WO2016092013A1

WO2016092013A1 - Paraseismic isolation device and assembly comprising a nuclear reactor and the paraseismic isolation device

Info

Publication number: WO2016092013A1
Application number: PCT/EP2015/079241
Authority: WO
Inventors: Nadim MOUSSALLAM
Original assignee: Areva Np
Priority date: 2014-12-10
Filing date: 2015-12-10
Publication date: 2016-06-16
Also published as: FR3029950B1; FR3029950A1

Abstract

Paraseismic isolation device and assembly comprising a nuclear reactor and the paraseismic isolation device. The paraseismic isolation device (1) comprises: a lower anchoring plate (21); an upper anchoring plate (23); and an isolator (25). The paraseismic isolation device (1) comprises an end plate (35) which is secured to one of the lower or upper ends of the isolator (25), and a fusible connection (37) connecting the end plate (35) to the lower anchoring plate (21) or to the upper anchoring plate (23).

Description

Seismic isolation device and assembly comprising a nuclear reactor and the seismic isolation device

The invention generally relates to seismic isolation systems intended to be interposed between the foundations and a structure such as a building or a nuclear reactor.

More specifically, according to a first aspect, the invention relates to a seismic isolation device intended to be interposed between foundations and a structure (5), the device comprising:

- a lower anchor plate, intended to be rigidly fixed to the foundations; - An upper anchor plate, intended to be fixed to the structure;

an isolator vertically interposed between the lower and upper anchor plates, the lower and upper anchor plates being respectively connected to lower and upper ends of the insulator, the insulator being sized to support a first predetermined voltage according to the vertical direction.

A device of this type is known for example from JP 2009 024 753. It makes it possible to considerably reduce the forces transmitted to the structure in the event of an earthquake. This device comprises in particular an insulator with great flexibility and high deformation capacity in a horizontal plane, while being relatively rigid in the vertical direction.

In addition to its seismic isolation function, this device generally supports the entire weight of the structure, so that a failure of this device would cause the fall of the structure, including for facilities containing nuclear materials, unacceptable consequences. It is therefore necessary to design the seismic isolation devices so that they function in the expected manner in the situations considered for the normal dimensioning of this device, but also in order to avoid a failure of the support of the vertical load in case of extreme earthquakes of levels much higher than those considered for the normal dimensioning. In the following, these earthquakes will be called "extreme earthquakes".

A predominant failure mode of seismic isolation devices of the above type is tearing or breaking of the insulator under combined shear and tension loading.

In this context, the invention aims to provide a seismic isolation device for limiting the voltage forces that can pass through the insulator for extreme earthquakes. To this end, the invention relates to a seismic isolation device of the aforementioned type characterized in that the seismic isolation device comprises an end plate rigidly fixed to one of the lower or upper end of the insulator, and a fusible link linking the end plate to the lower anchor plate or the upper anchor plate, the fusible link being selected to break or plasticize under the effect of a second predetermined voltage in the vertical direction, the second voltage being greater than the first voltage but lower than the voltage which can lead to a failure of the insulator.

The seismic isolation device of the invention operates substantially like that of JP 2009 024 753 for earthquakes of level less than or equal to the maximum level considered for the normal dimensioning of the device, that is to say for those generating the first one. predetermined voltage in the insulator. For this maximum level of earthquake, the insulator remains bound to the foundation and the structure. This allows on the one hand to comply with the sizing codes in force, especially in Japan and Europe (EN 15129 standard). The European standard imposes in particular a rolling stability criterion that the device of the invention makes it possible to respect. It should be noted that such a criterion would not be respected with a seismic isolation device having supports not rigidly related to the structure, and allowing a detachment of the structure in case of significant vertical response.

Furthermore, the device of the invention allows to resume a tilting moment of the structure, that is to say a rotational movement about a horizontal axis. Finally, the device of the invention makes it possible to ensure the absence of detachment of the structure for the maximum level of earthquake considered for the dimensioning, and thus to guarantee the absence of shock. Such shocks occur when the structure returns to position following a detachment.

On the other hand, in case of extreme earthquake, the fusible link will break or laminate, so that a separation is authorized between the structure and the foundations. Thus, the insulator is not destroyed or torn and is protected by the link, which acts as a fuse. When the structure returns to position, it is supported by the seismic isolation device adequately, since the seismic isolation device is still able to resume compressive forces.

The seismic isolation device may still have one or more of the following characteristics, considered individually or in any technically feasible combination:

- The fuse link comprises at least one fusible member selected from the following group: a screw, a rod, a plate, a cylinder, a toad; the fuse member is made of metal or of another material having the required breaking or plasticizing characteristics;

the seismic isolation device comprises an additional connection of the end plate to the lower or upper anchor plate, adapted to transmit a horizontal shear force between the end plate and the lower or upper anchor plate when the fuse link is intact and when the fuse link is broken or plasticized;

the additional connection comprises a lateral surface secured to or formed on the lower or upper anchoring plate and a complementary surface secured to or formed on the end plate, the lateral surface and the complementary surface being in contact with each other; the other and extending parallel to the vertical direction;

the lateral surface and the complementary surface extend in a substantially closed contour around the insulator;

the lower or upper anchoring plate comprises a concave zone delimited by a bottom and a peripheral edge, the end plate being engaged in the concave zone, the peripheral edge defining the lateral surface;

- The end plate bears against the bottom and is connected to the bottom by the fuse link when the fuse link is intact;

the height of the lateral surface in the vertical direction is chosen so that the end plate does not disengage from the concave zone when there is detachment between the end plate and the lower anchor plate or the plate; upper anchorage at the occurrence of an extreme earthquake;

- the peripheral edge is attached against the bottom;

at least one of the lateral surface and the complementary surface is coated with an anti-seizing coating.

According to a second aspect, the invention relates to an assembly comprising:

- foundations anchored in the ground;

a nuclear reactor provided with a raft;

at least one seismic isolation device as described above, the lower anchoring plate being rigidly fixed to the foundations, the upper anchoring plate being rigidly fixed to the base.

The assembly may further have at least one stop limiting the horizontal clearance of the nuclear reactor.

Other features and advantages of the invention will become apparent from the detailed description given below, for information only and in no way limitative, with reference to the appended figures, among which: - Figure 1 is a schematic representation of a nuclear reactor based on foundations through insulation devices according to the invention;

FIG. 2 is a simplified schematic representation of one of the seismic isolation devices of FIG. 1, at rest;

- Figure 3 is a view similar to that of Figure 2, and shows the operation of the seismic isolation device in case of extreme earthquake;

- Figures 4 to 6 show different variants of fusible members; and

- Figures 7 and 8 show alternative embodiments of the invention.

As shown in Figure 1, the seismic isolation device 1 is intended to be interposed between foundations 3 and a structure 5. The device 1 is intended, in case of earthquake, to reduce the forces transmitted by the ground to the structure .

In the example shown, the foundations 3 are arranged in an excavation

7, excavated in the ground 9. More particularly, the foundations 3 comprise a slab 1 1 resting on the bottom of the excavation 7 and a plurality of pillars 13 projecting vertically from the slab January 1. The pillars are arranged at a distance from each other.

The foundations 3 further comprise retaining walls 15, arranged against the walls of the excavation 7.

The structure 5 comprises in its lower part a raft 17.

In the example shown, a seismic isolation device 1 is interposed vertically between the upper surface of each of the pillars 13 and the raft 17.

Thus, the structure 5 rests exclusively on the pillars 13, the seismic isolation devices 1 taking together the entire weight of the structure.

Moreover, it clearly appears in FIG. 1 stops 19, limiting the horizontal clearance of the structure 5.

In the example shown, the stops 19 are carried by the retaining walls 15. They are arranged vertically at the level of the raft 17.

Structure 5, in the example shown, is a nuclear reactor. Alternatively, the structure 5 is another building, for example a building housing turbines, a factory, or a tower, or any other type of building.

It should be noted that the foundations 3 as a variant have a structure different from that shown in FIG. In particular, the raft 17 may rest not on pillars 13 but on one or more solid masses, or even directly on the slab 1 1.

The seismic isolation device 1 is shown in more detail in FIG. 2. It comprises: - A lower anchor plate 21, intended to be rigidly fixed to the foundations 3;

- An upper anchor plate 23, intended to be fixed to the structure 5;

an isolator 25 interposed vertically between the lower and upper anchoring plates 21, 23, the lower and upper anchor plates 21, 23 being respectively connected to the lower and upper ends of the insulator 25.

Lower anchor plate 21 is typically a steel plate.

It is, in the example shown, rigidly fixed to the foundations 3 by mechanical members 27, such as dowels, anchor rods, tie rods or any other suitable member.

Similarly, the upper anchor plate 23 is typically a steel metal plate, rigidly fixed to the structure 5 by mechanical members 29, for example pegs, anchor rods, tie rods or any other suitable member.

Insulator 25 is, in the example shown, a fretted elastomeric member. This member comprises for example a plurality of layers 31 made of elastomer, and a plurality of metal plates 33 interposed between the elastomer layers 31. The layers 31 and the plates 33 are of horizontal orientation, are stacked on each other and are typically joined together by a vulcanization process. Thus, the insulator 25 has great flexibility and great deformation capacity under the effect of a bias in a horizontal plane. These stresses will be called shear forces in the following description.

On the other hand, the insulator 25 is relatively rigid in the vertical direction. The vertical direction is substantially perpendicular to the layers 31, to the plates 33, and to the anchoring plates 21 and 23.

The insulator, as a variant, has any other constitution adapted to confer a large capacity of deformation under the effect of a shear force and, on the other hand, a relative rigidity in the vertical direction.

According to the invention, the seismic isolation device 1 comprises an end plate 35 rigidly attached to an upper end of the insulator 25, and a fusible link 37 linking the end plate 35 to the upper anchor plate. 23.

It should be noted that, under tension stress, the end plate 35 and the upper anchor plate 23 are rigidly fixed to each other in the vertical direction only by the fuse link. In the absence of fusible link, the plate 35 is likely to be debated with respect to the upper anchoring plate 23 in the vertical direction. Typically, the end plate 35 is a metal plate, horizontal orientation. It is typically bonded to the insulator 25. More specifically, it is rigidly attached to the layer 31 or to the plate 33 located highest in the stack constituting the insulator 25.

In this case, the lower anchor plate 21 is rigidly fixed to a lower end of the insulator 25. It is for example fixed by adhesion. Typically, it is attached to the lowest layer 31 or plate 33 in the stack constituting the insulator 25.

The insulator 25 is dimensioned to present margins relative to the maximum seismic level considered for the dimensioning. This earthquake results in a predetermined shear force to be transmitted from the lower anchoring plate 21 to the upper anchoring plate 23 and the structure 5, through the insulator 25. This level of earthquake is also reflected by a first predetermined voltage in the vertical direction, to be transmitted from the lower anchoring plate 21 to the upper anchoring plate 23, through the insulator 25. This first predetermined voltage corresponds to a vertical tensile force. The isolator 25 is designed to be able to transmit this first predetermined voltage, without degradation.

The insulator 25 is designed with a safety margin with respect to the first predetermined voltage, so that it can transmit forces greater than the first predetermined voltage, without degradation, as will be seen later. The first predetermined voltage therefore does not correspond to the maximum vertical voltage likely to be transmitted by the insulator 25 before rupture or major degradation.

The fuse link 37 is chosen so as to break, or to plasticize, under the effect of a second predetermined voltage in the vertical direction, the second voltage being greater than the first voltage, so as to largely guarantee the absence of rupture of the fuse device for the maximum level of design earthquake.

More specifically, the second predetermined voltage is between the first predetermined voltage and the maximum voltage in the vertical direction that can be transmitted by the insulator 25 without degradation thereof.

Thus, the fuse link plays a protective role vis-à-vis the insulator 25 under extreme earthquake level. As soon as the vertical voltage applied to the insulator exceeds the level for which the insulator is sized, i.e. the first predetermined voltage plus a margin, the fusible link will break or laminate, so that the end plate 35 becomes free with respect to the upper anchor plate 23 in the vertical direction. This rupture, or this plasticization, occurs in any event before a level of vertical tension resulting in the breakage or damage of the insulator is applied thereto.

The connections between the lower anchor plate 21 and the insulator 25, between the lower anchoring plate 21 and the foundations 3, between the end plate 35 and the insulator 25, and between the upper anchor plate 23 and the structure 5, are all more resistant to vertical tension than the fuse link 37.

In the example shown in Figure 2, the fuse link 37 comprises at least one fuse 39, preferably a plurality of fusible members. Each fusible member 39 connects the end plate 35 to the upper anchor plate 23, and is selected to break or laminate under the effect of a predetermined vertical tension. Together, the fusible members 39 constitute the fuse link 37.

Here is meant by breaking the fact that the fusible member 39 separates into at least two pieces completely independent of one another, without further physical connection between the pieces.

Plasticization means that the fusible member is deformed by elongation, without breaking the physical organ into two pieces independent of one another. The elongation of the fusible member or members allows a vertical displacement of the end plate 35 relative to the upper anchor plate 23, including a detachment. Elongation is a plastic deformation.

In the example shown in Figure 2, each fuse member 39 is a screw.

In this case, the end plate 35 comprises for each fuse member 39 a through hole 41, passing through the plate 35 throughout its thickness. The screw comprises a head 43, and a rod 45 of section smaller than the section of the orifice 41. The head 43 has a horizontal section greater than that of the orifice 41, and bears against a large lower face 47 of the end plate 35.

It should be noted that, in a horizontal plane, the cross section of the plate 35 is larger than the cross section of the insulator 25, so that the plate 35 has an annular portion projecting transversely beyond the isolator 25. The orifices 41 are formed in said annular portion.

One end 49 of the rod 45 is engaged in an orifice 51 of the upper anchoring plate 23. It is rigidly fixed in the orifice 51. For example, the end 49 is threaded and the orifice 51 carries an internal thread cooperating with the external thread of the end 49. The screw further comprises a zone of weakness 53, which is formed here in a section of the rod 45 engaged in the orifice 41. The zone of weakness 53 is for example a section of reduced diameter of the rod 45.

Thus, when the second predetermined voltage is applied to the fuse link, each of the fusible members 39 will break or plasticize at the level of the zone of weakness 53, thus allowing the end plate 35 to disengage with respect to the fuse plate. upper anchorage 23.

Alternatively, the fuse member is not a screw, but is a rod 55 (Figure 4), a plate 57 (Figure 5), a cylinder or a toad 59 (Figure 6).

The fuse member could still be any other suitable mechanical member.

The rod 55 has one end rigidly fixed to the upper anchoring plate 23, another end rigidly fixed to the end plate 35, the zone of weakness 53 being formed between the two ends. The stem can have all kinds of horizontal sections: circular, square, rectangular, etc.

In FIG. 5, the plate 57 is arranged substantially like the rod 55 of FIG. 4. An upper part of the plate 57 is rigidly fixed to the upper anchoring plate 23, and a lower part of the plate 57 is rigidly fixed. at the end plate 35. The zone of weakness 53 is formed between the upper and lower parts.

The toad 59 illustrated in FIG. 6 is of the type used for fixing rails on a railroad tie. It comprises a folded iron 60, a first end portion 61 of which is rigidly fixed to the upper anchoring plate 23. It comprises a second end portion 63 rigidly fixed to the end plate, and more precisely pressed against the lower face 47 of the end plate 35, and rigidly fixed to this large lower face 47. The zone of weakness 53 is formed in the iron between the first and second end portions 61 and 63.

The fuse member is made of metal, steel, lead or other material or an elastic material having the required breaking or plasticizing characteristics.

The seismic isolation device 1 further comprises an additional connection 65 from the end plate 35 to the upper end plate 23. The additional link 65 is adapted to transmit a horizontal shear force between the end plate 35 and the anchor plate 23. Specifically, it is provided and adapted to transmit said shear force at a time when the fuse link 37 is intact and when the fuse link 37 is broken or plasticized.

In the embodiment shown in FIG. 2, the additional link

65 comprises a lateral surface 67 formed on the upper anchoring plate 23, and a complementary surface 69 formed on the end plate 35, the side surface 67 and the complementary surface 69 being in contact with each other and extending parallel to the vertical direction.

Typically, the lateral surface 67 and the complementary surface 69 extend in a substantially closed contour around the insulator 25. The outline is typically completely closed, or alternatively present interruptions.

In the example shown in FIG. 2, the upper anchoring plate 23 comprises a concave zone 71. The concave zone 71 is cut in a large face of the upper anchoring plate 23 facing downwards. It is delimited by a bottom 73 and a peripheral edge 74 projecting downwards relative to the bottom 73. It is open downwards. Concave zone is here understood to mean a hollow zone. It is likely to have any kind of shape delimited by flat or curved faces, for example parallelepipedic.

The surface of the peripheral edge 74 facing the interior of the concave zone defines the lateral surface 67.

The end plate 35 is engaged in the concave zone 71.

It is supported by a large upper surface against the bottom 73, and is typically connected to the bottom 73 by the fusible link 37.

Typically, considered perpendicular to the vertical direction, the section of the end plate 35 is complementary to that of the concave zone 71.

In the example shown, the complementary surface 69 corresponds to the edge of the end plate 35.

The additional connection could be arranged differently, as shown in FIG. 7. For example, the peripheral edge 74 is defined by a ring 75 attached to the bottom 73 of the upper anchor plate 23. For example, the fixing 29 are integral with the ring, and pass through the edge 73 of the upper anchor plate 23 passing through holes 76. Thus, the bottom of the upper anchor plate 23 is pressed against the structure 5 by the ring 75. Preferably the edge 73 and the ring 75 are integrated in a reservation 78 dug in the structure 5. The reservation 78, perpendicular to the vertical direction, has an internal section complementary to the outer section of the bottom 73 and the 75 ring.

In order to facilitate the movement of the end plate 35 relative to the upper anchor plate 23, at least one of the lateral surface 67 and the complementary surface 69 may be coated with an anti-seizure coating. Preferably, both surfaces are coated with an anti-seizing coating. This coating is by example PTFE, or is a galvanized coating, or is an anti-seizing coating typically used in nuts and bolts.

Figure 3 illustrates the situation of the seismic isolation device, when it is loaded by stress and shear stresses, resulting from an extreme earthquake. In particular, this earthquake is such that the seismic isolation device 1 is subjected to a voltage greater than the first voltage plus the sizing margin, which has the effect of causing the breaking of the fuse link 37, as illustrated.

It can be seen that due to the shear force, the structure 5, with the upper anchoring plate 23 and the end plate 35, is offset horizontally with respect to the lower anchoring plate 21. In Figure 3, the upper anchor plate 23 and the end plate 35 are shifted to the right.

This movement is accompanied by a distortion of the layers 31, the insulator adopting an oblique shape.

On the other hand, because the fusible link 37 is broken, the upper anchor plate 23 has a degree of freedom in the vertical direction relative to the end plate 35. The upper anchor plate 23 may indeed be take off from the end plate 35 during a vertically vertical movement of the structure 5 with respect to the foundation 3. It thus creates a gap 77 between the bottom 73 of the anchor plate and the end plate 35.

So that the additional connection 65 continues to ensure the transmission of the shear forces when the fuse link 37 is broken or plasticized and a detachment occurs, the height of the lateral surface 67 is chosen so that the plate end 35 does not disengage from the concave zone 71 under stress from an extreme earthquake.

In other words, the height of the lateral surface 67 is chosen so large that the detachment of the upper anchor plate 23 is never sufficient, in the event of an extreme earthquake, for the end plate 35 to leave the concave zone 71.

It should be noted that the shear force to which the seismic isolation device 1 is subjected can be limited by the establishment of the stops 19. In effect, these stops 19 limit the displacement of the structure 5 in a horizontal plane, and therefore limit the displacement of the upper anchor plate 23 and the end plate 35 horizontally with respect to the lower anchor plate 21. Thus, even in the event of an extreme earthquake, the earthquake-proofing device 1 is subjected to a limited tension, because of the existence of the fuse link 37, and to a limited shearing force, because of the existence of stops 19.

Of course, the fuse link 37 can be implemented even if the seismic isolation device does not have the additional link 65.

An alternative embodiment of the seismic isolation device 1 will now be described with reference to Figure 8. Only the points by which this variant differs from that of Figures 1 to 3 will be detailed below. The identical elements or providing the same function will be designated by the same references as in the variant embodiment of FIGS. 1 to 3.

In the variant embodiment of FIG. 8, the fusible link 37 provides the function of the additional connection 65, namely to transmit the shear force between the end plate 35 and the upper anchor plate 23, at the same time when the fuse link 37 is intact and when the fuse link 37 is broken or plasticized.

In the variant embodiment of FIGS. 1 to 3, the additional connection 65 is provided by elements distinct from those providing the fuse link 37.

In the embodiment of Figure 8, the fuse link 37 has a plurality of fusible members 79 similar to the screws shown in Figure 2, but slightly different, however.

Each member 79 comprises, as previously described, a head 81 and a rod 83. The head 81 is pressed under and against the large lower face 47 of the end plate 35. The rod 83 has an end portion 85, located opposite the head 81, which is rigidly fixed to the upper anchoring plate 23. The rod further comprises an intermediate portion 87, connecting the end portion 85 to the head 81, engaged in the hole 41 of the end plate. The outer surface of the intermediate portion 87 is smooth, and therefore does not have external threads. The intermediate section 87 has an outer section complementary to the internal section of the orifice 41, considered perpendicular to the vertical direction. In other words, the outer surface of the intermediate portion 87 is pressed against the inner surface of the orifice 41.

The member 79 has a zone of weakness 89, at the junction between the rod 83 and the head 81.

Moreover, the upper anchoring plate 23 does not have the concave zone 71. The end plate 35 thus rests against a flat area of the large lower face of the upper anchor plate. Thus, the lateral surface 67 in the example of FIG. 8 corresponds to all the internal surfaces of the orifices 41, and the surface complementary 69 corresponds to all the external surfaces of the intermediate sections 87.

When the fuse link 37 is intact, the shear force is transmitted between the upper anchor plate 23 and the end plate 35 through the fusible members 79, and more specifically by the internal surfaces of the orifices 41 which are contact with external surfaces of intermediate sections 87.

The rupture or the plasticization of the fusible link 37 is caused by the deformation or rupture of the zone of weakness 89, for the members 79. Typically, the head 81 is detached from the rod 83. The rod 83 remains attached to the plate upper anchor 23, and remains engaged by its intermediate portion 87 in the orifice 41. The end plate 35 can slide along the rod 83, in a vertical direction, because the head is separated from the rod, or because the weak zone 89 has been deformed. On the other hand, because the rods 83 are not disengaged from the orifices 41, the shear forces continue to be transmitted between the end plate 35 and the upper anchor plate 23. The height of the end plate 35 is chosen important enough that the rods 83 are never disengaged in case of extreme earthquake.

In the description which has been given of the invention, it has been mentioned that the end plate 35 is rigidly fixed to the upper end of the insulator 25, and that the fusible link 37 links the end plate 35. to the upper anchor plate 23 of the device. According to an alternative not shown, the end plate 35 is fixed to a lower end of the insulator 25, and the fuse link 37 links the end plate 35 to the lower anchor plate 21. Similarly, the additional link 65 links the end plate 35 to the lower anchor plate 21, and is adapted to transmit the shear force between the end plate 35 and the lower anchor plate 21.

On the other hand, the fuse link and the additional link are of the same type as described above, including all the variants envisaged.

Claims

1. - Seismic isolation device (1) intended to be interposed between foundations (3) and a structure (5), the device (1) comprising:

- a lower anchor plate (21), intended to be rigidly fixed to the foundations (3);

an upper anchoring plate (23) intended to be fixed to the structure (5);

an isolator (25) interposed vertically between the lower and upper anchoring plates (21, 23), the lower and upper anchor plates (21, 23) being respectively connected to the lower and upper ends of the insulator (25), the insulator (25) being sized to support a first predetermined voltage in the vertical direction;

characterized in that the seismic isolation device (1) comprises an end plate (35) rigidly attached to one of the lower or upper ends of the insulator (25), and a fusible link (37) connecting the end plate (35) to the lower anchor plate (21) or to the upper anchor plate (23), the fusible link (37) being selected to break or laminate under the effect of a second voltage predetermined in the vertical direction, the second voltage being greater than the first voltage but lower than the voltage which can lead to a failure of the insulator (25).

2. - Device according to claim 1, characterized in that the fuse link (37) comprises at least one fuse member (39) selected from the following group: a screw, a rod, a plate, a cylinder, a toad.

3. - Device according to claim 2, characterized in that the fuse member (39) is made of metal or other material having the required breaking characteristics or plasticization.

4. - Device according to any one of the preceding claims, characterized in that the seismic isolation device (1) comprises an additional connection (65) of the end plate (35) to the lower anchor plate or upper (21, 23) adapted to transmit a horizontal shear force between the end plate (35) and the lower or upper anchor plate (21, 23) when the fusible link (37) is intact and when the fusible link (37) is broken or plasticized.

5. - Device according to claim 4, characterized in that the additional connection (65) comprises a lateral surface (67) secured to or formed on the lower or upper anchoring plate (21, 23) and a complementary surface (69). ) secured to or formed on the end plate (35), the lateral surface (67) and the complementary surface (69) being in contact with each other and extending parallel to the vertical direction.

6. - Device according to claim 5, characterized in that the lateral surface (67) and the complementary surface (69) extend in a substantially closed contour around the insulator (25).

7. - Device according to claim 5 or 6, characterized in that the lower or upper anchoring plate (21, 23) comprises a concave zone (71) delimited by a bottom (73) and a peripheral edge (75), the end plate (35) being engaged in the concave region (71), the peripheral edge (75) defining the lateral surface (67).

8.- Device according to claim 7, characterized in that the end plate

(35) bears against the bottom (73) and is connected to the bottom (73) by the fuse link (37) when the fuse link (37) is intact.

9. - Device according to any one of claims 7 or 8, characterized in that the height of the lateral surface (67) in the vertical direction is chosen so that the end plate (35) does not disengage the concave zone (71) when there is separation between the end plate (35) and the lower anchor plate (21) or the upper anchor plate (23) during the occurrence of a level earthquake extreme.

10. - Device according to any one of claims 7 to 9, characterized in that the peripheral edge (75) is attached against the bottom (73).

1 1 .- Device according to any one of claims 5 to 10, characterized in that at least one of the lateral surface (67) and the complementary surface (69) is coated with an anti-seizing coating.

12. - Set comprising:

foundations (3) anchored in the ground (9);

- a nuclear reactor (5) provided with a slab (17);

- At least one seismic isolation device (1) according to any one of the preceding claims, the lower anchoring plate (21) being rigidly fixed to the foundations (3), the upper anchoring plate (23) being rigidly attached to the raft (17).

13. - assembly according to claim 12, characterized in that the assembly comprises at least one stop (19) limiting the horizontal clearance of the nuclear reactor (5).