WO2004105048A2

WO2004105048A2 - Storage device for the transportation/storage of nuclear fuel assemblies

Info

Publication number: WO2004105048A2
Application number: PCT/FR2004/050201
Authority: WO
Inventors: Jacques Gardin; Christophe Roger
Original assignee: Cogema Logistics
Priority date: 2003-05-22
Filing date: 2004-05-18
Publication date: 2004-12-02
Also published as: FR2855311B1; WO2004105048A3; FR2855311A1

Abstract

The invention relates to a storage device for the transportation/storage of nuclear fuel assemblies, comprising a main structure provided with honeycomb-shaped cells (10) wherein lagging is provided, respectively defining a housing which can receive a nuclear fuel assembly, said individual lagging being formed by a plurality of metal sheets (16) each of which is provided with two longitudinal edges (18). According to the invention, for each honeycomb-shaped cell (10), said individual lagging (12) is provided with at least one metal sheet (16) which can be assembled on the main structure by sliding at least one part of the two longitudinal edges (18) respectively into two longitudinal grooves (20) provided on the main structure of the honeycomb-shaped cell (10).

Description

STORAGE DEVICE FOR THE TRANSPORT / STORAGE OF NUCLEAR FUEL ASSEMBLIES

DESCRIPTION

TECHNICAL AREA

The present invention relates to a storage device for the transport / storage of nuclear fuel assemblies, such as fresh fuel assemblies intended to constitute the energy source of nuclear power plants.

STATE OF THE PRIOR ART

Conventionally, such devices also called “basket” or “rack” for storage are of substantially cylindrical shape with circular section, and have a plurality of housings each suitable for receiving a nuclear fuel assembly. Typically, the storage device is in the form of a main aluminum structure, provided with cells inside which liners are assembled intended to delimit the various housings also of substantially cylindrical shape, and generally of square section or hexagonal. Furthermore, it should be noted that the liners are usually made of stainless steel alloyed with boron, insofar as the boron makes it possible to very satisfactorily ensure the subcriticality of the device, and in this sense that the stainless steel is fully compatible with the constraints linked to the materials authorized to be in contact with nuclear fuel assemblies.

Thus, in the prior art, several embodiments have been proposed in order to achieve such a storage device comprising a main structure in aluminum and linings in stainless steel alloyed with boron.

A first known solution consists in carrying out the linings by overmolding inside the cells of the main structure of the device. However, this technique is extremely restrictive, because of the large number of drawbacks that it generates. Indeed, it is first of all specified that the fact of using such a technique generates significant risks of weakening the mechanical strength of the main aluminum structure, insofar as the maintenance of each liner inside its respective cell is usually provided by stitching in the foundry.

Furthermore, it is noted that the liners of the storage device must necessarily satisfy very precise geometric and dimensional characteristics, in order to allow good maintenance of the fuel assemblies inside the housings. In other words, the section of each housing and the flatness of the faces of the associated liner are criteria to be strictly observed, which is only possible using a resumption by machining of the overmolded stainless steel coating.

Indeed, as an indicative example, the overmolded coating usually has a thickness at least equal to 10 mm imposed by the constraints of feasibility of overmolding, while the final thickness of the lining must be of the order of 3 mm. . Thus, the additional machining operation necessary to obtain a lining having adequate geometrical and dimensional characteristics, generates a relatively substantial additional cost, further adding to that of the loss of the machined material comprising boron noticeably expensive.

In addition, it is noted that the storage device can reach temperatures of the order of 200 ° C. In this way, we can see that the retaining technique used to secure the overmolded liners inside the cells is in no way suited to deal with the problems linked to differential expansion, which can arise due to the presence on the one hand of the main structure in aluminum, and on the other hand of these various linings in stainless steel. In addition, this drawback is all the more constraining as the length of the storage devices is relatively large, which of course promotes the harmful effects of differential expansion.

A second solution envisaged in the prior art relates to the creation of liners each comprising a plurality of sheets, these sheets being previously welded together before being slipped inside the respective cell provided in the main structure of the device.

Here again, the maintenance of each liner slipped inside its respective cell is usually ensured by stitching, which can cause significant risks of weakening the mechanical strength of the main aluminum structure, and this does not always resolve not the problems of differential dilation. In addition, the preliminary welding operations make it particularly difficult to respect the geometric constraints of the linings. As such, it is noted that the very feasibility of these welding operations is particularly affected by the presence of boron in the sheets constituting the linings, generally around 1.75%.

Thus, it can be noted that the deformations caused by the welding operations generate> problems of insertion by sliding of the linings inside their respective cells, as well as problems of maintaining the fuel assemblies in the housings provided for this purpose. effect.

Finally, a third proposed solution consists in assembling each of the sheets of a liner separately using screws intended to cooperate with the main aluminum structure.

Although this solution does not have the drawbacks of the previous solution relating to the feasibility of welding and compliance with the geometric constraints of the linings, the problems associated with the differential expansion of aluminum and stainless steel still remain.

On the other hand, the small thickness of the sheets of the liners requires the provision of a large number of screws to ensure satisfactory fixing of these sheets on the main structure of the device, which is largely restrictive in terms of assembly time of the various linings .

In addition, this screw assembly solution is in no way recommended, in the sense that the screws are capable of protruding inside the housings, and therefore present a non-negligible danger of damage to the fuel assemblies. nuclear when introduced into housing.

STATEMENT OF THE INVENTION

The object of the invention is therefore to propose a storage device for the transport / storage of nuclear fuel assemblies comprising a main structure provided with cells in which liners are assembled, each delimiting a housing capable of receiving a nuclear fuel assembly. , the device at least partially remedying the drawbacks mentioned above relating to the embodiments of the prior art.

To do this, the invention relates to a storage device for the transport / storage of nuclear fuel assemblies, the device comprising a main structure provided with cells in which liners are assembled each delimiting a housing capable of receiving a nuclear fuel assembly, each liner being formed of a plurality of sheets each having two longitudinal edges. According to the invention, for each cell, at least one sheet of the liner is capable of being assembled on the wall of the cell by sliding at least part of each of the two longitudinal edges, respectively in two longitudinal grooves provided on the wall of one cell. Advantageously, the operation of assembling at least one of the sheets constituting a liner of the storage device according to the invention is extremely easy and quick to implement, by carrying out a single sliding action of this sheet in grooves provided on the wall of the cell, and without having to prick or screw in the main structure defining the cells. Thus, the problems of weakening of the mechanical resistance of the main structure of the device and the risks of damage to nuclear fuel assemblies, encountered in the embodiments of the prior art, are therefore completely ruled out.

On the other hand, the two grooves provided on the wall of the cell concerned ensure precise positioning of the sheet intended to be introduced between these two grooves, so that it is then naturally possible to perfectly satisfy the characteristics and dimensional geometries of the liner and the housing associated with this sheet. As such, note that a satisfactory geometry of each final housing is all the easier to obtain when the grooves are designed so that the sheets are pressed against the wall of the associated cell. Also advantageously, the grooves are oriented longitudinally, namely in a direction substantially parallel to a main longitudinal axis of the storage device. In this way, each sheet maintained at its two longitudinal edges, respectively by two grooves, is therefore capable of being moved longitudinally relative to the main structure, which in particular makes it possible to cope with the problems of differential expansion occurring for example when the main structure defining the cells is made of aluminum, and the sheets of the linings are made of stainless steel alloyed with boron.

Still advantageously, it has been observed that the maintenance of the lining sheets by means of longitudinal grooves provided on the main structure ensures overall mechanical resistance of the device which is entirely compatible with the regulatory safety requirements for transport / storage. nuclear material, in particular with regard to the so-called "free fall" tests.

Preferably, for each lining of the device, at least two adjacent sheets are able to be assembled in pairs by means of engagement means and complementary engagement means, respectively provided on an edge. longitudinal of one of the two sheets and on a longitudinal edge of the other of the two sheets. With such an arrangement, the overall mechanical strength of the storage device is further enhanced. As such, it is possible to provide that the engagement means and the complementary engagement means of two adjacent sheets are designed so as to allow an assembly of these two sheets together, only before assembling them. here on the main structure. In other words, the engagement means and the complementary engagement means of two adjacent sheets allow, when they cooperate, to ensure a locking in translation in the longitudinal direction of one relative to the other. . Of course, this specificity also greatly contributes to increasing the overall mechanical strength of the storage device.

Preferably, when two adjacent sheets are assembled together by means of the engagement means and complementary engagement means, the engagement means partially protrude from the sheet comprising the complementary engagement means, and the complementary engagement means partially protrude from the sheet comprising the engagement means.

Thus, it can then be provided that the parts of the engagement means and of the complementary engagement means projecting respectively from the sheet comprising the complementary engagement means and from the sheet comprising the engagement means, correspond to parts of the edges longitudinal intended to slide in the longitudinal grooves provided on the main structure of the device.

According to a preferred embodiment of the present invention, the engagement means take the form of a niche portion having a plurality of primary teeth, and the complementary engagement means take the form of a niche portion having a plurality of secondary teeth, each of the secondary teeth being provided with flanges on either side of its distal end, so that two directly consecutive secondary teeth are able to retain a primary tooth having been introduced between the two directly consecutive secondary teeth.

Other advantages and characteristics of the invention will appear in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS This description will be made with reference to the accompanying drawings, among which; FIG. 1 represents a schematic perspective view of a storage device for the transport / storage of nuclear fuel assemblies, according to a preferred embodiment of the present invention,

FIG. 2 represents a partial sectional view taken along the plane II of FIG. I,

- Figure 3 shows a partial perspective view of two adjacent sheets of a liner of the storage device of Figure 1, these sheets being shown when they have not yet been assembled together, or yet assembled on the main structure of the device,

- Figure 4 shows a view similar to that shown in Figure 3, when the two sheets are assembled together, but they have not yet been assembled on the main structure of the device, the latter being also partially shown , and - Figure 5 shows a partial sectional view taken along the plane V of Figure I.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to Figure 1, there is shown a storage device 1 for transporting / storing nuclear fuel assemblies 2, according to a preferred embodiment of the present invention.

Note that the storage device 1 is intended to receive fuel assemblies 2 of any type, but preferably assemblies of fresh nuclear fuel.

As can be seen in Figure 1, the device 1 comprises a main structure 4, preferably made of cast aluminum, and having a cylindrical shape of circular section whose longitudinal main axis is indicated by the reference numeral 6 .

In addition, in this preferred embodiment of the present invention, the main structure 4 is produced by a stack of discs

8, but could of course be designed according to all other forms known to those skilled in the art, without departing from the scope of the invention.

Thus, the discs 8 are arranged so as to form a plurality of cells 10 each extending over substantially the entire length of the main structure 4, and in which the liners 12 are assembled, each delimiting a housing 14 capable of receiving an assembly. of nuclear fuel 2. It is specified that the housings 14 are preferably cylindrical, of square or hexagonal section depending on the shape of the fuel assemblies 2 to be received, and of axes parallel to the main longitudinal axis 6 of the structure main 4. In addition, it is indicated that if the lining

12 associated with a cell 10 extends substantially over the entire length of the latter, this liner 12 can however be produced in several longitudinal sections. Indeed, in the preferred embodiment of the present invention, the liner 12 of each cell 10 is in the form of several sections each extending over the entire thickness of a disc 8. Of course, without leaving the framework of the invention, it would also be possible to provide that the lining sections extend over a greater length, for example so as to overlap several discs 8 of the main structure 4, or even that the lining 12 takes the form a single section extending over the entire length of this same structure 4. As such, in the following description, the term “lining 12” will be used interchangeably to designate a section of lining extending only over the thickness of any disc 8 of the structure 4, to designate a section of liner extending over a length different from that previously indicated, or else to designate a liner taking the form of a single section extending over the entire length of a cell 10 formed by all of the disks 8. In addition, the term "cell 10" will be used to designate the part of a cell covered by its associated "liner 12".

With reference to FIG. 2, it can be seen that the lining 12 of a cell 10 comprises a plurality of sheets 16, these sheets 16 preferably being substantially plane, each in plan contact with the wall of the cell 10, and preferably produced stainless steel alloyed with boron. Thus, it should be understood that the wall (not referenced) of the cell 10 is generally made up of four vertical flat portions which are each in contact with one of the four sheets 16, as is clearly visible in FIG. 2. It is noted for information that the four sheets 16 forming the lining 12 of a cell 10 of square section, are of generally rectangular shape whose lengths are oriented substantially parallel to the main longitudinal axis 6 of the structure 4, and have with a thickness of the order of 3 mm. Each sheet 16 of a liner 12 is provided with two longitudinal edges 18, these edges 18 corresponding to the two lateral end portions extending substantially parallel to the main longitudinal axis 6 of the structure 4, when the liner 12 is assembled on this same main structure 4, as shown in FIG. 2.

In addition, in this preferred embodiment of the present invention, each sheet 16 of a liner 12 is capable of being assembled on the structure 4, and more specifically on the wall of the cell 10, by sliding at least part of each of its two longitudinal edges 18, respectively in two longitudinal grooves 20 provided on this wall of the cell 10. Note that these two longitudinal grooves 20 also extend substantially parallel to the main longitudinal axis 6 of the structure 4, and that they are preferably arranged at the level of the cell 10 so that the sheet 16 concerned correctly matches, over substantially its entire surface, the wall of this cell 10.

Thus, the geometry of the housing 14 obtained is very precise, and makes it possible to ensure extremely satisfactory maintenance of the fuel assembly 2 inside this same housing 14.

Note that in the preferred embodiment presented, the four sheets 16 of the liner 12 are mounted in the manner which has just been described. However, without departing from the scope of the invention, each liner 12 could comprise only a limited number of sheets 16 assembled in this way, such that only two of them, arranged adjacent to each other. Such a case arises in particular when the housings 14 are equipped with means (not shown) making it possible to exert mechanical forces in order to press the fuel assembly 2 against only two adjacent sheets 16 of the same liner 12. In this way , the other sheets 16 of the liner 12 not directly serving to maintain the assembly can then be mounted traditionally. With reference now to FIG. 3, one can see two adjacent sheets 16 of a liner 12, these two sheets 16 being intended to be assembled together before being mounted on the main structure 4 of the storage device 1. Although ^'only two plates 16 are shown in this figure, it should be noted that the cooperation between any two adjacent plates 16, the liner 12 shown in Figure 2, may be identical to that which will be described below. In this regard, we can see that the sheet

16 arranged substantially horizontally in FIG. 3 has a longitudinal edge 18 provided with engagement means 21, the latter preferably taking the form of a niche portion, having a plurality of primary teeth 22. The primary teeth 22 extend from substantially parallelepiped in the plane defined by the sheet 16 concerned, and are spaced by primary recesses 24. On the other hand, the sheet 16 disposed substantially vertically in Figure 3 comprises a longitudinal edge 18 provided with complementary engagement means 26, these preferably taking the form of a niche portion, having a plurality of secondary teeth 28. In addition, the secondary teeth 28 extend substantially parallelepipedally in the plane defined by the sheet 16 concerned, and are spaced apart by secondary recesses 30.

In addition, as can be seen in FIG. 3, each secondary tooth 28 is provided with flanges 32 on either side of its distal end, these flanges 32 projecting inside the two secondary recesses 30 present on each side. of the secondary tooth 28 considered. Thus, the engagement means 21 and the complementary engagement means 26 are designed so as to be able to authorize an assembly of the two sheets 16 with one another, before they are mounted on the main structure 4. Indeed, as as can be seen in FIG. 3, each secondary recess 30 is dimensioned so as to be able to be penetrated by a primary tooth 22, while each primary recess 24 is dimensioned so as to be able to be penetrated by a secondary tooth 28.

Due to the presence of the flanges 32, in order to ensure nesting between the engagement means 21 and the complementary engagement means 26, the sheet 16 arranged horizontally must penetrate the sheet 16 disposed vertically in a sliding direction sensibly perpendicular to the plane defined by this last sheet 16. Once this operation has been carried out, it can be seen in FIG. 4 that two secondary teeth 28 directly consecutive are able to retain the primary tooth 22 introduced into the secondary recess 30 arranged between these two same secondary teeth 28, mainly using the edges 32.

It is indicated that in this preferred embodiment of the present invention, the design of the engagement means 21 and complementary engagement means 26 authorizes the assembly of the adjacent sheets 16 only before they are mounted. on the main structure 4, due to the relative longitudinal blocking of the two sheets 16 provided by the presence of the teeth 22 and 28.

Of course, other designs allowing the two sheets 16 to be assembled can be provided for the engagement means 21 and the complementary engagement means 26, without departing from the scope of the invention. As such, it is specified that the chosen design could also allow an assembly of the sheets 16 therebetween, after they have been mounted on the main structure 4 of the device 1. Furthermore, it is also possible to indicate as 'illustrative example that when all four sheets 16 of a liner 12 are intended to be assembled in pairs before being mounted on the main structure 4, each of these sheets 16 then has engagement means 21 on one of its two longitudinal edges 18, and complementary engagement means 26 on the other of these same edges 18. Still with reference to FIG. 4, it can be seen that when the two sheets 16 are assembled together, a part 34 of each primary tooth 22 projects from the sheet 16 arranged vertically, this part 34 corresponding to the distal end of this tooth 22. In the same way, a part 36 of each secondary tooth 28 projects from the sheet 16 disposed horizontally, this part 36 corresponding to the distal end comprising the flanges 32. Consequently, the parts 34 and 36 of the means d engagement 21 and complementary engagement means 26 are the parts of the longitudinal edges 18 which are intended to slide inside the longitudinal grooves 20 provided on the structure 4, in order to ensure the assembly of the liner 12 on the latter .

Finally, it is noted that when the liner 12 is mounted on the main structure 4 so as to cover the cell 10, axial stops 38 can be mounted on this structure 4 in order to ensure the longitudinal retention of the liner 12 relative to the cell 10. In the preferred embodiment described where the liner 12 extends over the entire thickness of a disc 8, the stops 38 are preferably arranged on an upper face and on a lower face of this disc 8 , at each of the four angles of the square section of the cell 10, so as to allow the retention of the parts 34 and 36 of the longitudinal edges 18 of the sheets 16 constituting the lining 12. Of course, various modifications can be made by those skilled in the art to the storage device 1 which has just been described, only by way of nonlimiting example.

Claims

1. Storage device (1) for transport / storage of nuclear fuel assembly (2), said device (1) comprising a main structure (4) provided with cells (10) in which jackets (12) are assembled ) each delimiting a housing (14) suitable for receiving a nuclear fuel assembly (2), each liner (12) being formed of a plurality of sheets (16) each having two longitudinal edges (18), characterized in that for each cell (10), at least one sheet (16) of the path (12) is capable of being assembled on the wall of the cell (10) by sliding at least part of each of the two longitudinal edges ( 18), respectively in two longitudinal grooves (20) provided on said wall of the cell (10).

2. Device (1) according to claim 1, characterized in that for each liner (12) of the device (1), at least two adjacent sheets (16) are able to be assembled in pairs by means of means d engagement (21) and complementary engagement means (26), respectively provided on a longitudinal edge (18) of one of said two sheets (16) and on a longitudinal edge (18) of the other of said two sheets (16).

3. Device (1) according to claim 2, characterized in that the engagement means (21) and the complementary engagement means (26) of two adjacent sheets (16) are designed so as to allow these two sheets (16) to be assembled together, only before these are assembled on the wall of the cell (10).

4. Device (1) according to claim 3, characterized in that when two adjacent sheets (16) are assembled together by means of the engagement means (21) and complementary engagement means (26), the engagement means (21) partially protrude from the sheet (16) comprising the complementary engagement means (26), and the complementary engagement means (26) partially protrude from the sheet (16) comprising the means engagement (21).

5. Device (1) according to claim 4, characterized in that the parts of the engagement means (21) and complementary engagement means (26) projecting respectively from the sheet (16) comprising the engagement means complementary (26) and sheet (16) comprising the engagement means (21), correspond to parts

(34,36) longitudinal edges (18) intended to slide in said longitudinal grooves (20) provided on the wall of said cell (10).

6. Device (1) according to claim 5, characterized in that the engagement means (21) take the form of a niche portion having a plurality of primary teeth (22), and in that the complementary engagement means (26) take the form of a niche portion having a plurality of secondary teeth (28), each of the secondary teeth (28) being provided with flanges (32) on either side of its end distal, so that two directly consecutive secondary teeth (28) are able to retain a primary tooth (22) which has been introduced between said two directly consecutive secondary teeth (28).

7. Device (1) according to any one of the preceding claims, characterized in that the main structure (4) of the device (1) is made of aluminum, and in that the sheets (16) constituting the linings (12) are stainless steel alloyed with boron.

8. Device (1) according to any one of the preceding claims, characterized in that the housings (14) delimited by the liners (12) are of substantially square section.

9. Device (1) according to any one of claims 1 to 7, characterized in that the housings (14) delimited by the liners (12) are of substantially hexagonal section.

10. Device (1) according to any one of the preceding claims, characterized in that the sheets (16) of the liners (12) are each substantially planar.

11. Device (1) according to any one of the preceding claims, characterized in that the main structure (4) of the device (1) is composed of a plurality of superimposed discs (8).

12. Device (1) according to claim 11, characterized in that each sheet (16) extends over substantially the entire thickness of a disc (8).