Abstract:
An apparatus for dismantling a radioactively contaminated tubular installation part which is located under water contains a base part which can be fixed to the installation part and in which a rolling cutting apparatus is mounted. The rolling cutting apparatus can be positioned in or on the installation part and has at least one cutting roller which can be moved to the inner or outer surface of the installation part and can be moved along it. The apparatus can be used to dismantle and remove even installation parts to which access is difficult, for example the cyclones which are installed in the water/steam separator of a boiling water reactor.

Description:
BACKGROUND OF THE INVENTION  
     FIELD OF THE INVENTION  
       [0001]     The invention relates to an apparatus for dismantling a radioactively contaminated installation part. The invention also relates to a method, which is carried out using an apparatus such as this, for dismantling a water separator in a boiling water reactor.  
         [0002]     Particularly during the demolition of a nuclear power station that has been shut down, there are a large number of radioactively contaminated installation parts which must be dismantled into transportable components before they can be disposed of. In order to prevent the personnel carrying out the dismantling process from being radioactively contaminated, a dismantling process such as this must be carried out by remote control, under water. Furthermore, the dismantling process should be carried out using appliances and methods in which as little secondary waste, for example swarf or dust, as possible is produced which, in addition to contamination of the water, can also lead to a visual impediment, which impedes the ability to carry out the dismantling process correctly. Furthermore, installation parts such as these are often physically complicated structures with components to which access is difficult and which require the use of special dismantling apparatuses.  
         [0003]     One such complex installation part, by way of example, is the water/steam separator (referred to for short as the water separator in the following text) of a boiling water reactor. A water separator such as this is used for separation of the water/steam mixture that is created in the reactor pressure vessel of a boiling water reactor, and is illustrated in  FIG. 6 . The water separator  2  contains a large number of tubular cyclones  4 , in which steam and water are separated. The cyclones  4  are disposed in a mounting rack  6 , and are welded in the mounting rack  6  by of holding struts  10 , which are fixed to mounting rings  8 .  
         [0004]      FIGS. 7 and 8  show enlarged illustrations of a cyclone  4  such as this. This is a tubular installation part which is composed of a plurality of tubes  12   a - d , which are disposed coaxially with respect to one another and partially one inside the other. The inner tube  12   a  also has internal fittings in the form of a swirl body  16  in a conical tube section  14 . When disposing of the water separator, the cyclones  4  must be dismantled within the water separator, that is to say in spatially confined conditions, in order to remove them.  
       SUMMARY OF THE INVENTION  
       [0005]     It is accordingly an object of the invention to provide an apparatus for dismantling a radioactively contaminated installation part and a method for dismantling the installation part which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, with which it is possible to dismantle a tubular installation part, to which access is difficult and which is under water, into pieces.  
         [0006]     With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for dismantling a radioactively contaminated tubular installation part disposed under water. The apparatus contains a base part for fixing to the installation part; and a rolling cutting apparatus mounted in the base part. The rolling cutting apparatus is positioned in or on the installation part and has at least one cutting roller being moved to an inner or outer surface of the installation part and being moved along the installation part.  
         [0007]     The apparatus for dismantling the radioactively contaminated tubular installation part, which is under water, contains the base part which can be fixed to the installation part and in which the rolling cutting apparatus is mounted. The rolling cutting apparatus can be positioned in or on the installation part and has at least one cutting roller which can be moved to the inner or outer surface of the installation part and can be moved along it. The use of an apparatus which can be fixed to the installation part allows the installation part to be dismantled while it is still in the installed state within a component whose position is fixed during the dismantling process, for example within a reactor pressure vessel which is installed in a fixed position in a nuclear power station or within a part of a component such as this, which has been placed on the bottom of a flooded pond in the nuclear power station and has been removed from its installed position in advance. The use of a rolling cutting apparatus also prevents secondary waste from being created in the form of swarf or grinding dust, so that on the one hand this prevents contamination of the water, and on the other hand prevents visual impediment when checking the work carried out.  
         [0008]     An apparatus according to the invention is particularly suitable for dismantling the water separator, which contains a large number of cyclones, in a boiling water reactor, in which the cyclones are each separated into a plurality of tubular pieces, are removed from the water separator in pieces, and are stored in storage containers that are provided.  
         [0009]     Other features which are considered as characteristic for the invention are set forth in the appended claims.  
         [0010]     Although the invention is illustrated and described herein as embodied in an apparatus for dismantling a radioactively contaminated installation part and a method for dismantling the installation part, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.  
         [0011]     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIGS. 1 and 2  are diagrammatic, partially cutaway illustrations of an apparatus which has been inserted into an interior of a cyclone, in an initial or working position, according to the invention;  
         [0013]      FIG. 3  is a diagrammatic, partially cutaway illustration of an alternative embodiment of the apparatus according to the invention, which is suitable for use in pieces of tubing with a larger nominal width;  
         [0014]      FIG. 4  is a diagrammatic, illustration of a further alternative embodiment of the apparatus according to the invention, which is suitable for use in tubular installation parts for which more space is available in the outer area;  
         [0015]      FIG. 5  is a diagrammatic, partial plan view of a water separator whose cyclones have already been partially dismantled, with the apparatus in the working position, which is used for separation of holding struts, by which the cyclones are welded;  
         [0016]      FIG. 6  is a diagrammatic, perspective view of a water separator in a boiling water reactor;  
         [0017]      FIG. 7  is a diagrammatic, perspective view of a cyclone of the water separator; and  
         [0018]      FIG. 8  is a diagrammatic, longitudinal sectional view through the cyclone. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown an apparatus according to the invention which is fitted to or in a cyclone  4  in an initial position. The apparatus contains a base part  20  in which a shaft  22  is mounted such that it can rotate, at whose free end a rolling cutting apparatus  24  is disposed. In the installed state, the cyclone  4  is located in the water separator and is surrounded by adjacent cyclones, which are not illustrated in  FIG. 1  for clarity reasons. The rolling cutting apparatus  24  has two lever arms  28   a  and  28   b , which are mounted so that they can pivot about a respective pivoting axis  26   a ,  26   b , which runs at right angles to the shaft axis, and at the free end of each of which lever arms  28   a ,  28   b  a cutting roller  30  is mounted, whose roll axis, once the lever arms  28   a ,  28   b  have been pivoted out sideways, that is to say after the cutting rollers  30  have been moved to the inner circumference of the tube  12   a , runs parallel to its center axis  120 .  
         [0020]     In order to pivot the lever arms  28   a ,  28   b , the rolling cutting apparatus  24  contains a hydraulic actuating apparatus with a hydraulic cylinder  32  which acts axially, that is to say in the direction of the axis of the shaft  22 , and whose piston acts via transmission levers  34   a ,  34   b  on the lever arms  28   a ,  28   b , pivoting them outward or inward.  
         [0021]     A bearing plate  40  of the base part  20  is seated on the upper tube  12   d  of the cyclone  4 . A sleeve  42 , which extends in the axial direction, is fixed to the bearing plate  40 , is pushed over the tube  12   d  and is fitted at its free end with a plurality of radially acting clamping cylinders  44 , whose pistons are moved radially against the tube  12   d  and fix the apparatus with a force fit on the cyclone  4 . In other words, the base part  20  is fixed with a force fit to the installation part, in the example of the cyclone  4 , such that the base part  20  is supported by the installation part.  
         [0022]     A rotating drive  46 , which drives the shaft  22 , is disposed on the bearing plate  40 . The base part  20  is fixed at the end of a handling linkage  48 , by which the apparatus is positioned on or in the cyclone  4 .  
         [0023]     A rotating bushing  50  is disposed at the opposite end of the shaft  22  to the rolling cutting apparatus  24 , and is used to supply hydraulic fluid to the hydraulic cylinder  32 .  
         [0024]     When the cutting rollers  30  are positioned on the internal circumference of the tube  12   a , that is to say in the working position illustrated in  FIG. 2 , rotation of the shaft  22  now results in the tube  12   a  being cut through above the conical tube section  14  which contains the swirl body of the cyclone  4 .  
         [0025]     Once the inner tube  12   a  has been cut through above the tube section  14 , the cutting rollers  30  are moved back, and that part of the cyclone  4  which forms the upper, cut-off part of the inner tube  12   a  and the tubes  12   b - 12   d  is raised out of the water separator  2  with the aid of the handling linkage  48  ( FIG. 6 ) and is moved to a processing station in which this part is dismantled into further, smaller pieces. The upper holding struts  10  (see  FIG. 6 ) have been cut through with the aid of a hydraulic cutting tool in a previous step, for this purpose.  
         [0026]     As can be seen in  FIG. 3 , in an alternative refinement, the apparatus contains a rolling cutting apparatus  60  which can be inserted into the interior of a tube  12   e . The rolling cutting apparatus  60  is disposed analogously to the exemplary embodiment shown in  FIGS. 1 and 2  at the end of the shaft  22 , which is mounted such that it can rotate in the base part  20  which is seated on the tube. Components which have the same function effect but are designed differently are provided with the same reference symbols in  FIG. 3  as in  FIGS. 1 and 2 .  
         [0027]     The rolling cutting apparatus  60  contains two cutting rollers  30 , which are each mounted such that they can rotate about a rotation axis which runs parallel to the shaft  22 . The cutting rollers  30  can be moved to the inner surface of the tube  12   e  with the aid of a hydraulic actuating apparatus and by a hydraulic cylinder  61 , which acts transversely with respect to these rotation axes. The cutting rollers  30  are for this purpose mounted in two holding jaws  62 , which are mounted such that they can move transversely with respect to the center axis  120 . An embodiment such as this is particularly suitable for tubes  12   e  whose nominal width is sufficient to allow such a lateral movement to be carried out directly by a hydraulic cylinder  61  without any separate transmission being required for this purpose in order to change the direction between the positioning movement and the movement of the piston of the hydraulic cylinder.  
         [0028]     In the alternative refinement of the apparatus according to the invention as shown in  FIG. 4 , a mounting rack  70  with three arms  72  is mounted on the base part  20 , only one of which arms  72  is illustrated in  FIG. 4 , for clarity reasons. The mounting rack  70  surrounds the tube, which, in the exemplary embodiment, is the lower part of the inner tube  12   a  of the cyclone  4 , which remains after the cutting-off process as shown in  FIGS. 1 and 2 . The mounting rack  70  is mounted with the aid of the rotating drive  46  in the base part  20  such that it can rotate about a rotation axis which, after correct centering of the base part  20  on the inner tube  12   a , coincides with the center axis  120 . Each of the three arms  72  which are mounted on the base part  20  separated by an angle of 120° is fitted with a rolling cutting apparatus  74 , whose cutting roller  30  can be moved radially against the outer circumference of the lower part with the aid of a hydraulic actuating apparatus which contains a hydraulic cylinder  76 .  
         [0029]     The base part  20  also has a holding frame  78  with three holding arms  80 , which each clasp the mounting rack  70  and are fitted underneath the mounting rack  70  with the radially acting clamping cylinder  44 , by which the base part  20  is fixed to the tube  12   a , so that the apparatus is supported by the installation part in the same way as in the exemplary embodiments explained above—in the example the lower part of the inner tube  12   a.    
         [0030]     Dismantling of a tubular installation part with the aid of a rolling cutting apparatus such as this which engages on the outer circumference is expedient when, on the one hand, sufficient space is available outside the installation part, in that, by way of example, the tubular installation part is processed only in the removed state in a processing station which is provided specifically for this purpose, and when, furthermore, because of fittings within the tubular installation part, with the swirl body of the cyclone being located in the conical tube section  14  in the illustrated example, access into the interior of the tubular installation part is made more difficult or is impossible.  
         [0031]     Once the inner tube  12   a  has been successively dismantled, the remaining lower parts in  FIG. 5 , which are welded to the holding struts  10 , are cut off from the rest of the assembly with the aid of a rolling cutting apparatus  100 . For this purpose, the rolling cutting apparatus  100  contains four cutting rollers  30 , which are opposite one another in pairs. In each case one of the cutting rollers  30 , which are opposite one another in pairs, is mounted on the piston of a hydraulic cylinder  102  and can be moved against the holding strut  10  which runs between adjacent inner tubes  12   a . The holding strut  10  is cut through by a vertical oscillating movement, at right angles to the plane of the drawing, with the cutting rollers  30  being pressed against it at the same time, so that the lower parts of the inner tube  12   a  can be removed from the rest of the assembly. The upper holding struts (process step before the cutting off of the upper part of the cyclone  4  as illustrated in  FIGS. 1 and 2 ) can also be cut off in the same way.  
         [0032]     This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 059 586.0-54, filed Dec. 9, 2004; the entire disclosure of the prior application is herewith incorporated by reference.