the panning plate  112  and the tilting lever  113  in a horizontal direction. The guide rail  120 , which will be described later, may be fixed to a lower portion of the rail supporter  114 . 
     As illustrated in  FIG. 3 , the mounting fixture  110  having the above-described structure is stably fixed to the flange surface of the hand hole ‘H’ by bolts ‘S’, the guide rail  120  is coupled to the rail supporter  114 , and then the detector  130 , which will be described later, is inserted into the steam generator  10  along the guide rail  120 . By this structure, sludge or foreign objects may be inspected. 
     At this time, the mounting fixture  110  may optionally roll due to the screw holes  111   a  of the flange  111 . Simultaneously, the panning plate  112  may pan with respect to the flange  111  by coupling the connectors  111   b  and  112   a , which have corresponding shapes to each other, by using a dovetail coupling method in which the connectors  111   b  and  112   a  are coupled by sliding them onto each other. In addition, simultaneously, the tilting lever  113  may tilt with respect to the panning plate  112  by hinging the panning plate  112  to the tilting lever  113 . Thus, the rail supporter  114  coupled to the tilting lever  113  may rotate around the center of the hand hole ‘H’ right and left by about 10 to about 15 degrees, and may be finely adjusted in horizontal and vertical directions. 
     In addition, a horizontal and vertical level gage  119  may be installed on the rail supporter  114  so as to check a change in an angle of right and left rotation of the mounting fixture  110 , and a change in an angle of horizontal and vertical movement of the mounting fixture  110 , and thus a change in a movement angle of the mounting fixture  110  may be easily checked. 
       FIG. 9  is a schematic perspective view of a guide rail  120  of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention.  FIG. 10  is an exploded perspective view of the guide rail  120  of  FIG. 9 . 
     A first end of the guide rail  120  is coupled to a center stay rod ‘C’ disposed at a central portion of the steam generator  10 , and a second end of the guide rail  120  is coupled to the driver  140  that will be described later. The second end coupled to the driver  140  is fixed to the rail supporter  114  of the mounting fixture  110 , thereby guiding the detector  130  that will be described later into the steam generator  10  (into the gap of a bundle of heating tubes). 
     As illustrated in  FIG. 9 , the guide rail  120  includes a plurality of rod-shaped rods with a predetermined length, wherein the rods may be separately coupled, and thus the length of the guide rail  120  may be extended or reduced. According to the present embodiment, the guide rail  120  includes three guide rods  121 ,  122  and  123 . 
     In detail, as illustrated in  FIG. 10 , the guide rail  120  includes a first guide rod  121 , a second guide rod  122  and a third guide rod  123 . The first guide rod  121  includes a gripper  124  that is disposed at a first end of the first guide rod  121  so as to support and fix the center stay rod ‘C’ by tightening the center stay rod ‘C’, and a connecting block  125  that is formed at a second end of the first guide rod  121  and has a screw hole  125   a  so as to be coupled to the second guide rod  122 . 
     The second guide rod  122  includes a clamping bolt  126  that is formed at a first end of the second guide rod  122  and is screwed to the screw hole  125   a  formed in the connecting block  125  so as to be coupled to the first guide rod  121 , and a connecting block  125  that is formed at a second end of the second guide rod  122  and includes a screw hole  125   a  formed at the center of center of the connecting block  125  so as to be coupled to the third guide rod  123 , like in the first guide rod  121 . 
     In addition, the third guide rod  123  includes a clamping bolt  126  that is formed at a first end of the third guide rod  123  and is screwed to the screw hole  125   a  formed in the connecting block  125  of the second guide rod  122 , like in the second guide rod  122 , and the driver  140  supplying power is coupled to a second end of the third guide rod  123 . 
     According to the present embodiment, the first, second and third guide rods  121 ,  122  and  123 , that is, three guide rods constitute the guide rail. Alternatively, separate guide rods may be further used to extend or reduce the length of the guide rail  120 , if necessary. 
       FIG. 11  is a perspective view of a detector  130  of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention.  FIG. 12  is an exploded perspective view of the detector  130  of  FIG. 11 .  FIG. 13  is a schematic perspective view of a configuration of gears of a detecting portion  132  of a detector  130  of an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator, according to an embodiment of the present invention.  FIG. 14  is a front view for explaining a case where the detecting portion  132  of the detector  130  of  FIG. 11  moves right and left, according to an embodiment of the present invention.  FIG. 15  is a perspective view for explaining a case where a foreign object remover  132   d  is inserted into a guide rail  120 , according to an embodiment of the present invention.  FIG. 16  is a reference diagram for explaining a case where the foreign object remover  132   d  of  FIG. 15  is installed, according to an embodiment of the present invention. 
     As illustrated in  FIG. 5 , the detector  130  may be coupled to a lower end of the guide rail  120  so as to slide onto the lower end of the guide rail  120 , and may move forwards and backwards by the driver  140  that will be described later. Thus, the detector  130  is inserted into the steam generator  10  along the guide rail  120 , and thus may visually inspect foreign objects, and may simultaneously remove foreign objects. 
     Referring to  FIG. 11 , the detector  130  may visually inspect or remove sludge or foreign objects. The detector  130  may include the detecting portion  132  rotating right and left, a detection driving portion  134  supplying power to the detecting portion  132  so as to drive the detecting portion  132 , and a bracket portion  136  connecting the detecting portion  132  to the detection driving portion  134  so as to be coupled to the guide rail  120 . 
     The detecting portion  132  inserted into gaps of the heating tubes in the steam generator  10  is installed in front of the bracket portion  136  so as to inspect or remove sludge or foreign objects. As illustrated in  FIGS. 12 and 13 , the detecting portion  132  includes a body  132   a  coupled to the bracket portion  136  and having a bobbin ‘b’ formed in the body  132   a , a steel belt  132   b  disposed in the body  132   a  and having a first end wound on the bobbin ‘b’, a photographing sheet  132   c  coupled to a second end of the steel belt  132   b  and having an end at which a charge-coupled device (CCD) sensor and a light emitting display device (LED) are installed so as to generate a image signal of a visual inspection, and the foreign object remover  132   d  installed adjacent to the photographing sheet  132   c  so as to remove sludge and foreign objects, which are checked by the photographing sheet  132   c.    
     As illustrated in  FIG. 13 , the body  132   a  is configured so that a plurality of gears are engaged to each other, wherein the bobbin ‘b’ rotates as the gears rotate. In addition, the steel belt  132   b  is configured to be wound or loosened by a clockwise or counter clockwise rotation from a state where an end of the steel belt  132   b  is wound on the bobbin ‘b’. The body  132   a  includes an intermittent gear ‘g’ having a plurality of protrusions  132   a - 1  formed on a central portion thereof so that the steel belt  132   b  may be smoothly wound on the bobbin ‘b’. The steel belt  132   b  includes a coupling hole  132   b - 1  into which the protrusions  132   a - 1  formed on the intermittent gear ‘g’ are inserted so that the steel belt  132   b  may be wound or loosened on the bobbin ‘b’ according to rotation of the intermittent gear ‘g’. In addition, the steel belt  132   b  may be flexible so as to be easily wound or loosened on the bobbin ‘b’. 
     The foreign object remover  132   d  is installed adjacent to and behind the photographing sheet  132   c , and removes sludge or foreign objects detected by the photographing sheet  132   c . In addition, the foreign object remover  132   d  includes a wire  132   d - 1  extended into or out of the body  132   a  of the detecting portion  132 , and a foreign object removing tool  132   d - 2  installed at an end of the wire  132   d - 1  and having various shapes of a tong, a magnet, a ring, and the like. 
     As illustrated in  FIGS. 15 and 16 , an end of the foreign object remover  132   d  is inserted into a foreign object remover hole  128  formed in the guide rail  120 , and passes along a foreign object remover groove  128   a  of the guide rail  120 , which is manually performed by an operator when foreign objects are discovered. Then, as illustrated in  FIG. 12 , the wire  132   d - 1  is extended out of the detection driving portion  134 , and then passes through a flexible tube  138  that will be described. Then, the wire  132   d - 1  together with the detecting portion  132  is inserted into the gaps of the heating tubes along a groove formed in the body  132   a.    
     The detection driving portion  134  includes a housing  134   a  installed at a rear surface of the bracket portion  136 , transferring a driving force to the detecting portion  132  and coupled to the bracket portion  136 , a tilting motor  134   c  installed in the housing  134   a  and supplying power to the detecting portion  132  so as to rotate the detecting portion  132  towards both sides of the detecting portion  132 , as illustrated in  FIG. 14 , and a feeding motor  134   b  supplying power so that the photographing sheet  132   c  of the detecting portion  132  may be extended or reduced out of the body  132   a.    
     Although not illustrated, the tilting motor  134   c  rotates the body  132   a  in directions of both sides thereof through a spindle (not shown) disposed in the body  132   a , and the feeding motor  134   b  coupled to a bevel gear (not shown) disposed in the body  132   a  rotates the intermittent gear ‘g’ and the bobbin ‘b’ so that the steel belt  132   b  may be wound into the body  132   a.    
     The bracket portion  136  connecting the detecting portion  132  to the detection driving portion  134  may be formed so that an upper portion of the bracket portion  136  is coupled to a lower end of the guide rail  120 , as illustrated in  FIG. 14 . In addition, the bracket portion  136  may be formed so as to slide on the guide rail  120 . As illustrated in  FIG. 12 , the flexible tube  138  may be wound on the wire  132   d - 1  of the foreign object remover  132   d  so as to function as a guide used for the detecting portion  132  to smoothly rotate with respect to lateral surfaces of the bracket portion  136 , and for the foreign object remover  132   d  to be smoothly extended in or out of the detecting portion  132  in a rotating direction of the detecting portion  132 . 
       FIG. 17  is a perspective view of the driver  140 , according to an embodiment of the present invention.  FIG. 18  is an exploded perspective view of the driver  140  of  FIG. 17 .  FIG. 19  is a reference diagram for explaining a case where a moving belt  144  of the driver  140  is inserted into the guide rail  120 , according to an embodiment of the present invention. 
     As illustrated in  FIGS. 17 and 18 , the driver  140  may be coupled to an end of the guide rail  120 , for example, an end of the third guide rod  123  to which the mounting fixture  110  is coupled, may supply power to the detecting portion  132  so that the detecting portion  132  may be moved along the guide rail  120  into the steam generator  10 , and may include a main housing  142 , the moving belt  144 , and a driving motor  146 . 
     As illustrated in  FIG. 17 , an end of the main housing  142  is coupled to the guide rail  120 , and simultaneously may be coupled to the rail supporter  114  of the mounting fixture  110 . As illustrated in  FIG. 18 , the main housing  142  includes an intermittent gear  142   c - 1  engaged to a plurality of gears and having a plurality of protrusions formed on an outer circumference surface of the intermittent gear  142   c - 1 , wherein the intermittent gear  142   c - 1  is engaged to a pinion gear  142   c  so as to drive the moving belt  144 . 
     A first end of the moving belt  144  is wound on the bobbin ‘b’, and a second end of the moving belt  144  is coupled to the bracket portion  136  of the detector  130  so that the detector  130  may move along the guide rail  120 . That is, as illustrated in  FIG. 19 , the first end of the moving belt  144  may be wound on the bobbin ‘b’, and the second end of the moving belt  144  may be coupled to the detector  130  through a guiding groove  127  formed in a lower portion of the guide rail  120  so that the detector  130  may move by as much as a length by which the moving belt  144  wound on the bobbin ‘b’ is loosened. 
     The driving motor  146  is engaged to a plurality of gears disposed in the main housing  142  so that the gears may be engaged to each other and may rotate as the driving motor  146  rotates. Thus, the protrusions of the intermittent gear  142   c - 1  engaged to the pinion gear  142   c  are coupled into a plurality of through holes  145  formed in the moving belt  144  so as to drive the moving belt  144 , and thus the bobbin ‘b’ rotates so that the moving belt  144  may be wound or loosened on the bobbin ‘b’. 
     In detail, with regard to the driver  140 , the bobbin ‘b’ on which the moving belt  144  is wound, and a plurality of gears connected to a motor are disposed in the main housing  142 , and thus the moving belt  144  is driven so as to rotate the bobbin ‘b’ clockwise and counter clockwise, as illustrated in  FIG. 18 . In addition, the gears are coupled to the driving motor  146  that are disposed at one side of the gears. As the driving motor  146  rotates, a gear  142   c  rotates. Then, the intermittent gear  142   c - 1  engaged to the gear  142   c  rotates so that the moving belt  144  wound on the bobbin ‘b’ may be wound or loosened so as to move the detector  130 . 
     The gears installed in the main housing  142  includes a bevel gear  142   a  engaged to the driving motor  146 , and the pinion gear  142   c  engaged to the bevel gear  142   a  through a needle gear  142   b  and engaged to the intermittent gear  142   c - 1  having a plurality of protrusions formed on an outer circumference surface of the intermittent gear  142   c - 1 . When the driving motor  146  supplies power, the bevel gear  142   a  rotates, and therefore the pinion gear  142   c  engaged to the bevel gear  142   a  rotates so that the moving belt  144  may be wound on the bobbin ‘b’. 
     As illustrated in  FIG. 18 , with regard to the moving belt  144 , the through holes  145  are formed in a longitudinal direction of the moving belt  144  at predetermined intervals. intermittent gear  142   c - 1  of the pinion gear  142   c  may be inserted into the through holes  145  so that the moving belt  144  may be wound or loosened on the bobbin ‘b’ according to the rotation of the pinion gear  142   c . A roller  147  pressurizing the moving belt  144  downwards is installed at an upper side of the pinion gear  142   c  so that the intermittent gear  142   c - 1  of the pinion gear  142   c  may be correctly inserted into the through holes  145  of the moving belt  144 . 
     A handle  148  is installed at one side of the main housing  142  of the driver  140  so that a worker may manually wind or loosen the moving belt  144  on the bobbin ‘b’. In an emergency, the bobbin ‘b’ may be rotated by manually rotating the handle  148 , and thus the detector  130  may be moved. 
       FIG. 20  is a diagram for explaining a case where an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator is installed at a steam generator  10 , according to an embodiment of the present invention. 
     A local controller  150  is installed around the steam generator  10 , and controls the mounting fixture  110 , the guide rail  120 , the detector  130 , and the driver  140 . The local controller  150  includes a monitor and a control panel. A remote controller  160  is positioned in an operating room remote from the steam generator  10  in order to avoid radioactivity from the steam generator  10 . In addition, the remote controller  10  may perform automatic control using a special operating program, in addition to the same function as that of the local controller  150 , and may record and edit visual inspection data. The local controller  150  and the remote controller  160  have general structures, and thus their detailed description will not be given here. 
     The apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator may operate as follows. 
     First, the mounting fixture  110  is installed on a flange surface of the hand hole ‘H’ of the steam generator  10 . 
     The guide rail  120  on which the detector  130  and the driver  140  are previously mounted is coupled to the mounting fixture  110 . Then, a first end of the guide rail  120  is fixed to the center stay rod ‘C’ installed at the center of the steam generator  10  by the gripper  124  that is disposed at the first end of the guide rail  120 . At this time, the mounting fixture  110  is finely adjusted in horizontal and vertical directions by the control pins  116 , a control bolt  118 , and the like of the mounting fixture  110 . 
     Then, a cable connected to the driver  140  is extended so as to connect the driver  140  to the local controller  150  installed adjacent to the steam generator  10  and the remote controller  160  installed out of a container, and thus foreign objects may be visually inspected and may be removed. 
     After the apparatus for visually inspecting and removing foreign object in gaps of an upper portion of a bundle of a tube sheet of a secondary side of a steam generator is installed, electricity is supplied to the driver  140  through the local controller  150  and the remote controller  160  so as to loosen the moving belt  144  wound on the bobbin ‘b’, and thus the detector  130  may be inserted into the steam generator  10  through the guide rail  120 . 
     The body  132   a  of the detector  130  inserted into the steam generator  10  is rotated by the detection driving portion  134  in a desired direction, and then the bobbin ‘b’ and the intermittent gear ‘g’ may rotate so that the steel belt  132   b  is extended out of the body  132   a . At this time, while the photographing sheet  132   c  is installed at an end of the steel belt  132   b , the gap of the heating tube is inspected through a CCD camera installed at the photographing sheet  132   c , and an image signal of this inspection is transmitted to the remote controller  160 . 
     When foreign objects are discovered in the gap of the heating tube, a worker inserts the foreign object remover  132   d  installed on the detector  130  into the gap of the heating tube through the body  132   a  of the detecting portion  132 . 
     According to the present invention, an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator may visually inspect sludge and foreign objects in the gap of the heating tube disposed on the upper portion of the tube sheet of the secondary side of the steam generator, and simultaneously may remove foreign objects when foreign objects are discovered in the gap of the heating tube. 
     By performing an operation under high radioactivity by remote control, the amount of radioactivity exposed to a worker may be significantly reduced. 
     As described above, according to the present invention, although a technology used in an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator is very simple, technological effects thereof is excellent. 
     Accordingly, according to the present invention, an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator may visually inspect and simultaneously remove foreign objects effectively by inserting a detector visually-inspecting and optionally-removing foreign objects into the steam generator through a hand hole connected to an upper bundle of a secondary side of the steam generator. 
     In addition, due to a mounting fixture, a guide rail may be finely adjusted and stably supported in horizontal and vertical directions, and may be stably supported. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.