Abstract:
A control rod/fuel support grapple is provided which is capable of pulling up simultaneously a control rod and a fuel support from a reactor and also uncoupling the control rod and control rod drive mechanism. The control rod/fuel support grapple comprises a control rod holding unit for holding a control rod&#39;s hoist handle, a fuel support holding unit for holding a fuel support, and a coupling releasing unit or uncoupling the control rod and the control rod drive mechanism, coupled by virtue of a spud coupling. These three units are attached to a main body frame which is lowered into a reactor pressure vessel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control rod/fuel support grapple and, more particularly, a control rod/fuel support grapple which is capable of picking up simultaneously control rods and a fuel support in a boiling water reactor (referred to as a “BWR” hereinafter). 
     2. Description of the Related Art 
     FIG. 8 is a vertical sectional view showing a part of the core of the BWR. As shown in FIG. 8, a cylindrical core shroud  2  is provided in an inside of a reactor pressure vessel  1  and a plurality of fuel assemblies  3  are loaded in the core shroud  2 . A plurality of control rods  4  each having a cruciform lateral sectional shape are arranged vertically movable in clearances between the fuel assemblies  3 . Each of the control rods  4  has a hoist handle  4   d  at its top end. Core reactivity can be controlled by moving up and down these control rods  4  in the core. 
     A top end of the fuel assembly  3  is supported by an upper grid  5 . A bottom end of the fuel assembly  3  is supported by a core support plate  7  via a fuel support  6 . FIG. 9 is a perspective view showing a part of the upper grid  5  of the BWR. As shown in FIG. 9, a plurality of grids into which the top ends of a plurality of fuel assemblies  3  are inserted respectively are formed on the upper grid  5 . 
     As shown in FIG. 10, a plurality of fuel support sustaining holes  7   a  are formed in the core support plate  7 , and the fuel supports  6  can be supported by the core support plate  7  by inserting their cylindrical bottom portions into the sustaining holes  7   a  respectively. As shown in FIG. 11, for example, sustaining holes  6   a ,  6   b ,  6   c ,  6   d  and a cruciform shaped through hole  4   a  are formed on a substantially square cylinder type upper surface portion of the fuel support  6 . Then, bottom portions of four fuel assemblies  3  can be inserted into the sustaining holes  6   a ,  6   b ,  6   c ,  6   d  respectively and then supported thereon. The cruciform control rod  4  can be moved vertically through the cruciform through hole  4   a.    
     The sustaining holes  6   a ,  6   b ,  6   c ,  6   d  of the fuel support  6  are connected to orifices  6   e ,  6   f ,  6   g ,  6   h  formed on a side peripheral wall of the fuel support  6  respectively such that coolant is supplied from the orifices  6   e ,  6   f ,  6   g ,  6   h  to the fuel assemblies  3  via the sustaining holes  6   a ,  6   b ,  6   c ,  6   d  respectively. In addition, a slot  6   i  into which a fixing pin  7   b  (provided on the core support plate  7 ) is inserted is formed on an upper corner portion of the fuel support  6 . The fuel support  6  can be fixed to the core support plate  7  via the slot  6   i.    
     Also, as shown in FIG. 8, a plurality of control rod drive mechanisms (CRDs)  8  are provided so as to pass through a bottom portion of the reactor pressure vessel  1  vertically. The control rods  4  are detachably attached to the control rod drive mechanisms  8  respectively. Top ends of a plurality of control rod guide tubes  9  are coupled to the core support plate  7 . The fuel supports  6  are arranged on the top ends of the control rod guide tubes  9  respectively. The control rod  4  can be driven vertically by the control rod drive mechanism  8  such that the control rod  4  can be inserted into or withdrawn from the core through the inside of the control rod guide tube  9  and the cruciform through hole  4   a  of the fuel support  6 . 
     As shown in FIG. 12, the control rod  4  and the control rod drive mechanism  8  are coupled with each other by a spud coupling type coupling mechanism. More particularly, they are coupled via a spud coupling  10 . A coupling spud  11  whose periphery is divided by cuttings to form quartered latching pawls, for example, is pushed upward by a drive piston (not shown) of the control rod drive mechanism  8 . The coupling spud  11  can be tightly pushed into a clearance formed on the out side of a periphery of a lock plug  12  which is inserted into the fitting holes of a lower end  4   b  of the control rod  4 . As a result, the coupling spud  11  is supported by both an inner peripheral surface of the lower end  4   b  of the control rod  4  and an outer peripheral surface of the lock plug  12 , so that the control rod  4  and the control rod drive mechanism  8  can be coupled with each other. 
     There are two methods of uncoupling the control rod  4  and the control rod drive mechanism  8 , i.e., one is such a method that can be applied from a pedestal side of the bottom portion of the reactor and the other is such a method that can be applied from an upper side of the reactor. In the event that the releasing operation is applied from the pedestal side of the bottom portion of the reactor, as shown in FIG. 12, the lock plug  12  is pushed upward by an uncoupling rod  13  of the control rod drive mechanism  8  against a spring force of a spring  4   c , whereby a coupled state of the control rod  4  and the control rod drive mechanism  8  are uncoupled. 
     In turn, in the event that a releasing operation is applied from the upper side of the reactor, at first the fuel assembly  3  is pulled up from the core. Then, the fuel support  6  can be pulled up from the core by means of a manipulating tool which can manipulate the fuel support  6 . Then, the manipulating tool can be replaced with a dedicated control rod latch tool which can hold the control rod  4  and then release the control rod  4  and the control rod drive mechanism  8 . They can be released by operating a release handle  20  (latching handle)  4   e  (see FIG. 8) of the control rod  4  by use of this control rod latch tool, and thereafter the control rods  4  can be pulled up from the core. 
     At any rate, during a periodical inspection of the BWR, both reduction in working time and reduction in operator&#39;s exposure are desired. An exchange operation of the control rods  4  is not an exception. 
     In the related art, in order to reduce a time required for the exchange operation of the control rods, at first an uncoupling operation (coupling releasing operation) of the control rod and the control rod drive mechanism is carried out from the pedestal side of the bottom portion of the reactor by using the control rod drive mechanism, and then the control rods and the fuel support are picked up simultaneously from the core from the upper side of the reactor by using the conventional control rod/fuel support grapple, whereby the exchange operation of the control rods is performed. 
     However, as described above, in the exchange operation of the control rods by use of the control rod/fuel support grapple method in the related art, since at first the uncoupling operation of the control rod and the control rod drive mechanism has been carried out from the pedestal side of the lower portion of the reactor by using the control rod drive mechanism and then the control rods and the fuel support have been picked up from the core simultaneously from the upper side of the reactor by using the conventional control rod/fuel support grapple, two stage operations have been required which causes a longer working term. 
     In addition, in the event that the uncoupling operation of the control rod and the control rod drive mechanism is applied from the pedestal side of the bottom portion of the reactor, there has been a problem of the operator&#39;s exposure in the related art. For this reason, it has been requested that the operator&#39;s exposure would be reduced by executing the exchange operation of the control rods without the operation conducted at the bottom portion of the reactor. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a control rod/fuel support grapple (abbreviated as a “CR/FS grapple” hereinafter) which is capable of pulling up simultaneously control rods and a fuel support and also carrying out an uncoupling operation of the control rod and a control rod drive mechanism. 
     In order to achieve the above object, according to the present invention, there is provided a control rod/fuel support grapple comprising a control rod holding means for holding a hoist handle provided to a top end of a control rod, a fuel support holding means for holding a fuel support which supports a bottom end of a fuel assembly, a coupling releasing means for releasing a coupled state between the control rod and a control rod drive mechanism by virtue of spud coupling, and a main body frame to which the control rod holding means, the fuel support holding means, and the coupling releasing means are attached and which can be hung down into an inside of a reactor pressure vessel. 
     Preferably, the coupling releasing means includes a coupling releasing link mechanism for operating a control rod&#39;s release handle, and a coupling releasing cylinder for driving the coupling releasing link mechanism. 
     Still preferably, the control rod holding means can be displaced relative to the main body frame along a longitudinal direction of the control rod by a predetermined width. 
     Still preferably, the control rod/fuel support grapple further comprises an operational timing control mechanism for releasing a coupled state between the control rod and the control rod drive mechanism by using the coupling releasing means after the hoist handle being held by the control rod holding means. 
     Still preferably, the control rod holding means includes a pivotable hook adapted to be hooked onto the hoist handle, and a control rod holding cylinder for carrying out a pivot operation of the pivotable hook. 
     Still preferably, the coupling releasing means includes a coupling releasing link mechanism for operating a control rod&#39;s release handle, and a coupling releasing cylinder for driving the coupling releasing link mechanism, the control rod holding cylinder and the coupling releasing cylinder are driven by a common working fluid source, and the operational timing control mechanism is such a mechanism that can reduce an operation speed of the coupling releasing cylinder to be smaller than an operation speed of the control rod holding cylinder. 
     Still preferably, the operational timing control mechanism is composed of a damper mechanism for applying resistance to a piston rod of the coupling releasing cylinder in its operation. 
     Still preferably, the operational timing control mechanism is composed of a flow restrict mechanism which is provided in a middle of an working fluid pipe connected to the coupling releasing cylinder. 
     Still preferably, the hook is formed of a hook-shaped member, and a self-weight of the control rod operates to hold a hooked state of the hoist handle by the hook after the control rod has been lifted up via the hook. 
     Still preferably, the fuel support holding means includes a fuel support holding link mechanism for holding a top end of an orifice of the fuel support, and a fuel support holding cylinder for driving the fuel support holding link mechanism. 
     Still preferably, the fuel support holding link mechanism has contact a back-and-forth movable piece adapted to be connected to the top end of the orifice, and a stepped portion on which the upper portion of the orifice is placed being formed on the contact piece such that back and forth motions of the contact piece can be inhibited in a state that the upper portion of the orifice is placed on the stepped portion. 
     Still preferably, the control rod/fuel support grapple further comprises a detecting means for checking a holding state of the control rod holding means, a holding state of the fuel support holding means, and a releasing state of the coupling releasing means respectively. 
     Still preferably, the control rod holding means and the coupling releasing means are detachably attached to the main body frame, the fuel support holding means and both the control rod holding means and the coupling releasing means can be employed independently respectively as separate bodies by detaching the control rod holding means and the coupling releasing means from the main body frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front vertical sectional view showing a schematic configuration of a CR/FS grapple according to an embodiment of the present invention; 
     FIG. 2 is a side vertical sectional view showing the schematic configuration of the CR/FS grapple according to the embodiment of the present invention; 
     FIG. 3 is a plan view showing a state where an arm of the CR/FS grapple according to the embodiment of the present invention is inserted into a clearance between the control rod and the fuel support; 
     FIG. 4A is a view showing an operation of an uncoupling means n the CR/FS grapple according to the embodiment of the present invention, i.e., showing a first stage of the operation; 
     FIG. 4B is a view showing the operation of the uncoupling means in the CR/FS grapple according to the embodiment of the present invention, i.e., showing a second stage of the operation; 
     FIG. 4C is a view showing the operation of the uncoupling means in the CR/FS grapple according to the embodiment of the present invention, i.e., showing a third stage of the operation; 
     FIG. 5 is a schematic view showing an operation of a fuel support holding means in the CR/FS grapple according to the embodiment of the present invention; 
     FIG. 6 is a schematic system diagram showing a piping system for supplying a working air to a control rod holding air cylinder and an uncoupling air cylinder in the CR/FS grapple according to the embodiment of the present invention; 
     FIG. 7 is a schematic system diagram showing a modification in which a flow restrict mechanism is provided in place of a damper mechanism as an operational timing control mechanism in the CR/FS grapple according to the embodiment of the present invention; 
     FIG. 8 is a vertical sectional view showing a part of the core of the BWR; 
     FIG. 9 is a perspective view showing a part of an upper grid of the BWR; 
     FIG. 10 is a perspective view showing the fuel support arranged in a core support plate of the BWR and the control rod inserted into the fuel support; 
     FIG. 11 is a perspective view showing the fuel support of the BWR; and 
     FIG. 12 is a partial vertical sectional view showing a coupled state of the control rod and the control rod drive mechanism of the BWR by using a spud coupling. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A CR/FS grapple according to an embodiment of the present invention will be explained in detail with reference to the accompanying drawings hereinafter. 
     The CR/FS grapple according to one embodiment of the resent invention is employed such that, when a periodical inspection of the BWR, etc. is conducted, the CR/FS grapple is hung down into a reactor pressure vessel  1  (see FIG. 8) so as to release control rods  4  and a fuel support  6  from a core and, in turn, install the control rods  4  and the fuel support  6  from a fuel storage pool outside the reactor pressure vessel into the core. 
     FIGS. 1 and 2 are vertical sectional views showing a schematic configuration of the CR/FS grapple according to the embodiment of the present invention. FIG. 1 is a front vertical sectional view while FIG. 2 is a side vertical sectional view. As shown in FIGS. 1 and 2, the CR/FS grapple according to the embodiment of the present invention comprises a main body frame  24  to which a separating frame  18  is fitted attachably/detachably by fitting bolts  31 . A guide member  23  is provided at a lower end of the separating frame  18  to guide a hoist handle  4   d  (see FIG. 8) of the control rod  4 . 
     A square cylinder member  15  is provided in an inside of the separating frame  18  to be moved vertically by a predetermined width, but an upward movement of the square cylinder member  15  can be limited by a stopper  32  which is projected from an inner surface of the separating frame  18 . A stud  14  is secured to an top end of the square cylinder member  15 . The stud  14  is formed to have a square cylinder shape because a grid guide (not shown) which can guide the CR/FS grapple in passing through the upper grid  5  (see FIG. 8) can be attached to the stud  14 . The stud  14  is connected to a hoist rope, etc. which is wound on an auxiliary hoist of a refueling machine. The CR/FS grapple can be picked up by the hoist rope, etc. and then inserted into the inside of the reactor pressure vessel  1  (see FIG.  8 ). 
     A control rod holding air cylinder  17  is pivotally coupled to the square cylinder member  15  via a hinged coupling. A hook  16  which is formed of a hook-shaped member is pivotally coupled to a piston rod  17   a  of the air cylinder  17  via the hinged coupling. A bearing member  39  having a longitudinal hole  38  therein is provided on the separating frame  18 . A pivot axis  40  is inserted into the longitudinal hole  38  and is movable vertically. Then, the hook  16  is fitted to the bearing member  39  via the pivot axis  40  such that such hook  16  can be pivoted and moved vertically. 
     A limit switch  51  is provided in the close vicinity of the air cylinder  17 . An operation state of the air cylinder  17  can be detected by the limit switch  51 . The limit switch  51  is electrically connected to an indicator lamp  29  which is energized by a battery  28 . The result detected by the limit switch  51  can be displayed by the indicator lamp  29 . Therefore, the operator can check by eye whether or not the hook  16  is located in a hooking position. 
     A control rod holding means  50  consists of the square cylinder member  15 , the hook  16 , and the air cylinder  17 . Since the square cylinder member  15  can be moved up and down relative to the separating frame  18  by a predetermined width, the control rod holding means  50  can also be moved up and down relative to the separating frame  18 . At that time, because the separating frame  18  is fixed to a main body frame  24 , the control rod holding means  50  can be moved vertically relative to the main body frame  24  by a predetermined width, i.e., can be displaced relatively along a longitudinal direction of the control rod  4 . 
     A hoisting stroke of the control rod holding means  50  with respect to the separating frame  18  is designed to exceed a height of a projected portion of the hook  16  such that a mechanical lock mechanism can operate while keeping an engagement of the projection portion formed at the top end of the hook  16  with the hoist handle  4   d  (see FIG. 8) of the control rod  4 . 
     As shown in FIG. 2, a coupling releasing air cylinder  22  is fixed to the separating frame  18 . A piston rod  22   a  of the coupling releasing air cylinder  22  is connected to a coupling releasing link mechanism  20  via an actuating rod  21 . In this manner, the coupling releasing link mechanism  20  can be driven by the coupling releasing air cylinder  22 . 
     Also, an arm  19  is provided to extend along the actuating rod  21 . The arm  19  is also provided such that it can be moved vertically relative to the separating frame  18 . As shown in FIG. 3, during the exchange operation of the control rod  4 , the arm  19  is inserted into a clearance between the control rod  4  and the cruciform through hole  4   a  of the fuel support  6  from the upper side. 
     A coupling releasing means  60 , which can uncouple the control rod  4  and the control rod drive mechanism  8  by virtue of a spud coupling, is composed of the coupling releasing link mechanism  20 , the actuating rod  21 , the coupling releasing air cylinder  22 . 
     As shown in FIG. 2, a damper mechanism  30  is provided to a top end of the air cylinder  22  to apply resistance to a piston rod  22   a  of the coupling releasing air cylinder  22  in its operation. The damper mechanism  30  constitutes an operational timing control mechanism which can uncouple the control rod  4  and control rod drive mechanism  8  by using the coupling releasing means  60  after the control rod holding means  50  has held the hoist handle  4   d  (see FIG.  8 ). A damper drive axis  30   a  of the damper mechanism  30  is connected to the piston rod  22   a  of the air cylinder  22 . 
     FIG. 4A, FIG. 4B, and FIG. 4C show an operation of the coupling releasing link mechanism  20  in the CR/FS grapple. As shown in FIG. 4A, FIG. 4B, and FIG. 4C, the coupling releasing link mechanism  20  includes a first arm  20   a , a second arm  20   b , and a third arm  20   c.    
     A top end of the first arm  20   a  is pivotally coupled to a bottom end of the actuating rod  21 , a bottom end of the first arm  20   a  is pivotally coupled to one end of the second arm  20   b , and the other end of the second arm  20   b  is pivotally coupled to a middle portion of the third arm  20   c.    
     In addition, one end of the third arm  20   c  is pivotally coupled to the arm  19 . As shown in FIG. 4A, FIG. 4B, and FIG. 4C in sequence, when the piston rod  22   a  is lifted upward by driving the air cylinder  22 , the first arm  20   a  and the second arm  20   b  can be pulled up and also the third arm  20   c  can be pulled up until a horizontal position while being pivoted. 
     Further, a bend-shaped switching member  20   d  is swingably and pivotally coupled to the third arm  20   c . A limit switch  33  is provided over the switching member  20   d .The limit switch  33  is electrically connected to an indicator lamp  29  shown in FIG.  1 . On/off states of the limit switch  33  can be displayed by the indicator lamp  29 . 
     As shown in FIG.  1  and FIG. 2, a pair of fuel support holding plungers  25  are provided on a bottom surface of the main body frame  24 . A pair of fuel support holding air cylinders  26  for driving these holding plungers  25  are provided on the fuel support holding plungers  25 . Limit switches  27  are provided in the neighborhood of the air cylinders  26  respectively. Operation states of the air cylinders  26  can be detected by the limit switches  27  and then detected results can be displayed by the indicator lamp  29 . 
     Then, a fuel support holding means  70  which can hold the fuel support  6  (see FIG. 11) is composed of the fuel support holding plungers  25  and the fuel support holding air cylinders  26 . 
     The fuel support holding plungers  25  have contact pieces  34  respectively. As shown in FIG. 5, the contact pieces  34  can be moved back and forth by a fuel support holding link mechanism  35 . A pair of contact pieces  34  are arranged at positions corresponding to a pair of opposing orifices  6   e  ( f, g, h ) of the fuel support  6  shown in FIG.  11 . Stepped portions  34   a  on which the upper portions of the orifices  6   e  ( f, g, h ) are placed are formed on the contact pieces  34  respectively. 
     The fuel support holding link mechanism  35  has a first arm  35   a  and a second arm  35   b . One end of the first arm  35   a  is pivotally coupled to a rear end of the contact piece  34 , and the other end of the first end  35   a  is pivotally coupled to one end of the second arm  35   b , and the other end of the second arm  35   b  is pivotally coupled to outer peripheral wall  25   a  (see FIG. 1) of the fuel support holding plunger  25 . In addition, a bottom end of the actuating rod  36  which is coupled to the piston rod of the air cylinder  26  is pivotally coupled to a pivotable portion between the first arm  35   a  and the second arm  35   b.    
     FIG. 6 is a schematic system diagram showing a piping system for supplying a working air to a control rod holding air cylinder  17  and a coupling releasing air cylinder  22  in the CR/FS grapple. As can be seen from FIG. 6, the control rod holding air cylinder  17  and the coupling releasing air cylinder  22  employ commonly a set of low and high pressure working air sources. 
     In general, the working air sources which can be employed in the nuclear power plant consist of two sets of low and high pressure working air sources. Hence, a set of working air sources are commonly used for the control rod holding air cylinder  17  and the coupling releasing air cylinder  22 , while a set of remaining working air sources can be used to operate the fuel support holding air cylinders  26 . Therefore, there is no case where the site has lack of the working air sources. 
     FIG. 7 shows a modification in which a flow restrict mechanism  37  is provided in place of the damper mechanism  30  as an operational timing control mechanism in the CR/FS grapple. In this modification, a flow restrict mechanism  37  is provided in the middle of a low pressure side working fluid pipe  41  connected to the coupling releasing air cylinder  22 . 
     Next, referring to FIGS. 1 and 8, when the control rods  4  and the fuel support  6  are picked up from the inside of the water-filled reactor pressure vessel  1 , operations performed during the periodical inspection of the BWR by using the CR/FS grapple according to the present embodiment will be explained. 
     At the time when the lifting operation of the control rods  4  and the fuel support  6  is to be carried out, the fuel assemblies  3  fitted in predetermined grids have already been taken out from the inside of the reactor pressure vessel  1  by the refueling machine, etc. and the control rods  4  have been descended to their full pull-out states. 
     At first, a hoist rope wound on an auxiliary hoist, etc. of the refueling machine (not shown) is connected to the stud  14  of the CR/FS grapple, and then the CR/FS grapple is hung down inside of the reactor pressure vessel  1  to be inserted into the preselected grid. Thus, the separating frame  18  and the main body frame  24  are seated on the control rod  4  and the fuel support  6  respectively. 
     Then, a compressed air is supplied from an air system (working air source) of the refueling machine to the control rod holding air cylinder  17 , the coupling releasing air cylinder  22 , and the fuel support holding air cylinders  26  respectively. At that time, since the operational timing control mechanism composed of the damper mechanism  30  or the flow restrict mechanism  37  is provided to the coupling releasing air cylinder  22 , movement of the coupling releasing air cylinder  22  is delayed relative to that of the control rod holding air cylinder  17  in operation. 
     Therefore, at first the hook  16  of the control rod holding means  50  holds the hoist handle  4   d  of the control rod  4  and then the third arm  20   c  of the coupling releasing link mechanism  20  of the coupling releasing means  60  pulls up the release handle  4   e  of the control rod  4 , whereby the coupled state of the control rod  4  and the control rod drive mechanism  8  by using the spud coupling can be released. 
     Like the above, since the operational timing control mechanism is provided, a holding operation of the control rod  4  can be effected by the control rod holding means  50  before the coupled state is released by the coupling releasing means  60 . Since the time difference in the operations of the control rod holding air cylinder  17  and the coupling releasing air cylinder  22  is caused by the operational timing control mechanism composed of the damper mechanism  30  or the flow restrict mechanism  37 , a time difference can be generated in their respective operations even though the common working air source is employed for the control rod holding air cylinder  17  and the coupling releasing air cylinder  22 . In addition, since the common working air source is employed for both air cylinders  17 ,  22 , a time difference can be caused without fail in their operation even when a pressure of the supplied air from the working air source is varied. 
     The operation when the hoist handle  4   d  of the control rod  4  is held by the control rod holding means  50  will be explained hereunder. 
     After the separating frame  18  is seated on the control rod  4 , the piston rod  17   a  is drawn in by driving the control rod holding air cylinder  17  to pivot the hook  16  such that the hook  16  is shifted to the hooked position shown in FIG.  1 . 
     At that time, an operation state of the control rod holding air cylinder  17  can be detected by the limit switch  51  and then the detection result can be displayed on the indicator lamp  29 . Accordingly, the operator can check by eye whether or not the hook  16  is located in its hooking position. 
     Next, when the stud  14  is lifted by winding the hoist rope of the auxiliary hoist in this state, only the control rod holding means  50  which consists of the hook  16 , the control rod holding air cylinder  17 , and the square cylinder member  15  can be lifted up together with the stud  14  while the separating frame  18  is still seated on the control rod  4 . Then, the hook  16  grasps the hoist handle  4   d  of the control rod  4  and lifts it. At that time, it can be detected by sensing a weight applied to the hoist rope whether or not the hook  16  of the control rod holding means  50  has held the hoist handle  4   d  of the control rod  4 . 
     In this way, prior to lifting-up of an entire CR/FS grapple, it can be checked or confirmed whether the control rod  4  is held by the control rod holding means  50 , or not. Also, under the condition that the hoist handle  4   d  is grasped and then lifted up by the hook  16 , a hooked state by the hook  4  can be held by a self-weight of the control rod  4  since the hook  16  is formed like a hook-shape. As a result, the control rod  4  is prevented from dropping down and also safety can be maintained even if either supply of the compressed air to the control rod holding air cylinder  17  has been lost or operations have been performed wrong. 
     Subsequently, an operation performed when the coupled state of the control rod  4  and the control rod drive mechanism  8  by the spud coupling is released by the coupling releasing means  60  will be explained hereunder. 
     First of all, when the piston rod  22   a  is lifted up by driving the coupling releasing air cylinder  22 , the first arm  20   a  and the second arm  20   b  can be pulled up and also the third arm  20   c  can be pulled up to its horizontal position while it is being pivoted, as shown in FIG. 4A, FIG. 4B, and FIG. 4C in order. 
     Next, the overall coupling releasing link mechanism  20  as well as the arm  19  can be lifted up by rising up the piston rod  22   a  further from the state shown in FIG.  4 C. Then, the release handle  4   e  of the control rod  4  can be pulled up by the third arm  20   c , so that the coupling of the control rod  4  and the control rod drive mechanism  8  can be released. In addition, the switching member  20   d  can be pivoted when the third arm  20   c  is engaging with the release handle  4   e  and thus the limit switch  33  can be pushed up by one end of the switching member  20   d . Then, the limit switch  33  is operated to switch its on/off state and as a result the displaying state of the indicator lamp  29  is changed, whereby the operator can check or confirm by eye that the release handle  4   e  of the control rod  4  has been actuated. 
     Operations effected when the fuel support  6  is held by the fuel support holding means  70  are explained hereinbelow. 
     Prior to starting the holding operation of the fuel support  6 , the contact pieces  34  and the fuel support holding link mechanism  35  are positioned at locations shown by chain double-dashed lines in FIG.  5 . The actuating rod  36  is moved upward from this location by driving the fuel support holding air cylinders  26 . Thus, the contact pieces  34  are caused to advance to the orifices  6   e  ( f, g, h ) of the fuel support  6  and thus advance further more than the position indicated by solid lines in FIG.  5 . 
     Forward movements of the contact pieces  34  are continued until the first arm  35   a  and the second arm  35   b  are positioned from their downward-convex alignment to their linear alignment, and then the contact pieces  34  are switched to their backward movements when the first arm  35   a  and the second arm  35   b  are shifted from their linear alignment to their upward-convex alignment. Then, at the time point when the piston rods of the fuel support holding air cylinders  26  and the actuating rod  36  reach their upper limit positions of lifting strokes, the backward movements of the contact pieces  34  are stopped and therefore the contact pieces  34  are positioned, as shown by the solid lines in FIG.  5 . 
     At this time, operation states of the fuel support holding air cylinders  26  can be detected by the limit switches  27  and the detected results can then be displayed by the indicator lamps  29  respectively. Accordingly, the operator can check or confirm by eye whether or not the contact pieces  34  are in their held positions. 
     Then, in the situation indicated by the solid lines in FIG. 5, when the CR/FS grapple is pulled up by winding up the hoist rope of the auxiliary hoist, the upper portions of the orifices  6   e  ( f, g, h ) of the fuel support  6  are put on the stepped portions  34   a  of the contact pieces  34  so that the CR/FS grapple as well as the fuel support  6  can be pulled up together. 
     Since both forward and backward movements of the contact pieces  34  can be prevented in the situation that the upper portions of the orifices  6   e  ( f, g, h ) of the fuel support  6  are put on the stepped portions  34   a  of the contact pieces  34 , the fuel support  6  can be prevented from dropping down to thus maintain safety even if either supply of the compressed air to the control rod holding air cylinder  17  has been lost at the worst or wrong operations have been effected. 
     As described above, the CR/FS grapple can be lifted upward after the control rods  4  have been held by the control rod holding means  50  and also the fuel support  6  has been held by the fuel support holding means  70 , so that the control rods  4  and the fuel support  6  can be lifted up simultaneously and carried out together from the reactor pressure vessel  1 . 
     The CR/FS grapple according to the embodiment of the present invention may be employed when the control rods  4  and the fuel support  6  are carried into the inside of the reactor pressure vessel  1  and then installed therein. In this case, the control rods  4  and the fuel support  6  maybe lifted up and installed simultaneously. 
     In the CR/FS grapple according to the embodiment of the present invention, since the separating frame  18  may be detached from the main body frame  24  by releasing the fitting bolts  31  (see FIG.  2 ), the fuel support holding means  70  and an assembly consisting of the control rod holding means  50  and the coupling releasing means  60  can be employed independently respectively as separate bodies. 
     As a consequence, in a case that the control rods  4  cannot be pulled out until their full pull-out states due to a failure of the control rod drive mechanism  8 , at first only the fuel support  6  can be lifted up by using the fuel support holding means  70  to be picked out from the reactor pressure vessel  1 , and then the control rods  4  are hoisted by the control rod holding means  50  and the coupling releasing means  60  to be taken out from the reactor pressure vessel  1 . 
     As described above, according to the CR/FS grapple of the embodiment of the present invention, since both the control rods  4  and the fuel support  6  can be held by the control rod holding means  50  and the fuel support holding means  70  and also the coupled state of the control rods  4  and the control rod drive mechanism  8  by using the spud coupling can be released by the coupling releasing means  60 , there is no necessity of executing the coupling releasing operation from the pedestal side of the bottom of the reactor, unlike the aforesaid related art. Therefore, an efficiency of the exchange operation of the control rods  4  can be improved by reducing the term of the periodical inspection and the exposure of the operator. 
     More particularly, in contrast to the prior operation, it is possible to reduce the operation time by about thirty minutes per control rod  4 . The typical operation time of the prior operation was about 55 minutes per control rod  4 . Therefore, about 55% of the operation time can be reduced by using the present CR/FS grapple.