Buried nuclear facility with improved architecture

Abstract

The invention relates to a buried nuclear facility (10) comprising: - a vertical well (12) comprising, at a lower end, a bottom (12a) and, at an upper end, an opening (12b); - at least one reactor building (26) accommodated in the well; - at least one protective slab (20) for protection against external threats that completely seals the opening (12b) of the well, extending, in particular, above the at least one reactor building; - at least one nuclear reactor containment building (30) enclosed inside the at least one reactor building (26) and supported by at least one support slab (32) resting on the bottom of the well via a plurality of seismic isolation devices (DIS).

Description

Description Title of the invention: BURIED NUCLEAR INSTALLATION WITH IMPROVED ARCHITECTURE Technical Field

[0001] The present invention relates to the field of buried nuclear installations. Prior art

[0002] In particular, document WO 2018 / 204081 discloses a nuclear installation that can be buried in which a boiling water nuclear reactor containment vessel is housed in a silo built into the ground and rests on the bottom of the silo. The silo is closed at its top by a concrete cover to protect the nuclear reactor against external impacts and explosions.

[0003] In such an installation, vibrations generated at the level of the concrete cover by external aggressions (e.g. aircraft impacts, explosions, etc.) risk being transmitted to the silo and therefore to the containment vessel of the nuclear reactor which rests at the bottom of it.

[0004] To take this risk into account, the enclosure and its internal components (reactor core, etc.) must be sized accordingly, which increases the complexity and costs of designing and industrializing such an installation.

[0005] There is therefore a need to simplify the design of such a buried nuclear installation. Statement of the invention

[0006] The invention thus relates to a buried nuclear installation, comprising: - a vertical well comprising, at a lower end, a bottom and, at an upper end, an opening, -at least one reactor building housed in the shaft, - at least one slab providing protection against external attacks which completely closes the opening of the shaft, extending in particular above said at least one reactor building, -at least one nuclear reactor enclosure enclosed inside said at least one reactor building and supported by at least one support slab resting on the bottom of the well by means of a plurality of seismic isolation devices.

[0007] The reactor containment is decoupled, in terms of vibrations, from the bottom of the shaft thanks to the presence of the plurality of seismic isolation devices which isolate, from the bottom of the shaft, the support slab supporting the reactor containment and, therefore, which isolate the latter from the bottom of the shaft. Thus, thanks to this arrangement (architecture), vibrations in the protection slab will be transmitted in a highly attenuated manner to the reactor containment. The attenuated residual vibrations transmitted are taken into account in the dimensioning of the components internal to the containment (reactor core, etc.), thus significantly reducing the complexity and costs of designing and implementing such an installation.Thus, thanks to the seismic isolation devices which are designed to suit the seismic conditions, the vibrations at the slab level are filtered as much as possible and the attenuated residual vibrations transmitted therefore do not damage the reactor containment. It should be noted that the seismic isolation devices respond, by their dimensioning, to the loads they support. Said at least one reactor building is also housed entirely in the shaft without extending above the opening in order to be arranged under the protective slab and so that the entire installation is thus buried.

[0008] According to other possible characteristics: - the buried nuclear installation comprises at least one nuclear fuel storage pool housed in the well and supported by at least one support slab resting on the bottom of the well by means of a plurality of seismic isolation devices; the aspects and advantages set out above in relation to the reactor enclosure also apply to the nuclear fuel storage pool; -said at least one reactor building comprises a roof which covers said at least one nuclear reactor enclosure and, optionally, said at least one nuclear fuel storage pool, said at least one protective slab extending in particular above the roof and at a distance from it so as to provide a technical gallery between them; the technical gallery is inscribed in the diameter of the shaft; the technical gallery can be used in particular to connect together a lower part of the installation housed in the shaft (reactor building) and an upper part located on said at least one protective slab and serves in particular to connect together the prefabricated networks of these two parts by allowing the passage of different connections (cables, pipes, etc.) between these parts; -the installation comprises one or more vertical walls which border the interior of the shaft and said at least one protective slab is supported vertically: either directly on an embankment arranged outside the shaft, at the outer periphery of said shaft, a bellows device being arranged vertically between said at least one protective slab and the vertical wall(s) bordering the shaft (in this configuration said at least one reactor building of the buried nuclear installation is not mechanically linked to the protective slab located above (mechanical independence), which totally prevents direct transmission of vibrations from the protective slab to the reactor building by a mechanical connection, as is the case in the prior art discussed above), or directly on the vertical wall(s) bordering the interior of the shaft,either indirectly on the vertical wall(s) bordering the interior of the well by means of a damping joint device or directly on one or more supports arranged externally relative to the vertical wall(s) bordering the interior of the well; -said at least one reactor building comprises one or more vertical walls which are spaced horizontally from the vertical wall(s) (for example cast) bordering the interior of the well or which are attached to the vertical wall(s) (for example cast) bordering the interior of the well but not mechanically connected to them by one or more connecting devices;, - said at least one reactor building comprises at least one slab horizontal intermediate which is integral with the vertical wall(s) of said at least one reactor building and radially surrounds said at least one nuclear reactor enclosure, said at least one intermediate slab being arranged at an intermediate level of said at least one reactor building, above and at a distance from said at least one support slab supporting said at least one nuclear reactor enclosure; - said at least one support slab supporting said at least one nuclear reactor enclosure is separated from the wall(s) of the reactor building by one or more peripheral isolation joints or by a space between said at least one support slab and the wall(s) of the reactor building; - the installation comprises a vertical handling shaft which provides access to said at least one shaft support slab, next to said at least one reactor building and separately from the latter; - said at least one protective slab comprises a hopper which is located in an area of ​​the slab located above the vertical handling shaft; - said at least one nuclear fuel storage pool is arranged adjacent to said at least one reactor building, and is, for example, arranged in the vertical handling shaft or in another space adjacent to said at least one reactor building; - the protective slab is formed of one slab or two half-slabs which are fixed to each other; the use of two or more half-slabs makes it possible to reduce the weight of the load to be shifted from a half-slab construction area located near the shaft to the shaft and therefore to size the slab movement system accordingly, which simplifies the construction of the installation and the shifting operations, as well as the energy consumption of the shifting operations; this is particularly advantageous when one or more equipment or buildings are built on the half-slabs and therefore increase the weight of the load to be shifted; - the protective slab is configured so that it can be removed later in the event of modification or dismantling of the installation; - the seismic isolation devices each comprise one or more spring boxes; - the seismic isolation devices are distributed as uniformly as possible between the said at least one support slab and the bottom of the well; - seismic isolation devices are mounted on reinforced concrete blocks or pads which rest on the bottom of the well; - seismic isolation devices with a minimum nominal load of 1.6 MN are configured to dampen vertical and / or horizontal vibration waves; - the seismic isolation devices of the plurality of seismic isolation devices arranged under said at least one support slab supporting said at least one nuclear reactor enclosure are configured according to the loads imposed on them and therefore to dampen the vertical and / or horizontal vibration waves in a manner adapted to the loads they support; -the vertical well has a general rectangular or circular shape according to a view taken in a horizontal plane; -the installation includes one or more pieces of equipment or buildings placed on said at least one protective slab (these pieces of equipment or buildings do not directly provide nuclear safety functions, unlike those placed inside the shaft or, if they do, it is through redundancy with the equipment placed inside the shaft); - the equipment or buildings placed on said at least one protective slab are configured to provide support functions for the operation of the nuclear reactor and the entire nuclear installation; - the equipment or buildings arranged on said at least one protective slab comprise at least one of the following elements: a nuclear installation control room, a building providing ventilation functions, a building providing cooling functions, a room containing control and command cabinets for operating support and electricity production functions, an instrumentation room, a high-current electrical distribution room, a low-current electrical distribution room and batteries / inverters, a valve and exchanger room, a first aid diesel engine room. Brief description of the drawings

[0009] Other characteristics and advantages will appear during the description which follows, given solely as a non-limiting example and made with reference to the appended drawings, in which:

[0010] [Fig. 1] Figure 1 is a schematic view of a possible example of the installation of a buried nuclear installation according to a possible embodiment of the invention;

[0011] [Fig. 2A] Figure 2A is an enlarged partial schematic view of an area of ​​the buried nuclear installation of Figure 1 located between the protective slab and the walls bordering the shaft, showing a flexible joint provided between these two elements, according to a possible embodiment of the invention;

[0012] [Fig. 2B] Figure 2B is a partial schematic view illustrating the support of the protective slab according to an alternative embodiment;

[0013] [Fig. 2C] Figure 2C is a partial schematic view illustrating the support of the protective slab according to another variant embodiment;

[0014] [Fig. 2D] Figure 2D is a partial schematic view illustrating the support of the protective slab according to another variant embodiment;

[0015] [Fig. 2E] Figure 2E is a partial schematic view illustrating the support of the protective slab according to another variant embodiment;

[0016] [Fig. 3] Figure 3 is an enlarged schematic view, along a vertical section, of a buried nuclear installation according to a possible embodiment of the invention;

[0017] [Fig. 3A] Figure 3A is an enlarged schematic view of an exemplary seismic isolation device that may be used in the installation of Figure 3;

[0018] [Fig. 4] Figure 4 is a view of the buried nuclear facility of Figure 3 in a vertical section plane parallel to that of Figure 3;

[0019] [Fig. 5] Figure 5 illustrates, in a horizontal sectional view, another possible embodiment of a buried nuclear installation;

[0020] [Fig. 6] Figure 6 illustrates, in a vertical sectional view, the buried nuclear installation of Figure 5;

[0021] [Fig. 6A] Figure 6A is a partial schematic perspective view from above of two half-slabs for protection against external attacks spaced longitudinally from each other;

[0022] [Fig. 6B] Figure 6B is an enlarged partial schematic view of a connection zone between two half-slabs according to a possible embodiment;

[0023] [Fig. 6C] Figure 6C is a schematic perspective view from above of two half-slabs joined together;

[0024] [Fig. 7] Figure 7 illustrates, in a vertical sectional view, another possible embodiment of a buried nuclear installation;

[0025] [Fig. 8] Figure 8 illustrates, in a horizontal sectional view, another possible embodiment of a buried nuclear installation;

[0026] [Fig. 9] Figure 9 illustrates, in a horizontal sectional view, another possible embodiment of a circular buried nuclear installation;

[0027] [Fig. 10] Figure 10 illustrates the buried nuclear installation of Figure 9, in a vertical section view AA;

[0028] [Fig. 1 1 ] Figure 1 1 illustrates, in a horizontal sectional view, the protective slab of the buried nuclear installation of Figure 10;

[0029] [Fig. 12] Figure 12 illustrates, in plan view, the circular underground nuclear installation of Figures 8 and 10 under construction;

[0030] [Fig. 13] Figure 13 illustrates, in a vertical section view BB, the sliding of the slab of the installation of figure 12. Description of the embodiments

[0031] The invention which is described below with reference to the attached drawings concerns different possible embodiments of a new buried nuclear installation architecture.

[0032] As shown schematically in Figure 1, a buried nuclear installation 10 comprises a vertical shaft 12 dug into a ground 14 to a predetermined depth, for example of the order of 30-35 m using conventional excavation techniques and equipment.

[0033] This well 12 comprises, at a lower end, a bottom 12a, and, at an upper end, an opening 12b of dimensions substantially equal to those of the bottom. In this embodiment, the earth which is removed to form the well is, for example, used to form one or more embankments 16 arranged around the opening 12b of the well, thus forming an elevation relative to the surface of the ground 14. This arrangement can serve as a barrier against flooding. However, the presence of embankment is not obligatory.

[0034] The height or depth of the shaft 12 is defined between the opening 12b and the bottom 12a of the shaft and is chosen in order to be able to house entirely inside the shaft all of the elements making up the buried part of the nuclear installation 10 and which will be described later (reactor building, technical gallery, possible nuclear fuel storage pool, etc.), taking into account the height of the base that will be formed at the bottom of the shaft. The shaft 12 may have any general shape following a horizontal section (perpendicular to the plane of Figure 1) and, for example, may adopt a generally rectangular, square, circular section, etc. Generally speaking, the components of the buried part of the nuclear installation are located at a height that is lower than that of the ground surface and / or that of the lower surface of the embankment.

[0035] In the present embodiment, the well has for example a rectangular section and several vertical walls, of which only two walls 18a, 18b are shown in Figure 1 against the inner earth walls 19a, 19b of the well. These vertical walls 18a, 18b which border the space useful interior of the well are for example cast walls well known to those skilled in the art (reinforced concrete wall cast in the ground). These walls are generally anchored in the ground by prestressed anchor rods.

[0036] These walls serve to absorb the pressure of the earth surrounding the well and to ensure a seal (barrier) of the interior of the well, in particular against water likely to infiltrate into the surrounding earth. This sealing barrier can be supplemented by another barrier comprising a waterproofing membrane. Depending on the geometry of the well, a single wall (well with a circular section) or several vertical walls (well with a square, rectangular section, etc.), for example molded, can be considered. In a well with a rectangular section, for example, four walls are provided to delimit the useful interior space of the well.

[0037] As shown in Figure 1, the buried nuclear installation 10 comprises at least one protective slab 20 against external attacks on the well, such as falling objects (e.g., airplanes) or external explosions. For the simplification of the following description, said at least one protective slab 20 is considered here as being a single protective slab 20. However, everything relating to the buried nuclear installation that is the subject of the invention also applies to a protective slab that is formed of several slabs, and for example of two half-slabs as will be seen later in another embodiment. This protective slab 20 is arranged above the well 12 and extends horizontally so as to completely close the opening 12b of the well in which all the components of the buried part of the nuclear installation are housed.The general shape of the slab 20 is adapted to the shape of the section of the opening 12b of the well and, in the present embodiment, the general shape of the slab 20 is rectangular (however, the general shape is likely to adopt other shapes depending on the shape of the opening of the well and, for example, a circular shape). The protective slab 20 is generally made of reinforced concrete. Alternatively, the slab can be constructed of prestressed concrete or made according to a mixed construction with a lower facing consisting of a stiffened steel sheet on which flexible connectors are welded.

[0038] In the embodiment illustrated in Figure 1, the protective slab 20 is arranged in vertical support directly on the embankment 16 located at the outer periphery of the well, so that the weight of the slab does not rest directly on the upper edges, also called heads, of the walls 18a, 18b (the protective slab is a separate element from the embankment(s) 16 on which the slab rests, in particular by its peripheral edges). Thus, the protective slab 20 is mechanically independent of the buried structure and in particular of the walls 18a, 18b, which means that in the event of vibration of the slab (for example under the impact of an object external to the installation), the vibrations generated at the level of the slab will be transmitted to the embankment and damped by the earth and will therefore not be transmitted to the buried structure via the walls 18a, 18b.The protective slab 20 is preferably configured to be able to be removed later in the event of a major modification or dismantling of the installation 10. The configuration of the slab which allows it to be removed later (i.e. after installation to seal the well) is linked to the fact that it is either a single homogeneous slab which can therefore be shifted outside the area occupied by the well to clear the opening of the well (the shifting takes place in an axial direction which is parallel to the large dimension of the rectangular slab), or a slab resulting from the assembly of two half-slabs or more than two half-slabs and which thus becomes a single slab formed from a single piece which can also be shifted outside the well in the aforementioned axial direction in order to clear the opening of the well.It should be noted that this movement / sliding of the slab follows the opposite path to that linked to the installation of the slab during the construction of the installation.

[0039] It should be noted, however, that the mechanical independence mentioned above does not mean that the slab 20 and the walls 18a, 18b cannot be in indirect mechanical contact with each other, as described below with reference to FIG. 2A, or in direct mechanical contact with each other as is the case in FIGS. 2C and 2E described below. In the configurations of FIGS. 2A-2E, an embankment 16 is present. However, the protective slab does not rest on it but is arranged in such a way that adjacent to the embankment, against it, while being distinct from it. In the figures, the slab extends in height substantially at the same height as the embankment so as to form an upper surface flush with that of the embankment. However, the slab may be higher or lower than the embankment depending on the configurations envisaged.

[0040] Figure 2A is a partial enlarged view of the area between the slab 20 and the head 18a1 of the wall 18a of Figure 1 and shows the presence, between these two elements, of a bellows device 22 with a thick rubber wave of known type, arranged substantially vertically. This device 22 rests on the entire perimeter of the wall heads 18a, 18b. This perimeter here takes a rectangular shape but it can take a square, circular shape, etc., depending on the geometry of the (horizontal) cross-section of the well. The device 22 is for example connected to the wall heads, as well as to the lower surface 20a of the slab 20 (on an area which is in geometric correspondence with the wall heads 18a, 18b, directly above them) by respective fixing members 24a, 24b.In this embodiment, the edges of the bellows device 22 are, all around, fixed, for example, by stainless steel slats which compress them, these stainless steel slats themselves being fixed in the concrete by spaced anchor studs. The bellows device 22 makes it possible to ensure sealing between the two spaces E1 and E2 which it separates: space E1 corresponds to the useful space inside the well and in which the various elements / components of the buried installation are arranged and space E2 corresponds to the space adjacent to the backfill 16 (not visible in FIG. 2A).

[0041] It will be noted that with such an arrangement the intermediate space formed by the technical gallery G described below with reference to figures 3 and 4 can be isolated in terms of ventilation thanks to this rubber wall 22. It is thus possible to create a slight depression (-5 or -10mm of CE) thanks to this specific ventilation function.

[0042] According to an alternative embodiment shown in Figure 2B (view taken in a vertical plane perpendicular to the views of Figures 1 and 2A), the protective slab 20' is connected to the vertical walls 18c, 18d bordering the well by means of a flexible joint device 22'. In this alternative, the slab protection 20' rests vertically directly on one or more supports 23 arranged externally relative to the vertical walls 18c, 18d bordering the interior of the well. More particularly, the slab 20' comprises one or more peripheral edges 20b' jointly forming a skirt which extends vertically from the external periphery of the lower surface 20a' away from the latter. As shown in Figure 2B, the skirt 20b' rests on one or more supports 23 such as stringers which are supported by piles or sole plates 25 anchored vertically in the ground at a distance from the vertical walls 18c, 18d bordering the interior of the well.

[0043] According to another variant embodiment shown in Figure 2C, the protective slab 20 rests vertically directly on the vertical wall(s) 18c, 18d bordering the well, by means of a skirt 20b” similar to the skirt in Figure 2B.

[0044] Figures 3 and 4 are enlarged views of a buried nuclear installation 10' similar to that of Figure 1 but remain schematic for the purposes of the presentation. However, the support of the protective slab 20 differs from that of Figure 1 since the slab 20 is here in vertical support directly on the vertical wall(s) 18a, 18b (and also on the adjacent walls 8c and 18d which are not visible) bordering the shaft, by means of the skirt or peripheral edge 20b which extends downwards from the lower face 20a of the slab. The skirt 20b rests directly on the heads of the walls (only the walls 18a, 18b are shown in this section) which each have a peripheral rim forming an external shoulder, such as that 18a2 of the wall 18a.It will be noted that the following description applies to all embodiments and variants and, in general, is not limited to the method of supporting the protective slab or to the presence of backfill 16.

[0045] As shown in Figure 3, the well 12 comprises, at its lower end, a raft 12c constituting the bottom of the well on which the various elements / components of the buried installation will be installed. This raft was put in place in a known manner after the excavation of the well. An injected bottom may prove necessary to limit water inflows from the bottom if the ground is permeable.

[0046] The buried nuclear installation 10' here comprises a reactor building 26 housed entirely in the shaft 12 (under the protective slab 20 which completely closes the opening 12b of the shaft) and resting on the foundation 12c. It will be noted that several reactor buildings can be installed in the shaft 12, as will be seen later during the description of other embodiments.

[0047] In the present embodiment, the buried reactor building 26 comprises one or more vertical walls (depending on the geometry of the building). If the building has a rectangular or square horizontal section, it will necessarily have several walls (which is the case here with the rectangular shape), whereas it may have only one wall if it has a circular horizontal section (cylindrical shaft). The reactor building 26 also comprises a roof 28 which rests on the top of the wall(s) of the building (depending on the configuration) to cover the building, in order to define a closed space internal to the latter. In the example described, the reactor building 26 has a rectangular horizontal section and comprises four vertical walls, of which only two 26a, 26b facing each other are shown in FIG. 3, the other two adjacent vertical walls being perpendicular and not visible here.The walls of reactor building 26 rest on raft 12c. Roof 28 here is a reinforced concrete slab of simple structure, which means that it has a sufficient thickness of reinforced concrete to ensure its resistance under all the stresses to which it may be subjected. This slab can alternatively be a composite steel-concrete slab.

[0048] The walls of the reactor building 26 (wall 26a and the two other adjacent perpendicular walls not visible in Figure 3) are arranged opposite the vertical walls bordering the shaft (wall 18a and the two other adjacent perpendicular walls 18c and 18d, not visible in Figure 3 but visible in Figures 2B-2E), close to each other, leaving as little space as possible between them (this space is however not visible in Figures 3 and 4), without however being mechanically linked together, so as not to create a mechanical connection through which mechanical forces / vibrations would be likely to pass.

[0049] The respective walls facing the reactor building and the shaft may in particular be joined or joined in a variant as illustrated for example in Figures 2B and 2C.

[0050] According to an alternative embodiment of the installations of figures 2B and 2C, the walls of the reactor building 26 are spaced horizontally from the vertical walls bordering the shaft so as to provide a space between the respective facing walls. These facing walls spaced from one another are not mechanically connected to each other so as not to create a mechanical connection through which mechanical forces / vibrations would be likely to pass. The space thus provided between these facing walls can be a useful technical space to allow inspection by maintenance personnel, or even by cameras. In practice, this space can have a width of approximately 1.5 to 2 m.

[0051] Figures 2D and 2E illustrate such arrangements in which respectively the respective walls of the reactor building 26' (the wall 26a' and the two other adjacent walls perpendicular and not visible in Figures 2D and 2E) and the walls opposite the well (the wall 18d and the two other adjacent perpendicular walls 18a and 18b, not visible in Figures 2D and 2E) are spaced horizontally from each other as explained above. The vertical supports of the protective slab in Figures 2D and 2E correspond respectively to the supports in Figures 2B and 2C.

[0052] It will be noted that the arrangements described above between the respective walls facing the reactor building 26 and the shaft also apply to the method described above concerning the vertical support of the protective slab 20 on the embankment 16 (fig. 1).

[0053] As shown in Figures 3 and 4, the protective slab 20 is arranged above the roof 28 of the reactor building 26 which it covers entirely, at a distance (vertically) from the latter so as to provide between them a vertical space which has a function of technical gallery G (intermediate space between slab 20 and roof 28) of which the roof 28 forms the floor. This roof allows in particular, depending on the length of the gallery, the circulation of people and the routing of cables, conduits and other equipment or any other component serving as a connection between, on the one hand, the buildings which are external to the buried part of the installation, in particular those mounted on the protective slab 20 (e.g.: auxiliary equipment or buildings) and, on the other hand, the interior of the reactor building and, in fact, up to the reactor enclosure 30 contained in the building. To do this, through openings (not shown in the figures) can be arranged at separate locations in the slab, in its thickness, at the right of which the equipment or auxiliary buildings mentioned above are built. Each of these openings is used for the passage of cables, pipes, etc.(various connections) between the auxiliary building located above the slab and the reactor building located below the slab via the technical gallery located between the slab and the reactor building and through openings (not shown in the figures) provided in the roof of the reactor building for the passage of these various connections. Access to technical gallery G can be gained via the stairs (visible in Figure 3) which are provided in the shaft area which is adjacent to the area housing the reactor building.

[0054] The horizontal dimensions of the slab (in the length which appears in figures 3 and 4 but also in a horizontal direction perpendicular to the plane of these figures) are greater than those of the roof 28 which stops at the level of the upper edges or heads of the walls 26a, 26b of the reactor building 26.

[0055] The reactor building 26 contains, in the closed space which is delimited by its vertical walls 26a, 26b (and the two adjacent perpendicular vertical walls not visible in FIG. 3) and its horizontal roof 28, at least one nuclear reactor enclosure. In the present embodiment, a single nuclear reactor enclosure 30 is housed in the reactor building 26. The enclosure here has a rounded shape at its upper part in order to withstand internal pressure.

[0056] In the present embodiment, the nuclear reactor is of the PWR type, that is to say that it uses pressurized water technology. Such a reactor may mainly comprise inside the enclosure 30 sealed, in a known manner, a primary circuit which comprises: - a reactor vessel containing in particular the fuel elements and the control rods, -one or more steam generators, -primary pumps ensuring a loop circulation of the primary fluid which travels through the fuel elements of the reactor vessel by recovering the thermal energy released by the nuclear reaction and circulates in the primary part of the steam generators, where a heat exchange takes place between the primary fluid and the secondary part of the steam generators in order to produce steam at the top of said steam generators. The steam thus produced is evacuated from the steam generators through the steam pipes of a secondary circuit which passes through the walls of the enclosure 30 and carries it to one or more turbines outside the well to turn it or them and thus produce, at the alternator output, electric current distributed on a high voltage electrical network. The primary circuit also includes a pressurizer which has a primary circuit regulation function.

[0057] It will be noted that the walls bordering the well, the walls of the building and the roof 28 have much lighter structures than that of the wall of the enclosure 30, which makes it possible not to affect the integrity of the enclosure in the event that one of the preceding elements is projected against the enclosure 30.

[0058] Furthermore, independently of the previous preferred embodiment, the buried nuclear installation according to the invention can be applied to any other nuclear technology such as one of the following technologies: BWR, HTR, with powers adapted to the SMR model ("Small Modular Reactor" in English terminology). For example, the powers can range from 50MWe to N x50MWe, with N greater than 1 and, for example, N can take values ​​between 1 and 8, or even greater than 8. According to another example, the powers can range from 100MWe to N x100MWe, with N greater than 1 and, for example, N can take values ​​between 1 and 8, or even greater than 8.

[0059] To isolate the installation from external vibrations, the nuclear reactor enclosure 30 is here supported by a support slab 32 which rests on the raft 12c of the well by means of a plurality of seismic or vibration isolation devices DIS ensuring effective damping or attenuation of vibrations likely to propagate in the walls bordering the well (e.g.: 18a, 18b) and in the raft 12c and to reach the enclosure 30. In the present configuration, the enclosure 30 is not linked to the other vertical walls bordering the well and those of the reactor building. In this configuration, the reactor building 26 rests on the bottom of the well and the same is true for the support slab 32 which supports the enclosure 30. The reactor building is however not supported on the support slab 32. The support slab 32 forms a solid structure, made for example from a material such as concrete, so that the DIS devices can support it at any point of its continuous lower surface. A honeycomb structure or a lattice structure would not be suitable to play the role of the support slab 32.It will also be noted that the enclosure 30 is supported only by the support slab 32 but is not suspended from an upper part of the reactor building 26 such as the roof 28. The reactor building itself is also not suspended from an area located at the top of the shaft. The above applies to all the modes and variants described in this description.

[0060] Figure 3A is an enlarged view showing the possible structure of a DIS seismic isolation device.

[0061] The seismic isolation devices DIS distributed under the support slab 32, in the most uniform manner possible and depending on the load to be supported, each comprise a spring box BAR. More particularly, each spring box is a box or casing comprising flexible springs in the horizontal direction and in the vertical direction to dampen / filter both vertical and horizontal vibration waves.

[0062] As shown in Figures 3, 3A and 4, the seismic isolation devices DIS are mounted on supports P which rest on the raft 12c of the well.

[0063] These P supports are, for example, reinforced concrete blocks or pads.

[0064] For example, each BAR spring box has a minimum nominal load of 1.6 MN at the service limit state, i.e. it has a capacity of approximately 1.6 MN under permanent load.

[0065] If necessary, several BAR spring boxes can be arranged side by side on the same block or P post.

[0066] A possible example of a BAR spring box is, for example, provided by the company GERB and should be chosen according to the load to be supported. Each BAR spring box has, for example, a vertical stiffness of 56 MN / m and a horizontal stiffness of 31 MN / m.

[0067] Furthermore, spring boxes may also include dampers (e.g. viscous) incorporated into the body of the spring box or outside of it and separate from it and which complete the seismic isolation device.

[0068] The vertical and horizontal movements likely to be transmitted by the side walls and the bottom of the well are transmitted in a filtered manner to the support slab 32, which may possibly cause a swing effect of the enclosure 30 which, however, does not affect its integrity due to the effectiveness of the vibration filtering described above.

[0069] This pendulum effect is calculated based on the local seismic constraints filtered by the BAR spring boxes and thus makes it possible to best adjust the distances between the support slab 32 and the walls of the reactor building 26 (e.g.: 26a, 26b) and to optimize their respective thicknesses.

[0070] Indeed, in this example, the support slab 32 is separated from the walls of the reactor building, in particular 26a, 26b, simply by a horizontal space. However, one or more peripheral isolation joints may also be arranged between the support slab and the walls of the reactor building although this is not shown in Figures 3 and 4.

[0071] The support slab 32 on which the nuclear reactor enclosure 30 rests may have, in its central part (figure 3) located under the reactor vessel, a recess or cutout 32a (footprint of a volume) in direction of the base 12c which can be excavated to possibly install a device to deal with any accident occurring around, on or in the tank. As can be seen more precisely in Figures 3 and 4, the support slab 32 is separated from the walls of the reactor building by a space of relatively small width in which one or more peripheral isolation joints J, for example made of thick rubber, are arranged although they are not visible in the figures. These joints are designed to be inspected and replaced.

[0072] As shown in Figures 3 and 4, the reactor building 26” may also include a horizontal intermediate slab 34 which is integral with the vertical walls of the building (26a and 26b in Figures 3 and 4 and the two other adjacent vertical walls perpendicular). The intermediate slab 34 extends horizontally from these walls so as to radially surround the nuclear reactor enclosure 30, without however coming into contact with it, as shown in Figure 3. This slab is arranged at a level or a level along the vertical of the building which represents an intermediate position between the support slab 32 and the roof 28. This intermediate slab 34 is arranged parallel to the support slab 32, above and at a distance from it.In the case where it is necessary to reduce the swing effects of the nuclear reactor containment 30, and therefore the seismic accelerations experienced by the reactor, additional seismic isolation devices may be added. More particularly, these devices may be positioned horizontally in a radial arrangement around the containment 30, between this containment and the edge of the intermediate slab 34 which surrounds it (fig. 3).

[0073] Figure 3 also illustrates on the right part of the buried installation 10' a zone Z1 adjacent to the reactor building 26 which is housed inside the shaft but separately from this building. This zone Z1 is delimited between the wall 26b of the building and a facing wall P1 which is arranged opposite the wall 18b bordering the shaft. The zone Z1 forms a compartment internal to the shaft in which a staircase 36 can be arranged allowing personnel to circulate between the lower part of the shaft and its upper part (including access to the level of the protective slab).

[0074] In Figure 4 (section plane parallel to that of Figure 3), another zone Z2, adjacent to the zone containing the reactor building 26, is arranged between the wall 26b of the building and the opposite wall P1 which is arranged opposite the wall 18b bordering the shaft. The zone Z2 forms a vertical handling shaft which provides access in particular to the support slab 32 arranged in the lower part of the shaft. The protective slab 20 extends above the reactor building and the adjacent zones Z1 and Z2. As shown in this figure, an opening O (called a buffer) which is permanently closed during operation of the reactor (by means of a sliding or pivoting door not shown) and opened only to evacuate or bring in equipment, is arranged in the vertical wall 26b of the reactor building to connect the handling shaft Z2 and the interior of the reactor building.

[0075] A hopper 40 is for example arranged in the protective slab 20 directly above at least one of the zones Z1 and Z2. This hopper permanently occupies a closed position but can open when it is necessary to access the space located below and, in particular, to carry out maintenance operations via the handling shaft Z2, such as, for example, for maintenance operations, to evacuate, and re-enter by the same route, (components) or elements of the nuclear reactor enclosure. The reactor enclosure 30 has an opening Ot, called a buffer, which is placed (ideally) opposite the sliding door closing the opening O (of the reactor building). This opening Ot is arranged in the enclosure 30 and is permanently closed during operation of the reactor by means of a sliding or pivoting door (not shown).

[0076] Figure 5 is a horizontal sectional view of a buried nuclear installation 10” according to another embodiment in which two reactor buildings are housed in the shaft 12' adjacent to each other and separated from each other by an internal transverse wall 26.12. Thus, the installation 10” includes the reactor building of figures previous ones, referenced here 26.1 and another reactor building 26.2, for example identical and arranged next to the first building 26.1 in the shaft.

[0077] As shown in the figure, the walls 18a'-d' bordering the shaft surround the two buildings 26.1 and 26.2. The walls 18c' and 18d' are elongated relative to the walls 18c and 18d in order to be able to accommodate side by side two nuclear reactor enclosures 30.1 and 30.2 as well as the two reactor buildings 26.1 and 26.2 which contain them. As in the mode of the previous figures, each nuclear reactor enclosure rests on a support slab 32.1, 32.2 which is each mounted on seismic isolation devices DIS such as those described above. As shown in figure 5, these devices are distributed under each of the support slabs in the most uniform manner possible.It should be noted that the seismic isolation devices located directly above the nuclear reactor containment are, for example, arranged substantially along the circular perimeter of the containment, directly above it, insofar as it is around the perimeter of the containment that the largest masses are distributed, in particular, at the level of the heavily reinforced circular concrete wall. Each support slab. 32.1 . 32.2 thus presents in each part located under a reactor vessel 30.1 , 30.2, a recess or excavation 32a.1 , 32a.2 (footprint of a volume) which extends downwards, in an identical manner to the recess 32a of figures 3 and 4.

[0078] As in Figures 3 and 4, zones Z1 and Z2 are arranged adjacent to reactor building 26.1 and identical zones Z1' and Z2' are also arranged adjacent to building 26.2 with buffer openings O and O'.

[0079] Figure 6 shows a view along a vertical section of the buried nuclear installation 10” of Figure 5. This view shows the foundation 12c' on which the reactor buildings 26.1 and 26.2 and the protective slab 20.2 which is here formed of two protective half-slabs 20.2a and 20.2b which are fixed to each other at their junction 20.2c located substantially in line with the internal wall 26.12 separating the two reactor buildings. The fixing can be carried out by known techniques and, for example, keyed to each other or assembled to each other by reinforcements for reinforced concrete covering or by reinforcements for reinforced concrete connected by sleeves (couplers) in reserved areas which are concreted in the second phase, after completion of the junction of the reinforcements.

[0080] Furthermore, each reactor building is closed at its upper part by a roof 28.1, 28.2 (fig. 6) and the protective slab 20.2 defines with each of the facing roofs that it covers a technical gallery G' of larger dimensions than the technical gallery G of the previous figures. More particularly, each half-slab 20.2a, 20.2b located above the roof of the corresponding reactor building, provides with the latter a part of the technical gallery G', along its length.

[0081] Furthermore, as shown in the figures, each reactor building contains the corresponding nuclear reactor enclosure 30.1, 30.2 which is supported by the support slab 32.1, 32.2 each mounted on seismic isolation devices DIS and each reactor building may comprise an intermediate slab 34.1, 34.2 identical to what has been described above.

[0082] Figure 6A shows, in a perspective view from above, the two protective half-slabs 20.2a and 20.2b (without the other elements of Figure 6 for the sake of clarity) spaced apart from each other in a longitudinal direction X, for example in a position where each half-slab is on its construction area or zone near the well (not shown here). The half-slabs are thus constructed at a distance from each other and each have a free end face fa1, fa2 facing each other. These two faces fa1, fa2 are intended to be mechanically joined / assembled with each other to form a single slab as explained further on with reference to Figure 6B. As shown in Figure 6A, a peripheral edge R1, R2 is arranged respectively on the lower face of each half-slab 20.2a, 20.2b and extends vertically downwards in the manner of a skirt or a dropped edge.

[0083] Each half-slab 20.2a, 20.2b may have openings which are made through its thickness in order to allow the passage of cables, pipes, equipment and people depending on the opening(s) concerned. In Figure 6A there is an opening T1, T2 offset laterally from the longitudinal median axis (parallel to the X axis) of each half-slab. This opening is intended to form a hopper which will be used later for maintenance or handling and which will be placed above the well or handling area located along the reactor building. Other through openings (not shown here) can be arranged at separate locations on each half-slab on which auxiliary buildings can be built. Each of these openings is used for the passage of cables, pipes, etc. (various connections) between the equipment or building located above the half-slab and the reactor building located under the half-slab via the technical gallery located between the half-slab and the reactor building.It should be noted that after the passage of conduits, cables, pipes, etc., all openings crossing each half-slab for protection against external attacks are filled and made watertight and fireproof (the fireproof function must be effective for at least 2 hours).

[0084] Furthermore, each half-slab 20.2a, 20.2b may include imprints r1.1, r1.2, r2.1, r2.2 (figs. 6A and 6C) of the rails of an overhead crane which will be used subsequently to move various equipment on the slab and in particular for maintenance above the handling hoppers T1, T2.

[0085] In the position of Figure 6 (the half-slabs are positioned above the opening 12b' of the well), the half-slab 20.2a is arranged against the half-slab 20.2b and the two half-slabs are mechanically joined / assembled with each other, for example by keying, in order to mechanically form a single protective slab while ensuring continuity of the mechanical resistance of the slab at the junction or connection zone 20.2c between the half-slabs. To do this, the reinforcement or reinforcement must be continuous at this zone).

[0086] Figure 6B illustrates a possible example of mechanical connection between the half-slabs 20.2a and 20.2b. This figure is an enlarged partial view of a mechanical connection area between the two half-slabs. The connection between the two half-slabs 20.2a and 20.2b can be achieved by providing a keying zone Zcl between these half-slabs and which corresponds to zone 20.2c of Figure 6. The half-slabs are installed by providing a keying width greater than the overlap length of the longitudinal reinforcements which are located in the lower layer a1 i and a2i and in the upper layer a1 s and a2s of the half-slabs. The longitudinal reinforcements of each slab element (half-slab) overlap with the longitudinal reinforcements of the other slab element. Several layers of upper and lower reinforcements are necessary for each slab element but only one layer of upper reinforcement and one layer of lower reinforcement are shown for each slab element on the schematic diagram of Figure 6A to facilitate understanding.The longitudinal reinforcements in the other direction and the shear reinforcements are also installed (see schematically the perpendicular reinforcements a3i and a3s in the figure). In addition, temporary formwork Cfp can be fixed under the slab elements and the concreting of the keying zone is then carried out in order to mechanically connect the two slab elements together. The temporary formwork Cfp is removed and removed a few days after concreting the keying zone. It should be noted that other solutions can be considered to ensure the continuity of the longitudinal reinforcement: couplers, welding of the bars.

[0087] The 20.2 slab obtained after assembly of the two half-slabs 20.2a, 20.2b is a protective slab against external attacks on the well and thus protects the components of the installation housed in the 12' well.

[0088] Generally speaking, each half-slab is installed so that it can be removed later in the event of dismantling the installation (at the end of its life) or even in the event of modification to it, for example to carry out major maintenance work in terms of the safety and operation of the installation. For example, the replacement of one or more steam generators may justify such an operation. The configuration of the slab which allows it to be removed later (i.e. after installation to seal the shaft) is linked to the fact that this is a slab resulting from the assembly of two half-slabs (or even more than two half-slabs in a variant not shown) and which thus becomes a single slab formed from a single piece which can be shifted outside the shaft in an axial / longitudinal direction X in order to clear the shaft opening. It should be noted that this axial / longitudinal displacement / sliding of the slab follows the opposite shifting path to that linked to the installation of the slab during the construction of the installation. The same is true for a single slab which is homogeneous in its construction.

[0089] Everything described above also applies in this embodiment where two reactor buildings are housed in the shaft and will therefore not be repeated.

[0090] Figure 7 illustrates, in a vertical section, another embodiment of a buried nuclear installation 100 which differs mainly from the embodiment of Figures 3 and 4 by the presence of a nuclear fuel storage pool, identified in the figure by the acronym PECN, located in a zone Z2” of the shaft adjacent to that where the reactor building 126 is located. The elements corresponding to the embodiment of Figures 3 and 4 and which are repeated here are preceded by the number “1” and will not be described again. The PECN pool rests on a support slab DS which is mounted on seismic isolation devices DIS' similar to those described above.However, due to the weight of the nuclear reactor vessel 130, the DIS seismic isolation devices supporting the latter are configured / sized to dampen vertical and horizontal vibration waves with a damping coefficient higher than those of the DIS seismic isolation devices which must support less heavy loads. The very constitution of the devices may vary or their number may vary in order to achieve this objective).

[0091] A roof 128 extends here over reactor building 126 and the adjacent zone Z2”. It will be noted that the arrangement of the roof over zone Z2” may be only local, extending over the PECN pool, but without however extending over the entire zone Z2”.

[0092] As shown in Figure 7, an opening O' (called a buffer) which is permanently closed during operation of the reactor (by means of a sliding door not shown), is arranged in the vertical wall 126b of the reactor building. The opening O' is opened only to access the interior of the reactor building when the evacuation of material(s) and / or the introduction of new material(s) are necessary. The protective slab 120 extends above the reactor building 126 and the zone Z2" adjacent to the latter, and therefore the PECN pool.

[0093] As in the mode of figures 3 and 4, a similar technical gallery G” is provided between the roof 128 and the protective slab 120.

[0094] Everything described above also applies in this embodiment and will not be repeated.

[0095] Figure 8 illustrates, in a horizontal sectional view (top view), another embodiment of a buried nuclear installation 200 similar to the buried nuclear installation 10” of Figures 5 and 6. The elements corresponding to the mode of Figures 5 and 6 and which are repeated here are preceded by the number “2” and will not be described again. The difference between these two embodiments lies in the presence of a nuclear fuel storage pool PECN' in an area of ​​the shaft which is adjacent to the two reactor buildings 226.1 and 226.2. This pool is located in the extension of the wall 226.12 which separates the two reactor buildings and is adjacent to each of the two buildings, because it extends on either side of this wall. This intermediate position between the two buildings makes it possible to store, in this pool, fuel elements coming from one or other of the reactors of the enclosures 230.1 and 230.2.It will be noted that, as for the embodiment of figure 7, the swimming pool is supported by a concrete slab DS' mounted on seismic isolation devices DIS' which have, for example, the same characteristics as those of figure 7. Furthermore, in a variant not shown, two swimming pools can alternatively be provided, each in an area adjacent to a building and dedicated to the latter. Tl

[0096] Analogously to the arrangement of the zones in Figure 5, the facility 200 comprises zones Z1” and Z2” (vertical handling shafts) which are located adjacent to the shaft area containing the reactor building 226.1. Similarly, the facility 200 comprises further zones Z1'” and Z2'” (vertical handling shafts) which are located adjacent to the shaft area containing the reactor building 226.2. The zones Z1” and Z2” and the zones Z1'” and Z2'” are arranged symmetrically with respect to the intermediate position of the PECN' pool located between them. Each of the zones has, for example, the same functions as the corresponding zone in Figure 5.

[0097] As with the arrangement of Figure 5, the installation 200 comprises a slab (not shown) formed of two half-slabs.

[0098] Everything described above also applies in this embodiment and will not be repeated.

[0099] It will be noted that the protective slab of the various installations described above with one or more reactor buildings can be supported in different ways, as described above with reference to figures 2A to 2E, whether or not there is one or more embankments 16.

[0100] Generally, buried nuclear installations according to certain embodiments of the invention may comprise two or more reactor buildings, such as those of Figures 5, 6 and 8, thus making it possible to have smaller reactor cores providing less power (e.g.: 100 MWe) than that of a larger installation with greater power (e.g.: 800 MWe, or even higher powers). For example, to provide a power of 800 MWe, a buried nuclear installation according to the invention may be configured according to four shafts of 200 MWe each, each shaft being able to produce 2x100 MWe or 1x200 MWe.

[0101] The power modularity offered by these smaller installations also comes with a simplification of installations and a reduced implementation cost compared to a larger power installation.

[0102] Figures 9 to 11 illustrate a buried installation 300 according to another embodiment. Figure 9 is a plan view of the installation along a horizontal section of the shaft (under the protective slab) in which the shaft 312 (of generally cylindrical shape) has a circular section with a wall, for example a cast wall 318 of annular section which borders the interior of the shaft. The reactor building 326 also has a circular shape and contains a nuclear reactor enclosure 330 as described above. These circular and annular shapes have the advantage of better resisting thrusts coming from the outside (the earth in the case of the shaft) and overpressures (internally, coming from the enclosure or the reactor building). In particular, the annular-shaped cast wall 318 (in section) works like a ring compressed by the earth thrust which is directed radially relative to the cast wall.The diaphragm wall 318 is self-stable and the number of anchors of the wall in the ground is thus reduced, which in particular simplifies the design and construction. It will be noted that the wall 318 more generally has a cylindrical crown shape according to a three-dimensional view and the internal space of the well which is bordered by the wall 318 occupies a cylindrical shaped space.

[0103] In this embodiment, a PECN nuclear fuel storage pool can be arranged inside the reactor building 326 but off-center relative to the enclosure 330, as illustrated in FIG. 9. The installation 300 also comprises a zone Z3 forming a handling shaft and which is also off-center relative to the enclosure 330, as well as a zone Z4, off-center, in which a staircase 336 is arranged making it possible to connect the different levels of the shaft 312, from the base 312c to the protective slab 320 visible only in FIG. 10.

[0104] Figure 10 is a vertical sectional view along section plane AA of Figure 9 and shows an arrangement close to that of Figure 7 except that, in Figures 9 and 10, the entire reactor building 326 and enclosure 330 is supported by the same support slab 332 and the nuclear fuel storage pool PECN” is also supported by the same support slab 332. This support slab 332 itself rests on a plurality of seismic isolation devices DIS of the same configuration as those described above. It should be noted that in a circular configuration, it is simpler to produce only one circular support slab. Providing two separate (independent) support slabs, one to support the reactor building 326 and the other to support the PECN pool, as positioned in Figure 9, would lead to removing part of the circular slab to accommodate the slab supporting the pool, which would affect the integrity of the support slab of the reactor building 326 and risk weakening this support slab.

[0105] On the contrary, when the well has a generally rectangular shape (in section) or even square, and accommodates at least one reactor building and an adjacent pool, it is more suitable, and in particular more economical, to have two independent support slabs and therefore with vibration isolation devices DIS adapted to support different loads depending on the support slab. Figure 11 illustrates in top view (horizontal section) a possible general shape for the protective slab 320 which must close the upper opening 312b of the well 312 (figure 10). As shown in figure 11, the slab 320 has a generally essentially circular shape with dimensions corresponding to those of the opening 312b to be covered and completely closed.The slab 320 comprises, at two diametrically opposite zones of its circumference, two external radial extensions 320a and 320b, here symmetrical with respect to each other, which each start from the circular circumference of the slab to each end with a flat face (cut or beveled) 320a1 and 320b1. The two flat faces 320a1 and 320b1 are parallel to each other and are used to convey the protective slab to a position located above the opening 312b of the shaft by sliding, from an area located outside the shaft but close to it. This area is for example used to construct the protective slab while the reactor building is under construction.

[0106] Generally speaking, Figures 9 and 10 include most of the common elements described with reference to the previous figures and which do not will not be described again here, namely in particular the raft 312c, the recess 312c1 (optional), the support slab 332, the intermediate slab 334 (optional), the roof 328, the technical gallery G'” between the roof 328 and the slab 320. In the present mode, the gallery G'” (fig. 10) occupies a circular space in top view and not a rectangular one as in the previous modes.

[0107] A handling hopper (not shown) is also arranged in the protective slab 320 of figure 11 in an off-center manner, relative to the enclosure 330, directly above the zone Z3 of figure 9.

[0108] In the present embodiment, the protective slab is shown bearing directly on the wall 318 which in particular carries an external peripheral rim 318a like the embodiment of figures 6 and 7 and the wall 318 is spaced from the wall 326a of the reactor building 326. However, the different arrangements described with reference to figures 2A to 2E are also applicable here. Figures 12 and 13 represent, on the left part of each figure, the protective slab 320 constructed on its construction area or zone Zed located near the well 312, in top view and in vertical section BB respectively. On the right part of figure 12 the horizontal section view shows the elements located under the protective slab 320 whose contours appear transparently above the well.

[0109] On the left part of Figure 12, several pieces of equipment / buildings (not shown) can be built on the slab 320 during the construction of the reactor building in the shaft. For example, an auxiliary building providing cooling functions, an auxiliary building providing ventilation functions and a control room for the installation can be built. Other pieces of equipment / buildings can of course be built on the slab in place of at least some of these buildings or in addition. An opening T can also be arranged in the thickness of the slab 320 to serve in particular as a hopper at the level of the handling zone Z3 of the shaft 312 (right part in Figures 12 and 13), when the slab is put in place above the shaft.

[0110] The protective slab 320 can be slid from its construction zone Zed to a position located above the opening 312b of the well using for example two parallel guide beams L1, L2 (fig. 12) each intended to cooperate with a lateral peripheral edge falling from one of the two flat faces 320a1 and 320b1 of the slab. [01 1 1 ] A system for moving the slab 320 by translation comprises, for example, two jacks V1, two blocks M1 on which the jacks can be fixed and to which two traction cables Ca1 are attached, the cables passing through the external radial extensions 320a and 320b of the slab in their length and being fixed to the faces of these extensions which are opposite the shaft (anchoring A1). Alternatively, the operation of shifting the half-slabs can be carried out on an air cushion using for example so-called APS modules of the Freyssinet system which are sliding supports with an air cushion arranged under each half-slab. More specifically, the air-cushion sliding supports can be arranged between the lower faces of the two longitudinal edges or skirts of the slab or each half-slab and the upper face of the two sliding beams (the coefficient of friction is very low, of the order of 1%).

[0112] The right part of Figure 13 illustrates the slab 320 after sliding, in the position of complete closure of the opening 312b of the shaft, above the roof 328 of the reactor building 326. As for the previous modes, the installation thus configured has a compact vertical arrangement with the reactor building(s) in the shaft, the technical gallery above and below the protective slab (half-slab) and the auxiliary equipment / buildings above the slab.

[0113] It should be noted that the shifting of the 320 slab which has just been described can be applied to the other slabs or half-slabs described above with reference to the preceding figures even if the shape of the latter is different. The shifting principle remains the same.

[0114] According to an alternative embodiment not shown, the reactor building can adopt a general shape of square (horizontal) cross-section fitting inside the internal space of circular (horizontal) cross-section of the well (bordered by the annular wall 318).

[0115] According to another embodiment variant not shown, the shaft retains a circular (horizontal) cross-section which is here divided into two separate compartments each forming a surface occupying a semicircle and a reactor building of circular, square or rectangular (horizontal) section occupies each of the two semicircles. This variant can be adapted to low-power technologies, for example of the order of 100 MWe each to avoid a diameter which would be too large for the upper protection slab if the reactors were of larger dimensions).

Claims

Claims

1. Buried nuclear installation (10), comprising: - a vertical shaft (12) comprising, at a lower end, a bottom (12a) and, at an upper end, an opening (12b), - at least one reactor building (26) housed in the shaft, -at least one protective slab (20) against external attacks which completely closes the opening (12b) of the well, extending in particular above said at least one reactor building, -at least one nuclear reactor enclosure (30) enclosed inside said at least one reactor building (26) and supported by at least one support slab (32) resting on the bottom of the well by means of a plurality of seismic isolation devices (DIS).

2. Buried nuclear installation according to the preceding claim, characterized in that it comprises at least one nuclear fuel storage pool (PECN) housed in the well and supported by at least one support slab (DS) resting on the bottom of the well by means of a plurality of seismic isolation devices (DIS').

3. Buried nuclear installation according to claim 1 or 2, characterized in that said at least one reactor building (26) comprises a roof (28) which covers said at least one nuclear reactor enclosure (30) and said at least one nuclear fuel storage pool (PECN) when the latter is present, said at least one protective slab (20) extending in particular above the roof and at a distance from it so as to provide a technical gallery (G) between them.

4. Buried nuclear installation according to one of claims 1 to 3, characterized in that it comprises one or more vertical walls (18a-d) which border the interior of the well, said at least one protective slab (20; 20'; 20") being in vertical support: - directly on an embankment (16) arranged outside the well, at the outer periphery of said well, a bellows device (22) being arranged vertically between said at least one protective slab and the vertical wall(s) (18a-d) bordering the interior of the well, or - directly on the vertical wall(s) (18a-d) bordering the interior of the well, or - indirectly on the vertical wall(s) (18a-d) bordering the interior of the well by means of a damping joint device (229 and / or - directly on one or more supports (23, 25) arranged externally relative to the vertical wall(s) (18a-d) bordering the interior of the well.

5. Buried nuclear installation according to the preceding claim, characterized in that said at least one reactor building (26) comprises one or more vertical walls (26a, 26b; 26a', 26b'; 26a", 26b"; 26a 1, 26bl; 26a2, 26b2) which are spaced horizontally from the wall or vertical walls (18a-d) bordering the interior of the shaft or attached to the wall or vertical walls (18a-d) bordering the interior of the shaft.

6. Buried nuclear installation according to the preceding claim, characterized in that said at least one reactor building (26) comprises at least one horizontal intermediate slab (34; 134) which is integral with the vertical wall(s) (26a", 26c", 26d"; 126c, 126d) of said at least one reactor building and radially surrounds said at least one nuclear reactor enclosure (30; 130), said at least one intermediate slab (34) being arranged at an intermediate level of said at least one reactor building (26), above and at a distance from said at least one support slab (32; 132) supporting said at least one nuclear reactor enclosure.

7. Buried nuclear installation according to claim 5 or 6, characterized in that said at least one support slab supporting said at least one nuclear reactor enclosure is separated from the wall(s) of the reactor building by one or more peripheral isolation joints or by a space between said at least one support slab and the wall(s) of the reactor building.

8. Buried nuclear installation according to one of the preceding claims, characterized in that it comprises a well of vertical handling (Zl, Z2) which provides access to said at least one support slab (32) of the well, next to said at least one reactor building and separately from the latter.

9. Buried nuclear installation according to the preceding claim, characterized in that said at least one protective slab (20; 20.1) comprises a hopper (40) which is located in an area of ​​said at least one slab located above the vertical handling shaft (Zl, Z2).

10. Buried nuclear installation according to claim 2 or 3, characterized in that said at least one nuclear fuel storage pool (PECN) is arranged adjacent to said at least one reactor building.

11. Buried nuclear installation according to one of the preceding claims, characterized in that said at least one protective slab is formed of a slab (20; 20'; 20"; 20.1; 120; 320) or two half-slabs (20.2a, 20.2b) which are fixed to each other.

12. Buried nuclear installation according to one of the preceding claims, characterized in that said at least one protective slab is configured to be able to be removed subsequently in the event of modification or dismantling of the installation.

13. Buried nuclear installation according to one of the preceding claims, characterized in that the seismic isolation devices (DIS, DIS') each comprise one or more spring boxes (BAR).

14. Buried nuclear installation according to one of the preceding claims, characterized in that the seismic isolation devices (DIS, DIS') are distributed as uniformly as possible and according to the vertical loads to be supported between said at least one support slab and the bottom of the well.

15. Buried nuclear installation according to one of the preceding claims, characterized in that the isolation devices seismic (DIS, DIS') are mounted on reinforced concrete blocks or pads which rest on the bottom of the well.

16. Buried nuclear installation according to one of the preceding claims, characterized in that the seismic isolation devices (DIS, DIS') are configured to dampen vertical and / or horizontal vibration waves.

17. Buried nuclear installation according to one of the preceding claims, characterized in that the vertical well (12) has a generally rectangular or circular shape according to a view taken in a horizontal plane.

18. Buried nuclear installation according to one of the preceding claims, characterized in that it comprises one or more pieces of equipment or buildings arranged on said at least one protective slab.

19. Buried nuclear installation according to the preceding claim, characterized in that the equipment or buildings arranged on said at least one protective slab are configured to provide support functions for the operation of the nuclear reactor and the entire nuclear installation.

20. Buried nuclear installation according to claim 18 or 19, characterized in that the equipment or buildings arranged on said at least one protective slab comprise at least one of the following elements: a control room for the nuclear installation, a building providing ventilation functions, a building providing cooling functions, a room containing control and command cabinets for operating support and electricity production functions, an instrumentation room, a high-current electrical distribution room, a low-current electrical distribution room and batteries / inverters, a valve and exchanger room, a first-aid diesel engine room.

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