Technical field

The invention relates to a cleaning device for cleaning a female thread of a closure head for a reactor pressure vessel, having a base body that may be inserted into the female thread and that has a longitudinal axis. The invention furthermore relates to a method for cleaning a female thread of a closure head for a reactor pressure vessel.

Background of the invention For closure heads, reactor pressure vessels known from the prior art have a plurality of threaded holes, as a rule circular and arranged adjacent to one another, to which the closure head for the reactor pressure vessel is attached with corresponding bolts. The threaded holes are frequently embodied with a female thread having an M155 or M180 nominal diameter. In order to prevent damage to the threaded holes when opening and closing the closure head, and in order not to expose maintenance personnel to unacceptable radioactive radiation, remotely controlled screwdriver devices are used to screw the bolts of the closure head into the female thread of the reactor pressure vessel and to unscrew them therefrom. For ensuring appropriate sealing, once the bolts have been unscrewed, grease adhering in the threaded bores is removed. In methods known from the prior art, more than 60 liters of solvent per reactor pressure vessel are required for this. Once used, the solvents are contaminated with radioactivity and must be appropriately disposed of, which is a complex process.

Description of the invention Proceeding from this situation, it is an object of the invention to provide a device and a corresponding method for removing residues remaining in a female thread of a reactor pressure vessel, for example greases, in a simpler and more environmentally sound manner, following unscrewing of a closure head.

The object is attained using the features of the independent claims. Advantageous embodiments are provided in the subordinate claims.

Consequently, the object is attained by a cleaning device for cleaning a female thread of a closure head for a reactor pressure vessel, having

a base body that may be inserted into the female thread and that has a longitudinal axis,

at least two reels arranged parallel to one another, the axes thereof extending parallel to the longitudinal axis,

a cleaning tape that may travel through at least one of the reels and at least part of which is wound up on the reels, another part of the cleaning tape running between the reels, and,

a pressing element that is arranged between the reels and that may be moved radial to the longitudinal axis by means of a drive in order to cause the other part of the cleaning tape to mesh with thread turns in the female thread.

One essential aspect of the suggested cleaning device is that residues such as greases, etc. may be removed from turns in the female thread in a particularly effective manner using the other part of the cleaning tape that is caused by the pressing element to mesh with the thread turns in the female thread. Compared to devices and methods known from the prior art, in which it is not uncommon for more than 60 liters of solvent to be required, the solvent having to be contaminated by use and thus having to be undergo complex disposal, the suggested cleaning device permits reliable and automated removal of firmly adhering residues in female threads of the closure head for a reactor pressure vessel without solvents being required and having to undergo complex disposal.

By turning at least one of the reels, the other part of the cleaning tape may be simply and rapidly replenished, since a previously unused, prewound other part of the cleaning tape may travel between the reels and thus, using the pressing element, may be caused to mesh with the thread turns. If all of the cleaning tape has traveled between the reels or has been completely used up, the reels, together with the cleaning tape, may be exchanged in a simple manner. The used reels may be replenished by exchanging the cleaning tape so that there is only a minor amount of waste. When unwound, the cleaning tape may be 0.5 m, 1 m, 2 m, 5 m, 10 m, or 20 m in length, for example. A plurality of windings of the cleaning tape may be provided on the reels. The ends of the cleaning tape may preferably be detachably attached to the reels. At least one reel is preferably acted upon with resilient force such that the other part of the cleaning tape is tautened between the reels. Alternatively, it may be provided that when the pressing element is moved towards the longitudinal axis, the cleaning tape is tautened by at least one reel so that the other part of the cleaning tape also moves towards the longitudinal axis.

The cleaning device may preferably be used as part of an automated and/or remotely controlled tool for maintaining threaded holes on reactor pressure vessels. For example, the cleaning device may be arranged on a base structure of the tool that may be placed onto the reactor pressure vessel in order to be lowered vertically into threaded holes, likewise extending vertically, for cleaning the latter. In principle, the cleaning device may be used for any type of reactor pressure vessel, for example pressurized water reactors or boiling water reactors. As a rule, the reactor pressure vessel has a cover that is joined to a lower pressure vessel part of the reactor pressure vessel by means of the closure head. Bolts that may be inserted into the female thread, and nuts, are usefully used for securing the closure head. The cleaning device is preferably used subsequent to a scraper head device in order to remove any remaining grease film from the thread turns. The pressing element is preferably in touching contact with the other part of the cleaning tape on a side of the cleaning tape on a side of the cleaning tape facing the longitudinal axis or facing a center axis of the base body formed by the longitudinal axis in order to press the cleaning tape with the other, opposing side against the female thread, using the radial movement away from the longitudinal axis. In principle there are a number of options for embodying the pressing element. According to one preferred refinement, the pressing element is embodied as a scraper strip and/or has a plurality of male thread-like notches that extend away from the base body at regular intervals, like a toothed rack. The number of notches in the scraper strips preferably corresponds to the number of turns in the female thread. More preferably, the male thread like notches are embodied corresponding to the female thread, in particular in a form fit therewith when meshed. The drive may be purely mechanical, electrical, or electromechanical for moving the pressing element in particular parallel to the longitudinal axis. The pressing element may be caused by the drive to extend preferably radially away from the longitudinal axis and to retract radially towards the longitudinal axis.

The base body, pressing element, and drive are preferably dimensioned such that the other part of the cleaning tape, when extended, meshes with the turns in the female thread, in particular in a form fit, and, when retracted, the base body having the pressing element, the cleaning tape, and the reels may be inserted into and withdrawn from the female thread. For inserting and withdrawing the base body into and from the female thread, an electromechanical drive may be provided that is used to hold the cleaning device on the previously described tool and to move the cleaning device vertically into and out of the female thread. A plurality of adjacent female threads are preferably provided on the lower pressure vessel part and extend in particular about a circular opening of the lower pressure vessel part, which opening may be closed by the closure head, and are inserted therein. The cleaning tape, reels, and pressing element preferably have the same extension with respect to the longitudinal axis, wherein the pressing element and the reels may project beyond the cleaning tape towards the longitudinal axis.

There are also many options for embodying the cleaning tape. According to one preferred refinement, the cleaning tape is made of felt or a woven textile. As a rule, felt is construed to be a textile fabric made of an unordered fiber material that is difficult to separate. Felt may be produced from synthetic fibers and/or plant fibers by dry needling or by consolidation with water streams exiting from a nozzle bar under high pressure. Preferably a felt according to DIN standard 61200 is produced. It is particularly easy to remove grease film from the female thread turns using felt. If the grease film is removed and absorbed by the felt or the other part of the cleaning tape, by rotating the reel a previously unused other part of the cleaning tape may be caused to mesh with the female thread turns and the used other part of the cleaning tape may be wound up on a reel. According to another preferred embodiment, the cleaning device has at least one roller, the roller being arranged on the base body opposing the pressing element. Two rollers that are arranged spaced apart from one another are preferably provided that are arranged on the base body opposing the pressing element in order to attain a balanced arrangement in terms of force and statically when the base body is inserted into the female thread. The two rollers arranged spaced apart from one another and the pressing element are preferably arranged in transverse extension of the base body like a type of triangle. Preferably two rollers arranged spaced apart from one another arranged on the base body are arranged, one at each end of the pressing element, in particular on the cover surfaces of the base body. When the base body is inserted into the female thread, when the cleaning tape is meshed with the female thread, the rollers are preferably touching the female thread.

According to one preferred refinement, for attaching the reels to the base body in a simple manner, a locking device is provided on the base body for attaching the reels to the base body. The locking device is preferably embodied as clips. More preferably, a locking device for each transverse side of the reel is provided on the base body. In the extension of their center axis the reels preferably have an overhang, in particular a circular overhang in profile, that may be locked into the locking device. The reels may be attached to the base body and exchanged in a simple manner using the locking device.

According to another preferred refinement, a guide device engaging with the pressing element is provided in order to make it possible for the pressing element to move exclusively radially. The guide device may be embodied like a toothed rack, by means of which the pressing element may be moved, on the one hand, and on the other hand may be moved exclusively radially.

With respect to the drive, according to one preferred refinement, an actuating element actuatable in the direction of the longitudinal axis is provided, the actuating element being embodied like a slide and being movement-coupled to the pressing element for moving the pressing element radial to the longitudinal axis. The actuating element is usefully actuated for moving, in particular for extending and retracting, the pressing element by means of an electromechanical drive, for example using a motor, a hydraulic element, or pneumatically. The electromechanical drive is preferably arranged outside of the base body spaced apart therefrom towards the longitudinal axis. The actuating element translates a movement towards the longitudinal axis into a movement radial to the longitudinal axis so that when the base body is inserted into the female thread the pressing element may be caused to mesh with the turns in the female thread.

In principle there are many options for embodying the base body. According to one particularly preferred refinement it is provided that the base body has a cylinder-like shape, the pressing element and/or the other part of the cleaning tape are arranged on the lateral surface of the cylinder- like shape, and the pressing element and the other part of the cleaning tape advance out of the lateral surface when moving away from the longitudinal axis. The pressing element and/or the other part of the cleaning element are preferably positioned against the lateral surface in a fluid and/or dust-tight manner so that residues that have been cleaned out of the turns in the female thread cannot travel into the cylinder-like interior of the base body. The lateral surface preferably has a recess for the pressing element and/or the other part of the cleaning element.

In a retracted position, that is, when the other part of the cleaning tape is not meshed with the turns in the female thread, the pressing element and/or the other part of the cleaning tape preferably does not project beyond the lateral surface and/or is flush against the lateral surface. The cylinder-like base body is preferably closed at its one cover surface that may be inserted into the female thread, while, at the opposing cover surface, the drive for moving the scraper strips is removed from the interior of the cylinder-like base body or is insertable into the interior. In the case of the previously described actuating element, the latter may extend within a core element extending radially towards the longitudinal axis and may be bordered radially, as shown in the sectional view, by the roller, the pressing element, and/or the other part of the cleaning tape.

A motor is usefully provided for driving the base body and is set up to rotate the base body about the longitudinal axis. The motor may be arranged inside the base body or outside of the opposing cover surface. The motor is advantageously provided on the previously described tool, however, in order to rotate the base body having the pressing element, the reels, and the cleaning tape about the longitudinal axis. In principle the pressing element may be embodied from any material. According to one preferred refinement, the pressing element is made of plastic and/or is actuated with resilient force so that the pressing element, and thus also the other part of the cleaning tape, is urged radially away from the longitudinal axis by the resilient force. The plastic is preferably a hard plastic that may be used for removing the firmly adhering residual grease in the turns in the female thread, without damaging the turns, by rotating the base body. For actuating with resilient force, the pressing element may be embodied with a spring provided between drive and pressing element in order to exert a uniform pressure on turns in the female thread. The object of the invention is also attained using a closure head for a reactor pressure vessel having a cleaning device as described in the foregoing, the closure head having the female thread and, when the base body is inserted into the female thread, the pressing element meshing with the female thread due to moving radially away from the longitudinal axis. Due to the form-fit embodiment, in particular radial to the longitudinal axis, the cleaning tape caused to mesh with the female thread by means of the pressing element can itself remove undesired residues from thread valleys in the thread turns by rotating the base body.

In this context, according to one preferred refinement it is provided that, when the base body is inserted into the female thread, the other part of the cleaning tape is caused to mesh with the female thread due to the pressing element moving radially away from the longitudinal axis. The other part of the cleaning tape is preferably positioned touching the thread valley and/or the thread flanks of the female thread when the base body is inserted into the female thread. In principle the cleaning device and the closure head may be used with any threads. In one preferred refinement, the female thread is embodied as a metric Iso thread having M155 or Ml 80 nominal diameter. It is furthermore preferred that the base body with retracted pressing element, that is, pressing element moved inward towards the longitudinal axis, has a diameter, in extension radial to the longitudinal axis, smaller than the nominal diameter of the female thread, and, when the pressing element is extended, has a larger or the same nominal diameter. It is furthermore preferred that the female thread and/or the notches has/have a thread pitch of > 4.5 or 6. The object of the invention is furthermore attained using a cleaning apparatus with a cleaning device as described in the foregoing or with a closure head as described in the foregoing, having a rod-like cleaning device for cleaning off the cleaning tape, a cleaning bar being provided on the cleaning element in order to wipe away, along an extension of the cleaning element, residues on the cleaning element that were cleaned off by the cleaning tape.

The cleaning element is preferably embodied separately from the cleaning device and/or the closure head, for instance as a separate device provided on the tool. Like the pressing element, the cleaning element preferably also has a longitudinal extension, wherein, however, instead of notches, a linearly extending edge is provided. On the edge of the cleaning element, the cleaning tape may be cleaned off along is longitudinal extension, so that residues cleaned off of the female thread are transferred to the cleaning element. The cleaning bar is preferably driven electromechanically in order to wipe off the residues transferred from the cleaning tape onto the cleaning element along the edge and thus to collect such residues for further disposal. Once the cleaning tape has removed undesired residues from the female thread, the cleaning tape may be cleaned off in a simple manner using the suggested cleaning element and the residues that have been cleaned off may be collected by the cleaning bar. Finally, the object of the invention is attained using a method for cleaning a female thread of a closure head for a reactor pressure vessel, having a base body that may be inserted into the female thread and that has a longitudinal axis, having at least two reels arranged parallel to one another, the axes thereof extending parallel to the longitudinal axis, having a cleaning tape, at least part of which is wound up on the reels, another part of the cleaning tape running between the reels, and having a pressing element that is arranged between the reels, having the steps:

Inserting the base body into the female thread;

Moving the pressing element of radially away from the longitudinal axis so that the other part of the cleaning tape meshes with the turns in the female thread; and,

Rotating the base body about the longitudinal axis.

The suggested method permits, in a particularly simple and reliable manner, removal of undesired residues, such as for example grease, from turns in the female thread. To this end, the base body having pressing element, which is initially oriented towards the longitudinal axis, is inserted into the female thread. Then the pressing element is moved or extended radially away from the longitudinal axis out of the aforesaid retracted position until the other part of the cleaning tape meshes, preferably in a form fit, with the turns in the female thread. By rotating the base body about the longitudinal axis, for example by means of a motor driving the base body, the cleaning tape“scratches” undesired residues out of the thread valleys of the turns in the female thread.

For moving the pressing element when the base body is inserted into the female thread, according to one preferred refinement of the method it is useful for the actuation of an actuating element that is movement-coupled, like a slide, to the pressing element to occur radial to the longitudinal axis towards the longitudinal axis for moving the pressing element.

According to another preferred refinement, the method has the steps:

Moving the pressing element, by means of the drive, radial to the longitudinal axis;

Moving the base body out of the female thread; and,

Cleaning off the scraper strips on a rod-like cleaning element by rotating the cleaning tape in touching contact with the cleaning element against the cleaning element. For one skilled in the art, additional embodiments and advantages of the method result analogous to the cleaning device, closure head, and/or cleaning element described in the foregoing.

Brief description of the drawings

The invention is explained in greater detail in the following, making reference to the enclosed drawings and using one preferred embodiment. Fig. 1 is a schematic perspective elevation of a cylinder- like cleaning device having a cleaning tape according to one preferred embodiment of the invention; Fig. 2 is a schematic perspective rear view of the cleaning device according to Fig. 1, with cleaning tape removed;

Fig. 3 is a schematic top view of the cleaning device according to Fig. 1 and Fig. 2;

Fig. 4 is a schematic side view of the cleaning device according to Fig. 1 through

Fig. 3; and,

Fig. 5 is a schematic perspective elevation of a segment of a lower part of a reactor pressure vessel having the cleaning device according to Figs. 1 through 3.

Detailed description of the exemplary embodiments

Fig. 1 is a schematic perspective elevation of a cleaning device 1 for cleaning a female thread 2 of a closure head 3 for a reactor pressure vessel 4, a segment of which is depicted in Fig. 5, according to a preferred embodiment. The cleaning device 1 has a cylinder- like base body 5 that forms a longitudinal axis and has two reels 6 arranged parallel to one another, the axes of which extend parallel to the longitudinal axis. A part of a cleaning tape 7 is wound onto the reels 6, while another part of the cleaning tape 7 extends between the reels 6. The transverse extension of the cleaning tape 7 is smaller or approximately equal to the depth of the female thread 2. The cleaning tape 7 is made of felt or woven textile. Using the reels 6, the cleaning tape 7 may be caused by a motor to travel along its longitudinal extension, so that other parts of the cleaning tape 7 may be arranged successively between the reels 6.

The cleaning device 1 furthermore has a pressing element 8 that is arranged between the reels 6 and that may be moved radial to the longitudinal axis by means of a drive 9 in order, when the base body 5 is inserted into the female thread 2, to cause the other part of the cleaning tape 7 to mesh with the turns 2 in the female thread 2. In a top view onto the base body 5, depicted in Fig. 3, provided laterally on the pressing element 8 are flat guides 8a for the cleaning tape 7 that, like the pressing element 8, extend towards the longitudinal axis and are pivoted by about 45° to a longitudinal side of the pressing element 8. Reels 6, cleaning tape 7, and pressing element 8 are arranged on the base body 5. As a scraper strip like a toothed rack, the pressing element 8 is provided with a plurality of male thread-like notches 10 that extend away from the base body 5. Pressing element 8, reels 6, and cleaning tape 7 extend between opposing cover surfaces 11 of the base body 5 and are arranged parallel to the longitudinal axis of the base body 5, with respect to the transverse extension of the cleaning tape 7. The pressing element 8 may be moved by means of the drive 9 radial to the longitudinal axis between a retracted position, in which the pressing element 8 and thus also the other part of the cleaning tape, do not project beyond a lateral surface of the cylinder-like base body 5, and an extended position, depicted in Fig. 1, in which the pressing element 8 and thus also the other part of the cleaning tape 7 advance out of the lateral surface and projects radially beyond the latter.

Fig. 2 is a schematic perspective rear view of the cleaning device 1 according to Fig. 1 with the cleaning tape 7 removed. Provided interiorly on both cover surfaces 11 inside the base body 5 in the form of clip elements are locking devices 12 in each of which a reel 6 may lock with pins provided on its two transverse sides in order to be able to exchange the reels

6 in a simple manner. The drive 9 is embodied as an actuating element like a slider, so that the pressing element 8 and thus the other part of the cleaning tape 7 may be moved towards the longitudinal axis radial to the longitudinal axis by actuating the actuating element on the upper cover surface 11. Furthermore, as may be seen in Fig. 2 and Fig. 3, two rollers 13 are provided on the base body 5 at the height of the cover surfaces 11. When the pressing element

8 is extended, both the rollers 13 and the other part of the cleaning tape 7 pressed against the female thread 2 by the pressing element are positioned against the female thread 8, wherein, as may be seen in Fig. 3, the two rollers 13 and the pressing element 8 are arranged on the base body 5 in a triangular shape.

The cleaning device 1 is part of a tool 14, depicted in Fig. 5, for maintaining female threads 2 of the closure head 3 of a segment of a reactor pressure vessel 4. Once a cover (not shown) of the reactor pressure vessel 4 has been opened, the tool 14 may be placed onto the lower part of the pressure vessel, as shown in Fig. 5, after bolts (not shown) have been removed from the female thread 2. The base body 5 with the retracted pressing element 8 is lowered downward vertically using the cleaning device 1 by means of a lowering movement into one of the female threads 2 until the lower cover surface 11 comes to rest in the thread bore of the female thread 2.

Then the pressing element 8 is moved by means of the drive 9 radially away from the longitudinal axis towards the female thread 2 until the male thread-like notches 10 cause the other part of the cleaning tape 7 to mesh with the turns in the female threads 2. In addition, the pressing element 8, made of a hard plastic, is acted upon by a resilient force such that the resilient force urges the pressing element 8 radially away from the longitudinal axis towards the female thread 2 and thus presses the other part of the cleaning tape 7 against the female thread 2. By rotating the base body 5 about the longitudinal axis thereof by means of a motor 15, the cleaning tape 7“scratches” off residues deposited on the turns in the female thread 2.

Once the residues have been removed from the turns in the female thread 2, the pressing element 8 is moved radial to the longitudinal axis by means of the drive and the reel 6 is tautened so that the other part of the cleaning tape 7 moves towards the longitudinal axis and the base body 5 is guided upward out of the female thread 2 in a vertical movement. The residues cleaned out of the female threads 2 and accumulated on the cleaning tape 7 may be cleaned off by means of a rod- like cleaning element (not shown). The residues now on the cleaning element may then be collected for disposal by means of a cleaning bar provided on the cleaning element.

To this end, the cleaning tape 7 is passed by the opposingly arranged rod-like cleaning elements such that the residues are wiped off of the cleaning tape 7 onto the rod-like cleaning elements. The cleaning bar, not visible, then uses a vertical movement to wipe off residues deposited on the rod-like cleaning elements and collects these residues in a collection unit.

The exemplary embodiments described are merely examples that may be modified and/or improved in many ways within the scope of the claims. Each feature that was described for a specific exemplary embodiment may be used independently or in combination with other features in any other exemplary embodiment. Each feature that was described for an exemplary embodiment of a specific category may likewise be used in an exemplary embodiment from another category.

Reference list

Cleaning device 1

Female thread 2 Closure head 3

Reactor pressure vessel 4

Base body 5

Reel 6

Cleaning tape 7 Pressing element 8

Guide 8a

Drive 9

Notch 10

Cover surface 11 Guide device l la

Locking devices 12

Roller 13

Tool 14

Motor 15