Patent Publication Number: US-2005117691-A1

Title: Method and apparatus for disposing of a fuel assembly channel of a boiling water reactor plant

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This is a continuing application, under 35 U.S.C. § 120, of copending international application No. PCT/EP03/05339, filed May 22, 2003, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. 102 26 245.4, filed Jun. 13, 2002; the prior applications are herewith incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to a method for disposing of a fuel assembly channel or casing. The invention also relates to a method and an apparatus for disposing of radioactively contaminated parts of a boiling water reactor plant.  
      Internal components of a nuclear reactor plant that come into contact with the cooling water of the primary circuit are radioactively contaminated to a considerable extent and, if they were installed in the reactor core, are additionally activated. On account of operationally induced wear, which affects core internal components to a particularly high degree, it is necessary for these parts to be removed and replaced with new ones. The parts that have been removed have to be conditioned under strict safety conditions to make them suitable for disposal. Such a wearing part in a boiling water reactor is also the fuel assembly channel, which has been embrittled as a result of high levels of radiation, of a spent fuel assembly, as illustrated in a plan view of the bottom side and of one of the longitudinal sides in  FIGS. 1A and 1B , respectively, for example. The wall  2  of such a fuel assembly channel  4  surrounds a substantially cuboidal cavity  6 . The fuel assembly channel  4  is open at its end sides and is provided with supporting struts  8   a  at opposite corners of just one end side, which struts are used to secure the fuel assembly channel  4  to a non-illustrated fuel assembly top fitting. Furthermore, in its lower region, the fuel assembly channel  4  is provided with further elements, in the present example, lugs  8   b  and external plates  8   c,  which are specific to the type of channel illustrated in the example. During conditioning of such a fuel assembly channel, the channel is generally compressed and, then, cut into small pieces. However, such a procedure is complex.  
     SUMMARY OF THE INVENTION  
      It is accordingly an object of the invention to provide a method and apparatus for disposing of a fuel assembly channel of a boiling water reactor plant that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that represents a simplification compared to the procedure described in the prior art and that enables disposal of radioactively contaminated parts of a boiling water reactor plant.  
      With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for disposing of a hollow fuel assembly channel of a fuel assembly of a boiling water reactor plant, including the steps of providing the hollow fuel assembly channel that is to be disposed and stabilizing the fuel assembly channel with a support structure.  
      According to the invention, the fuel assembly channel is stabilized using a support structure. In other words, the fuel assembly channel is not destroyed, but, rather, is provided with one or more components that support it and impart a greater strength or stability to it. This means that complex pressing and destruction of the fuel assembly channel is no longer required, which simplifies its disposal. A fuel assembly channel that has been so conditioned or prepared for disposal may, moreover, serve simultaneously as a transport container for further parts that are to be disposed of and have been conditioned accordingly, in particular, for core internal parts or for small-volume core scrap.  
      With the objects of the invention in view, there is also provided a method for disposing of a hollow fuel assembly channel of a fuel assembly of a boiling water reactor plant, including the step of stabilizing the hollow fuel assembly channel that is to be disposed with a support structure.  
      With the objects of the invention in view, there is also provided a method for disposing of radioactively contaminated parts of a boiling water reactor plant, including the steps of providing a radioactively contaminated, hollow fuel assembly channel that is to be disposed, stabilizing the fuel assembly channel with a support structure, and utilizing the support structure as transport container for the fuel assembly channel.  
      With the objects of the invention in view, there is also provided a method of disposing radioactively contaminated parts of a boiling water reactor plant, including the steps of stabilizing a radioactively contaminated, hollow fuel assembly channel that is to be disposed with a support structure and transporting the fuel assembly channel with the support structure as a transport container for the fuel assembly channel.  
      In accordance with another mode of the invention, the fuel assembly channel is provided with a carry handle. The handle allows it to be handled in the same way and using the same devices as provided for the handling of the fuel assembly.  
      In accordance with a further mode of the invention, the support structure is pre-assembled and introduced into the fuel assembly channel. Such a configuration considerably shortens the processing time required at the fuel assembly channel to fit the support structure.  
      In particular, the fuel assembly channel is closed off on one of its end sides with the aid of a base plate that is disposed on the support structure and serves as a base. As such, it can be used as a container for holding small-volume core scrap.  
      With regard to the method according to the invention, because the stabilized fuel assembly channel is used as transport container for further radioactively contaminated parts, it can be disposed of at particularly low cost together with the core scrap.  
      In accordance with an added mode of the invention, the support structure is provided with a base plate forming a base of the support structure and the closing step is carried out by closing off the one side with the base plate.  
      In accordance with an additional mode of the invention, the leaves are separated from a control element that is to be disposed of and are introduced into the stabilized fuel assembly channel. Because the longitudinal and transverse dimensions of the leaves of a control element may correspond substantially to those of a fuel assembly channel, these leaves can be accommodated in a fuel assembly channel in an extremely space-saving form, which channel is capable of accommodating the leaves of three control elements.  
      In particular, the support structure uses an internal partition to divide the fuel assembly channel into at least two subregions that are supported when the leaves are being introduced into one of the subregions. This facilitates filling of the fuel assembly channel.  
      In accordance with yet another mode of the invention, the stabilizing step is carried out by inserting the support structure inside the hollow fuel assembly channel.  
      In accordance with yet a further mode of the invention, there are provided the steps of dividing the stabilized fuel assembly channel into at least two subregions with an internal partition of the support structure and supporting the leaves in the subregions when the leaves are introduced therein.  
      In accordance with yet an added mode of the invention, there are provided the steps of separating control rod leaves that are to be disposed from a control rod and introducing the separated control rod leaves into the stabilized fuel assembly channel.  
      With the objects of the invention in view, there is also provided an apparatus for disposing of radioactively contaminated parts of a boiling water reactor plant, including a transport container having a support structure, the support structure shaped to stabilize a radioactively contaminated fuel assembly channel that is to be disposed.  
      In accordance with yet an additional feature of the invention, the support structure has a carrying handle for transporting the transport container.  
      In accordance with again another feature of the invention, the fuel assembly channel has a side and an opening on the side and the support structure has a base plate shaped to close off the opening on the side of the fuel assembly channel.  
      In accordance with again a further feature of the invention, the fuel assembly channel has an interior and the support structure divides the interior of the fuel assembly channel into at least two subregions when the support structure is disposed in the fuel assembly channel and has at least one partition plate disposed on the base plate and perpendicular to the base plate.  
      With the objects of the invention in view, there is also provided an apparatus for disposing of a radioactively contaminated fuel assembly channel of a boiling water reactor plant, the assembly channel having a side, an opening on the side, and an interior, the apparatus including a transport container having shape sized to fit in the interior of the fuel assembly channel to be disposed and configured to stabilize structurally the fuel assembly channel and a support structure having a carrying handle for transporting the transport container and a base plate shaped to close off the opening on the side of the fuel assembly channel.  
      Other features that are considered as characteristic for the invention are set forth in the appended claims.  
      Although the invention is illustrated and described herein as embodied in a method and apparatus for disposing of a fuel assembly channel of a boiling water reactor plant, it is, nevertheless, not intended to be limited to the details shown because 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.  
      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  
       FIG. 1A  is a plan view of a prior art fuel assembly channel as viewed from the right end of  FIG. 1B ;  
       FIG. 1B  is a fragmentary, side elevational view of the fuel assembly channel of  FIG. 1A ;  
       FIG. 2A  is a plan view of a support structure according to the invention as viewed from the right end of  FIG. 2B ;  
       FIG. 2B  is a fragmentary, side elevational view of the support structure of  FIG. 2A ;  
       FIG. 3A  is a plan view of a fuel assembly channel according to  FIGS. 1A and 1B  that has been stabilized with the support structure of  FIGS. 2A and 2B  as viewed from the right end of  FIG. 3B ;  
       FIG. 3B  is a fragmentary, side elevational view of the stabilized fuel assembly channel of  FIG. 3A ;  
       FIG. 4A  a plan view of the stabilized fuel assembly channel of  FIGS. 3A and 3B  as viewed from the right end of  FIG. 4B  and is filled with leaves of control rods; and  
       FIG. 4B  is a fragmentary, side elevation view of the stabilized fuel assembly channel of  FIG. 4A  filled with the leaves of the control rods. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring now to the figures of the drawings in detail and first, particularly to  FIGS. 2A and 2B  thereof, there is shown a support structure  10  having a base plate  12  that bears a partition plate  14  running perpendicular to the flat side of the base plate  12  and, in particular, is welded to the partition plate  14 . The longitudinal extent of the partition plate  14  is greater than the longitudinal extent of the fuel assembly channel  4  and, at its free end that is remote from the base plate  12 , the partition plate  14  is provided with a recess  16  that forms a carry handle  18 . A spacer plate  20  is secured to the base plate  12 , transversely with respect to the partition plate  14  and perpendicular to the base plate  12 , passing through the partition plate  14 , which is provided with a slot  22  in this region.  
       FIGS. 3A and 3B  show the fuel assembly channel  40  that has been stabilized using the support structure  10 . For such a purpose, the support structure has been introduced into the empty fuel assembly channel  4  from the base side until the base plate  12  closes off the empty fuel assembly channel  4  and forms a base. The carrying handle  18 , then, projects beyond the fuel assembly channel  4 . It can also be seen from  FIGS. 3A and 3B  that the fuel assembly channel  4  is divided into two subregions  42 ,  44  by the partition plate  14 .  
      In accordance with  FIGS. 4A and 4B , control rod leaves  24 , which, in a previous working step, have been separated from control rods that are to be disposed of and of which an arch  26  of another carrying handle  18 , which has been halved by previous dismantling and is shown in  FIG. 4b , have been introduced into the fuel assembly channel  40  that has been stabilized using the support structure  10 .  
      The spacer plate  20  serves to support the control rod leaves  24  so that the space used to accommodate the control rod leaves  24  remains free of disruptive internals located in the lower region of the fuel assembly channel  4 . At the same time, four subchambers  46 , which can be used to accommodate small-volume core scrap, are formed beneath the control rod leaves  24 .