Patent Publication Number: US-11393602-B2

Title: Packaging for transporting and/or storing radioactive materials having a design that facilitates the handling of the mass of radioactive materials

Description:
This is the National Stage of PCT international application PCT/FR2019/051454, filed on Jun. 14, 2019 entitled “PACKAGING FOR TRANSPORTING AND/OR STORING RADIOACTIVE MATERIALS HAVING A DESIGN THAT FACILITATES THE HANDLING OF THE MASS OF RADIOACTIVE MATERIALS”, which claims the priority of French Patent Application No. 1855265 filed Jun. 15, 2018, both of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to the field of packaging for transporting and/or storing radioactive materials, for example radioactive waste placed in barrels, or nuclear-fuel assemblies. 
     PRIOR ART 
     From the prior art, numerous designs for packaging for transporting and/or storing radioactive materials are known. Generally, the packaging has a housing cavity receiving a mass of radioactive materials, this cavity being defined by a lateral body, a bottom, and a lid mounted removably on the lateral body. 
     To extract the mass of radioactive materials, the lid is first of all removed from the main body. Next the mass is gripped by a handling device in order to be extracted from the housing cavity. In order to ensure such extraction, the handling device must be connected to the mass of radioactive materials, for example at a head end of this mass. 
     Nevertheless, in some cases, the mass requires being gripped at the lateral face thereof by the handling device. A radial clearance is then generally provided between this mass and the internal surface of the lateral body delimiting the housing cavity. Thus the handling device can be introduced axially into this radial clearance, in order to be connected to the lateral face of the mass of radioactive materials. This radial clearance does however lead to oversizing the packaging, with negative consequences in terms of weight, cost and bulk. 
     DESCRIPTION OF THE INVENTION 
     To respond to the problem identified below, the object of the invention is packaging for transporting and/or storing radioactive materials according to the features of claim  1 . 
     Thus, when the lateral-body reconstitution part is removed, the hollowed-out zone procures lateral access to the mass of radioactive materials, easily enabling it to be gripped laterally. This is because the hollowed-out zone allows the introduction of a handling device between the internal surface of the reduced-thickness part of the lateral body, and the mass of radioactive materials. 
     This facilitated gripping is advantageously obtained without increasing the width of the lateral body, which guarantees control of the costs, of the total weight of the packaging, and the bulk thereof. 
     Furthermore, the lateral-body reconstitution part makes it possible to reconstitute the thickness of the lateral body locally at the reduced-thickness part thereof, leading to an absence of leakage of shielding. 
     Finally, at least part of the lid, and preferably the lid in its entirety, can be arranged in the hollowed-out zone of the lateral body defined laterally by the reduced-thickness part of this lateral body. The mechanical strength of the packaging is therefore satisfactory in the event of lateral or oblique falling, since the lid is protected by the lateral body. 
     The invention moreover has at least one of the following optional features, taken in isolation or in combination. 
     The reconstitution part extends in an uninterrupted fashion all around the longitudinal axis, in order thus to form a closed structure over 360°, such as for example an annular structure, of constant or variable thickness. Preferably, the reconstitution part is such that the assembly that it forms with the lateral body has constant thickness, in order to procure homogeneous and satisfactory shielding performance. This structure closed over 360° may be produced in a single piece, or by the succession of angular sectors arranged end to end, without clearance. 
     Alternatively, the reconstitution part extends over only an angular sector of less than 360°, and in this case several reconstitution portions can be provided within the packaging, spaced apart angularly from one another. 
     The lateral-body reconstitution part: 
     a) is independent of the lateral body and of the lid; and 
     b) forms an integral part of the lid, which also comprises a main part for axial closing off of the housing cavity defining an axial end surface of this cavity, the lateral-body reconstitution part being arranged projecting axially in the direction of the bottom from the axial-end surface; or 
     c) is formed by combining a primary and a secondary lateral-body reconstitution portion, 
     the primary portion forming an integral part of the lid, which also comprises a main part for axial closing off of the housing cavity defining an axial-end surface of this cavity, the primary portion including firstly a lateral wall forming the internal surface and arranged projecting axially in the direction of the bottom from the axial end surface, and secondly a fixing flange arranged at an axial end of the lateral wall and intended to be in abutment against the transition surface, 
     the secondary portion being independent of the lateral body and of the lid, and arranged radially between the internal surface of the reduced-thickness part of the lateral body, and the assembly formed by the lateral wall of the primary portion of the lid and the main part of this lid. 
     The packaging comprises means for fixing the lid on the lateral body, the fixing means passing through the lateral-body reconstitution part as well as the transition surface of the lateral packaging body. This embodiment is preferentially adopted in case b), when the lateral-body reconstitution part is integrated in the lid. 
     In case c), these fixing means preferentially pass through the fixing flange of the primary portion of the lateral-body reconstitution part. The length thereof may thus be advantageously reduced, passing only through this fixing flange, and not the secondary portion of the reconstitution part. 
     Alternatively, the fixing means could cooperate with the first axial end of the lateral body, without departing from the scope of the invention. This alternative embodiment is then preferred when the lateral-body reconstitution part is independent of the lateral body and of the lid, the reconstitution part being in this case able to be held axially without clearance or with axial clearance between the lid and the transition surface. 
     A sealing system is gripped axially between the transition surface of the lateral body and an axial end of the lateral-body reconstitution part. This embodiment is preferentially adopted in the aforementioned cases b) and c). 
     Here again, the sealing system could alternatively be gripped axially between the first axial end of the lateral body and a portion of the lid covering this end, without departing from the scope of the invention. This alternative embodiment is then preferred in case a), when the lateral-body reconstitution part is independent of the lateral body and of the lid. 
     The lid is entirely covered laterally by the reduced-thickness part of the lateral body, in order to reinforce the mechanical strength in the event of a fall. Nevertheless, part of this lid could be arranged externally with respect to the lateral body, in the axial direction, and this without departing from the scope of the invention. 
     The packaging further includes an additional lid fixed to the lateral body. 
     The packaging further includes an impact-damping cap covering at least part of the lid, as well as the first axial end of the lateral body. 
     The internal surface of the lateral-body reconstitution part laterally delimits an axial section of the lateral cavity, the axial section extending over an axial length greater than or equal to 50 mm. Preferentially, the length of this axial section corresponding for example to 20% of the total axial length of the housing cavity, and at a maximum to 50% of this total axial length of the housing cavity. 
     The transition surface of the lateral body forms an internal shoulder. Alternatively, this surface could take other forms providing the transition of thickness in the lateral body, such as an oblique surface, a stepped surface, etc. 
     An object of the invention is a parcel comprising packaging as described above, loaded with a mass of radioactive materials housed in the housing cavity, the mass of radioactive materials, preferably in the form of a barrel, being located at the part laterally facing the lateral-body reconstitution part. 
     Another object of the invention is a discharging method according to claim  12 . 
     Other advantages and features of the invention will emerge in the following non-limitative detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This description will be given with regard to the accompanying drawings, among which: 
         FIG. 1  shows a view in longitudinal axial section of packaging for storing and/or transporting radioactive materials, according to a preferred embodiment of the present invention; 
         FIG. 2  shows a view similar to the one in the previous figure, in an exploded view; 
         FIG. 3  is a plan view of the packaging shown in the preceding figures, with the packaging shown without the head damping cap thereof; 
         FIG. 4  shows a view similar to the previous one, with the packaging being in the form of another preferred embodiment of the invention; and 
         FIG. 5  shows a view similar to the previous ones, with the packaging being in the form of another preferred embodiment of the invention. 
     
    
    
     DETAILED DISCLOSURE OF PREFERRED EMBODIMENTS 
     With reference first of all to  FIGS. 1 to 3 , packaging  1  for storing and/or transporting radioactive materials is shown, according to a preferred embodiment of the invention. 
     This packaging  1  is shown in the vertical storage position, wherein the longitudinal axis  2  thereof is oriented vertically. It corresponds to the aforementioned case b), and includes a packaging bottom  4  opposite to a removable lid  6  in the direction of the height  8 , parallel to the longitudinal axis  2 . In addition to the bottom  4  and lid  6  spaced apart from each other along the axis  2 , the packaging  1  includes a lateral body  10  extending around this axis  2 . The lateral body  10  extends between a first axial end  10   a  on the lid  6  side, and a second end opposite to the first, situated at the bottom  4  side. The lateral body  10  is thus closed by the lid  6  at a first axial end  10   a , also referred to as the head end. It is also closed by the bottom  4  at the second axial end  10   b.    
     The bottom  4  and the lid  6  delimit axially a housing cavity  12  within which a mass of radioactive materials  13  is received, here a barrel sealingly confining radioactive waste. This type of barrel is also known by the term canister. When this mass  13  is housed in the cavity  12 , as shown in  FIGS. 1 and 2 , it forms with the packaging  1  a parcel  100 . The housing cavity  12  is also delimited laterally by the lateral body  10 , a specificity of which particular to the invention will now be described. 
     Internally, this lateral body  10  includes a thickness-change zone  14 , which is represented by a transition surface  16  here in the form of a shoulder. The lateral body  10  thus comprises a reduced-thickness part  20   a , as well as a greater-thickness part  20   b  separated from the part  20   a  by the shoulder  16 . The reduced-thickness part  20   a  thus extends from the shoulder  16  towards the first end  10   a . More precisely, it is delimited axially between this shoulder  16  and the first end  10   a  of the lateral body  10 , corresponding to the axial end surface of this body. Moreover, the greater-thickness part  20   b  is delimited axially between the shoulder  16  and the second end  10   b.    
     Preferably, the reduced-thickness part  20   a  has a constant thickness. It includes an internal surface  24  laterally delimiting a hollowed-out zone  26  of the lateral body  10 , this hollowed-out zone  26  consequently being delimited axially by the transverse surface of the shoulder  16 , and by the transverse surface of the first end  10   a  of this body  10 . In this preferred embodiment wherein the external surface of the lateral body is cylindrical with a circular cross-section, the internal surface  24  of the reduced-thickness part  20   a  thereof is also preferentially cylindrical with a circular cross-section. Thus the hollowed-out zone  26  is in the form of a cylindrical volume, also with a circular cross-section. 
     In a similar manner, the greater-thickness part  20   b  also has a constant thickness. It includes an internal surface  28  laterally delimiting the major part of the housing cavity  12 , as far as the bottom  4 . The internal surface  28  of this greater-thickness part  20   b  is also preferentially cylindrical with a circular cross-section, with a diameter less than that of the internal surface  24  of the reduced-thickness part  20   a  of the lateral body. 
     One of the other particularities of the invention lies in the presence of a lateral-body reconstitution part  30 , which is here in the form a closed ring extending over 360° around the axis  2 , in the hollowed-out zone  26 . This reconstitution part  30  has an external surface  32  with a form complementary to that of the internal surface  24  of the reduced-thickness part  20   a  of the lateral body. In addition, its internal surface  34  laterally delimits a top part of the housing cavity  12 , namely that located above the greater-thickness part  20   b  of the lateral body, that is to say above the shoulder  16 . In this regard, it should be noted that the internal surface  34  of the ring  30  has a form identical or similar to that of the internal surface  28  of the greater-thickness part  20   b , in order to result in a housing cavity  12  with a homogeneous and constant shape. This is because the thickness of the part  20   b  of the lateral body is substantial identical to the total thicknesses of the part  20   a , and of the ring  30  arranged laterally adjacent to this part  20   a.    
     The internal surface  34  and the internal surface  24  are concentric, centred on the axis  2 . They are thus spaced apart radially from each other in relation to this axis  2 , so as to have a minimum radial separation Emin greater than 30 mm, or more preferentially greater than 50 mm. Through the concentricity of the surfaces  24 ,  34  and through their shapes, the radial separation between them is preferentially constant or substantially constant throughout the circumferential direction. 
     In this preferred embodiment, the reconstitution part  30  in the form of a ring forms an integral part of the lid  6 . The latter then comprises a main part  36  serving for the axial closure of the housing cavity  12 , this main part  36  being preferentially in the form of a slab arranged orthogonally to the axis  2 . The lid  6  also includes this reconstitution part  30 , arranged projecting axially in the direction of the bottom  4 , from an internal surface of the main axial-closure part  36  corresponding to an axial end surface  38  of the cavity. The two components  30 ,  36  of the lid  6  may be produced in a single piece, or attached fixedly to each other, by welding or by equivalent fixing means. Moreover, the lid  6  could also include an impact damper (not shown) at the axial end surface  38  thereof, so that it is axially opposite the head end of the mass of radioactive materials  13 . In a similar manner, such an impact damper could be secured to the mass  13 , or simply placed axially between this mass  13  and the lid  6 . 
     As can be seen in  FIG. 1 , the lid  6 , and in particular the main axial-closure part  36  thereof, is entirely covered laterally by the reduced-thickness part  20   a  of the lateral body  10 . This makes it possible to reinforce the mechanical strength of the packaging in the event of a lateral or oblique fall, since the lid  6  is perfectly protected by the lateral body. This mechanical strength is also provided by means for fixing the lid  6  on the lateral body  10 , which here take the form of a plurality of screwed elements  40  parallel to the axis  2 . These elements  40  pass first of all through the periphery of the main axial-closure part  36 , and then the reconstitution part  30 , in order finally to pass through the shoulder  16  and to come to be screwed in the top end of the part  20   b  of the lateral body. The screwed elements are spaced apart evenly around the axis  2 , and the heads thereof are located in countersinks  42  formed on the external surface  44  of the main axial-closure part  36 . By virtue of these countersinks  42 , the screwed elements  40  do not project from this closure part  36 . This makes it possible to assemble a second lid (not shown) on the lateral body  10 , over the lid  6 , or to make the bottom  45  of an impact-damping cap  46  approach as closely as possible the external surface  44  of the main axial-closure part  36 . This cap  46 , referred to as a head damper cap, provides in effect a base  45  that delimits a hollow  48  wherein a head portion of the reduced-thickness part  20   a  are housed, as well as the closure part  36  of the lid  6 . These two elements are thus covered laterally by the head damper cap  46 , it being moreover specified that a similar base-damper cap  50  laterally covers a bottom portion of the greater-thickness part  20   b , as well as the bottom  4 . 
     The packaging also comprises a sealing system axially gripped between the shoulder  16  and a bottom axial end of the reconstitution part  30 . It is a case for example of two seals  54  centred on the axis  2  and arranged at the interface between the aforementioned two elements, inside the fixing crown formed by the screwed elements  40 . These seals provide the confinement of the barrel  13  in the housing cavity  12 , which then forms a confinement chamber. 
     With this design particular to the present invention, the cavity  12  is thus delimited axially by the bottom  4  and the main closure portion  36  of the lid, and delimited laterally by the two internal surfaces  34 ,  28 . Moreover, the internal surface  34  of the ring  30  laterally delimits a top axial section of the cavity  12 , with a length L 1  greater than or equal to 50 mm. 
     In the loaded configuration of the packaging, and when the lid  6  is fixed on the lateral body  10  as shown in  FIG. 1 , the reconstitution ring  30  is pressed axially against the shoulder  16 , via the screwed elements  40 . In this configuration, the shielding is correctly provided at the top part of the lateral body  10 , by virtue of its reconstitution of thickness via the ring  30 . The top part of the barrel  13  is then located laterally opposite this ring  30 , with a preferentially small radial clearance between the two of them. A small axial clearance is also observed between the barrel  13  resting on the bottom  4  in the vertical position in  FIG. 1 , and the axial-end surface  38  of the main closure part  36  of the lid  6 . 
     After the removal of the lid  6  performed during an operation of discharging the barrel  13 , an annular space  56  of the hollowed-out zone  26  is created between the internal surface  24  of the reduced-thickness part  20   a , and the external surface of a top portion of the barrel  13 . The annular space  56  thus has a radial thickness greater than or equal to 30 mm, and preferably greater than or equal to 50 mm. 
     This annular space  56 , visible in  FIG. 2  and delimited axially towards the bottom by the shoulder  16 , forms a lateral access to the barrel  13  for gripping thereof. This is because a handling device  58  can be introduced axially into this annular space  56  left free and with sufficient radial thickness, in order to be connected to the external lateral surface of the barrel  13 . It is a case for example of drum clamps or a grapnel  58 , which can be easily inserted in the dedicated space  56 , without any need for oversizing the width of the packaging. Once the attachment has been made, the barrel  13  can be extracted axially from the cavity  12 . 
       FIG. 4  shows another preferred embodiment of the invention, having great similarities with the previous embodiment. Moreover, on all the figures, the elements bearing the same numerical references correspond to identical or similar elements. 
     In this other embodiment corresponding to the aforementioned case a), the main difference lies in the lateral-body reconstitution part, which is no longer a ring integrated in the lid  6 , but is a ring  30  independent of the lateral body  10  and of the lid  6 . This ring  30  is in fact arranged axially between the lid  6  in the form of a slug, and the shoulder  16  separating the two parts  20   a ,  20   b  of the body  10 . 
     In this embodiment, the seal or seals  54  can be offset between the first end  10   a  of the lateral body  10 , and the internal surface of the lid  6  covering this end. As a countersink/recess  62  is preferentially provided at the first end  10   a  in order to receive the lid  6 , the seals  54  are thus arranged in the countersink bottom of this first end  10   a . Likewise, the screwed fixing elements  40  can be arranged here in order to cooperate with the head portion of the reduced-thickness part  20   a , passing through the periphery of the lid  6  as well as the countersink bottom defined by the first axial end  10   a.    
     Finally, in this embodiment, the lid  6  is also entirely covered laterally by the reduced-thickness part  20   a , being entirely housed in the countersink/recess  62  of the first axial end  10   a . In the countersink bottom, in the form of a shoulder as for the transition surface  16 , the seal  54  is moreover situated inside the fixing crown formed by the screwed elements  40 . 
       FIG. 5  shows yet another embodiment, similar to the previous ones. It corresponds to the aforementioned case c), having the particularity of having a lateral-body reconstitution part  30  formed by two separate elements. 
     It is a case of a combination of a primary portion  30   a  having great resemblances to the reconstitution part  30  of the embodiment in  FIGS. 1 to 3 , and a secondary portion  30   b  having great resemblances to the reconstitution part  30  of the embodiment in  FIG. 4 . 
     This is because the primary portion  30   a  forms an integral part of the lid  6 , which also comprises the main axial-closure part  36  of the housing cavity  12 . More precisely, the primary portion  30   a  includes first of all a lateral wall in the form of a thin ring  70 , projecting downwards from the axial end surface  38  defined by the main portion  36  of the lid. The ring  70  is centred on the axis  2 , and the internal face thereof forms the internal surface  34  radially delimiting the cavity  12 . At the axial end thereof opposite to the one connected to the main portion  36 , the ring  70  carries fixedly a fixing flange  72 . The latter adopts the form of a thin disc centred on the axis  2 , projecting radially outwards from the ring  70 . The radial extent thereof corresponds substantially to that of the shoulder  16 , against which it is intended to come into abutment. To do this, the screwed elements  40  form a crown, each element of which passes through the fixing flange  72 , and then the shoulder  16  in order to press these two elements  72 ,  16  against each other. The length of the screwed elements  40 , necessary for fixing the lid  6 , thus proves to be particularly small compared with the similar elements in the case b) shown in  FIGS. 1 to 3 . 
     If the fixing flange  72  is capable of reconstituting the thickness of the lateral body  10  in the vicinity of the shoulder  16 , there remains, after the fixing on the lid  6 , an annular space  74  between the internal surface  24  and this same lid. This space is entirely or partially filled in by the secondary portion  30   b  of the reconstitution part  30 . This secondary portion  30   b  is independent of the lateral body  10  and of the lid  6 , like the reconstitution part  30  of case a) shown in  FIG. 4 . 
     It takes the form of another ring  30   b , one of the axial ends of which is in abutment against the flange  72  axially delimiting the annular space  74 , and the other axial end of which is located close to or in the plane of the first end  10   a , and/or close to or in the plane of the external surface  44  of the main closure part  36 . Radially, this ring  30   b  is located between the internal surface  24  and the radially external surface of the assembly formed by the ring  70  of the primary portion  30   a , and the main part  36  of this lid. In this regard, it should be noted that the main part  36  and the primary portion  30   a  can be produced in a single piece, or more preferentially by assembling a plurality of elements with one another, preferably by welding. 
     The axial locking of the reconstitution ring  30   b  takes place through the bottom of the head damping cap  46 , or by the presence of an additional lid (not shown) axially covering the lid  6  and fixed to the body  10 . This additional lid may moreover be provided in all the other embodiments described previously. 
     Naturally, various modifications can be made by a person skilled in the art to the invention that has just been described, solely by way of non-limitative examples and in accordance with the scope defined by the accompanying claims. In particular, the various preferred embodiments can be combined with one another.