Abstract:
A container, a device, and a method encapsulate a fuel rod or a fuel rod portion in a gas-tight manner. The container has a hollow cylindrical container part which is closed at the free ends of the container part in a fluid-tight manner by a respective single-piece closure stopper. The closure stopper is provided with a channel that fluidically connects the flushing chamber of the container part to the exterior exclusively in an intermediate position, which is assumed prior to reaching an end position during the assembly process and in which the closure stopper additionally projects out of the container part by an axial length compared to the end position of the closure stopper.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application, under 35 U.S.C. §120, of copending international application No. PCT/EP2013/050558, filed Jan. 14, 2013, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent applications DE 10 2012 201 131.5 filed Jan. 26, 2012, DE 10 2012 203 347.5 filed Mar. 2, 2012, and DE 10 2012 210 409.7 filed Jun. 20, 2012; the prior applications are herewith incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a container, a device and a method for the gas-tight encapsulation of a fuel rod or of a fuel rod section. 
         [0003]    For transportation and/or storage purposes, defective fuel rods or fuel rod sections are inserted in a vacuum-tight and a fluid-tight fashion into containers or capsules such as are known for example from German patent DE 196 40 393 B4, from European patent application EP 1 248 270 A1, from European patent EP 1 600 982 B1, and from international patent disclosure WO 2010/084122 A1. Since the encapsulation of a fuel rod or of a fuel rod section is performed as close as possible to the original storage location, that is to say underwater within the fuel element storage basin, it is inevitable that water infiltrates into the open container during the insertion of the fuel rod or fuel rod section. The water must however be removed from the fuel rod container because, owing to decay heat, the water would evaporate and lead to an inadmissibly high internal pressure. For this reason, the closure elements used in the containers known from German patent DE 196 40 393 B4, from European patent application EP 1 248 270 Al and from European patent EP 1 600 982 B1 have a duct via which gas can be injected such that the water situated in the container is expelled. In the case of the closure plugs known in each case from German patent DE 196 40 393 B4 and from European patent application EP 1 248 270 A1, a coaxial duct is provided in each closure plug, in which coaxial duct there is arranged a spring-loaded valve which, by way of a closing element, closes off the duct in fluid-tight fashion. For the expulsion of the water, the closing elements are raised from their valve seat by a ram, and via a duct that is then opened, a gas is injected and the water is expelled via the likewise open duct of the oppositely situated closure element. In the case of the two known containers, the expulsion of the water takes place when the closure elements are, as a result of a screwing, welding or deformation process, situated in their final assembled position in which they close off the container in a fluid-tight fashion. 
         [0004]    In the container known from European patent EP 1 600 982 B1, a closure element is provided which can be screwed onto an external thread of the container and in which a seal element is mounted in axially displaceable fashion. In an intermediate position of the closure element, in which the closure element is not yet fully tightened, a parting joint exists between the sealing surface of the sealing element and the face surface, which interacts with the sealing surface to form a sealing pairing, of the hollow cylindrical container part, which parting joint communicates with a lateral ventilation opening in the closure element and, in the intermediate position, fluidically connects the exterior to the scavenging chamber of the hollow cylindrical container part. 
         [0005]    In order, in the case of the closure elements known from German patent DE 196 40 393 B4, from European patent application EP 1 248 270 A1 and from European patent EP 1 600 982 B1, to permit both an expulsion of the water situated in the container and also, in a final assembled state, reliable fluid-tight closure of the container, the closure elements are of multi-part and relatively complex construction. Furthermore, the handling thereof involves a correspondingly high level of manipulation effort. 
         [0006]    In the case of the container known from international patent disclosure WO 2010/084122 A1, there is provided as a closure element a cap which is pushed onto a hollow cylindrical container part and connected to the face surface thereof in cohesive fashion. The closure of the container is performed in a fluid-tight chamber. Before the closure, that is to say when the cap has not been mounted onto the hollow cylindrical container part, the liquid situated in the chamber is drawn out, and a vacuum-drying process is subsequently performed. Owing to the fact that, within the container equipped with a fuel rod, narrow gaps are present between the fuel rod and the internal wall of the container, it is in some circumstances possible for residual water to remain in the container. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention is therefore based on the problem of specifying a container for the gas-tight encapsulation of a fuel rod or of a fuel rod section, the closure element of which container is of simple construction and permits a simple and reliable fluid-tight, that is to say gas-tight and liquid-tight, closure of the container. The invention is furthermore based on the object of specifying a device and a method by which a container containing a fuel rod or fuel rod section can be closed with the least possible residual water content. 
         [0008]    Accordingly, the container has a hollow cylindrical container part which, at its two free ends, is closed off in fluid-tight fashion by a respective unipartite closure plug. The closure plug is provided with a duct which fluidically connects the scavenging chamber of the container part to the exterior exclusively in an intermediate position which is assumed during the assembly process before an end position is reached and in which the closure plug projects out of the container part by an axial projecting length. 
         [0009]    Since the closure plug is of unipartite form, the closure plug can be of technically very simple form and produced with little outlay. Since, furthermore, the duct situated in the closure plug fluidically connects the scavenging chamber of the container part to the exterior only when the closure plug is situated in an intermediate position, no additional closing elements are required within the duct, such that the duct, too, can be manufactured in a simple manner by way of bores or recesses. 
         [0010]    Within the context of the present invention, the expression “closure plug” should be understood to mean that, for the insertion of the closure plug into the hollow cylindrical container part, only a “plugging” action is required, that is to say a pushing-in action in the axial direction and no rotational movement. 
         [0011]    The intermediate position is a position in which the closure plug has already been pushed into the hollow cylindrical container part but has not yet reached the end position in which it closes off the hollow cylindrical container part in fluid-tight fashion by a cohesive or form locking connection. 
         [0012]    In one advantageous embodiment of the invention, the duct has a first duct section which runs parallel to the longitudinal axis of the closure plug from an inner face side of the closure plug and which issues into a second duct section, the latter running transversely with respect to the longitudinal axis and extending from a shell surface of the closure plug. A duct of this type can be produced in a simple manner by way of bores in a longitudinal or transverse direction respectively. 
         [0013]    To hold the closure plug securely in the intermediate position, detent devices are provided on the closure plug and/or hollow cylindrical container part on the outer circumference and/or on the inner circumference respectively, which detent devices detachably fix the closure plug in the intermediate position. 
         [0014]    If the closure plug, in the fully assembled position, is seated by way of an annularly encircling flange on a face surface of the hollow cylindrical container part, it is possible for the closure plug and hollow cylindrical container part to be connected to one another in a fluid-tight fashion, in a simple manner from a manufacturing aspect, by an annularly encircling weld seam or brazed seam between the flange and the face surface. 
         [0015]    As an alternative to a cohesive connection of this type, the closure plug may also be fixed in a fluid-tight fashion in the hollow cylindrical container part by a shrink-fit connection. 
         [0016]    With regard to the device, the device has a first and a second processing chamber, the processing chambers being arranged spaced apart from one another on a common system axis. The first and second processing chambers are furthermore provided with a first and second opening, respectively, for receiving a free end, which issues into the processing chamber, of the container, such that the first and second processing chambers, when a container is arranged between them, can be fluidically connected to one another exclusively via the container itself. The first processing chamber has an inlet and the second processing chamber has an outlet for a scavenging gas, wherein each processing chamber has means for closing the container in gas-tight fashion. 
         [0017]    Since the first and second processing chambers, when a container is arranged between the processing chambers, can be fluidically connected to one another exclusively via the container itself, it is sufficient for scavenging gas to be injected exclusively into the first processing chamber, which scavenging gas is then inevitably forced through the hollow cylindrical container part via openings situated in the closure plug, and passes exclusively through the container part into the second processing chamber. As a result, the water situated in the container part is reliably expelled. It is thus not necessary for a scavenging gas line to be connected directly to a duct arranged in the closure plug. 
         [0018]    In one advantageous embodiment of the device, the processing chambers are arranged so as to be displaceable along the system axis. In this way, the container can be arranged between the processing chambers. By displacement of the processing chambers, the free ends of the container are guided through the openings so as to project into the processing chambers. 
         [0019]    In a particularly advantageous embodiment of the invention, each processing chamber is provided with a pressure ram which annularly surrounds the opening and which can be advanced in the direction of the system axis toward the opening and by which, by way of an advancing movement in the direction of the system axis, a force with a component acting transversely with respect thereto is exerted on a sealing ring which is arranged on the opening and which surrounds the opening. By means of this measure, the container can in a simple manner be connected in a fluid-tight fashion to the respective processing chamber by use of the opening, such that the processing chambers are mechanically connected to one another exclusively by the container. 
         [0020]    In an alternative embodiment of the device, the first and second processing chambers are rigidly connected to one another along the system axis by a connecting pipe which projects by way of its face-side ends into the first and second processing chambers. The container can be inserted into the connecting pipe such that the container projects by way of its free ends beyond the connecting pipe. The construction of the device is simplified by means of this measure because the processing chambers no longer need to be mounted so as to be displaceable relative to one another. 
         [0021]    In a further advantageous embodiment, the inlet and outlet are formed by an inlet pipe and an outlet pipe respectively, which issue into the first and second processing chambers respectively and the central axes of which coincide with the system axis and between which the connecting pipe is arranged in each case with an axial spacing, such that, between the face sides facing toward one another, there remain a first and a second free space respectively. Here, the connecting pipe can be connected in a fluid-tight fashion to the inlet pipe and to the outlet pipe by a first and second sleeve, respectively, which is arranged so as to be axially displaceable into a first position, wherein the first and second sleeves are displaceable into a second position in which the first and second free spaces are open to the first and second processing chambers respectively. In this embodiment, it is no longer necessary for the scavenging gas to be conducted through the processing chambers because, in the latter, a fluid-tight duct that serves as a scavenging chamber is created by the inlet and outlet pipe and the connecting pipe, such that, during the insertion of the container into the device, which takes place under water, no water can infiltrate into a working chamber of the processing chamber, which working chamber is situated outside the scavenging chamber and in which working chamber the tools required for the fluid-tight closure of the container are situated. 
         [0022]    It is preferable for a sealing element to be arranged between the container and connecting pipe, which sealing element can be set such that the inlet pipe and outlet pipe are fluidically connected to one another exclusively via the container. 
         [0023]    In order, in addition to the expulsion of the water from the container by the scavenging gas that is forced in, to also remove any water that has infiltrated into a defective, non-sealed fuel rod or into fuel rod sections and thus into the fuel matrix, it is provided in one advantageous embodiment of the device that the inlet and outlet can be connected to one another, via a bypass line that runs outside the processing chambers, in such a way that a closed gas circuit is formed, wherein, in the gas circuit, there are arranged a pump and a heating device for respectively circulating and heating a heating gas situated in the gas circuit. In this way, the water bound in the fuel matrix can be evaporated, and the fuel matrix dried. 
         [0024]    If each processing chamber has a pressure ram for exerting a pressure force that acts in the direction of the system axis, the closure plug of a container can be pushed into the hollow cylindrical container part in a particularly simple manner. 
         [0025]    If each processing chamber has a welding head which is mounted such that it can be rotated about, and advanced toward, the system axis, the closure plug can be welded to the hollow cylindrical container part without it being necessary for the container part to be set in rotational motion for this purpose. 
         [0026]    Furthermore, if each processing chamber contains a cleaning brush which is mounted such that it can be rotated about, and advanced toward, the system axis, the parts to be welded can be cleaned in situ before the welding process, and the quality of the weld seam can thus be improved. 
         [0027]    The outlay in terms of construction is furthermore reduced if the welding head and cleaning brush are arranged on a common rotary ring. 
         [0028]    With regard to the method, the object of the invention is achieved by a method using the device according to the invention and the container according to the invention. The method includes the following method steps:
       a) introducing a free end of the container part, which is equipped with the closure plug in the intermediate position and which contains the fuel rod or the fuel rod section, through the first opening into the first processing chamber, and introducing the opposite free end through the second opening into the second processing chamber, such that the first and second processing chambers are fluidically connected to one another exclusively via the container part itself; and   b) injecting a scavenging gas into the first processing chamber, and expelling the water situated in the container part and in the processing chambers that are fluidically connected to one another via the container part, through the build-up of a positive pressure.       
 
         [0031]    In a particularly advantageous embodiment of the invention, after the expulsion of the water, heating gas is pumped through the container part, in order thereby to additionally reduce the water content in the container part by evaporation of the water. In other words: no vacuum drying takes place. If the heating gas is furthermore circulated in a closed gas circuit until a final value is attained at which the moisture content increases no further, it is possible from the moisture content to determine the absolute amount of water, which is gaseous during recirculation of the heating gas, situated within the container, such that precise statements can be made regarding the remaining water content in the container after the closure of the container. 
         [0032]    The closure plug is subsequently pressed into the container part as far as the end position and is connected in fluid-tight fashion to the container part. 
         [0033]    The closure plug is preferably cohesively connected to the container part by an annularly encircling weld seam or brazed seam, or is alternatively fixed in fluid-tight fashion in the container part by a shrink-fit connection. 
         [0034]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0035]    Although the invention is illustrated and described herein as embodied in a container, a device and a method for encapsulating a fuel rod or a fuel rod portion in a gas-tight manner, 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. 
         [0036]    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 SEVERAL VIEWS OF THE DRAWING 
         [0037]      FIG. 1  is a diagrammatic, longitudinal sectional view of a container according to the invention with a closure plug pre-mounted in an intermediate position; 
           [0038]      FIG. 2  is a detailed, sectional view of the container that is closed off with the closure plug along an annular weld seam; 
           [0039]      FIGS. 3A and 3B  are diagrammatic, partial, longitudinal section views showing in each case mutually opposite processing chambers of a device according to the invention, with the container mounted in a working position, during the expulsion of water; 
           [0040]      FIGS. 4A and 4   b  are diagrammatic, partial, longitudinal section views showing in each case mutually opposite processing chambers of an alternative embodiment of the device according to the invention, with the container mounted in a working position during the expulsion of water; and 
           [0041]      FIGS. 5A and 5   b  are diagrammatic, partial, longitudinal section views showing the processing chambers in the working position assumed after the expulsion of water and drying have taken place and during a welding process. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown a container  2  having a hollow cylindrical container part  8  which is open at its face or end sides  4  and  6 . At the face sides  4 ,  6 , a respective unipartite closure plug  10  has been partially pushed in as far as an intermediate position. Each closure plug  10  has a head part  11  and a cylindrical shank  12 , the outer diameter of which is only slightly smaller than the inner diameter of the container part  8 . The head part  11  has an annularly encircling flange  13 , an outer diameter of which corresponds to the outer diameter of the container part  8 . In the intermediate position, the closure plug  10  projects beyond the hollow cylindrical part  8  by an additional projecting length s in relation to the end position of the closure plug  10 , such that a part of the shank  12  situated below the head part  11  is situated outside the container part  8 . 
         [0043]    Each closure plug  10  is provided with a duct  14  which, in an intermediate position, fluidically connects an interior  15  to the exterior  16 . 
         [0044]    A sintered metallic filter element  18  is arranged in the cylindrical container part  8  at that free end which is situated at the bottom during handling, which filter element  18  prevents coarse particles from being able to escape from the still-open container  2  after the container has been equipped with a fuel rod  20  or fuel rod section indicated by dashed lines in  FIG. 1 . If it is the intention to encapsulate a defective fuel rod  20  into which water has infiltrated, the fuel rod has previously been opened in the region of its two end plugs, and the gaseous radioactive fission products contained therein, which escape through the openings, have been discharged in a targeted fashion. 
         [0045]    The duct  14  which, in the intermediate position, is fluidically connected to the exterior  16  is formed, in the example, by a central first duct section  24 , which runs along a longitudinal central axis  22  and extends from a face side  23  facing toward an interior  15  and which is in the form of a blind bore, and by at least one second duct section  26 , a through bore in the example, which runs perpendicular to the first duct section  24 , wherein the first duct section  24  issues into the second duct section  26 . The location or locations at which the second duct section(s)  26  intersect(s) a shell surface  27  of the closure plug  10 , that is to say the issuing openings of the one or more second duct sections  26 , is/are arranged in that region of the shank  12  of the closure plug  10  which is situated outside the container part  8  when the closure plug  10  is in the intermediate position. 
         [0046]    The shank  12  of the closure plug  10  is equipped, between its face side  23  that projects into the container part  8  and the one or more issuing openings, with an annular recess or groove  28  which serves for receiving a securing ring  30 . The hollow cylindrical container part  8  is likewise equipped, on its inner surface in the region of the free ends, with a respective annularly encircling turned-in portion  32  into which the securing ring  30  inserted into the groove  28  engages with detent action when the closure plug  10  is inserted into the hollow cylindrical container part  8 . The securing ring  30  and groove  28  accordingly serve as detent devices that detachably fix the closure plug  10  in the intermediate position. 
         [0047]    At its face side  33  facing away from the hollow cylindrical container part  8 , the closure plug  10  is provided with a threaded bore  34  which serves for the screwed engagement of a bar-type tool that is used for handling the closure plug  10 . A groove  36  (indicated by dashed lines) that runs perpendicular to the threaded bore  34  serves as a torque support as a bar-type tool (not illustrated in the figure) is screwed into the threaded bore  34 . 
         [0048]      FIG. 2  shows the container  2  with the upper closure plug  10  in an end position in which it has been pushed deeper into the container part  8 , by the distance s, until the flange  13  has set down by way of its sealing surface on the face surface of the hollow cylindrical container part  8  and the issuing openings of the one or more second duct sections  26  are situated within the container part  8 . In the end position, the flange  13  is welded to the face sides  4  of the container part  8  along an annularly encircling weld seam  40 , such that the closure plug  10  closes off the container part  8  in fluid-tight fashion. 
         [0049]    As per  FIGS. 3A ,  3 B, a device for closing off the container  2  illustrated in  FIG. 1  in a gas-tight fashion at both sides contains a first (upper) processing chamber  50  ( FIG. 3A ) and a second (lower) processing chamber  52  ( FIG. 3B ). The first and second processing chambers  50 ,  52  are spaced apart from one another and are arranged such that they can be positioned on a common, vertically oriented system axis  53  and such that they can be displaced relative to one another along the system axis  53 . The first and second processing chambers  50 ,  52  are provided with first and second insertion openings  56 ,  57  which face toward one another and which are formed by first and second guide sleeves  54 ,  55  and which are arranged opposite one another in the direction of the system axis  53  and through which the container part  8  equipped with the fuel rod  20  or a fuel rod section is, by way of its face-side free ends and the closure plugs  10  pre-mounted there in the intermediate position, inserted and oriented such that the longitudinal central axis  22  of the container part  8  and the system axis  53  of the device coincide. 
         [0050]    After the face-side ends of the container part  8  equipped with the pre-mounted closure plug  10  have been inserted through the insertion openings  56 ,  57 , the first and second processing chambers  50 ,  52  are closed off in fluid-tight fashion in the region of the insertion openings  56 ,  57  by virtue of a sealing ring  60  which annularly surrounds the container  2  being subjected, by virtue of an annular pressure ram  64  likewise equipped with an elastic sealing ring  62  being advanced axially in the direction of the system axis  53 , to a force with a component acting perpendicular to the system axis  53 , such that the sealing ring  60  is pressed against the outer circumference of the container part  8  and against the inner edge of the insertion opening  56 ,  57 , thus closing a gap situated between the container part  8  and the insertion opening  56  and  57  respectively. In the assembled position, in which the closure plugs are still situated in the intermediate position, the first and second processing chambers  50 ,  52  are fluidically connected to one another exclusively via the container part  8 . 
         [0051]    The first processing chamber  50  has an inlet  66  via which scavenging gas G, for example argon Ar, can be injected at high pressure. At its bottom side, the first processing chamber  50  is provided with an outlet  67  which has a valve  68  which is closed for the purpose of building up an internal pressure. The second processing chamber  52  is provided, on its bottom side, with a siphon which serves as an outlet  69  for the scavenging gas G. 
         [0052]    In each processing chamber  50 ,  52 , a rotary ring  70  is mounted so as to be rotatable about the system axis  53 , on which rotary ring a cleaning brush  72  and a welding head  74  are mounted, such that they can be advanced toward the system axis  53 , by use of a respective rocker arm  76  and  78 . The rotary ring  70  is driven, via a pinion  80 , by an encapsulated motor  82 . An observation camera  90  makes it possible to monitor the work operations to be performed for the closure of the container. 
         [0053]    In each of the first and second processing chambers  50  and  52 , opposite the opening  54  or  56  respectively, there is arranged a pressure ram  92  actuated by a stroke-action cylinder  91 , by which pressure ram the closure plug  10  can be subjected to a pressure force acting in the direction of the system axis  53 . 
         [0054]    After insertion of the container part  8  equipped with the closure plug  10  in the intermediate position into the first and second processing chambers  50 ,  52  as far as a stop formed in each case by the pressure ram  92 , the openings  56  and  57  are closed off. Subsequently, with a valve  68  open, the scavenging gas G is introduced at high pressure into the first processing chamber  50 . The first processing chamber  50  is brought into a dry state in this way. After the closure of the valve  68 , the scavenging gas G then flows through the container part  8  equipped with the closure plugs  10  in the intermediate position and expels, via the outlet  69 , water situated in the container part  8  and in the second processing chamber  52 . If gas bubbles rise from the outlet  69 , this is an indication that the first and second processing chambers  50 ,  52  and the container part  8  no longer contain water. If a valve is installed in the outlet  69 , it is possible, after the closure of the valve, for the supply of scavenging gas G to be stopped and for the positive pressure prevailing in the processing chambers  50 ,  52  to be dissipated. 
         [0055]    The cleaning brushes  72  are subsequently advanced and, by a rotational movement of rotary rings  70 , the face surfaces on the face sides  4 ,  6  of the container  2  and the sealing surfaces of the flanges  13  are cleaned. After cleaning has been performed, the cleaning brushes  72  are retracted, and the pressure rams  92  are actuated, which pressure rams push the closure plugs  10  into the container  2  until the sealing surface of the flange  13  sets down on the respective face surface of the hollow cylindrical container part  8 . After the sealing plugs  10  have been pushed in, welding heads  74  are advanced and, by a rotational movement of the rotary ring  70 , the closure plug  10  is welded to the hollow cylindrical container part  8  along an annular weld seam  40  (see  FIG. 2 ). As an alternative to this, the closure plug  10  and container part  8  may also be brazed with one another along an annular brazed seam. Instead of a cohesive connection of this type, a shrink-fit connection may also be provided by virtue of the ends of the container  2  being inductively heated and the closure plugs  10  being pushed into the ends that have been expanded in this way. After the ends have cooled, the closure plug is fixed in fluid-tight fashion in the container part  8 . 
         [0056]    After the welding has been performed, the pressure rams  64  are retracted, the container  2  is received in a holder, and at least one of the processing chambers  50 ,  52  is axially displaced such that the container  2  can be withdrawn. 
         [0057]    In the exemplary embodiment as per  FIGS. 4A and 4B , the two processing chambers  50 ,  52  are connected to one another rigidly, and in fluid-tight fashion with respect to the outside, by a connecting pipe  100 . The connecting pipe  100  projects by way of its face-side ends into the first and second processing chambers  50  and  52  respectively. The container  2  with its closure plugs  10  inserted in an intermediate position is inserted into the connecting pipe  100 . In the intermediate position, the interior  15  of the container  2  is fluidically connected to the exterior. The cylindrical container part  8  of the container  2  projects beyond the connecting pipe  100  at both sides. 
         [0058]    In the first and second processing chambers  50 ,  52 , there are arranged an inlet pipe  102  and an outlet pipe  104  respectively, the central axes of which coincide with the system axis  53 , and which form the inlet  66  and the outlet  69  for the scavenging gas G. 
         [0059]    The connecting pipe  100  is arranged between the inlet pipe  102 , which issues into the first processing chamber  50 , and the outlet pipe  104 , which issues into the second processing chamber  52 , with an axial spacing a to each, such that, between the face sides facing toward one another, there remains a first and a second free space  106  and  108  respectively. 
         [0060]    In the working position illustrated in  FIGS. 4A and 4B , the inlet pipe  102  and connecting pipe  100 , and the connecting pipe  100  and outlet pipe  104 , are connected to one another in fluid-tight fashion by a first and a second sleeve  110  and  112  respectively, the sleeves being axially displaceable and mounted so as to be rotatable about the system axis  53 , and form a rectilinear, relatively narrow scavenging chamber  113  which is fluidically separated from a first and a second working chamber  114 ,  115  respectively, in which the tools and drives required for the closure of the container  2  are situated, of the first and the second processing chamber  50 ,  52  respectively. 
         [0061]    The connecting pipe  100  is provided, on its inner circumference at its face-side end projecting into the first processing chamber  50 , with an adjustable seal element  116 , in the example an inflatable sealing ring, by which, after the container  2  has been inserted into the connecting pipe  100 , a gap chamber  118  situated between the container  2  and the connecting pipe  100  can be closed such that the scavenging gas G flowing in the scavenging chamber  113  flows exclusively through the container  2 , and the inlet pipe and outlet pipe  102  and  104  respectively are fluidically connected to one another exclusively via the container  2 . Owing to the connecting pipe  100  connected in fluid-tight fashion to the processing chambers  50 ,  52 , it is adequate for the gap to be closed by a single sealing element  116  in order to achieve the desired guidance of the scavenging gas G through the container  2 . 
         [0062]    By a stroke-action cylinder  119  arranged in each of the first and second processing chambers  50 ,  52 , it is possible for the first and second sleeve  110  and  112  respectively to be axially displaced such that the first and the second free space  106  and  108  respectively can be opened or closed with respect to the first and the second processing chamber  50 ,  52  respectively. 
         [0063]    Those ends of the inlet pipe  102  and of the outlet pipe  104  which project out of the processing chambers  50 ,  52  are provided, in each case, with a connection piece  120  onto which there is sealingly mounted a stroke-action cylinder  122  which, like the stroke-action cylinder  91  in the exemplary embodiment of  FIGS. 3A and 3B , drives a pressure ram  124  which is displaceable axially in the direction of the system axis  53  and by which the closure plugs  10  can be pushed into their final position. 
         [0064]    A gas supply line  128  is connected via a valve  126  to the inlet pipe  102 , via which gas supply line the scavenging gas G can be introduced at high pressure into the inlet pipe  102  in order to expel the water situated in the container  2 . The water emerging into the outlet pipe  104  is then discharged via a water expulsion line  132  that can be closed off by a valve  130 . 
         [0065]    The inlet pipe  102  and outlet pipe  104  are connected via two-way valves  134  and  136  to a bypass line  138  which connects the inlet pipe  102  and outlet pipe  104  to one another in a closed gas circuit. In the bypass line  138  there are arranged a pump  140  and a heating device  142  by which a heating gas H situated in the bypass line  138  can be pumped through the inlet pipe  102 , the container  2  and the outlet pipe  104  in order thereby to dry the fuel rod  20  situated in the container  2 . During the drying process, the valves  126  and  130  are closed. 
         [0066]    For the precise positioning of the container  2 , the second sleeve  112  is provided with a radially extendable stop element  143 , on which the container part  8  is seated by way of its lower face side  6 . 
         [0067]    The first and second sleeves  110 ,  112  are provided in each case with an annularly encircling flange which serves as a support for the welding head  74  and the cleaning brush  72  and which is simultaneously configured as a rotary ring  70  which meshes with a pinion  146  driven by a motor  145 , such that the cleaning brush  72  and welding head  74  can be rotated about the system axis  53 . 
         [0068]    By use of temperature sensors  150 , pressure sensors  152  and moisture sensors  154 , the temperature T, the pressure P and the humidity X in the inlet pipe  102  and in the outlet pipe  104  are measured in order to be able to detect the progression of the drying process. The drying process is ended when the moisture content in the heating gas H attains a final value at which the moisture content rises no further and there is accordingly no longer any liquid water situated in the gas circuit. For a known volume of the container  2 , it is possible for the absolute amount of water situated within the container  2  in the gaseous phase to be determined, and for adherence to specifications with regard to the maximum admissible water content to be reliably monitored. To achieve complete evaporation of the water, the volume of the gas circuit is several times greater than the volume of the hollow chamber situated in the container  2  when a fuel rod  20  has been inserted therein. 
         [0069]    The mode of operation of the device during the encapsulation of a defective fuel rods  20  provided with openings in the region of its ends will be explained in more detail below. 
         [0070]    Firstly, the device is opened. For this purpose, the upper stroke-action cylinder  122  arranged on the inlet pipe  102  is dismounted from the device. Before the dismounting process, the first and second sleeves  110  and  112  have been displaced into the position shown in  FIGS. 4A and 4B , in which they produce a fluid-tight connection between the inlet pipe  102  and the connecting pipe  100  and between the connecting pipe  100  and the outlet pipe  104 , such that the water that infiltrates, as a result of the dismounting of the, into the scavenging chamber  113  formed from the inlet pipe  102 , connecting pipe  100  and outlet pipe  104  cannot pass into the processing chambers  50 ,  52 . 
         [0071]    Furthermore, the working chamber  114 , which surrounds the scavenging chamber  113 , of the processing chambers  50 ,  52  is permanently charged with scavenging gas (not illustrated) in order to thereby additionally prevents the infiltration of water. 
         [0072]    The container  2  loaded with the fuel rod  20  is subsequently inserted, by a handling tool not illustrated in  FIG. 4A , into the connecting pipe  100  until the container sets down on the extended stop element  143 . 
         [0073]    Thereafter, the stroke-action cylinder  122  is mounted in fluid-tight fashion onto the connection piece  120  again. The processes explained below take place with the device in a working position as illustrated in  FIGS. 4A and 4B . After the stroke-action cylinder has been mounted, scavenging gas G is, by virtue of the valve  126  being opened, introduced at high pressure into the inlet pipe  102  and forced through the interior, and with a valve  136  open, the water situated in the scavenging chamber  113  is initially expelled. 
         [0074]    Through subsequent pressurization of the inflatable seal  116  with a compressed gas, the gap between the connecting pipe  100  and container part  8  is closed, such that the scavenging gas G flows exclusively through the container  2 , with water being expelled from the latter in this way. During the process, via openings that may have previously been provided on the top and bottom ends of the fuel rod  20  (not illustrated), water is also removed from the fuel rod  20 . The gas flow is maintained until the humidity X measured by the humidity sensor  154  arranged on the outlet pipe  104  falls below a predefined threshold value and signals an adequate level of dryness. Subsequently, any water still situated in the bypass line  138  is expelled by virtue of the valve  136  being opened and the pump  140  being set in operation. The valves  128  and  130  are subsequently closed. 
         [0075]    Subsequently, for the purpose of drying the fuel rod  20 , the heating device  140  is set in operation. The pump  140  drives the scavenging gas G, which is situated in the scavenging chamber  113 , via the heating device  142 . In the heating device  142 , the scavenging gas G is heated and passes, as heating gas H, via the thermally insulated water expulsion line  132  to the scavenging chamber  113  and to the lower closure plug  10  of the container  2 . From here, the heating gas H passes into the interior of the container  2  and to the filter element  18 . By virtue of the heating gas H being conducted in this direction, residual water is blown out of the filter element  18 , such that the heating gas H can pass through more easily. By the heating gas H flowing along the fuel rod  20 , the water situated therein in the fuel matrix is evaporated, is released into the container  2  via the openings provided previously on the top and bottom ends of the fuel rod  20 , and is transported with the heating gas H into the scavenging chamber  113  via the upper closure plug  10 . From there, the moisture-laden heating gas H is supplied via the valve  134  back to the pump  140 . The gas circuit is thus closed. The temperature T of the heating gas H is detected by the temperature sensors  150  and is fed, via a distributor  156 , to an evaluation and control unit which is not illustrated in the figures and which controls the pump  140  and heating device  142  and regulates the temperature T to a predefined target value. The evaluation and control unit also controls the other active components in the device—valves, pump, processing devices, stroke-action cylinder, motor drives etc. 
         [0076]    The passage of the heating gas H in the container  2  is monitored by the pressure sensors  152 . The heating gas H is circulated in the gas circuit until the upper and lower humidity sensors  154  register adequate saturation. This is an indication that all of the water in the fuel matrix has evaporated and no further water is being released. At this point, the heating and circulation of the heating gas H can be terminated. By opening the valve  126 , fresh scavenging gas G can flow in. By cyclically opening and closing the valve  130 , the scavenging gas G is alternately discharged via the water expulsion line  132  or conducted through the container  2 . Finally, the valves  130 ,  134 ,  136  are closed and pressure equalization between the scavenging chamber  113  and working chamber  114 ,  115  of the processing chambers  50 ,  52  is performed. The valve  126  is subsequently closed. 
         [0077]    Thereafter, the first sleeve  110  is pushed onto the connecting pipe  100  by the stroke-action cylinder  122 , such that the free space  106  is open to the interior of the first processing chamber, and the brush  72  and welding head  74  situated at the level of the face side  4  of the container part  8 . Following the actuation of the brush advancement, that is to say the application of the brush  72  to the contact surfaces to be cleaned, the first sleeve  110  is set in rotation, and thus the brush  72  is also moved around the container  2 , by virtue of the pinion  146  being driven. After the cleaning process, the brush  72  is retracted into the initial position again. 
         [0078]    Subsequently, the stroke-action cylinder  122  is actuated, and, by the piston rod thereof, the upper closure plug  10  is pushed onto the container part  8 . Thereafter, the welding head  74  is advanced radially and moved around the container  2  by rotation of the first sleeve  110 . The working position is illustrated in  FIG. 5A . After the welding process, the upper welding head  74  is also moved into the initial position again, and the sleeve  110  is also moved into the initial position again. 
         [0079]    The cleaning and welding in the second processing chamber  52  subsequently takes place analogously, wherein, before the displacement of the second sleeve  112  into the position required for the cleaning and welding processes, the stop element  143  is retracted.  FIG. 5B  likewise shows a situation in which the welding head  74  is situated in a working position. 
         [0080]    For the withdrawal of the closed container  2 , the device is opened. For this purpose, the pressure ram  124  of the upper stroke-action cylinder  122  is retracted and is thereafter dismounted from the device. As a result of the dismounting process, the scavenging chamber  113  of the device is flooded with water. The container  2  is then gripped by a bar-type tool, the inflatable sealing element  116  is ventilated, and the pressure ram  124  of the lower stroke-action cylinder  122  is moved into the initial position again. 
         [0081]    The drying process illustrated in conjunction with  FIGS. 4A ,  4 B,  5 A, and  5 B may basically also be performed in the case of the device illustrated in  FIGS. 3A and 3B  by virtue of the device being supplemented by the heating circuit illustrated in  FIGS. 4A ,  4 B,  5 A and  5 B.