EP3042378B1 - Package comprising improved means for shock absorbance between an assembly containing radioactive materials and the cover of the packaging - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of packages of radioactive materials, comprising a package and an assembly containing radioactive material housed in a cavity defined by the package. This set may for example include waste cases or assemblies of nuclear fuel.

STATE OF THE PRIOR ART

A package for storing and / or transporting radioactive material generally comprises, as outer shell, a package having a lateral body, a bottom and a lid. These parts of the package define a housing cavity of a set containing radioactive materials, for example a basket housing nuclear fuel assemblies or waste cases.

The safety demonstration of the packaging in charge of the assembly is based in particular on regulatory fall tests. For the case of a fall from a height of 9 meters in the direction of the axis of the package passing through the bottom and the lid of the latter, on the head damping cover covering the lid of the package, the The total mass of the assembly containing the radioactive materials presses on the same cover during the impact on the ground. During this fall called "axial drop", very significant efforts are generated in the closing system of the lid on the lateral body of the package. In particular, the fixing screws are highly stressed, and under certain conditions, the mobile assembly in the cavity of the package can impact the lid with a particularly damaging effect on the closure system.

In order to ensure the tightness of the package after the axial drop, it may therefore be necessary to limit the forces transmitted by the assembly on the lid, to the means of a shock absorbing system placed on the inner surface of the lid.

Such a system is known from the document JP 2011013035 A . Generally, such a system comprises at least one deformable damping device and a biasing device associated with this damping device. The two aforementioned devices are respectively fixed on the assembly containing the radioactive materials and on the inner surface of the lid. For example, in the case where this set includes cases, each case placed next to the cover incorporates a deformable damping device while facing the latter, it is placed a wedge-shaped biasing device, fixed on the inner surface of the lid.

To obtain optimal compression of the damping device, and thus best dissipate the mechanical energy through the deformation of the damping device, precise alignment is required between the latter and its associated biasing device.

But if the lid of the package, on which is fixed one of the devices, is generally positioned precisely on the lateral body of the package, there is however a side game often significant between the assembly and the inner wall of lateral body, in particular to allow the loading thereof into the cavity, resulting in misalignment.

In order to ensure the best possible alignment between these two devices, it can therefore be envisaged to greatly limit the side clearances defining the position of the cases relative to the load shims. In other words, this leads in particular to reduce the clearance between the assembly containing the radioactive materials and the inner surface of the lateral packaging body.

The reduction of these lateral games poses not only operational constraints when loading the cases in the housing of the basket and when loading the basket in the cavity of the package, but also induces manufacturing constraints because of the need to to control low tolerances.

Of course, these disadvantages presented in the context of an assembly integrating cases are met regardless of the nature of this set, that is to say, regardless of the shape of the devices containing the radioactive materials.

STATEMENT OF THE INVENTION

The invention therefore aims to at least partially overcome the disadvantages mentioned above, relating to the achievements of the prior art.

To do this, the subject of the invention is a package comprising a packaging for storing and / or transporting radioactive materials and an assembly containing radioactive materials housed in a cavity of the package extending along a longitudinal axis. of the package and being closed by a cover traversed by this axis, the package comprising a shock-absorbing system of the assembly against the cover, the system comprising at least one plastically deformable damping device and a device biasing said deformable damping device.

According to the invention, one of the biasing device and deformable damping device is mounted movably on the lid in a plane orthogonal to the axis of the package, and has self-centering means relative to the other of the two devices provided on said assembly containing the radioactive materials.

The invention thus makes it possible to obtain satisfactory relative positioning of the two devices of the damping system, whatever the position of the assembly containing the radioactive materials in the cavity of the package. This results in a better efficiency of the damping system, without requiring a precise positioning of the assembly in the cavity. Therefore, the invention provides a simple and clever solution to meet on the one hand the operational constraints during loading and on the other hand the manufacturing constraints encountered with the designs of the prior art.

Preferably, said biasing device is also a deformable damping device. Also, in the event of an axial drop on the cover, its deformation makes it possible to dissipate even better the mechanical energy of fall. In that case Figure, each of the two devices then performs on the one hand a deformable damper function, and other by a biasing function of the other device.

Preferably, the assembly comprises a storage basket as well as devices containing radioactive materials placed in housings defined by said basket, and said other of the two devices is provided on one of the devices containing radioactive materials or on said basket. . Alternatively, said devices containing radioactive materials can be placed directly in the cavity of the package without a storage basket.

Preferably, said other of the two devices is integrated with one of the devices containing radioactive materials, preferably at an end dedicated to its handling. Also, it is preferably done so that the handling end of the device containing radioactive materials is provided to dampen the shock in case of axial drop on the lid.

Preferably, each device containing radioactive material takes the form of a nuclear fuel assembly or a radioactive waste case.

In this case, it is preferentially provided that said set containing radioactive materials comprises a plurality of cases, stacked and divided into several columns. It is further associated with each column of cases, a deformable damping device and its associated biasing device.

Preferably, the deformable damping device and its associated biasing device respectively have two frustoconical surfaces of self-centering, axes parallel to the axis of the package.

Preferably, said deformable damping device has one or a plurality of plastically deformable damping elements arranged between two force distribution plates.

Preferably, said deformable damping device has an annular overall shape, said plastically deformable damping elements being distributed circumferentially along the damping device.

Preferably, said deformable damping device comprises a mounting plate fixed on the lid of the package, said mounting plate covering a movable plate of said deformable damping device, said movable plate being movable in a plane orthogonal to the axis of the package in a space defined between the mounting plate and the cover. Naturally, this type of arrangement can also be retained when it is the biasing device which is mounted movably on the cover. Also, in the latter case, it is said biasing device which comprises a mounting plate fixed on the lid of the package, the mounting plate covering a movable plate of said biasing device, said movable plate being movable in a plane orthogonal to the axis of the package in a space defined between the mounting plate and the lid.

In any case, the space takes the form of an annular slot open radially outwards.

Nevertheless, other arrangements are possible to obtain the mobility of the damping / biasing device relative to the lid. It may for example be legs or tongues through stirrups or the like with side games to provide mobility for self-centering.

Preferably, said movable plate mentioned above is one of said force distribution plates of the deformable damping device. In this case, the design remains simple since when this plate is annular, it is not necessary to mount additional elements to cooperate with the space defined between the mounting plate and the cover. Indeed, the outer periphery or the inner periphery of this annular plate can be housed with clearance in the aforementioned space.

Preferably, said plastically deformable damping elements are made of aluminum or one of its alloys.

Finally, the invention also relates to a method of closing a package as described above, comprising a step of self-centering the deformable damping device relative to its associated solicitation device, the step of self-centering being performed automatically by moving said one of the device biasing and deformable damping device relative to the lid, in a plane orthogonal to the axis of the package, when mounting the lid on a lateral body of the package.

Other advantages and features of the invention will become apparent in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente une vue en coupe d'un colis selon un mode de réalisation préféré de la présente invention, la coupe étant prise selon la ligne I-I de la figure 2 ;
• la figure 2 représente une vue du colis prise en coupe transversale selon la ligne II-II de la figure 1 ;
• la figure 3 est une vue en perspective d'une partie de l'un des étuis de déchets radioactifs contenu dans le colis ;
• les figures 4a et 4b schématisent différentes étapes d'un procédé de fermeture du colis selon un mode de réalisation préféré de l'invention ;
• la figure 5 montre une vue en perspective d'un mode de réalisation préféré d'un dispositif d'amortissement déformable destiné à équiper le colis montré sur les figures précédentes ;
• la figure 6 montre en vue en demi-coupe longitudinale du dispositif d'amortissement, prise selon le plan P de la figure 5 ;
• la figure 7 montre une vue en perspective de l'une des plaques de répartition d'efforts du dispositif d'amortissement montré sur les figures 5 et 6 ;
• les figures 8a et 8b sont des vues schématisant le comportement du dispositif d'amortissement et celui de son dispositif de sollicitation associé, lors d'une chute axiale ; et
• les figures 9a à 9c schématisent différentes étapes d'un procédé de fermeture du colis lorsque celui-ci est équipé du dispositif d'amortissement déformable montré sur les figures 6 et 7.

This description will be made with reference to the appended drawings among which;

• the figure 1 represents a sectional view of a package according to a preferred embodiment of the present invention, the section being taken along the line II of the figure 2 ;
• the figure 2 represents a view of the parcel taken in cross-section along line II-II of the figure 1 ;
• the figure 3 is a perspective view of a portion of one of the radioactive waste cases contained in the package;
• the Figures 4a and 4b schematize various steps of a method of closing the package according to a preferred embodiment of the invention;
• the figure 5 shows a perspective view of a preferred embodiment of a deformable damping device for equipping the package shown in the preceding figures;
• the figure 6 shows in longitudinal half-section view of the damping device, taken along the plane P of the figure 5 ;
• the figure 7 shows a perspective view of one of the force distribution plates of the damping device shown in FIGS. Figures 5 and 6 ;
• the Figures 8a and 8b are views schematizing the behavior of the damping device and that of its associated biasing device, during an axial fall; and
• the Figures 9a to 9c schematically different steps of a package closing process when it is equipped with the deformable damping device shown on the figures 6 and 7 .

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

With reference first to figures 1 and 2 there is shown a package 100 for storing and / or transporting radioactive material in the form of a preferred embodiment of the present invention.

The package comprises first a package 1 provided with a lateral body 2, a bottom 4 and a lid 6 closing an opening of the package opposite the bottom 4. The package has a longitudinal axis 8 centered relative to the side body 2, and through the lid and the bottom of the same packaging.

The package forming the outer envelope of the package defines a cavity 10 for housing a set 12 containing radioactive material. This assembly 12, also centered on the axis 8, here comprises a storage basket 14 and a plurality of devices containing the radioactive materials which are here waste cases 16. The cases are here stacked and divided into several columns, each column may for example have two to five cases stacked on each other, preferably by interlocking their ends facing two by two.

In the embodiment shown, as is best seen on the figure 2 , it is for example provided nine columns of cases, eight of which are distributed around the axis 8 of the package, and one of which is centered on the same axis 8. These columns of cases 16 are placed in housing 18 of complementary shape provided on the basket 14.

As shown in dotted lines on the figure 1 at the ends of the package considered in the direction of the axis 8, the package may be equipped with damping hoods 20 respectively protecting the lid 6 and the bottom 4 of the package.

With reference to the figure 3 , it is shown an embodiment for one of the cases 7. It may be a standard case for receiving compacted waste, or vitrified waste.

Patties 22 incorporating the radioactive waste are placed inside a space defined by a side wall 24, at the ends of which is a leading end 26 and a bottom end 28. In general, as this is visible on the figure 3 , the leading end 26 has a projecting shape, while the bottom end 28 has a recess, these two ends of substantially complementary shapes being provided to fit the holsters on each other, to form the columns. aforementioned cases.

More specifically, as regards the head end, it is shaped to allow the handling of the case. Also, the end 26 takes a generally mushroom shape defining an annular plug 30 open radially outwardly. Upward, this plug 30 is defined by an upper plate 32, while downwards, it is defined by an annular plate continuing with a portion forming a frustoconical surface 34 of axis corresponding to the axis of the case 16. At this end end 26, the plate defining the surface 34 then joins the side wall 24, with the aid of a portion defining an annular groove 36 open radially outwardly.

On the figure 1 the upper end of the cases has been represented only roughly. Nevertheless, it is noted that at the head of each of the holster columns, the head end 26 of the case located closest to the lid is an integral part of a shock absorbing system of the assembly 12 against the lid 6.

More precisely, this damping system 40 is broken down into several subsystems 40 'each associated with one of the columns of cases 16. In the preferred embodiment envisaged, the leading end 26 allowing the handling of the holster forms both a deformable damping device in the event of impact, and a device for biasing another deformable damping device 42 mounted on the cover 6. Therefore, it should be understood that in each subsystem 40 ', the device 42 is both a deformable damping device intended to be biased by the upper end 26 forming a biasing device, and on the other hand constitutes a device for biasing this damping device deformable 26 formed by the leading end of the holster. Also, it must be understood that the two devices 26, 42 are intended to solicit mutually in case of axial drop occurring at the head of the package, which allows them to deform plastically both and thus absorb the best mechanical energy shock that is related to the fall, as this will be explained in more detail below.

One of the peculiarities of the present invention lies in the fact that the deformable damping device 42 is movably mounted on the inner surface of the lid 6, in a plane orthogonal to the axis 8.

It is therefore in this plane corresponding to the inner surface 46 of the cover 6 that the device 42 can be moved relative to the cover, by means of a suitable mechanical connection represented only schematically on the figure 1 , and identified by the reference numeral 48. In addition to the mobile assembly of the device 42, the latter has self-centering means with respect to the device 26, these self-centering means being here made using a frustoconical surface 50 intended to cooperate with the frustoconical surface 34 of the device 26 forming the handling end of the case 16. Also, in the embodiment shown, the two devices 42, 26 allow their self-centering through the mobile mounting device 42 on the cover 6, and by the implementation of two frustoconical self-centering surfaces 50, 34, preferably coaxial axis parallel to the axis 8.

In this preferred embodiment, the biasing device 26 intended to cooperate with the deformable damping device 42 is provided on the upper case of the column associated with the subsystem 40 '. Nevertheless, an alternative could be to provide these biasing means 26 on the basket 14, without departing from the scope of the invention. For example, the device 26 could then surround the opening of the associated housing 18, at an upper end of the basket 14.

Back to the preferred embodiment, the Figures 4a and 4b schematically different successive steps of a package closing process. This method comprises a self-centering step of the deformable damping device 42 relative to the biasing device 26, the latter, because of its large mass, then being immobile throughout the closing step. This self-centering step is performed automatically by moving the device 42 relative to the cover 6, thanks to the connection 48, as shown schematically by the arrow 54 on the figure 4b . This automatic displacement in the plane orthogonal to the axis 8 is the result of the cooperation between the two self-centering surfaces 34, 50, the self-centering being obtained progressively as the cover 6 is set in place on the side body of the package. In this respect, the positioning of the cover 6 axially in the direction of the casing columns 16 is shown schematically by the arrow 56 on the figure 4a .

Therefore, by aligning progressively and very accurately with the case column, the deformable damping device 42 allows optimal operation in case of shock occurring during an axial fall of the package. This provides a satisfactory damping of the shock of the assembly 12 against the lid, thus ensuring the sealing of the cavity 10 forming containment. Indeed, thanks to the dissipation of the mechanical energy of shock of this assembly 12 against the cover 6, the attachment means of the latter on the lateral body 2 of the package 1 can better withstand the risk of radiological leakage and / or detaching the lid.

Furthermore, it is noted that during such an axial fall, the self-centering of the device 42 of each subsystem 40 'can continue, when it has not been fully achieved when closing the lid. packaging.

Now with reference to Figures 5 to 8b a preferred embodiment of the deformable damping device 42 will be described.

Firstly, it is noted that this device has a generally annular shape, of axis parallel to the longitudinal axis of the package. With reference specifically to Figures 5 and 6 the device 42 has a plurality of damping elements 60 which here take the form of solid or hollow cylinders made of aluminum or one of its alloys, or else any other material known for its shock-absorbing properties by plastic deformation. Each cylinder 60 has at its two opposite ends pins 62 which are housed in complementary recesses provided on two plates 64, 66 of force distribution.

The plate 64 is provided at the interface with the lid 6, preferably near or in contact with the inner surface 46 of the same lid. The other force distribution plate 66 is here incorporated into an annular piece 63 defining, opposite the plate 66, the frustoconical self-centering surface 50. The damping elements 60 are thus inserted between the two plates. 64, 66, and uniformly distributed in the circumferential direction along the damping device 42.

In the embodiment shown on the Figures 5 and 6 , eight deformable cylinders are arranged between the force distribution plates 64, 66. For the mounting of the device 42 on the inner surface 46 of the cover 6, there is provided a mounting plate 70 fixedly assembled on the same surface 46, using fasteners 72 of the screw type. The mounting plate 70, generally disk-shaped, has a central portion bearing against the surface 46 of the cover, and at the periphery of this central portion, a recess for presenting an annular end 70 'away from the surface 46. Indeed, between this end portion 70 'of the plate 70 and the surface 46, there is defined a space 74 in the form of an annular slot open radially outwardly. It is inserted the inner periphery 64 'of the force distribution plate 64, a lateral play being provided between the plate 70 and the plate 64 so as to allow a displacement of the latter in all directions of the orthogonal plane to axis 8 of the package. As this displacement of limited amplitude can occur in any direction of the aforementioned plane, the self-centering capacity of the device 42 is very satisfactory.

Of course, to allow the free movement of the inner periphery 64 'of the force distribution plate 64, the inner diameter of the inner periphery 64' is strictly greater than the outer diameter of the bottom of the slot open radially outwardly . The clearance provided between these two elements is preferably retained so as to obtain a displacement of the damping device 42, with respect to a centered position of the same device on the mounting plate 70, for example up to 30mm and this in each of the directions of the plane orthogonal to the axis 8 of the package.

As is visible on the figure 7 , the force distribution plate 64 has orifices for receiving the pins 62 of the deformable elements 60, but also has tabs 78 orthogonal to the plane of the plate. These tongues 78 preferably result from a cutting within the plate 64, continued by folding at 90 degrees of each tab obtained. These fixing tongues 78, which are here four in number, are intended to ensure the attachment of the plate 64 on the annular piece 63, for example by welding.

Finally, this same annular piece 63 has several tabs 80 which are fixedly attached to it, preferably by welding, and which are provided to be able to participate in the self-centering of the device 42 relative to the corresponding case column. Indeed, these tabs 80 have a terminal shape inclined to approach the axis of the device 42 in the direction of the force distribution plate 64. These pre-centering tongues 80 are located radially towards the internal to the frustoconical self-centering surface 50 of the annular piece 63, and allow for example to cooperate with the end plate 32 of the upper case of each column, when placing the cover on the lateral body of the package.

Similarly, the annular piece 63 may have another frustoconical surface 50 ', adjacent the surface 50 and forming therewith a V whose tip is oriented towards the case column. The surface 50 'is also provided to participate in the self-centering of the device 42 relative to the corresponding case column, cooperating with a complementary frustoconical surface 50 "made at the entrance of the housing 18, and shown on the figure 1 .

In this respect, Figures 9a to 9c schematically different steps of a package closing process when it is equipped with the deformable damping device 42 shown on the figures 6 and 7 .

As mentioned above, during the establishment of the cover 6 on the packaging body, the self-centering of the device 42 can be achieved by the cooperation of the frustoconical surfaces 50, 34, and / or by the cooperation frustoconical surfaces 50 ', 50 ", and / or by the cooperation of the tabs 80 with the plate Of course, when several of these pairs of elements are active during the placement of the cover, the order in which they intervene may be random, depending on the initial position of the cover. damping device 42 on the lid, and the position of the column of cases 16 in the housing 18.

On the Figures 8a and 8b , it is shown respectively the cooperation between the device 42 and the device 26 which self-solicit in order to create their deformation for the purpose of damping the shock caused by the axial fall of the package, with the lid of the packaging oriented to the impact surface.

On the figure 8a , it is shown the cooperation between these two devices 42, 26 before the fall, when the frustoconical surfaces of self-centering 50, 34 cooperate with each other by being in contact. During the fall, as is schematized on the figure 8b it is the entire device 26 which deforms, in particular by folding at the annular groove 36 provided for this purpose. Simultaneously, the deformable damping elements 60 are compressed between the two force distribution plates 64, 66, which leads to their crushing allowing the dissipation of the impact energy.

Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples. The scope of the invention is defined in the claims.

Claims (14)

1. Package (100) comprising a packaging (1) for storing and/or transporting radioactive materials and an assembly (12) containing radioactive materials housed in a cavity (10) of the packaging extending along a longitudinal axis (8) of the packaging and being closed by a cover (6) crossed by said axis (8), the package comprising a system (40) for dampening impact of the assembly (12) against the cover (6), the system comprising at least one plastically deformable dampening device (42) and a loading device (26) of said deformable dampening device,
   characterised in that one of the loading device (26) and deformable dampening device (42) is mounted moveable on the cover (6) in a plane orthogonal to the axis (8) of the packaging, and has means (50) of self-centring relatively to the other of said two devices (26) provided on said assembly (12) containing the radioactive materials.
2. Package according to claim 1, characterised in that said loading device (26) is also a deformable dampening device.
3. Package according to claim 1 or claim, 2 characterised in that the assembly (12) comprises a storage basket (14) and devices (16) containing radioactive materials placed in housings (18) defined by said basket, and in that the other of said two devices (26, 42) is provided on one of the devices (16) containing radioactive materials or on said basket (14).
4. Package according to any of the preceding claims, characterised in that the other of said two devices (26, 42) is integrated in one of the devices (16) containing radioactive materials, preferably at an end dedicated to its handling.
5. Package according to any of the preceding claims, characterised in that each device (16) containing radioactive materials takes the form of a nuclear fuel vessel or a nuclear waste canister.
6. Package according to claim 5, characterised in that said assembly (12) containing radioactive materials comprises a plurality of canisters (16), stacked and spread out in several columns, and in that, with each column of canisters is associated a deformable dampening device (42) and its associated loading device (26).
7. Package according to any of the preceding claims, characterised in that the deformable dampening device (42) and its associated loading device (26) have respectively two truncated self-centring surfaces (50, 34), of axes parallel to the axis of the packaging.
8. Package according to any of the preceding claims, characterised in that said deformable dampening device (42) has one or a plurality of plastically deformable dampening elements (60) arranged between two load spreading plates (64, 66).
9. Package according to claim 8, characterised in that said deformable dampening device (42) has an overall annular shape, said plastically deformable dampening elements (60) being spread out circumferentially along the dampening device.
10. Package according to claim 8 or claim 9, characterised in that said deformable dampening device (42) comprises a mounting plate (70) fixed on the cover of the packaging, said mounting plate covering a moveable plate (64) of said deformable dampening device (42), said moveable plate (64) being displaceable in a plane orthogonal to the axis of the packaging in a space (74) defined between the mounting plate (70) and the cover (6),
    or characterised in that said loading device (26) comprises a mounting plate fixed on the cover of the packaging, said mounting plate covering a moveable plate of said loading device (26), said moveable plate being displaceable in a plane orthogonal to the axis of the packaging in a space defined between the mounting plate and the cover (6).
11. Package according to claim 10, characterised in that said space (74) takes the shape of an annular slot open radially towards the exterior.
12. Package according to claim 10 or claim 11, characterised in that said moveable plate (64) is one of said load spreading plates.
13. Package according to any of claims 8 to 12, characterised in that said plastically deformable dampening elements (60) are made of aluminium or of an alloy thereof.
14. Method of closing a package (100) according to any of the preceding claims, characterised in that it comprises a step of self-centring the deformable dampening device (42) relatively to its associated loading device (26), the step of self-centring being carried out automatically by displacement of said one of the loading device and deformable dampening device (42) relatively to the cover (6), in a plane orthogonal to the axis (8) of the packaging, during the mounting of the cover (6) on a lateral body (2) of the packaging.

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