METHOD FOR CONSTRUCTING AN UNDERGROUND NUCLEAR FACILITY

Abstract

The invention relates to a method for constructing an underground nuclear installation on a site (10) comprising a shaft (12) bored into the ground (14, 16) and defining a bottom (12a), at a given depth relative to the ground surface, and an opening (12b, 12b1, 12b2) located at the level of the ground surface surrounding the shaft. The method comprises the following phases: - construction of a protective slab (D1, D2; D; 230) against external aggressions on an area (Zcd) of the ground surface, referred to as the slab construction area, located next to the opening (12b, 12b1, 12b2) of the shaft, - construction of a reactor building (B1, B2) inside the shaft (12), the phases of construction of the protective slab (D1, D2; D; 230) and the reactor building (B1, B2) being carried out in parallel. Figure for the abridged version: Fig. 3

Description

Title of the invention: METHOD FOR CONSTRUCTING AN UNDERGROUND NUCLEAR FACILITY technical field

[0001] The present invention relates to the field of buried nuclear installations. Previous technique

[0002] A nuclear installation is known, notably from document WO 2018 / 204081, in which a boiling water nuclear reactor containment structure is housed in a silo built into the ground and rests on the bottom of the silo. The silo is closed at its upper part by a concrete cover to protect the nuclear reactor against external impacts and explosions.

[0003] According to current construction methods used for building such an underground nuclear installation, the first step is to excavate the ground to pour a foundation slab at the bottom and create a silo. A reactor building is then constructed inside the silo by erecting concrete walls. The nuclear reactor containment building and its components (primary circuit) are installed inside the reactor building, which is then sealed. Once the various external equipment for the reactor building (e.g., cooling sources as indicated in document WO 2018 / 204081) is installed, the silo is sealed at its top with a concrete lid.

[0004] The order of the construction sequences identified above imposes an overall construction schedule for the nuclear installation.

[0005] In view of the above, it would be useful to design a method for constructing an underground nuclear installation that saves time on the overall construction schedule of the installation. Description of the invention

[0006] The invention thus relates to a method of constructing an underground nuclear installation on a site, the site comprising a shaft dug into the ground so as to define a bottom, at a given depth relative to the ground surface, and an opening located substantially at the level of the ground surface surrounding the shaft, characterized in that the method comprises the following construction phases: -the construction of at least one protective slab against external aggressions on an area of ​​the ground surface, known as the construction zone, which is located next to the well opening, -the construction of at least one reactor building inside the shaft, the construction phases of said at least one protective slab and said to minus one reactor building being carried out in parallel.

[0007] According to the aforementioned method, at least one protective slab is constructed while the construction of at least one reactor building is underway. This means that the construction of at least one reactor building in the well is not delayed, and even less so the installation of all internal components and equipment in the well, before constructing said protective slab, unlike the conventional method used in the aforementioned prior art document. The above construction method thus provides a considerable time saving on the overall construction schedule of the installation. Furthermore, by constructing said protective slab next to the well and then transporting it over the well, the construction operations or phases of the installation are facilitated.In particular, once constructed next to the well, the at least one slab only needs to be moved a few dozen meters to be placed on the well. The at least one slab is constructed close to the well so that it can be moved with minimal effort (this would not be the case if the at least one slab had to be moved over a considerable distance, such as several hundred meters). Therefore, it is not necessary to bring a pre-constructed slab from a distant site and place it on the well.

[0008] According to other possible characteristics: -the method includes a construction phase for one or more pieces of equipment or buildings on said at least one protective slab, the construction phase of equipment(s) or building(s) beginning during the construction phase of said at least one reactor building and while said at least one protective slab (D1, D2; D; 230) is on the slab construction area; the construction of (auxiliary) equipment(s) or building(s) is possible as soon as said at least one protective slab is finished (in one piece or in half-slabs, or even in more than two slab elements); this allows considerable time to be saved on the overall construction schedule (overall assembly time) compared to a situation where this or these pieces of equipment or buildings would be built only after the placement of said at least one slab on the well opening;It should be noted that when the slab is formed of several slab elements (two or more half-slabs), each piece of equipment or building is built on a single slab element, i.e., no equipment or building is built straddling two slab elements; -the equipment or building(s) constructed 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 and, as such, are called 'auxiliary' equipment or buildings as opposed to the equipment or so-called 'main' buildings which perform nuclear safety functions and which are positioned underground inside the shaft; in other words, these are equipment or buildings located above said at least one slab protecting against external aggressions and which may be subject to external aggressions insofar as the functions necessary for the safety of the reactor which they perform, in cases of degraded or accidental situations, are redundant with the safety functions of the reactor of the equipment or buildings located below said at least one slab;-the equipment or building(s) constructed on said at least one protective slab include 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 operational support and electricity production functions, an instrumentation room, a high-voltage electrical distribution room, a low-voltage electrical distribution room and batteries / inverters, a valve and heat exchanger room, a first-aid diesel engine room; -the construction phase of said at least one reactor building includes the installation of at least one nuclear reactor containment structure and / or at least one nuclear fuel storage pool; the nuclear fuel storage pool may alternatively be located next to the reactor building(s), in the shaft, in particular in an area of ​​the shaft adjacent to that housing the reactor building(s); during this construction phase, the containment structure and / or the pool may be built in the shaft (before sliding said at least one slab) and not only installed in the latter; -the construction phase of said at least one reactor building includes the construction, on the one hand, of a wall or several walls surrounding said at least one nuclear reactor containment and / or said at least one nuclear fuel storage pool and, on the other hand, of a roof covering the wall or walls so as to enclose, inside said at least one reactor building, said at least one nuclear reactor containment and / or said at least one nuclear fuel storage pool; the nuclear fuel storage pool may alternatively be located next to the reactor building or buildings, in the shaft and therefore not be enclosed in a reactor building; -the construction method includes a sliding phase of said at least one protective slab, from the slab construction area to the point of the well opening, so that said at least one protective slab seals the well by being positioned above said at least one reactor building at the end of the sliding phase; it should be noted that when one or more pieces of equipment or buildings are constructed on said at least one protective slab before its sliding, said at least one slab is thus slid with the equipment or buildings it supports; - the construction method includes, after the sliding phase of said at least one protective slab, a phase of developing an intermediate space, called a technical gallery, between said at least one protective slab and said at least one reactor building; the technical gallery is inscribed within the diameter of the shaft; the technical gallery serves in particular to connect between them, 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 between them the prefabricated networks of these two parts by allowing the passage of various links (cables, pipes...) between these parts; -The construction method includes the construction phase of a single slab or two half-slabs (slab elements), or even more than two half-slabs or slab elements on the slab construction area which are slid one after the other to the right of the shaft opening, then assembled together so as to close the shaft at the end of the sliding; the use of two or more half-slabs makes it possible to reduce the weight of the load to be slid and therefore to size the slab movement system accordingly, which simplifies the design of the installation and the sliding operations; this is particularly advantageous when one or more pieces of equipment or buildings are built on the half-slabs because, in the end, the loads to be slid per half-slab are lower than if the same equipment or buildings were built on a single slab; - the sliding phase of said at least one protective slab takes place at the end of the construction of said at least one reactor building; thus, time continues to be saved on the overall schedule compared to a situation where one would wait for the complete completion of the construction of said at least one reactor building before constructing said at least one protective slab above the reactor building; -the sliding phase of said at least one protective slab takes place after the installation of said at least one nuclear reactor containment and / or said at least one nuclear fuel storage pool and the construction of the wall(s) and roof of said at least one reactor building; after sliding said at least one protective slab, it is indeed difficult to put such components in place in the shaft; -at least one protective slab is put in place at the opening of the well so that it can be removed later in the event of modification or dismantling of the nuclear installation; - when the shoring phase is complete, the construction phase of equipment or building(s) continues on at least one shoring-up protective slab; this allows, Here again, to save time on the overall construction schedule of the installation; - when the shunting phase is completed, the construction phase of said at least one reactor building continues, in particular inside the shaft; -prior to the start of the construction phase of said at least one reactor building, the construction method includes the creation in the shaft of one or more vertical walls bordering the inside of the shaft; - said at least one protective slab is slid up to the edge of the well opening so as to rest vertically: directly onto an embankment placed at the outer periphery of the shaft, a bellows device being arranged vertically between said at least one protective slab and the vertical wall(s) bordering the interior of the shaft, or directly onto the vertical wall(s) bordering the inside of the well, or indirectly onto the vertical wall(s) bordering the inside of the well via a damping seal and / or directly on one or more supports arranged externally relative to the vertical wall(s) bordering the inside of the well; - the vertical well has a general rectangular, square or circular shape depending on a view taken in a horizontal plane; -The construction method includes a phase of construction of a turbine building on an area of ​​the ground surface surrounding the shaft, called the turbine building construction area, and may also include the construction of other buildings; the turbine building construction area may be arranged opposite to the slab construction area in relation to the shaft or another location; the phase of construction of a turbine building may also take place during one and / or the other of the phases mentioned above in order to save time on the overall construction schedule.

[0009] The invention also relates to an underground nuclear installation obtained by the construction method described above, according to one or more of the aspects mentioned above, or even according to all of the aspects. Brief description of the drawings

[0010] Other features and advantages will become apparent in the following description, given solely by way of non-limiting example and with reference to the accompanying drawings, on which:

[0011] [Fig-1] The [Fig. 1] is a schematic view of a possible example of a site for the implantation of an underground nuclear installation according to a possible embodiment of the invention;

[0012] [Fig.2] Fig.2 is a schematic top perspective view of a first phase of a construction method according to an embodiment of the invention;

[0013] [Fig.3] The [Fig.3] is a view analogous to that of the [Fig.2] illustrating a second phase of the construction method according to an embodiment of the invention;

[0014] [Fig.3A] The [Fig.3A] is a partial schematic top perspective view of two half-slabs separated longitudinally from each other;

[0015] [Fig.3B] The [Fig.3B] is a partial schematic view in vertical cross-section showing the through openings of a half-slab and also a representation of a technical gallery;

[0016] [Fig.4] The [Fig.4] is a view analogous to that of the [Fig.3] illustrating a third phase of the construction method according to an embodiment of the invention;

[0017] [Fig. 5] [Fig. 5] is a schematic vertical longitudinal sectional view illustrating the third phase of the construction method of [Fig.4];

[0018] [Fig.5A] The [Fig.5A] is a partial enlarged schematic view, in vertical cross-section, of a possible longitudinal guidance system for a half-slab;

[0019] [Fig.6] The [Fig.6] is a view analogous to that of the [Fig.4] illustrating a fourth phase of the construction method according to an embodiment of the invention;

[0020] [Fig.7] The [Fig.7] is a view analogous to that of the [Fig.4] illustrating a fifth phase of the construction method according to an embodiment of the invention;

[0021] [Fig.7A] The [Fig.7A] is an enlarged partial schematic view of a connection zone between two half-slabs according to a possible embodiment;

[0022] [Fig.7B] The [Fig.7B] is a schematic perspective top view of two half-slabs joined together;

[0023] [Fig.7C] The [Fig.7C] is an enlarged partial schematic view of an area of ​​the buried nuclear installation of the [Fig.7] located between a protective half-slab and the walls bordering the shaft according to a possible embodiment of the invention;

[0024] [Fig.7D] The [Fig.7D] is a partial schematic view illustrating the support of the protective slab according to an alternative embodiment;

[0025] [Fig.7E] The [Fig.7E] is a partial schematic view illustrating the support of the protective slab according to another embodiment variant;

[0026] [Fig.7F] Fig.7F is a partial schematic view illustrating the support of the slab of protection according to another embodiment;

[0027] [Fig.7G] The [Fig.7G] is a partial schematic view illustrating the support of the protective slab according to another embodiment variant;

[0028] [Fig.8] Fig.8 is a schematic vertical cross-sectional view illustrating the installation buried nuclear [Fig.7];

[0029] [Fig.9] Fig.9 illustrates, in a vertical cross-sectional view, another method of production possible use of an underground nuclear installation;

[0030] [Fig. 10] Fig. 10 illustrates, in a horizontal cross-sectional view, another method of possible construction of an underground nuclear facility;

[0031] [Fig. 11] Fig. 11 illustrates, in top view, a possible embodiment of a circular underground nuclear installation under construction;

[0032] [Fig. 12] The [Fig. 12] illustrates, following a vertical cross-sectional view, the installation of the [Fig.1 1] after the slab sliding phase;

[0033] [Fig. 13] The [Fig. 13] illustrates, in top view, a schematic variant of a possible configuration of buried nuclear installations;

[0034] [Fig. 14] The [Fig. 14] illustrates, in top view, another variant of a schematic realization of a possible configuration of buried nuclear installations;

[0035] [Fig. 15] Fig. 15 illustrates, in top view, another schematic embodiment of a possible configuration of buried nuclear facilities. Description of embodiments

[0036] The invention which is described below with reference to the attached drawings relates to different possible embodiments of a method of constructing a new architecture of a nuclear installation buried on a site.

[0037] As shown schematically in [Fig. 1], a site 10 for the installation of an underground nuclear facility includes a vertical shaft or pit 12 which has been excavated (excavation phase) in soil or ground 14 to a predetermined depth, for example on the order of 30-35m using conventional excavation techniques and equipment. These dimensions may, however, vary.

[0038] This well 12 comprises, at a lower end, a bottom 12a and, at an upper end, an opening 12b with dimensions substantially equal to those of the bottom. In this embodiment, the earth removed during the construction of the well is, for example, used to form one or more embankments 16 arranged around the well opening 12b, thus creating a raised area relative to the ground surface 14. This arrangement can serve as a flood barrier. It should be noted that the presence of embankments is optional, as the earth removed during excavation can be transported elsewhere. However, in the present embodiment, the embankment(s) 16 are present around the well opening 12b, and the well opening 12b is considered to be located substantially at the level of the upper surface of the embankment(s) surrounding the opening 12b.This upper surface can therefore be considered as the 'ground surface' surrounding the opening 12b within the meaning of the invention. In the case where there is no backfill, everything described thereafter applies directly to the ground surface 14 surrounding the well opening ([Fig.1]).

[0039] The height or depth of the well 12 is defined between the opening 12b and the bottom 12a of the well and is chosen so as to be able to house inside the well all of the The components of the buried part of the nuclear installation, which will be described later, take into account the height of the foundation slab that will be formed at the bottom of the shaft. Shaft 12 can have any general shape along a horizontal section (perpendicular to the vertical plane of [Fig. 1]) and, for example, can have a generally rectangular, square, or circular cross-section. In the present embodiment, the shaft has, for example, a rectangular cross-section, but the elongated dimension of the shaft is intentionally not shown in [Fig. 1], which is a schematic diagram. The elongated shape will be visible in the following figures.

[0040] Next, several vertical walls are formed against the inner earthen walls 19a, 19b of the well so as to enclose the well's internal usable space. Only two vertical walls 18a, 18b are shown in [Fig. 1], whereas the rectangular-section well has four. These vertical walls 18a, 18b, enclosing the well's internal usable space, are, for example, diaphragm walls well known to those skilled in the art (reinforced concrete walls cast in the ground). These walls are generally anchored in the ground by prestressed tiebacks.

[0041] The function of these walls is to resist the pressure of the earth surrounding the well and to ensure a watertight seal (barrier) for the interior of the well, particularly against water that might infiltrate the surrounding soil. This watertight barrier can be supplemented by another barrier incorporating a sealing membrane. Depending on the geometry of the well, a single wall (wells with a circular cross-section) or several vertical walls (wells with a square, rectangular, etc. cross-section), for example, cast-in-place walls, can be used.

[0042] As shown in [Fig. 1], the ground surface (here, the upper surface of the embankment(s) 16) surrounding the shaft opening 12b includes, near this opening, on one side of the shaft, a zone Zed dedicated to the construction of a protective slab for the future underground nuclear installation. The proximity of zone Zed to the shaft should be understood as a reasonable distance to allow the protective slab to be slid from this zone to the shaft opening without incurring excessive stress, as would be the case if a slab had to be transported over several hundred meters. This distance is therefore on the order of the largest dimension of the slab (length of a rectangle, diameter of a circle, etc.) and, in practice, is greater than this largest dimension.For example, a single slab, generally rectangular in shape, can be approximately 40 meters long. This will define the end of the Zed construction zone that is furthest from the shaft, for example, at a distance of at least 40 meters from the shaft, or even in the range of 45 to 50 meters. This slab's function is, in particular, to protect the installation against external hazards, such as falling objects (e.g., aircraft) or external explosions. The protective slab is generally made of reinforced concrete. Alterna. Specifically, the slab can be constructed in prestressed concrete or made using a mixed construction with a lower facing consisting of a stiffened steel sheet fixed and welded to the slab onto which flexible connectors are welded.

[0043] The Zed zone constitutes a construction area that is prepared before the construction of the protective slab, for example by creating a platform on which the slab will be built. This preparation phase can take place after the construction of the shaft walls described above or, concurrently, during the construction of the shaft walls.

[0044] Furthermore, the ground surface (here referring to the upper surface of the embankment(s) 16) surrounding the well opening 12b may include, near this opening, on the opposite side of the well from the side containing the Zed area, a Zcbt area dedicated to the construction of an (optional) turbine building intended to house a turbogenerator. It should be noted, however, that the nuclear installation may also (or alternatively) be used to produce thermal energy to supply a heating network. The two areas, Zed and Zcbt, are arranged on either side of the well opening 12b along the same longitudinal alignment (X-axis). The foundation work for the turbine building is carried out in the Zcbt area and may take place during the preparation work for the Zed construction area of ​​the protective slab.It should be noted that the Zcbt zone can be arranged according to a different layout and not necessarily in alignment with the Zed zone and the well in the event that, with the aligned configuration, the building housing the turbogenerator would interfere with the sliding of the protective slab.

[0045] The well 12 includes, at its lower end, a foundation slab 12c forming the bottom of the well on which the various elements / components of the buried installation will be placed and housed inside the well. This foundation slab is installed in a known manner after the well excavation and the formation of the diaphragm walls. A grouted bottom may be necessary to limit water ingress through the bottom if the ground is permeable.

[0046] We will now describe in more detail, with reference to Figures 2 to 7, different construction phases of a possible example of a method for constructing an underground nuclear installation comprising, for example, two reactor buildings and where the protective slab is, for example, formed of two half-slabs. It should be noted, however, that everything described (like everything described above) applies, in particular, to the construction of an installation comprising a single reactor building with a single protective slab above it, or even two half-protective slabs above it (in the case where the aim is to reduce the weight of the loads to be moved due to a large reactor building) or even more than two reactor buildings with as many protective slabs as reactor buildings (or with more protective slabs than reactor buildings), and with a shaft of any shape (rectangular, square, circular, etc.). If several shafts need to be built, the positioning of the preparation areas for the protective slab(s) must be studied on a case-by-case basis.

[0047] As shown in perspective in [Fig. 2], the preparation of the construction area Zed involves the construction of a reinforced concrete platform (Ptfl) which is positioned in alignment (axial or longitudinal direction X) with the longest dimension (length) of the rectangular shape of the horizontal section of the shaft and centered with respect to the median longitudinal axis of this rectangle. The Ptfl platform has a generally rectangular shape in top view so as to accommodate the two protective half-slabs along its length.

[0048] Furthermore, two parallel guide / sliding beams L1 and L2, aligned along the longitudinal axis X, are arranged symmetrically with respect to each other on the Ptfl platform. These beams L1 and L2, generally made of reinforced concrete, are anchored in the ground, for example, each by means of vertical piles pl, p2 (foundation piles) regularly spaced along the X axis. These beams will support the protective half-slabs during their translational movement towards the shaft and, for this purpose, can be fitted, on their upper surface, with plates made of a material having a low coefficient of friction with stainless steel, for example, Ipalen. Plates, for example, made of stainless steel, can be fixed to the underside of the half-slabs and will come into contact with the plates, for example, Ipalen, of the beams.

[0049] During this preparatory phase of the construction method, a displacement system is also planned to move the two protective half-slabs D1, D2 by sliding from their construction zone or area Zed to their final position sealing the shaft, above the shaft opening, once they have been constructed. This same displacement system can also be applied to a single protective slab or to more than two slab elements.

[0050] By way of example, a system for moving the two protective half-slabs may include, on the side of the shaft opposite the side where the construction zone Zed is located, one or more supports securely anchored in the ground (or fixed to the top of the diaphragm wall) and one or more motorized mechanical traction devices attached to the support or supports and exerting a tensile force on cables securely attached to each half-slab. More specifically, the vertical section of [Fig. 5], which is a view of the construction site at a more advanced stage of construction than [Fig. 2], shows a support formed by an anchor block M1, a hydraulic cable jack VI mounted on the block M1, and a traction cable or strand Cal attached at one end to jack VI. The traction cable Cal extends longitudinally above the shaft and through the half-slab DI closest to the shaft (for example, a tube or sleeve is installed during construction within the thickness of the half-slab, at mid-height, and extends along its entire longitudinal dimension) to emerge at its opposite end from the half-slab Dl. The protruding end of the cable is, for example, equipped with an anchor head that can be fixed to a load distribution plate (passive anchorage Al) attached to the face of the protective half-slab Dl opposite the shaft. This arrangement is designed to be duplicated with two anchor blocks, two jacks, and two traction cables to exert a balanced longitudinal tension on the half-slab.Furthermore, a longitudinal guidance system can be installed on each stringer to prevent any deviation during the translation of the half-slab, and in particular to prevent it from becoming misaligned. Alternatively, a system using cables and one or more winches can be used.

[0051] Figure 5A shows a partial enlarged view, in vertical cross-section relative to the longitudinal axis X of the sliding motion of Figure 5, of the displacement and guidance system of a half-slab Dl on the side of the sliding beam L2 (not visible in Figure 5). Thus, the traction cable Ca2 (symmetrical to the cable Cal of Figure 5) passes through the dropped peripheral edge forming the skirt RI of the half-slab Dl along its length. The L2 sliding beam is fitted, on its upper face, with one or more Pi plates made of a material with a low coefficient of friction with stainless steel, for example, Ipalen, and one or more Pa plates or sheets, for example, made of stainless steel, are fixed to the lower face of the RI edge of the half-slab and positioned in contact with the lower Pi plate(s). Furthermore, a support post Ps is partially anchored in the ground and fixed to the L2 sliding beam.The support post Ps carries, in its unburied portion and on its inner face oriented towards the edge RI of the half-slab, a guide rail rg which is in contact with the outer face of the edge RI and serves to guide the longitudinal sliding / translation movement of the half-slab. A symmetrical arrangement is provided on the other part of the edge RI of the half-slab located above the sliding beam L1 of [Fig. 5]. Other longitudinal guidance systems can alternatively be considered to guide the half-slab D1 (and the other half-slab D2) and thus prevent any non-longitudinal movement of the latter.

[0052] In parallel with these operations, the construction of the turbine building foundation on the construction area Zcbt can be carried out ([Fig.2]) by first constructing, for example, a reinforced concrete platform Ptf2, here aligned along the longitudinal axis X, and on which, for example, a slab Dbt is constructed to serve as the floor for the turbine building. The turbine building is then- The turbine building is positioned close to the reactor building to minimize the length of the steam pipes that must reach the turbine building. However, the turbine building's layout is designed to avoid interfering with the future sliding of the DI and D2 slabs.

[0053] In parallel with the operations to prepare the construction area for the half-slabs, the construction of at least one reactor building inside the shaft begins, which saves time on the overall construction schedule of the installation since construction tasks are thus carried out in parallel. In this embodiment, the construction of two reactor buildings B1 and B2 begins by first constructing the walls, for example in reinforced concrete, of the reactor buildings which are visible in [Fig. 2] and rest on the foundation slab 12c, namely two large parallel longitudinal walls 20 and 22, two smaller transverse walls 24 and 26 arranged along the length of the shaft, as well as a separating transverse wall at mid-distance between walls 24 and 26. It should be noted that a third longitudinal wall (not visible in [Fig. 2])2] but which will be represented in particular in Figures 7D and 7E described later under reference 27), parallel to the two longitudinal walls 20 and 22, is constructed in the shaft between wall 22 and the shaft diaphragm wall which is located on the front face of the shaft in [Fig. 2] (this shaft wall is referenced 18c in Figures 7D and 7E). The space delimited between wall 22 and this third wall 27 is used, for example, for the construction of a shaft area which is arranged adjacent to the shaft area where the reactor buildings are housed and which may include a vertical handling area and include one or more staircases, equipment ancillary to the operation of the reactors, or even one or more nuclear fuel storage pools.

[0054] The longitudinal wall 22 is pierced in its thickness, near each of its two opposite longitudinal ends, so as to locally provide an opening Ol.l and 02.1 which, each, connects the interior of the corresponding reactor building B1, B2 with the space adjacent to this building along the wall 22. This opening (called a buffer) is permanently closed during the operation of the reactor (by means of a sliding or pivoting door not shown) and opened only to evacuate or bring in equipment.

[0055] Figure 3 illustrates a more advanced phase of the construction method where the Construction of the two protective half-slabs DI and D2 begins in the designated construction zone / area Zed. Zone Zed is subdivided into two sub-zones or secondary areas separated from each other along the longitudinal direction X, and each concrete half-slab is constructed in one of these two distinct sub-zones or secondary areas, each positioned above one of the two guide beams L1 and L2, symmetrically with respect to the other half-slab. A longitudinal space is left between the two half-slabs. Each protective half-slab is generally made of reinforced concrete. Alternatively, each half-slab can be constructed of prestressed concrete or using a composite construction with a lower facing consisting of a stiffened steel plate to which flexible connectors are welded. It should be noted that the construction, parallel to the longitudinal X-axis, of a second "line" of construction for an underground nuclear facility can be considered, as will be described later.

[0056] Figure 3A shows, in a top perspective view (enlarged compared to the view in Figure 3), the two protective half-slabs D1, D2 (without the other elements of Figure 3), each on its secondary construction area. The half-slabs are thus constructed at a distance from each other and each has a free end face fal, fa2 opposite the other. These two faces fal, fa2 will be mechanically joined / assembled to form a single slab as explained later with reference to Figure 7A. As shown in Figure 3A, a peripheral edge RI, R2 is provided on the underside of each half-slab D1, D2 and extends vertically downwards like a skirt or a drip edge.

[0057] Each half-slab D1, D2 has openings through its thickness to allow the passage of cables, pipes, equipment, and people (for stair access), depending on the opening(s) in question. In Figures 3 and 3A, an opening T1, T2, offset laterally from the longitudinal median axis of each half-slab, is shown. This opening is intended to form a hopper that will be used later for maintenance or handling and will be located above the handling area situated between the longitudinal wall 22 and the non-visible front wall of the shaft (wall 27 in Figures 7D and 7E). Other through-openings are provided at separate locations on each half-slab, on which buildings will be constructed, as will be seen later. Each of these openings serves for the passage of cables, pipes, etc.(various connections) between the building located above the half-slab and the reactor building located below the half-slab via a technical gallery located between the half-slab and the reactor building, which will be described later.

[0058] Figure 3B is a schematic vertical cross-sectional view of a half-slab Di (along its smallest dimension) showing, for example, two through openings D1 and Di2 (a larger number of openings can be envisaged in a variant if the number of buildings increases) positioned respectively at the location of future buildings constructed on the half-slab, and an opening Ti, located on one side of the half-slab, acting as a stairwell and which is, for example, closed by a hatch Ti shown in both positions in Figure 3B. After selectively installing the different connections through each opening Dil (ex: pipes), Di2 (ex: cables), the latter is sealed in a manner known to the skilled craftsman, in particular to ensure sealing and fire protection.

[0059] Furthermore, each half-slab Dl, D2 has impressions rl. 1, rl.2, r2.1, r2.2 (figs. 3 and 3A) of the rails of an overhead crane which will be used later to move various equipment on the slab and in particular for maintenance above the handling hoppers Tl, T2.

[0060] Meanwhile, the construction of the two reactor buildings B1 and B2 continues with the installation, in each building, for example, of an intermediate slab d1, di2 ([Fig. 3]) which has an opening 01, 02 in its central part to accommodate a nuclear reactor containment structure. Simultaneously, the free space defined between the longitudinal wall 22 of buildings B1, B2 and the third longitudinal wall not visible in [Fig. 3] is fitted out, for example, by the construction of two multi-story structures SI, S2, each against the wall of one of the two reactor buildings. These structures serve, for example, as staircases or access platforms to certain instruments or equipment necessary for monitoring the operation of the reactor(s). The two structures SI, S2 are separated from each other by a transverse wall 32 which divides the free space into two compartments C1, C2, each dedicated to one reactor building.

[0061] According to an alternative embodiment not shown here, a nuclear fuel storage pool may be constructed / installed, for example, in the space / compartment mentioned above, adjacent to the shaft area housing the two reactor buildings, along wall 22, extending on either side of the intermediate transverse wall 28 (along the areas occupied by the two reactor buildings). Alternatively, two nuclear fuel storage pools may be constructed / installed, for example, in the space mentioned above. Each pool is located adjacent to one of the two reactor buildings and is dedicated to that building. As with the construction of the building(s), the construction / installation of the pool(s) in the shaft is carried out concurrently with the construction of the protective half-slabs next to the shaft.

[0062] In parallel, the construction of a turbine building 30 begins ([Fig.3]).

[0063] Fig. 4 illustrates an even more advanced phase of the construction method during which the construction of one or more pieces of equipment or buildings begins on each protective half-slab that has been built.

[0064] This equipment or these buildings are configured to provide support functions for the operation of the nuclear reactor and the entire nuclear installation and, as such, are called 'auxiliary' equipment or buildings as opposed to the so-called 'main' equipment or buildings which provide nuclear safety functions and which are positioned underground inside the shaft. In other words, these are equipment or buildings located above the slab and which can be subjected to external aggressions insofar as the functions necessary for the safety of the reactor that they fulfill, in degraded or accidental cases or situations, are redundant with the safety functions of the reactor of the equipment or buildings located below the slab.

[0065] This equipment or these buildings constructed on each half-slab of protection may include at least one of the following: a nuclear installation control room, a building providing ventilation functions, a building providing cooling functions, a room containing control and command cabinets for operational support and electricity production functions, an instrumentation room, a high-voltage electrical distribution room, a low-voltage electrical distribution room and batteries / inverters, a valve and exchanger room, a first-aid diesel engine room.

[0066] In [Fig.4], the half-slab DI thus supports two buildings b 1.1 and b 1.2, while the half-slab D2 supports two buildings b2.1 and b2.2. In this embodiment, the buildings b 1.1, b 1.2, b2.1 and b2.2 are respectively, an auxiliary building providing cooling functions, an auxiliary building providing ventilation functions, an auxiliary room for first-aid diesel engines and a control room for the installation.

[0067] Meanwhile, the construction of the two reactor buildings Bl and B2 continues with the construction of a nuclear reactor containment building El, E2 of a known type in each of the buildings.

[0068] When each containment structure is completed (Figs. 4 and 5), a roof (not shown) is installed, for example by pouring a concrete slab, over each reactor building Bl, B2, resting on the building walls so as to cover and enclose the entire structure. The roof of each reactor building is positioned at a distance from the shaft opening 12b to provide a free space above the roof where a service gallery will be installed between the roof and the half-slab that will be placed above it. As each half-slab is constructed and topped with buildings independently from one half-slab to the next, and as each reactor building is also constructed independently of the others, the roof of reactor building B2 is not necessarily installed at the same time as the roof of reactor building Bl (moreover, containment structure E2 is not necessarily completed at the same time as containment structure El).The roof of reactor building B2 can be put in place after that of reactor building BL.

[0069] Two staircases 34, 36 are for example each constructed in one of the two compartments Cl, C2 arranged along the longitudinal wall 22 of buildings Bl, B2, at side of the corresponding structure SI, S2. These stairs 34, 36 are arranged for example each in a location which will be situated under the hopper Tl, T2 of each half-slab.

[0070] Construction of turbine building 30 can continue during this construction phase ([Fig.4]).

[0071] Figure 6 illustrates a subsequent phase of the construction method in which the DI protective half-slab is slid longitudinally (along the X-axis) using the displacement and guidance systems described above with reference to Figures 5 and 5A (this displacement system is not shown in Figure 6 for clarity), from the secondary area of ​​the construction zone Zed to the point of part 12bl of the shaft opening located above the roof of reactor building B1 (Figure 5), passing over part 12b2 of the shaft opening located above the roof of reactor building B2. The sliding is carried out over a distance of several tens of meters and, for example, over a distance greater than twice the length of the half-slab. Thus, the DI half-slab partially seals the well by being positioned above the reactor building B1 at the end of the sliding operation ( [Fig.6]) and also extending over compartment Cl (area adjacent to reactor building Bl). The DI half-slab can rest on the shaft diaphragm walls defined above or be supported in various ways, as will be seen later. The sliding phase of the first DI half-slab takes place at the end of the construction phase of reactor building B1, once the main building construction tasks have been completed.

[0072] For example, the roof of reactor building B2 can be put in place after the sliding of the first half-slab DI but before that of the second half-slab D2. Similarly, during the sliding of the first half-slab D1, the construction of the buildings on the second half-slab D2 can continue, as well as the construction of containment E2 if these are not completed.

[0073] It should be noted that during this sliding phase, the construction of the reactor building B1 is not yet completely finished and various small equipment (e.g. ventilation, wiring, tests...) still need to be installed.

[0074] Figure 7 illustrates a subsequent phase of the construction method in which the second protective half-slab D2 is slid longitudinally (along the X-axis) at the end of the construction phase of reactor building B2 (the remarks made above concerning the sliding of the half-slab D1 with respect to the construction of building B1 apply here) by implementing the displacement system described above with reference to Figures 5 and 5A (this displacement system is not shown in Figure 7 for clarity), from the secondary area of ​​the construction zone Zed to the right of part 12b2 of the shaft opening located above the roof of the Reactor building B2 ([Fig. 5]). Thus, half-slab D2 partially seals the shaft by being positioned above reactor building B2 at the end of the sliding operation ([Fig. 7]) and also extending above compartment C2 (the area adjacent to reactor building B2). Half-slab D2 rests on the lower structure in the same way as half-slab D1. With the two protective half-slabs thus positioned, the shaft opening 12b is completely sealed. The anchor blocks can then be demolished. It should be noted that when the two half-slabs D1 and D2 rest on the heads of the diaphragm walls, reinforced concrete lateral stops can, for example, be constructed around the entire perimeter of the shaft, connected to the diaphragm walls, in order to laterally restrain the slab formed by the two half-slabs on these walls. Furthermore, a seal is created between the outer peripheral surface of the slab and the diaphragm walls.

[0075] Alternatively, the sliding operation of the half-slabs can be carried out on an air cushion using, for example, so-called APS modules of the Freyssinet system, which are air-cushioned sliding supports arranged under each half-slab. More specifically, the air-cushioned sliding supports can be arranged between the lower faces of the two longitudinal edges or skirts of the slab or of each half-slab and the upper face of the two sliding stringers (the coefficient of friction is very low, on the order of 1%). [Fig. 5A] illustrates where these sliding supports can be positioned.

[0076] In the position shown in [Fig. 7], half-slab D2 is positioned against half-slab D1, and the two half-slabs are mechanically joined / assembled to each other, for example by keying, to mechanically form a single protective slab, ensuring continuity of the slab's mechanical resistance at the junction or connection zone between the half-slabs (for this purpose, the reinforcement must be continuous at this zone). [Fig. 7A] illustrates a possible example of a mechanical connection between half-slabs D1 and D2. This figure is an enlarged partial view of a mechanical connection zone between the two half-slabs. The connection between the two half-slabs D1 and D2 can be achieved by providing a keying zone Zcl between these half-slabs.The half-slabs are installed with a keyway width greater than the overlap length of the longitudinal reinforcement bars in the lower layers ali and a2i and the upper layers al s and a2s of the half-slabs. The longitudinal reinforcement bars of each slab element (half-slab) overlap the longitudinal reinforcement bars of the other slab element. Several layers of upper and lower reinforcement are required for each slab element, but only one upper and one lower reinforcement layer are shown for each slab element in the schematic diagram [Fig. 7A] for ease of understanding. Understanding. Longitudinal reinforcement in the opposite direction and shear reinforcement are also placed (see schematically the perpendicular reinforcements a3i and a3s in the figure). Furthermore, temporary formwork Cfp can be fixed under the slab elements, and the keyway is then concreted to mechanically connect the two slab elements. The temporary formwork Cfp is removed a few days after the keyway has been concreted. Note that other solutions can be considered to ensure the continuity of the longitudinal reinforcement: couplers, bar welding, etc.

[0077] Fig. 7B illustrates the slab obtained after assembly of the two half-slabs D1, D2, for example as explained in the embodiment example described above, but which can be obtained in a different way not described in detail here.

[0078] The slab obtained after assembly of the two half-slabs D1, D2 is a protective slab against external aggressions to the well and thus protects the components of the installation which are housed in the well.

[0079] Generally, each half-slab is installed in such a way that it can be removed later in the event of dismantling the installation (at the end of its service life) or even in the event of a major modification to it, for example, to carry out extensive maintenance work affecting 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 that allows it to be removed later (i.e., after installation to seal the shaft) is due to the fact that it is a slab resulting from the assembly of two half-slabs (or even more than two half-slabs in a variant not shown), thus becoming a single, continuous slab that can be slid out of the shaft along the aforementioned axial / longitudinal X direction in order to clear the shaft opening.It should be noted that this axial / longitudinal displacement / sliding of the slab follows the reverse slip path of that related to the placement of the slab during the construction of the installation. The same is true for a single slab homogeneous in its construction.

[0080] It should be noted that during the sliding phase of half-slab D2, the construction of reactor building B2 is not yet entirely complete, and various small pieces of equipment (e.g., ventilation, wiring, testing equipment, etc.) still need to be installed. Furthermore, during this sliding phase of half-slab D2, the construction of the auxiliary buildings on half-slab D1 can continue if it is not yet finished. Similarly, after the sliding of half-slab D2, the construction of the auxiliary buildings on half-slab D2 can continue if it is not yet finished. It should be noted, however, in general, that the sliding of the half-slabs can be carried out at a variable stage of completion of the construction of the buildings on the half-slabs. Depending on the requirements and the approach taken, One approach is to construct as many buildings as possible on each half-slab (maximizing building prefabrication), while simultaneously maximizing fabrication within the reactor building (and containment structure) before sliding the corresponding half-slab into position. Alternatively, the buildings are partially constructed on each half-slab (at an appropriate intermediate stage of construction) while the major construction work on the reactor building (and containment structure) is carried out. The corresponding half-slab is then slid into position over the relevant section of the wellhead opening. The finishing work on the reactor building (and containment structure) is then completed, including the introduction of any missing equipment and materials through the maintenance access shafts in the half-slabs.

[0081] Furthermore, during the sliding phase of the two half-slabs, the construction of the turbine building 30 can continue and be completed once the sliding phase is finished ([Fig. 7]). Alternatively, the construction of the turbine building 30 can be completed before any sliding and therefore independently of any constraints.

[0082] The construction of the underground nuclear installation illustrated in [Fig.7] is largely complete, with only some finishing work remaining to be carried out.

[0083] As briefly mentioned above, the protective slab joining the two half-slabs DI and D2 can be placed in vertical support directly on the embankment(s) 16 of [Fig. 1] located at the outer periphery of the shaft, so that the weight of the slab does not rest directly on the upper edges, also called heads, of the vertical walls of the shaft, in particular the vertical walls 18a, 18b. Thus, the protective slab 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(s) and dampened by the earth and will therefore not be transmitted to the buried structure via the vertical walls of the shaft.

[0084] It should be noted, however, that the mechanical independence mentioned above does not mean that the slab and the vertical walls of the shaft, in particular 18a and 18b, cannot be in indirect mechanical contact with each other, as described below with reference to [Fig. 7C], or in direct mechanical contact with each other as is the case in Figures 7E and 7G described below. For the sake of simplicity, the buildings constructed on the half-slabs are not shown in Figures 7C-7G.

[0085] Figure 7C is a partial enlarged view of the area between a half-slab (e.g., D2) of the slab and the head 18al of the wall 18a, and shows the presence, between these two elements, of a bellows device 42 with a thick rubber wave of a known type, arranged substantially vertically. This device 42 rests on the entire perimeter of the heads of the vertical walls of the well. This perimeter is rectangular in shape. However, it can take a square, circular, etc., shape, depending on the geometry of the well's cross-section. The device 42 is, for example, connected to the wall heads, as well as to the lower surface Si2 of the slab (in an area that corresponds geometrically to the wall heads, specifically 18a, 18b, directly above them) by respective fixing elements fl, f2. In this embodiment, the edges of the bellows device 42 are fixed all around, for example, by stainless steel strips that compress them, these stainless steel strips being themselves fixed in the concrete by spaced anchor bolts.The bellows device 42 ensures a seal between the two spaces el and e2 that it separates: space el corresponds to the usable 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(s) 16 (not visible on [Fig.7C]).

[0086] It should be noted that with such an arrangement, the intermediate space formed by the technical gallery G, which will be described below with reference to [Fig. 8], can be isolated from ventilation by means of this rubber wall 22. A slight negative pressure (-5 or -10 mm CE) can thus be created thanks to this specific ventilation function. The negative pressures can be identical to those that will be in place in the reactor building outside the containment structure, thus ensuring continuous confinement for the spaces subject to containment under the slab.

[0087] An alternative embodiment is shown in [Fig. 7D] along a vertical cross-section perpendicular to the cross-section of [Fig. 7C] and which shows the vertical walls 18c, 18d bordering the shaft that are adjacent to the perpendicular walls 18a, 18b of Figures 1 and 7C. [Fig. 7D] represents the protective half-slab DI which is connected to the vertical walls bordering the shaft, in particular 18c, 18d, by means of a flexible joint device 42'. In this embodiment, the protective half-slab DI is vertically supported directly on one or more supports 44 arranged externally relative to the vertical walls, in particular 18c, 18d, bordering the interior of the shaft. More specifically, the protective half-slab DI has one or more peripheral edges R which together form a skirt extending vertically from the outer periphery of the lower surface Sil away from it. As shown in [Fig.[7D], the RI skirt rests on one or more supports 44 such as stringers which are supported by piles or footings 46 anchored vertically in the ground at a distance from the vertical walls bordering the inside of the shaft.

[0088] According to another embodiment shown in [Fig.7E], the protective half-slab DI is supported vertically directly on the vertical wall(s) (e.g., 18c, 18d) bordering the shaft, by means of a skirt RI similar to that of [Fig.7D].

[0089] As illustrated in Figures 7D and 7E, the respective walls facing the building Reactor B1 and the well can be contiguous or adjacent.

[0090] As shown in Figures 7D and 7E, the respective walls of the reactor building and the well are close to each other, with the smallest possible space between them, but without being mechanically connected. The embodiment variants of Figures 7D and 7E described above illustrate such an arrangement with the walls of reactor building B1 (the same applies to the walls of reactor building B2), here wall 20, and the walls of the well opposite, here wall 18d. The same applies to the walls not shown in Figures 7D and 7E but shown, for example, in Figures 1 and 2, namely wall 26 of reactor building B1 and the opposite wall 18b of the well (for building B2, this is wall 24 opposite wall 18a of the well). The longitudinal wall 27 bordering externally the area adjacent to the reactor buildings is also close to the wall opposite 18c of the shaft.

[0091] According to an alternative embodiment of the installations shown in Figures 7D and 7E, the walls of the reactor building are horizontally spaced from the vertical walls bordering the well so as to provide a gap between the respective facing walls. These facing walls, spaced apart from each other, are not mechanically connected to each other in order to avoid creating a mechanical link through which mechanical forces / vibrations could be transmitted.

[0092] Figures 7F and 7G illustrate such arrangements in which the respective walls of the reactor building Bl' (wall 20' and the two other perpendicular adjacent walls not visible in Figures 7F and 7G) and the walls facing the shaft (wall 18d and the two other perpendicular adjacent walls 18a and 18b, not visible in Figures 7F and 7G) are horizontally separated from each other as explained above. The longitudinal wall 27' bordering the outer edge of the shaft area adjacent to the reactor buildings is also facing the shaft wall 18c. In the examples shown in Figures 7F and 7G, the dimensions of the space between the facing walls have been deliberately exaggerated for the purposes of explanation. This space may be useful for technical inspection by maintenance personnel or even by cameras. In practice, this space can have a width of approximately 1.5 to 2m.The vertical supports of the protective half-slab in figures 7F and 7F correspond respectively to the supports in figures 7D and 7E.

[0093] Everything described previously in relation to Figures 7C-7G also applies to the other half-slab D2 and the relevant reactor building B2, B2', as well as to a single slab. The same applies to a configuration with more than two half-slabs. Figures 8 to 12 illustrate various underground nuclear facilities that have been constructed using the method described above.

[0094] Figure 8 illustrates the underground nuclear installation 10 comprising the two reactor buildings B1 and B2 of Figures 2 to 7 in a longitudinal vertical cross-sectional view (X-axis). For the sake of simplicity, the buildings constructed on the two half-slabs and described above are not shown here.

[0095] Each reactor building B1, B2 is closed at its upper part by a roof 31, 33, and the protective slab formed by the two half-slabs D1, D2 joined together at their junction J defines, with the two facing roofs, a technical gallery G. Each roof is a reinforced concrete slab of simple structure, meaning that it has sufficient thickness of reinforced concrete to ensure its resistance under all the stresses to which it may be subjected. This slab may alternatively be a composite steel-concrete slab.

[0096] Each reactor building B1, B2 encloses, with its vertical walls and roof, the corresponding nuclear reactor containment structure E1, E2, which here has a circular shape and is rounded at its upper part to withstand internal pressure in the event of an explosion. The protective slab formed by the two half-slabs D1, D2 rests, for example, by its vertical peripheral edge forming a skirt R on the walls bordering the shaft (e.g., 18a, 18b in [Fig. 8]). Alternatively, one of the configurations in Figures 7C-7G can be applied here.

[0097] The technical gallery G serves in particular to connect a lower part of the installation housed in the shaft (reactor building containing a reactor containment) and an upper part located on the protective half-slabs (auxiliary buildings, in particular those defined above) and serves in particular to connect the prefabricated networks of these two parts by allowing the passage of various links (cables, pipes, etc.) between these parts. In other words, the technical gallery G forms a vertical intermediate space ensuring the movement of people and the routing of cables, conduits and other equipment or any other component serving as a link between the two upper and lower parts defined above. The [Fig.Figure 3B, already partially described above, illustrates a possible configuration of the technical gallery G between an upper slab or half-slab Di (the auxiliary building(s) are not shown for simplicity in this presentation) and the lower roof T of the corresponding reactor building. In this figure, the openings D1 and Di2 in the thickness of the slab or half-slab Di serve for the selective passage of piping (D1) and electrical cables (Di2) and other connecting elements not shown (for example, through other through-openings not shown) between the auxiliary building(s) built on the slab or half-slab Di and the technical gallery G, and then between the latter and the reactor building below through corresponding openings O1 and O12 in the roof T of the building. Note, for example, that the electrical cables passing through the opening Di2 are... connected to a UT (treatment unit) collector unit, and other electrical cables run from this unit through the Oi2 opening in the roof for connection to equipment in the reactor building. Generally, the connections are made in a sector-by-sector manner, with separate (and for example, staggered) connections between the area above the slab or half-slab and the technical gallery, on the one hand, and connections between the area below the slab or half-slab and the technical gallery, on the other hand, as opposed to making the connections to link the area above to the area below simultaneously after these areas have been completed.It should be noted in particular that some of the connections for equipment housed in auxiliary buildings can be put in place while the buildings are being constructed on the slab or half-slab, before it is slid over the shaft, which also provides an undeniable time saving.

[0098] Advantageously, one benefit of the technical gallery is that it provides flexibility in the construction method by allowing assembly in several segments rather than a single assembly at the end (when the upper and lower zones are more or less fixed in their construction), with the added risk of causing delays if modifications are required to the various connections. In the event of modifications, the advantage of having a three-part segmentation (technical gallery, section above the technical gallery, and section below the technical gallery) is that it avoids having to redo the entire circuit (pipes, cables, etc.) since only the relevant section of the circuit can be modified (e.g., the section of the electrical wiring between the top of the slab and the technical gallery).

[0099] The nuclear installation has a high compactness and a limited ground footprint by arranging the nuclear installation according to several vertically superimposed levels and the functional intermediate space G complements this arrangement and further improves the compactness of the installation.

[0100] In the present embodiment, the nuclear reactor is of the PWR type, i.e., it uses pressurized water reactor technology. Such a reactor may include, primarily within the sealed containment structure, in a known manner, a primary circuit comprising: - a reactor vessel containing, in particular, the fuel elements and control rods, -one or more steam generators, -Primary pumps ensuring a closed-loop circulation of the primary fluid which flows through the fuel elements of the reactor vessel, recovering the thermal energy released by the nuclear reaction and circulating in the primary section Steam generators, where heat exchange takes place between the primary fluid and the secondary section of the steam generators to produce steam at the top of said steam generators. The steam thus produced is discharged from the steam generators through the steam piping of a secondary circuit which passes through the walls of the containment structure and carries it to one or more turbines outside the well to rotate them and thus produce, at the output of the alternator, electrical current distributed on a high-voltage electrical grid. The primary circuit also includes a pressurizer which has, among other things, a function of regulating the primary circuit.

[0101] Furthermore, regardless 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 power outputs adapted to the SMR model (Small Modular Reactor in Anglo-Saxon terminology). By way of example, the power outputs can range from 50 MWe to N x 50 MWe, 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 power outputs can range from 100 MWe to N x 100 MWe, with N greater than 1 and, for example, N can take values ​​between 1 and 8, or even greater than 8.

[0102] Each nuclear reactor containment El, E2 rests on the foundation slab 12c which may have, in its central part located under the reactor vessel, a recess or excavation 12cl, 12c2 (imprint of a volume) directed downwards and which may be excavated to possibly install a device to deal with any accident occurring around, on or in the vessel.

[0103] Each reactor building Bl, B2 may also include a horizontal intermediate slab dil, di2 (shown in [Fig. 3] already described) which is integral with the vertical walls of the building, namely walls 20, 22, 26, 28 for building Bl and walls 20, 22, 24, 28 for building B2. The intermediate slab dil, di2 extends horizontally from these walls so as to radially surround the nuclear reactor containment E1, E2, without, however, coming into contact with it. This slab is positioned at a level or elevation along the vertical of the building which represents an intermediate position between the foundation slab 12c and the roof 31, 33. This intermediate slab is arranged parallel to, above, and at a distance from the foundation slab 12c.

[0104] Everything that has just been explained concerning this embodiment and in particular the arrangement of the installation with the technical gallery also applies to the modes described above or below.

[0105] As shown in [Fig. 9], another buried nuclear installation 10' comprises a single reactor building B in vertical section along a direction Y which is perpendicular to the longitudinal direction (axis X) along which the protective slab The single D slab was slid from its construction area, located next to the shaft in which reactor building B is built and housed, to above this shaft to seal its opening. For the sake of simplicity, the buildings constructed on the slab, which are analogous to those described above and built on the two half-slabs, are not shown here, but they are all built on the same slab (as an alternative, the buildings built on slab D may differ, at least in part, from the buildings built on the two half-slabs). It should be noted, however, that slab D can alternatively be slid along the Y direction of [Fig. 9].

[0106] In [Fig. 9], the protective slab D against external aggressions rests directly, via its dropped peripheral edge R, on the heads of the diaphragm walls bordering the shaft, of which only walls 18c and 18d are shown. Each of these walls has a peripheral rim forming an external shoulder, here 18cl and 18dl. This arrangement can also be applied to any of the embodiments already described. Alternatively, one of the configurations in Figures 7C-7G can be applied here.

[0107] As already described with reference to [Fig. 8], reactor building B, with its vertical walls, here 20' and 22' (the two other perpendicular walls are not shown in this view), and its roof 35, encloses the nuclear reactor containment E, which is, for example, analogous to any of the nuclear reactor containment structures E1, E2. A service gallery G' is located between slab D and roof 35, as in [Fig. 8]. Access to the service gallery G' is via stairs (not visible in [Fig. 9]) located in area Z of the shaft adjacent to the area housing the reactor building. Although not visible in [Fig. 8], access to the service gallery G is also possible via stairs located in the area of ​​the shaft adjacent to the reactor building(s).

[0108] The nuclear reactor containment E rests on the foundation slab 12c' which may have, in a manner not shown in [Fig.9], in its central part located under the reactor vessel, a recess or excavation (imprint of a volume) directed downwards and which may be excavated to possibly install a device to deal with any accident occurring around, on or in the vessel.

[0109] The reactor building B may also include a horizontal intermediate slab di (analogous to one of the slabs dil, di2 of [Fig. 8]) which is integral with the vertical walls of the building, namely walls 20', 22' and other adjacent walls not shown. The intermediate slab di extends horizontally from these walls so as to radially surround the nuclear reactor containment E, without, however, coming into contact with it. This slab is positioned at a level or elevation along the vertical of the building which represents an intermediate position between the foundation slab 12c' and the roof 35. This intermediate slab is arranged parallel to the foundation slab 12c', above and at a distance from it.

[0110] As shown in [Fig. 9], a maintenance area or shaft Z is provided in shaft 12' (adjacent area) located next to reactor building B, between the vertical wall 22' of the building and the parallel wall 27' of the installation, which is opposite wall 18d of shaft 12'. An opening O in the lower part of wall 22' connects area Z to the interior of the reactor building. This opening O (called a buffer) is permanently closed during reactor operation (by means of a sliding or hinged door, not shown) and opened only to remove or bring in equipment. The area and the opening have the same characteristics as openings 01.1 and 02.1 in [Fig. 2] and compartments C1 and C2 in Figures 3 and 4.Opposite this opening O, another opening O' (called a buffer) is provided in the containment E, which is permanently closed during reactor operation (by means of a sliding or pivoting door not shown). A hopper t is provided in the thickness of the slab D at the level of zone Z and plays the same role as the hoppers T1 and T2 of figures 3 and 4.

[0111] As shown in [Fig. 10], another underground nuclear installation 100 comprises a single reactor building B in vertical section along the longitudinal direction (X-axis) in which the single protective slab D was slid from its construction area located next to the shaft in which the reactor building B is constructed and housed, up to above this shaft to seal its opening. For the sake of simplicity, buildings constructed on the slab and analogous to those described above and constructed on the two half-slabs are not shown here. It should be noted, however, that the slab D can alternatively be slid in a direction perpendicular to the longitudinal direction (X-axis).

[0112] As in the configuration of [Fig. 9], reactor building B comprises walls (e.g., 124, 126), here set apart from the shaft walls (e.g., 18a, 18b), and a roof 135 which together enclose a nuclear reactor containment E3, surrounded by an intermediate slab di3 fixed on one side to wall 124. Containment E3, like the entire building B, rests on the foundation slab 112c and may also include a recess 112cl. A technical gallery G3 is provided between slab D and roof 135, as in Figures 8 and 9.

[0113] Alternatively, one of the configurations in Figures 7C-7G can be applied here.

[0114] Installation 100 of [Fig. 10] also includes a known type of spent nuclear fuel pool (PECN), which is supported by the foundation slab 112c and on which the intermediate slab di3 also rests. Here, the PECN pool is located inside the reactor building.

[0115] However, in an unshown variant, the pool is located outside the reactor building, for example in an area of ​​the well that is adjacent to the area housing the building, such as the area which includes zone Z of [Fig.9].

[0116] According to an unshown variant of the installation in [Fig. 8], such a nuclear fuel storage pool is located in an area of ​​the shaft adjacent to the shaft area housing the two reactor buildings. More specifically, the nuclear fuel storage pool can be located between the two compartments Cl and C2 of Figures 3 and 4, partially encroaching on the area occupied by each of them, on either side of wall 32.

[0117] Figures 11 and 12 illustrate a method of constructing an underground nuclear installation 200 according to another embodiment where the shaft 212 dug in the ground has a horizontal section of circular shape (shaft of general cylindrical shape), as well as the reactor building B' which is housed therein and the protective slab 230 also has a generally circular shape (in horizontal section) to fit the general shape of the shaft opening.

[0118] Fig. 11 is a plan view of the installation 200 under construction following A horizontal section shows, on the left, slab 230 under construction in construction zone Zed', and on the right, shaft 212 (generally cylindrical in shape) with a circular cross-section and a diaphragm wall 218 with an annular cross-section bordering the inside of the shaft. Reactor building B' is also circular and contains a nuclear reactor containment structure E' as described above. These circular and annular shapes offer the advantage of better resistance to external pressures (from the earth in the case of the shaft) and internal overpressures (from the containment or the reactor building). In particular, the annular diaphragm wall 218 acts as a ring compressed by the earth pressure directed radially relative to the diaphragm wall.The diaphragm wall 218 is self-supporting, thus reducing the number of tiebacks anchoring the wall to the ground, which notably simplifies design and construction. It should be noted that the wall 218 generally has a cylindrical crown shape in three-dimensional view, and the internal space of the shaft, which is bordered by the wall 218, occupies a cylindrical shape.

[0119] In this embodiment, a nuclear fuel storage pool PECN' is arranged inside the reactor building B' but offset from the containment E', as illustrated in [Fig. 11]. The installation 200 also includes, inside the reactor building B', a zone Z' forming a handling shaft which is also offset from the containment E', as well as a zone Z”, also offset, in which a staircase is provided to connect the different vertical levels of the shaft 212, from the base 212c to the upper protective slab.

[0120] As with the embodiment described with reference to Figures 1 to 7, the protective slab 230 is constructed on Faire Zed', with auxiliary buildings on top (at least partially constructed on the slab before its sliding), while the reactor building B' is being constructed in the shaft. Everything described above with reference to Figures 2 to 7 concerning the sequencing in time of the different construction phases (in particular, the order and duration of the phases relative to each other) of the half-slabs and the reactor building applies here to slab 230 and reactor building B' and will not be repeated.

[0121] In Figures 11 and 12, the Zed' area includes a Ptf platform, like the Ptfl platform of [Fig.2] (if the soil condition requires it), and two guide / slip stringers Ll', L2' mounted on p piles anchored in the ground (again, depending on the soil condition), analogous to the stringers Ll and L2 of Figures 2 to 7 and their anchor piles.

[0122] On the left side of [Fig. 1 1] (top view), several pieces of equipment / buildings b3.1, b3.2, b3.3 were constructed (more or less completely, according to degrees of completion that vary depending on the needs and the approach followed, as explained above) on slab 230 during the construction of the reactor building in the shaft. For example, buildings b3.1, b3.2, b3.3 are, respectively, an auxiliary building providing cooling functions, an auxiliary building providing ventilation functions, and a control room for the installation. Other pieces of equipment / buildings can, of course, be constructed on the slab in place of these buildings or in addition to them.An opening T similar to the openings T1 and T2 of the two half-slabs in Figures 3, 4 and 6 is also provided in the thickness of slab 230 to fulfill the same function and in particular to serve as a hopper at the handling area Z' of shaft 212 (right part on [Fig.1 1]), when the slab is put in place above the shaft.

[0123] Figure 11 illustrates, in a top view (horizontal section), a possible general shape for the protective slab 230 that is to cover the upper opening 212b of the shaft 212 (Figures 11 and 12). As shown in Figure 11, the slab 230 has a generally circular shape with dimensions corresponding to those of the opening 212b to be covered. The slab 230 has, at two diametrically opposed areas of its circumference, two external radial extensions 230a and 230b, here symmetrical to each other, each originating from two diametrically opposed portions 230c, 230d of the circular circumference of the slab and each terminating in a flat face (cut or beveled edge) 230a and 230b. The two flat faces 230a. 1 and 230b. 1 are parallel to each other and each forms a lateral peripheral edge which is intended to cooperate with the guiding stringer located below ([Fig.l 1]) to move the protective slab 230 by sliding, from its . The construction zone Zed' is moved to a position above the shaft opening ([Fig. 12]). The slab 230 displacement system is essentially identical to that described with reference to [Fig. 5] and includes, for example, similar elements: two jacks VI, two blocks Ml, and two traction cables Cal passing lengthwise through the external radial extensions 230a and 230b and attached to the faces of these extensions opposite the shaft. The sliding action takes place over a distance greater than the slab's external diameter, but which, however, does not exceed several slab diameters to facilitate slab handling.

[0124] The left part of [Fig. 12] illustrates the slab 230 constructed with the auxiliary equipment / buildings above it, before sliding and the right part of this figure illustrates this same slab 230 with its buildings, after sliding, in the position of sealing the opening 212b of the shaft, above the roof 235 of the reactor building B'.

[0125] In general, figures 11 and 12 include most of the elements described with reference to figures 8 to 10, with different references which will not be described again here, namely in particular the foundation slab 212c, the intermediate slab di4, the roof 235, the technical gallery G4 between the roof 235 and the slab 230. In the present mode, the gallery occupies a circular space in top view and not a rectangular one as in the previous modes but it retains the same functionalities and advantages as before in another form.

[0126] In the present mode, the protective slab 230 is shown resting directly on the wall 218, which is separated from the wall 220 of the reactor building B'. However, the various arrangements described with reference to Figures 7B to 7F are also applicable here.

[0127] According to an alternative embodiment not shown, the reactor building can adopt a general shape of square cross-section (horizontal) fitting inside the internal space of circular cross-section (horizontal) of the well (bounded by the annular wall 218).

[0128] According to another embodiment not shown, the shaft retains a circular (horizontal) cross-section which is divided into two distinct compartments, each forming a surface occupying a semicircle, and a reactor building with a circular, square or rectangular (horizontal) cross-section occupies each of the two semicircles. This variant can be adapted to low-power technologies, for example on the order of 1000W each, to avoid a diameter that would be too large for the upper protective slab if the reactors were larger.

[0129] According to yet another embodiment not shown, the shaft, having a rectangular or square shape, is configured to house a single large reactor building, and two or more half-slabs are used to seal the shaft in order to reduce the weight of the load to be ripped, which would otherwise be much higher. with a single slab.

[0130] According to other embodiments, several buried nuclear installations can adopt different configurations with several shafts which are arranged for example in a general shape of square, rectangle or circle.

[0131] Thus, for example, [Fig. 13] represents two parallel lines 300, 302 for the construction of underground nuclear facilities, with two facilities 304, 306 (for line 300) and 308, 310 (for line 302) constructed on each line. In this configuration, facilities 304 and 308 are constructed in parallel along the two parallel construction lines 300, 302. The same applies to facilities 306 and 310. The protective slabs 304a, 308a, which are constructed on preparation areas or zones located next to the shafts concerned, are slid along parallel lines and in the same direction until they respectively seal the shafts 304b, 308b. The sliding of the slabs 306a, 310a which are built on areas or preparation areas located next to the shafts concerned until they respectively plug the shafts 306b, 310b is carried out in the opposite direction.In this configuration, the shafts are, for example, circular and the slabs square. The shafts could, however, be square. Alternatively, the slabs could be circular with circular shafts. The number of construction lines for buried nuclear facilities can vary, however, and, for example, be reduced to one line or be more than two lines depending on the requirements.

[0132] Figure 14 illustrates a configuration in which circular slabs are slid into circular shafts in a general cross or diagonal arrangement. The protective slabs 404a, 406a, 408a, and 410a, which are constructed on preparation areas or zones adjacent to the shafts in question, are slid along the intersecting axes 400 and 402, which represent the construction lines, until they seal the shafts 404b, 406b, 408b, and 410b, respectively. The protective slabs 404a and 406a (and 408a and 410a, respectively) are slid in opposite directions along the same construction line. Alternatively, the slabs and shafts may be square.

[0133] Depending on the terrain morphology and its occupation during the construction phases, the configurations described above may prove appropriate. The method of constructing an underground nuclear installation involving one or more slabs built next to one or more shafts (possibly with auxiliary buildings constructed on top while the slab(s) are still next to the shaft(s)) while one or more reactor buildings are constructed in the adjacent shaft(s) allows for maximum adaptability according to the terrain morphology and its occupation during the construction phases.

[0134] It should be noted that other alternative configurations can be envisaged by making vary the construction line arrangements and the shapes of the protective slabs and shafts, as well as the number of slabs and shafts.

[0135] In general, the parallel construction of buried nuclear facilities is very advantageous in terms of planning, especially when there is a multiplication of wells with the aim of increasing power.

[0136] It should be noted that one or more turbine buildings can be placed between the construction lines, whether they are parallel to each other ([Fig. 13]) or crossed ([Fig. 14]).

[0137] Figure 15 illustrates an alternative configuration to that of Figures 2, 3, 4, 6, and 7, in which a rectangular shaft 500 (analogous to shaft 12) is arranged along a construction line 502 aligned with the longitudinal axis X mentioned in the preceding figures. In this configuration, the shaft 500 is intended to house two reactor buildings such as reactor buildings B1 and B2 in the preceding figures. The protective half-slabs D1' and D2', for example, identical to half-slabs D1 and D2 (in particular those illustrated in Figure 3A), are each constructed on a preparation / construction area adjacent to the area of ​​the shaft opening that the slab is intended to cover, namely area 500a for half-slab D1' and area 500b for half-slab D2'.Thus, the sliding of each half-slab is carried out over a shorter distance compared to that over which half-slabs D1 and D2 are slid, since each half-slab D1', D2' only has to travel the distance separating it from the adjacent shaft plus the length of the shaft area to be covered. This represents a distance greater than the longitudinal dimension of a half-slab, but which can, for example, be less than twice that dimension. Everything concerning the description of the mode in Figures 2, 3, 4, 6, and 7 also applies here, with some adaptations related to the different positioning of the half-slabs.

[0138] The features and advantages mentioned above in relation to the method of constructing an underground nuclear installation involving one or more slabs built next to one or more shafts (with possibly on top of them auxiliary buildings built while the slab or slabs are still next to the shaft or shafts) while one or more reactor buildings are built in the adjacent shaft or shafts also apply to all the modes and variants described above (in particular those illustrated in Figures 13 to 15) and will not be repeated.

[0139] Generally, underground nuclear installations according to certain embodiments of the invention may comprise two or more reactor buildings, thus allowing for smaller reactor cores providing less power (e.g., 50 or 1000 MWe) than a larger, higher-power installation (e.g., 800 MWe, or even higher power outputs). For example, to provide 800 MWe of power, an underground nuclear installation according to the invention may be configured with four 200 MWe wells, each well capable of producing 2x100MWe or x200MWe.

[0140] The power modularity offered by these smaller installations is also accompanied by a simplification of installations and a reduced implementation cost compared to a larger power installation.

[0141] In general, regardless of the embodiment or variant described above, the construction method according to the invention makes it possible to significantly reduce the overall construction schedule of an underground nuclear facility during the construction phase that occurs after site preparation and before the cold and hot tests of the facility and the criticality tests. During this construction phase, different tasks or operations are carried out in parallel, resulting in considerable time savings.

[0142] In particular, the construction of one or more slabs or slab elements on a construction area adjacent to the well may begin while the well is in its excavation phase and / or subsequently during various civil engineering operations carried out for the construction of the well. Slab construction may continue during the construction of one or more reactor buildings in the well, or slab construction may begin only after the well is completed and thus begin almost simultaneously with the construction of one or more reactor buildings in the well. During the construction of one or more reactor buildings in the well, one or more pieces of equipment or auxiliary buildings are at least partially constructed on the slab or slabs or slab elements located next to the well.

[0143] The sliding of the slab(s) or slab elements above the well can take place after the largest equipment and components have been constructed or installed in the well, particularly in the reactor building(s) (in particular, the roof of the building(s) must have been installed). Once the slab(s) or slab elements are slid into the final well-sealing position, internal construction and various internal well fittings can continue, in particular by using the technical gallery constructed between the well-sealing slab(s) or slab elements and the roof of the reactor building(s) for the phased installation of the various connections (electrical cables, piping, etc.).) between the auxiliary buildings supported by the slab(s) or slab elements and the equipment and components of the reactor building(s), by installing connections between the auxiliary buildings and the technical gallery, on the one hand, and between this technical gallery and the equipment and components of the reactor building(s), on the other. The order in which these connection installation sequences are carried out may vary. The level of prefabrication can be increased, which will allow the installation of modules that will facilitate installation in the different areas. different zones, thus bringing about a considerable time saving in addition to the gains already obtained by the method and construction sequences described above.

[0144] It should be noted that the equipment or buildings arranged on the half-slabs, or on the slab if it is a single slab, may take other forms and perform other functions than those described above depending on the nuclear technology envisaged.

Claims

Claims

1. Method for constructing a buried nuclear installation on a site (10), the site comprising a shaft (12) dug into the ground (14, 16) so as to define a bottom (12a), at a given depth relative to the ground surface, and an opening (12b, 12bl, 12b2) located substantially at the level of the ground surface surrounding the shaft, characterized in that the method comprises the following construction phases: - the construction of at least one protective slab (Dl, D2; D; 230) against external aggressions on an area (Zed) of the ground surface, called the slab construction zone, which is arranged next to the opening (12b, 12bl, 12b2) of the shaft, - the construction of at least one reactor building (Bl, B2) inside the shaft (12), the construction phases of said at least one protective slab (Dl, D2; D ; 230) and said at least one reactor building (Bl, B2) being carried out in parallel.

2. Method of constructing a buried nuclear installation according to claim 1, characterized in that the method comprises a phase of constructing one or more equipment or buildings (b 1.1, b 1.2, b2.1, b2.2; b3.1, b3.2, b3.3) on said at least one protective slab (Dl, D2; D; 230), the phase of constructing equipment(s) or building(s) starting during the phase of constructing said at least one reactor building (Bl, B2) and while said at least one protective slab (Dl, D2; D; 230) is on the slab construction zone (Zed).

3. Method of constructing a buried nuclear installation according to the preceding claim, characterized in that the equipment or buildings (b 1.1, b 1.2, b2.1, b2.2; b3.1, b3.2, b3.3) constructed on said at least one protective slab (D1, D2; D; 230), are configured to provide support functions for the operation of the nuclear reactor and the entire nuclear installation.

4. Method of constructing a buried nuclear installation according to claim 2 or 3, characterized in that the equipment or buildings constructed on said at least one protective slab (D1, D2; D; 230) comprise at least one of the following elements: a nuclear installation control room (b2.2; b3.3), a building providing ventilation functions (b1.2; b3.2), a building providing cooling functions (bl.l; b3.1), 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 (b2.1).

5. Method of constructing a buried nuclear installation according to one of the preceding claims, characterized in that the construction phase of said at least one reactor building (B1, B2) comprises the installation of at least one nuclear reactor enclosure (El, E2; E; E3; E') and / or at least one nuclear fuel storage pool (PECN; PECN').

6. Method of constructing a buried nuclear installation according to the preceding claim, characterized in that the construction phase of said at least one reactor building (B1, B2; B; B3; B') comprises the construction, on the one hand, of a wall or several walls (20, 22, 24, 26, 28; 20', 22'; 124, 126; 220) surrounding said at least one nuclear reactor enclosure (El, E2; E; E3; E') and / or said at least one nuclear fuel storage pool (PECN; PECN') and, on the other hand, of a roof (31, 33; 35; 135; 235) covering the wall(s) so as to enclose, inside said at least one reactor building, said at least one nuclear reactor enclosure and / or said at least one nuclear fuel storage pool.

7. Method of constructing a buried nuclear installation according to one of the preceding claims, characterized in that the construction method comprises a phase of shifting said at least one protective slab (Dl, D2; D; 230), from the slab construction zone (Zed) to the right of the opening (12b, 12b 1, 12b2) of the shaft, so that said at least one protective slab (Dl, D2; D; 230) closes the shaft by being arranged above said at least one reactor building (Bl, B2; B; B3; B') at the end of shifting.

8. Method of constructing a buried nuclear installation according to the preceding claim, characterized in that the construction method comprises, after the phase of shifting said at least one protective slab (D1, D2; D; 230), a phase of fitting out an intermediate space, called a technical gallery, between said at least one protective slab and said at least one reactor building (B1, B2; B; B3 ;B').

9. Method of constructing a buried nuclear installation according to claim 8 or 9, characterized in that the construction method comprises the phase of constructing a single slab (D; 230) or two half-slabs (Dl, D2) on the slab construction zone which are slid one after the other up to the right of the opening (12b, 12bl, 12b2) of the well, then assembled with each other so as to seal the well at the end of slid- ing.

10. Method of constructing a buried nuclear installation according to one of claims 7 to 9, characterized in that the phase of shifting of said at least one protective slab (Dl, D2; D; 230) takes place at the end of the construction phase of said at least one reactor building (Bl, B2; B; B3; B').

11. Method of constructing a buried nuclear installation according to claim 6 and according to one of claims 7 to 10, characterized in that the phase of sliding said at least one protective slab (Dl, D2; D; 230) takes place after the installation of said at least one nuclear reactor enclosure (El, E2; E; E3; E') and / or said at least one nuclear fuel storage pool (PECN; PECN') and the construction of the wall(s) and the roof of said at least one reactor building (Bl, B2; B; B3; B').

12. Method of constructing a buried nuclear installation according to one of claims 7 to 11, characterized in that said at least one protective slab (Dl, D2; D; 230) is placed in line with the opening (12b, 12bl, 12b2) of the well so as to be able to be removed subsequently in the event of modification or dismantling of the nuclear installation.

13. Method of constructing a buried nuclear installation according to one of claims 2 to 4 and according to one of claims 7 to 12, characterized in that, when the shifting phase is completed, the phase of construction of equipment(s) or building(s) (b 1.1, b 1.2, b2.1, b2.2; b3.1, b3.2, b3.3) continues on said at least one shifted protective slab (D1, D2; D; 230).

14. Method of constructing a buried nuclear installation according to one of claims 7 to 13, characterized in that, when the shifting phase is completed, the construction phase of said at least one reactor building (B1, B2; B; B3; B') continues.

15. Method of constructing a buried nuclear installation according to one of the preceding claims, characterized in that, prior to the start of the construction phase of said at least one reactor building (B1, B2; B; B3; B'), the construction method comprises the production in the well (12) of one or more vertical walls (18a-d; 218) bordering the interior of the well.

16. Method of constructing a buried nuclear installation according to one of claims 7 to 12 and according to the preceding claim, characterized in that said at least one protective slab (D1, D2; D; 230) is shifted to the right of the opening of the well so as to come into vertical support: - directly on an embankment (16) arranged at the outer periphery of the well, a bellows device (42) being arranged vertically between said at least one protective slab (D1, D2; D; 230) 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 and / or - directly on one or more supports (44, 46) arranged externally relative to the vertical wall(s) (18a-d) bordering the interior of the well.

17. Method of constructing a buried nuclear installation according to one of the preceding claims, characterized in that the vertical shaft (12; 12'; 112; 212) has a generally rectangular, square or circular shape according to a view taken in a horizontal plane.

18. Method of constructing a buried nuclear installation according to one of the preceding claims, characterized in that the construction method comprises a phase of constructing a turbine building (30) on an area (Zcbt) of the ground surface surrounding the well, called the turbine building construction area.