SE1000649A1 - Apparatus and method for delivering equipment in connection with a nuclear power reactor - Google Patents

Description

10 the inside of the pressure vessel 10. The part 24 may be connected to the Iifting device with the help of a line or, as illustrated in Fig 1, by means of one or more rigid poles 26 connected to the part 24 and to the Iifting device 20. The Iifting device 20 may be arranged such that the pole 26 can be tilted to a desired angle. Persons 28 controlling or monitoring the operation can be positioned on the bridge 22 or on a platform 18 at the side of the water pool 14. 30 indicates flexible means, for example electrical cables and / or hoses for a hydraulic fluid, which may be used to control the operation of the part 24.

During inspection and maintenance, a rail 32 may be provided on top of the core shroud 12. Furthermore, Fig. 1 shows schematically different tubular parts 34 that may remain within the pressure ves- cell 10 during inspection and maintenance.

US 2005/0135904 A1, US 5 878 099 and US 5586155 describe different apparatuses for performing inspection or for delivering tools to different spaces in nuclear reactors. However, these appa- ratuses have a rather complicated construction and it may be diffi- cult to position these apparatuses in the pressure vessel 10 when the pressure vessel contains hindering parts, such as the tubular parts 34 shown in Fig 1. lt may therefore be difficult to use these apparatuses for delivering equipment to the rather narrow space that exists between the core shroud 12 and the wall of the pressure vessel 10 in a nuclear reactor.

SUMMARY OF THE INVENTION A first aspect of the invention concerns an apparatus. An object thereby is to provide an apparatus that can be easily positioned and used for delivering equipment to spaces in a nuclear power reactor which are difficult to reach. The apparatus should be able to deliver equipment to the space between a core shroud and the reactor pressure vessel in a nuclear power reactor when the nuclear power reactor is not in operation and the top of the reactor pressure ves- sel has been removed. The apparatus should be such that it is pos- sible to position the apparatus correctly, in spite of hindering de- vices, such as the tubular parts described above, that may be lo- cated in the pressure vessel. The reactor pressure wessei and the core shroud positioned therein are located in water and a rail is thereby positioned in the vicinity of the upper periphery of the core shroud. The rail extends along at least a substantial portion of said upper periphery. ln particular it should be possible to in a relatively simple manner attach the apparatus to said rail and to control the apparatus such that equipment can be delivered to different locations between the core shroud and the reactor pressure vessel.

A second aspect of the invention is to provide a method of operat ~ ing an apparatus according to the invention. Also concerning the method, it is an object to be able to easily position the apparatus and to use the apparatus for delivering equipment to spaces in a nuclear power reactor, in particular to the space between the core shroud and the reactor pressure vessel.

The objects of the first aspect of the invention are achieved by an apparatus that comprises: a first device adapted to be lowered from above to the rail in order to be attached to the rail in such a manner that it can travel along the rail, where said first device comprises a first docking member adapted to engage with a second docking member; a second device comprising said second docking member and an extendable unit, said extendable unit being adapted to extend es- sentially in a vertical direction, as seen when the apparatus is used, and designed to have a variable extension, the second device also comprising a holder for holding the equipment to be delivered, said holder being attached, directly or via further parts, to a lower por- tion of said extendable unit; where the second docking member is positioned and designed so as to come into engagement with the first docking member by mov- ing the second device towards the first device, when the first device has previously been attached to the rail, and the rail is positioned in the vicinity of the upper periphery of the core shroud, until the sec- ond docking member engages the first docking member, whereby the second device has been docked with the first device.

The apparatus thus comprises two devices which are designed to dock with each other. Since the apparatus has two such devices, each device is smaller than if the devices were assembled as one device. This makes it easier to manipulate the two devices in order to position the apparatus in the desired position inside the pressure vessel. Furthermore, since the apparatus comprises two devices, each device will have a lower weight than the whole apparatus. Also this makes it easier to position the apparatus as desired. Since the devices are equipped with the mentioned docking members, it is easy to position the second device correctly on the first device. lt is therefore possible to position the second device on the first device, when the first device has previously been attached to the rail lo- cated in the pressure vessel. lt should be noted that it is possible to attach the first device to the rail before the rail is positioned inside the pressure vessel. How- ever, according to the invention it is possible, and preferred, that the rail is first positioned inside the pressure vessel in the intended position in the vicinity of the upper periphery of the core shroud, and whenthe rail is positioned in this position, the first device will be attached to the rail. lt is therefore not necessary to take out the rail from the pressure vessel for attaching the first device thereto. lt should be noted that the rail extends in a substantially horizontal plane. Preferably, the rail extends along the entire periphery of the top of the core shroud such that the rail forms a closed loop, pref- erably a circle. The rail may be a rail that has previously been used for, for example, holding inspection equipment.

Preferably the first and second docking members are positioned such that the second device is moved and docked to the first device by lowering the second device from above onto the first device.

When it is stated herein that the apparatus is used, it is meant that the apparatus is positioned in the intended use position, i.e. the first device is attached to the rail, and the rail is positioned in the vicinity of the upper periphery of the core shroud, and the second device has docked with the first device. The primary reason for referring to the intended use position is to make clear what it meant by upper, lower, horizontal, vertical etc.

The extendable unit-is preferably positioned on the second device such that when the second docking member engages the first dock- ing member, i.e. when the second device has docked with the first device, the extendable unit is able to reach down from the first de- vice into a space on the outside of the core shroud. The extendable unit is preferably constructed as a telescope that comprises several parts that can be moved into each other.

The purpose with the apparatus is to deliver equipment. However, the apparatus can of course also be used for removing equipment from the nuclear reactor, in particular from the mentioned space be- tween the core shroud and the reactor pressure vessel. The appa- ratus can also be used for holding measurement equipment in order to move this equipment to different locations, in particular to the mentioned space, in order to perform different measurements in or- der to investigate the status of different parts of the nuclear reactor.

The measurement equipment can for example be a camera or means for carrying out eddy current measurements.

The mentioned first device is, according to an embodiment, a trolley that can travel along the rail.

The holder may be a gripper that is able to grip the equipment in question. The gripper may, according to an embodiment, be con- trolled by hydraulic means, such as a hydraulic cylinder, provided on the apparatus.

According to an embodiment of the apparatus according to the in- vention, the first and second docking members are designed such that when the second device has been docked with the first device, and the first device is attached to the rail, and the rail is positioned in the vicinity of the upper periphery of the core shroud, the second device is secured in a substantially horizontal plane relative to the first device, but such that the second device is removable from the first device by simply lifting the second device in a substantiaily ver- tical direction away from the first device. This embodiment makes it easy to remove the second device from the first device. Still, the second device is secured horizontally relative to the first device.

According to a further embodiment, the first docking member is ar- ranged movable on the first device, such that when the first device is attached to the rail, and the rail is positioned in the vicinity of the upper periphery of the core shroud, the first docking member is movable in a substantially radial direction, with regard to the pe- riphery of the core shroud, whereby, by moving the first docking member also the second device, when the second device has been docked with the first device, will move in said radial direction rela- tive to the first device and therefore also relative to the core shroud.

According to this embodiment, it is possible to move the second de- vice, and thereby also the holder, radially in order for the holder to reach a desired position. The movement of the first docking mem- ber on the first device may for example be carried out hydraulically, such as by a hydraulic cylinder.

According to a further embodiment, the first device is provided with a drive device and a drive member, where the drive device is able to drive the drive member and where the drive member is adapted to engage with the rail such that when the drive device drives the drive member, and the drive member engages with the rail, the first device will move along the rail, whereby also the second device, when the second device has been docked with the first device, will move accordingly. The drive device may for example be an electric motor arranged on the first device. The drive member may for ex- ample be a toothed gear that engages a corresponding track on the rail. According to this embodiment, it is thus possible to move the first device, and thereby also the second device, along the periph- ery of the core shroud.

According to a further embodiment, the extendable unit is rotatably arranged on the second device, such that, when the apparatus is used, the extendable unit is arranged rotatabie around a substan- tially vertical axis, and where the apparatus comprises an extend- able unit rotating drive means which is able to cause the extendable unit to rotate. According to this embodiment, it is thus possible to rotate the extendable unit. This makes it possible to move the equipment held by the holder accordingly. The extendable unit ro- tating drive means may for example constitute hydraulic means, such as a hydraulic cylinder.

According to a further embodiment, the second device also com- prises an arm positioned between the extendable unit and the holder, where the arm is arranged rotatabie relative to the ex- tendable unit such that, when the apparatus is used, the arm is able to rotate around a substantially horizontal axis located in the area of the lower end of the extendable unit, and wherein the apparatus comprises an arm rotating drive means which is able to cause the arm to rotate. This embodiment provides a further possibility of moving the holder. This increases the flexibility of moving the holder in order to be able for it to reach positions that are otherwise diffi- cult to reach. Furthermore, the increased flexibility makes it easier to move the second device past interfering parts, when the second device is moved to, or from, the first device. The arm rotating drive means may for example constitute hydraulic means, such as a hy- draulic cylinder.

According to a further embodiment, the second device also com- prises a rotation unit positioned between the arm and the holder, where the rotation unit is arranged rotatabie relative to the arm such that, when the apparatus is used, the rotation unit is able to rotate around an axis located in the area of that end of arm that is' remote from the extendable unit, and wherein the apparatus com- prises a rotation unit drive means which is able to cause the rota- tion unit to rotate. This embodiment further improves the possibili- ties of moving the holder. The rotation unit drive means may for ex- ample constitute hydraulic means, 'such as a hydraulic cylinder.

According to a further embodiment, the second device also com- prises a substantially C-shaped part, which, as seen when the ap- paratus is used, comprises an upper substantially horizontally ex- tending portion, a lower substantially horizontally extending portion and a substantially vertically extending portion located between and connected to said upper and lower portions, where the lower por- tion is positioned at substantially the same level as the upper end of the extendable unit and wherein the sum of the length of the upper and lower portions is less than 50% of the length of the substan- tially vertically extending portion. The C-shaped part makes it easier to move the second device past hindering parts that are located above the core shroud. ln particular, it makes it easier to move the second device past tubular parts which, as explained above, may be located in the pressure vessel. By rotating the second device it is possible to move the second device past such hindering devices.

According to a further embodiment, the apparatus comprises a length control device arranged to control the length of the extend- able unit in the vertical direction, as seen when the apparatus is used. With the length control device it is thus possible to control how much the extendable unit extends in the vertical direction.

According to a further embodiment, said length control device com- prises a winch for controlling the length of a line extending from the winch to a lower portion of the extendable unit, as seen when the apparatus is used, whereby the length of the extendable unit is con- trollable by, by means of the winch, controlling said length of the line between the winch and the lower portion of the extendable unit.

The use of a winch has been found to be advantageous for control- ling the extension of the extendable unit. As mentioned above, the extendable unit may be a telescope. The end of, the line may thereby for example be attached to the inner telescopic part, for ex- ample attached to the top of this inner telescopic part.

According to a further embodiment, the first device comprises a plu- rality of wheels which, when the first device is attached to the rail, will bear against the rail in order to facilitate the movement of the first device along the rail. With the help of such wheels, the first de- vice can move smoothly along the rail.

According to a further embodiment, at least one wheel is movable between a first and a second position, wherein in the first position the wheel is located such that the first device can be moved onto the rail and wherein in the second position the wheel is located such that the first device will be attached to the rail, wherein the first device comprises a wheel moving member, by means of which the wheel can be moved between said first and second positions.

With the help of such a movable wheel, the first device may thus be secured to the rail.

According to a further embodiment, the second device comprises a lifting interface located, as seenwhen the apparatus is used, at the upper part of the second device, said lifting interface being adapted to mate with a lifting pole connected to a lifting device, such that when the lifting interface is mated with the lifting pole attached to the lifting device, the second device is able to be moved by means of the lifting device. With the help of such a lifting interface it is possible to secure the lifting pole to the second device. This makes it easier to handle the second device.

The object of the second aspect of the invention is achieved by a method of operating an apparatus according to any one of the em- bodiments above, the method comprising the following steps: connect the first device to a lifting device located above the water in which the reactor pressure vessel of a nuclear power reactor is lo- cated, where a core shroud is located in the reactor pressure ves- sel, where the nuclear power reactor is not in operation and the top of the reactor pressure vessel has been removed and wherein a rail is positioned in the vicinity of the upper periphery of the core shroudsuch that the rail extends along at least a substantial portion of said upper periphery, lower the first device until it is positioned on the rail, secure the first device to the rail such that it is attached to the rail in such a manner that it can travel along the rail, connect the second device to a lifting device located above the wa- ter, lower the second device and move it to the first device until the sec- ond docking member engages the first docking member, control the apparatus by controlling a plurality of movable parts of the apparatus until the holder reaches a desired position in the area between the core shroud and the reactor pressure vessel.

With this method advantages corresponding to those explained above in connection with the apparatus according to the invention are achieved.

According to a further manner of performing the method, the method also comprises the following steps: when connecting the second device to the lifting device, attach a lifting pole to the second device such that the second device is moved by the lifting device by being connected thereto via said lift- ing pole, keep the second device attached to the lifting device, via said lifting pole, while the apparatus is controlled by controlling a plurality of movable parts of the apparatus until the holder reaches the desired position.

By attaching the second device to a lifting pole, it is easier to ma- nipulate the second device. Furthermore, since the second device is 11 held by the lifting device while the holder is moved to the desired position, the weight of the second device can be held by the lifting device, which means that the second device does not exert much force on the first device. This makes it easier to manipulate the first device and the first device does not risk being damaged by being submitted to high forces. The first device can therefore have a r ~ ela ~ tively simple construction, which makes it lighter. This makes it eas- ier to position the first device onto the rail. Furthermore, the appara- tus according to the invention does therefore not submit the rail to any high forces.

Further details and advantages of the present invention will become clear from the description below.

LETTER DESCRIPTION OF THE DRAWINGS 'Fig 1 shows schematically a perspective sectional view of a part of a nuclear reactor.

Fig 2 shows schematically a perspective view of an embodiment of a first device that forms part of the apparatus according to the invention.

Fig 3 shows schematically a perspective view of an embodiment of a second device, which forms part of an apparatus according to the invention.

Fig 4 shows schematically a perspective view of an embodiment of an apparatus according to the invention, when the apparatus has been attached to a rail positioned in the vicinity of the upper periphery of a core shroud.

Fig 5 is a flow chart that illustrates a manner of carrying out a method according to the invention. 12 DESCRIPTION OF PREFERRED EMBODIIVIENTS Fig. 1 has been described above. This figure shows schematically the environment in which the apparatus according to the present invention is used. ln particular, the apparatus according to the in- vention is to be positioned on the rail 32, such that the apparatus can be used to deliver equipment to the rather narrow space be- tween the core shroud 12 and the wall of the reactor pressure ves- sel 10. The apparatus can be used for delivering different kinds of equipment, for example repair parts for jet pump riser pipes (not shown in the figure) that may be located in the mentioned space.

The lifting device 20 can be used for manipulating the apparatus according to the invention and for positioning the apparatus on the rail 32.

Fig 2 shows schematically an embodiment of a first device that forms part of .the apparatus according to the invention. The first de- vice can according to this embodiment also be called a trolley. The trolley comprises a number of wheels 44, 46 which are designed to bear against the rail 32 when the apparatus is used. The trolley may thus travel along the rail. To the right in the figure two wheels 44 are shown. These wheels 44 are held by a rotatable shaft 45, such that the wheels 44 are movable between a first and a second posi- tion by rotating the shaft 45. The shaft 45 can be rotated by grip.- ping a wheel moving member 48 connected to the shaft 45. The wheel moving member 48 can forexample be gripped and con- trolled by a gripper connected to the lifting device 20. When the wheels 44 are in a first position, the trolley can be lowered onto the rail 32. The wheels 44 can then be moved to the second position. ln this position the trolley will be attached safely to the rail 32. The trolley may also have a second movable pair of wheels 44. One such wheel 44 can be seen further to the left in Fig 2.

The trolley has a drive device 42, which may be an electric motor.

This drive device 42 drives a drive member 43, here a toothed wheel. The toothed wheel 43 engages a corresponding track (not 13 shown) on the rail 32. When the electric motor 42 drives the wheel 43, the trolley will therefore travel along the rail 32.

The trolley has a first docking member 40, which here has two pins 40a, 40b, which are adapted to dock with a corresponding second docking member (to be described below). The first docking member 40 is arranged movable on the trolley, such that the first docking member 40 is movable in a radial direction with regard to the pe- riphery of the core shroud 12. This radial movement may for exam- ple be caused by hydraulic means, such as a hydraulic cylinder 41.

Fig 3 shows schematically an embodiment of a second device that forms part of an apparatus according to the invention. The second device comprises an upper C-shaped part 76. This part 76 has, as seen when the apparatus is used, an upper horizontally extending portion 78, a lower horizontally extending portion 80 and a vertically extending portion 82 connected to the upper 78 and lower 80 por- tions. The upper 78 and lower 80 portions are substantially shorter than the vertical portion 82. ln particular, the sum of the length of the upper 78 and lower 80 portions is less than 50% of the length of the vertical portion 82.

The second device also comprises an extendable unit 62, which may be formed as a telescope, for example comprising five tele- scopic parts. The extendable unit 62 is adapted to extend in the vertical direction when the apparatus is used. The extendable unit 62 thus has a variable extension in the vertical direction. The upper end of the extendable unit 62 is positioned at about the same level as the lower portion 80 of the C-shaped part 76.

The second device also has a winch 84 that is positioned close to the upper end of the second device. A line 86 extends from the winch 84 to the inner telescopic part of the extendable unit 62. The line 86 may for example be drawn on the outside of the vertical por- tion 82, via wheels (not shown) into the inside of the extendable unit 62, such that the lower end of the line 86 is attached to the in- ner telescopic part. With the help of the winch 84, the length of the 14 line 86 between the winch 84 and the lower portion of the extend- able unit 62 can thus be controlled. ln this manner it can be con- trolled how much the telescope 62 is to extend in the vertical direc- tion.

The second device also has a second docking member 60, which according to this embodiment comprises two tubular parts 60a and 60b, which are designed to mate with the pins 40a and 40b shown in Fig 2. The second device can thus be moved downwards towards the trolley shown in Fig. 2, until the parts 60a and 60b come into en- gagement with the parts 40a and 40b, whereby the second device has been docked with the first device.

When the second device has been docked with the first device, the second device is thus secured in a horizontal plane relative to the first device. However, the second device is removable from the first device by simply lifting the second device in a vertical direction away from the first device.

The docking member 60 can be arranged such that its position on the vertical portion 82 is adjustable.

The extendable unit 62 is arranged to be rotatable around a vertical axis. The second device comprises according to this embodiment an extendable unit rotating drive means 66 in the form of a hydrau- lic cylinder, with the help of which the extendable unit 62 can be caused to rotate for example: h25 ° around the vertical axis.

An arm 68 is connected to the lower telescopic part of the extend- able unit 62. The arm 68 is arranged to be rotatable around a hori- zontal axis located in the area of the lower end of the extendable unit 62. The second device comprises an arm rotating drive means 70, for example a hydraulic cylinder, which is able to cause the arm 68 to rotate. The arm rotating drive means 70 may be located inside the extendable unit 62.

The second device also comprises a rotation unit 72 which is con- nected to that end of the arm 68 that is remote from the extendable unit 62. The rotation unit 72 is arranged to be rotatable relative to the arm 68 such that, for example when the arm 68 extends hori- zontally, the rotation unit is able to rotate around a vertical axis.

The second device comprises a rotation unit drive means 74, for example a hydraulic cylinder, which is able to cause the rotation of the rotation unit 72.

At the end of the rotation unit 72 a holder 64 is positioned. The holder 64 can also be called a gripper and is designed to hold the equipment that is to be delivered to the mentioned space between the core shroud 12 and the wall of the pressure vessel 10. The holder 64 is able to grip and release the equipment in question. For this purpose the holder 64 may be equipped with for example a hy- draulic cylinder 65 which may cause the holder to grip and release the equipment.

For the sake of simplicity, the tubes with hydraulic fluid leading to the different hydraulic cylinders are not shown in Fig 3. However, these tubs to the hydraulic cylinders 65, 74 and 70 can for. example be drawn inside the extendable unit 62 and also inside the vertical portion 82. Similarly, the tube leading to the hydraulic cylinder 66 can be drawn inside the vertical portion 82.

The second device also comprises a lifting interface 88 located in the upper part of the second device. This lifting interface 88 is adapted to mate with a lifting pole 26 that can be connected to the lifting device 20 shown in Fig 1. lt is thereby possible to move the second device to a desired position with the help of the lifting pole 26 connected to the lifting device 20.

Fig 5 shows a schematic flow chart of a manner operating the appa- ratus according to the invention. The method may comprise the fol- lowing steps: 16 connect the first device (the trolley) to the lifting device 20 which is located above the water in which the reactor pressure vessel 10 with the core shroud 12 is located and wherein a rail 32 has been positioned such that it extends along the upper periphery of the core shroud 12, lower the trolley until it is positioned on the rail 32, grip and rotate the wheel moving member 48 until the wheels 44 are moved to a position in which the trolley is secured to the rail 32; in this position the trolley can travel along the rail 32, grip equipment to be delivered with the help of the holder 64 and connect the second device to the lifting device 20, via a lifting pole 26, lower the second device until the second docking member 60 en- gages the first docking member 40; when moving the second de- vice, the second device may be rotated and the different movable parts thereof may be controlled such that the second device is able to pass by hindering parts like the tubes 34, when the second device has been docked with the trolley, the appa- ratus is controlled until the holder 64 reaches the desired position; this control can thus be carried out moving the trolley along the rail; by moving the first docking member 40 (and thereby also the sec- ond device) radially; by rotating the extendable unit 62; by control- ling the length of the extendable unit with the help of the winch 64, by rotating the arm 68 and by rotating the rotation unit 72; the second device is attached to the lifting device 20 during the whole procedure, such that the second device does not exert any substantial force onto the trolley, when the holder 64 has reached the desired position, the equipment may be attached to the desired part. 17 Of course, the apparatus according to the invention can also be used for removing parts from the mentloned space between the core shroud 12 and the "pressure vessel 10 or for moving for exam- ple inspection equipment to the desired location.

Fig 4 schematically shows the core shroud 12 and the rail 32 and also tubular parts 34 that may be located above the core shroud 12.

Fig 4 shows the situation when the apparatus according to the in- vention has been positioned in the use position, such that the trol- ley is attached to the rail 32 and the second device has been docked with the trolley.

The invention is not limited to the described embodiments but may be varied and modified within the scope of the following claims.

Claims (15)

10 15 20 25 30 35 18 Claims 1. An apparatus for delivering equipment to the space between a core shroud and the reactor pressure vessel (10) in a nuclear power reactor when the nuclear power reactor is not in operation and the top of the reactor pressure vessel (10) has been removed and the reactor pressure vessel and the core shroud (12) positioned therein are located in water and when a rail (32) is positioned in the vicinity of the upper periphery of the core shroud (12) such that the rail (32) extends along at least a substantial portion of said upper periphery, wherein said apparatus comprises: a first device adapted to be lowered from above to the rail (32) in order to be attached to the rail (32) in such a manner that it can travel along the rail (32), wherein said first device comprises a first docking member (40) adapted to engage with a second docking member (60); a second device comprising said second docking member (60) and an extendable unit (62), said extendable unit (62) being adapted to extend essentially in a vertical direction, as seen when the appara- tus is used, and designed to have a variable extension, the second device also comprising a holder (64) for holding the equipment to be delivered, said holder (64) being attached, directly or via further parts, to a lower portion of said extendable unit (62); wherein the second docking member (60) is positioned and de- signed so as to come into engagement with the first docking mem- ber (40) by moving the second device towards the first device, when the first device has previously been attached to the rail (32), and the rail (32) is positioned in the vicinity of the upper periphery of the core shroud (12), until the second docking member (60) engages the first docking member (40), whereby the second device has been docked with the first device. An apparatus according to claim 1, wherein the first (40) and second (60) docking members are designed such that when the second device has been docked with the first device, and the first device is attached to the rail (32) , and the rail (32) is positioned in the vicinity of the upper periphery of the core shroud (12), the sec ~ 10 15 20 25 30 35 19 ond device is secured in a substantially horizontal plane relative to the first device, but such that the second device is removable from the first device by simply Iifting the second device in a substantially vertical direction away from the first device. An apparatus according to claim 1 or 2, wherein the first docking member (40) is arranged movable on the first device, such that when the first device is attached to the rail (32), the first docking member (40). ) is movable in a substantially radial direction, with re- gard to the periphery of the core shroud (12), whereby, by moving the first docking member (40) also the second device, when the second device has been docked with the first device, will move in said radial direction relative to the first device and therefore also relative to the core shroud (12). An apparatus according to any one of the preceding claims, wherein the first device is provided with a drive device (42) and a drive member (43), wherein the drive device (42) is able to drive the drive member (43 ) and wherein the drive member (43) is adapted to engage with the rail (32) such that when the drive device (42) drives the drive member (43), and the drive member (43) engages with the rail (32) , the first device will move along the rail (32), whereby also the second device, when the second device has been docked with the first device, will move accordingly. An apparatus according to any one of the preceding claims, wherein the extendable unit (62) is rotatably arranged on the sec- ond device, such that, when the apparatus is used, the extendable unit (62) is arranged rotatable around a substantially vertical axis, and wherein the apparatus comprises an extendable unit rotating drive means (66) which is able to cause the extendable unit (62) to rotate. An apparatus according to any one of the preceding claims, wherein the second device also comprises an arm (68) positioned between the extendable unit (62) and the holder (64), wherein the arm (68) is arranged rotatable relative to the extendable unit (62) 10 15 20 25 30 35 20 such that, when the apparatus is used, the arm (68) is able to rotate around a substantially horizontal axis located in the area of the lower end of the extendable unit (62 ), and wherein the apparatus comprises an arm rotating drive means (70) which is able to cause the arm (68) to rotate. An apparatus according to claim 6, wherein the second device also comprises a rotation unit (72) positioned between the arm (68) and the holder (64), wherein the rotation unit (72) is arranged rotatable relative to the arm (68) such that, when the apparatus is used, the rotation unit (72) is able to rotate around an axis located in the area of that end of arm (68) that is remote from the extend- able unit (62) , and wherein the apparatus comprises a rotation unit drive means (74) which is able to cause the rotation unit (72) to rotate. 8. An apparatus according to any one of the preceding claims, wherein the second device also comprises a substantially C-shaped part (76), which, as seen when the apparatus is used, comprises an upper substantially horizontally extending portion (78), a lower sub- stantially horizontally extending portion (80) and a substantially ver- tically extending portion (82) located between and connected to said upper (78) and lower (80) portions, wherein the lower portion (80) is positioned at substantially the same level as the upper end of the extendable unit (62) and wherein the sum of the length of the upper (78) and lower (80) portions is less than 50% of the length of the substantially vertically extending portion (82) . An apparatus according to any one of the preceding claims, comprising a length control device (84) arranged to control the length of the extendable unit (62) in the vertical direction, as seen when the apparatus is used. An apparatus according to claim 9, wherein said length control device (84) comprises a winch (84) for controlling the length of a line (86) extending from the winch (84) to a lower portion of the ex- tendable unit (62), as seen when the apparatus is used, whereby 10 15 20 25 30 35 21 the length of the extendable unit (62) is controllable by, by means of the winch (84), controlling said length of the line (86 ) between the winch (84) and the lower portion of the extendable unit (62). 11. An apparatus according to any one of the preceding claims, wherein the first device comprises a plurality of wheels (44, 46) which, when the first device is attached to the rail (32), will bear against the rail (32) in order to facilitate the movement of the first device along the rail (32). 12. An apparatus according to claim 11, wherein at least one wheel (44) is movable between a first and a second position, wherein in the first position the wheel (44) is located such that the first device can be moved onto the rail (32) and wherein in the second position the wheel (44) is located such that the first device will be attached to the rail (32), where the first device comprises a wheel moving member (48), by means of which the wheel (44) can be moved be- tween said first and second positions. 13. An apparatus according to any one of the preceding claims, wherein the second device comprises a lifting interface (88) lo- cated, as seen when the apparatus is used, at the upper part of the second device, said lifting interface (88 ) being adapted to mate with a lifting pole (26) connected to a lifting device (20), such that when the lifting interface (88) is mated with the lifting pole (26) attached to the lifting device (20), the second device is able to be moved by means of the lifting device (20). 14. A method of operating an apparatus according to any one of the preceding claims, the method comprising the following steps: connect the first device to a lifting device (20) located above the water in which the reactor pressure vessel (10) of a nuclear power reactor is located, where a core shroud (12) is located in the reactor pressure vessel (10), where the nuclear power reactor is not in operation and the top of the reactor pressure vessel (10) has been removed and wherein a rail (32) vis positioned in the vicinity of the 10 15 20 25 30 22 upper periphery of the core shroud (12) such that the rail (32) ex- tends along at least a substantial portion of said upper periphery, lower the first device until it is positioned on the rail (32), secure the first device to the rail (32) such that it is attached to the rail (32) in such a manner that it can travel along the rail (32), connect the second device to a lifting device (20) located above the water, lower the second device an d move it to the first device until the sec- ond docking member (60) engages the first docking member (40), control the apparatus by controlling a plurality of movable parts of the apparatus until the holder (64) reaches a desired position in the area between the core shroud (12) and the reactor pressure vessel (10). 15. A method according to claim 14, also comprising the following steps: when. connecting the second device to the lifting device (20), attach a lifting pole (26) to the second device such that the second device is moved by the lifting device (20) by being connected thereto via said lifting pole (26), keep the second device attached to the lifting device (20), via said lifting pole (26), while the apparatus is controlled by controlling a plurality of movable parts of the apparatus until the holder (64) reaches the desired position.