Core catcher housing and water supply valve insert for same

Abstract

The invention relates to core catchers, and more particularly to sacrificial packing for receiving and distributing nuclear reactor core melt. The technical result of the claimed invention is that of increasing the reliability of a core catcher by ensuring that cooling water is fed to the corium (core melt) inside the housing of the core catcher at a given calculated time after the moment when the corium enters the core catcher housing. This technical result is achieved in that the thermal shield of the core catcher housing is provided with an insert which provides for the protection of a water supply valve against the mechanical and thermal effects of corium, and which also makes it possible to set a calculated time at which water is supplied into the core catcher housing. The use of the claimed insert for a water supply valve (4) makes it possible to ensure that cooling water is fed into the core catcher housing at a given time determined by calculations.

Description

[0001] MELT LOCALIZATION DEVICE HOUSING AND WATER SUPPLY VALVE INSERT FOR IT

[0002] Field of technology

[0003] The invention relates to melt localization devices (hereinafter referred to as MLD), in particular, to sacrificial fillers intended for receiving and distributing the melt of the active zone of a nuclear reactor.

[0004] The greatest radiation hazard is posed by accidents involving core meltdown, which can occur with multiple failures of core cooling systems.

[0005] In such accidents, the melt of the active zone - corium, melting the internal structures of the reactor and the reactor vessel, flows beyond its limits and, due to the residual heat remaining in it, can damage the integrity of the sealed shell of the nuclear power plant - the last barrier to the release of radioactive products into the environment.

[0006] To avoid this, it is necessary to localize the active zone melt (corium) leaking from the reactor vessel and ensure its continuous cooling until complete crystallization. This function is performed by a melt localization device, which prevents damage to the hermetic shell of the NPP and, thus, protects the population and the environment from radiation exposure during severe accidents at nuclear reactors.

[0007] The active zone melt enters the casing of the CLR and is distributed in it due to interaction with the filler, which is a sacrificial material consisting of a composition of steel and relatively light and low-melting oxides, which, in accordance with the claimed invention, are made in the form of elements arranged in plates installed on top of each other.

[0008] Corium consists of two main components: oxide (the main components of which are a mixture of uranium, zirconium, and iron oxides with a small amount of metals) and metallic (the main components of which are a mixture of iron, zirconium, and some amount of uranium, zirconium, and iron oxides).

[0009] One of the most important aspects of corium cooling is the start time of cooling water supply directly to the corium located in the core catcher vessel. Cooling water supply to the corium should be started after the corium inversion process is completed to eliminate the steam-zirconium reaction of water and melted in-reactor structures. Late start time of cooling water supply to the corium may lead to destruction of the core catcher equipment and damage to the integrity of the NPP sealed shell due to the effect of high temperatures from the corium.

[0010] The supply of cooling water to the corium located in the core catcher housing is carried out through special devices, for example, water supply valves (hereinafter referred to as WSFV), which provide the supply of cooling water to the melt located in the core catcher housing from the cooling water supply system or from the reactor shaft.

[0011] Prior art

[0012] A housing [1] of a ULR is known, containing external and internal metal walls, connected at the top and forming a vertical cylindrical part, a rounded part and a bottom recessed towards the center, thermal protection installed in the upper part of the housing on the inside of the internal wall, water supply valves installed in the upper part of said housing.

[0013] A known casing [2] of a ULR comprises external and internal metal walls connected at the top and forming a vertical cylindrical part, a rounded part and a bottom recessed towards the center, thermal protection installed in the upper part of the casing on the inside of the inner wall, and water supply valves installed in the upper part of the casing. A known casing [3] of a ULR comprises external and internal metal walls connected at the top and forming a vertical cylindrical part, a rounded part and a bottom recessed towards the center, thermal protection installed in the upper part of the casing on the inside of the inner wall, and water supply valves installed in the upper part of the casing.

[0014] A known housing [4] of a ULR contains external and internal metal walls connected at the top and forming a vertical cylindrical part, a rounded part and a bottom recessed towards the center, thermal protection installed in the upper part of the housing on the inside of the internal wall, and water supply valves installed in the upper part of the housing.

[0015] A known housing [5] of a ULR contains external and internal metal walls connected at the top and forming a vertical cylindrical part, a rounded part and a bottom recessed towards the center, thermal protection installed in the upper part of the housing on the inside of the internal wall, and water supply valves installed in the upper part of the housing.

[0016] A known housing [6] of a ULR contains external and internal metal walls connected at the top and forming a vertical cylindrical part, a rounded part and a bottom recessed towards the center, thermal protection installed in the upper part of the housing on the inside of the internal wall, and water supply valves installed in the upper part of the housing.

[0017] One disadvantage of the specified UL housings is the low reliability of the KPV installed in its walls, due to the absence of any mechanisms (structures) that protect the KPV from damage caused by mechanical impacts from the corium. Another disadvantage of the specified UL housings is the low accuracy of predicting the time of cooling water flow into the UL housing, due to the absence of mechanisms (elements) in the KPV design that allow pre-setting the required characteristics for the KPV opening time, which eliminates premature opening of the KPV or its blocking due to the impact of the corium.

[0018] Disclosure of invention

[0019] The technical result of the claimed invention consists in increasing the reliability of the melt localization device by ensuring a guaranteed supply of cooling water to the corium (melt) in the core catcher body within a time specified by calculations, which has passed since the corium entered the core catcher body.

[0020] The tasks that the claimed invention is aimed at solving are to ensure protection of the KPV from mechanical impacts from the corium, to prevent damage to the KPV and to eliminate the possibility of opening the KPV when corium passes from the guide device.

[0021] The set tasks are solved due to the fact that in the body of the melt localization device, comprising an outer shell (1) and an inner shell (2), forming a container in the form of a crucible, intended for receiving the melt, thermal protection (3), installed in the upper part of the body on the inside of the inner shell (2), water supply valves (4), installed in the upper part of the body, each of which comprises a horizontal section (5), installed through an opening (1a) in the outer shell (1), an opening (2a) in the inner shell (2), an opening (3a) in the thermal protection (3), and a vertical section (6), installed outside the outer shell (1), according to the invention, in the opening (3a) of the thermal protection (3) an insert is installed, comprising a first compartment (7), inside which a second compartment (8), at least one third compartment (9), a fourth compartment (10) are placed, wherein the third compartment (9) and the fourth compartment (10) are installed in such a way,that the fourth compartment (10) is connected to the second compartment (8) through the first opening (11), at least one third compartment (9) is connected to the fourth compartment (10) through at least one second opening (12), on the one hand the first compartment (7) and the second compartment (8) are connected by a first plate (13), in which a third opening (15) is made, intended for connecting the horizontal section (5) of the water supply valve (4) with the second compartment (8), on the other hand the first compartment (7), the second compartment (8), the third compartment (9) are connected by a second plate (14), in which at least one fourth opening (16) is made, intended for connecting the fourth compartment (9) with the inner space of the melt localization device housing.,

[0022] This design of the CCLR body with the CPV (4) installed using an insert allows for the supply of cooling water to the inner space of the CCLR body at a time specified by calculations from the start of corium supply to the CCLR body. Plates (13), (14) of the inserts protect the CPV (4) from mechanical and temperature effects, damage and allow for adjusting the time before the CPV (4) opening by changing their thicknesses and physical properties, and compartments (7), (8), (9), (10) of the insert, due to their mutual arrangement, provide for recirculation of the steam-gas mixture formed in the upper part of the CCLR body as a result of the interaction of the melt with the filler. In total, compartments (7), (8), (9), (10), plates (13), (14) and openings (11), (12), (16) allow for adjusting the time delay by changing the design of the insert without changing the design of the CPV.

[0023] Additionally, in the melt localization device body, according to the invention, the insert is installed in such a way that the first plate (13) adjoins the inner shell (2) of the melt localization device body, which makes it possible to correct the time delay by providing direct thermophysical interactions between the insert and the melt localization device body. Additionally, in the melt localization device body, according to the invention, the insert is installed in such a way that the first plate (13) is located with a gap from the inner shell (2) of the melt localization device body, which makes it possible to correct the time delay by providing indirect thermophysical interactions between the insert and the melt localization device body.

[0024] Additionally, in the body of the melt localization device, according to the invention, the first plate (13) of the insert is installed from the inner shell (2) of the body of the melt localization device through a gasket, which makes it possible to correct the time delay by providing direct or indirect thermophysical interactions between the insert and the body of the melt localization device.

[0025] According to the invention, the water supply valve insert of the melt localization device housing comprises a first compartment (7), inside which a second compartment (8), at least one third compartment (9), a fourth compartment (10) are arranged, wherein the third compartment (9) and the fourth compartment (10) are arranged in such a way that the fourth compartment (10) is connected to the second compartment (8) through the first opening (11), at least one third compartment (9) is connected to the fourth compartment (10) through at least one second opening (12), on the one hand the first compartment (7) and the second compartment (8) are connected by a first plate (13), in which a third opening (15) is made, intended for connecting the horizontal section (5) of the water supply valve (4) to the second compartment (8), on the other hand the first compartment (7), the second compartment (8), the third compartment (9) are connected by a second plate (14), in which at least one fourth opening (16) is made,designed to connect the fourth compartment (9) with the internal space of the melt localization device body,

[0026] This design of the water supply valve insert of the melt localization device body allows for the supply of cooling water to the internal space of the MLCR body at a time specified by calculations from the start of corium supply to the MLCR body. Plates (13), (14) of the insert protect the KPV (4) from mechanical and temperature effects, damage and allow for adjusting the time before the KPV (4) opening by changing their thicknesses and physical properties, and compartments (7), (8), (9), (10) of the insert, due to their mutual arrangement, ensure recirculation of the steam-gas mixture formed in the upper part of the MLCR body as a result of the interaction of the melt with the filler. In total, compartments (7), (8), (9), (10), plates (13), (14) and openings (11), (12), (16) allow for adjusting the time delay by changing the insert design without changing the KPV design.

[0027] Additionally, in the water supply valve insert of the melt localization device body, according to the invention, the cavities limited by the first plate (13), the second plate (14), the walls of the first compartment (7), the second compartment (8), the third compartment (9), the fourth compartment (10) of the water supply valve insert (4) are filled with heat-insulating and / or heat-conducting material (17), which makes it possible to establish the required heat-insulating and heat-conducting characteristics for the WSC insert (4) and, thereby, ensure the actuation of the WSC (4) at a time specified by calculations, elapsed from the moment of the corium entering the LMCR body.

[0028] Additionally, the insert of the water supply valve of the melt localization device body, according to the invention, additionally comprises a first group of rods (18) installed along the perimeter of the second compartment (8), wherein the first end (18a) of each rod (18) is connected to the outer surface (8a) of the wall of the second compartment (8), and the second end (186) is made with a gap (18b) from the inner surface (7a) of the wall of the first compartment (7), as well as a second group of rods (19) connecting the first plate (13) and the second plate (14). The presence of rods (18), (19) provides additional strength of the insert due to the adhesion of the heat-conducting and / or heat-insulating material to them.

[0029] Additionally, in the insert of the water supply valve of the body of the melt localization device, according to the invention, the second plate (14) is made in the form of an octagon with ribs (14a) connected to the second plate (14) by means of welded joints (20), and the ends (146) of the ribs (14a) protrude beyond the edges (14b) of the second plate (14), which makes it possible to increase the protection of the KPV (4) from mechanical impacts from the corium and prevent damage to the KPV (4).

[0030] Additionally, in the insert of the water supply valve of the body of the melt localization device, according to the invention, the second plate (14) is made in the form of a monolithic circle, which makes it possible to increase the protection of the KPV (4) from mechanical impacts from the corium and prevent damage to the KPV (4).

[0031] Additionally, in the insert of the water supply valve of the body of the melt localization device, according to the invention, the second plate (14) is made in the form of a circle with ribs (14g) obtained by milling, which makes it possible to increase the protection of the KPV (4) from mechanical impacts from the corium and prevent damage to the KPV (4).

[0032] Additionally, in the insert of the water supply valve of the body of the melt localization device, according to the invention, the second plate (14) has central grooves (14d) and peripheral grooves (14d), and is installed with said grooves with a stop in the end surfaces (76), (86) of the first compartment (7) and the second compartment (8), which makes it possible to ensure the manufacturability of the KPV insert due to the possibility of dismantling the plate (14), and also to increase the rigidity of the fastening of the plate (14).

[0033] Additionally, in the insert of the water supply valve of the body of the melt localization device, according to the invention, the first compartment (7), the second compartment (8), the third compartment (9), the fourth compartment (10) are made in the form of cylindrical tubes, which makes it possible to ensure the manufacturability of the insert due to the use of standard cylindrical tubes.

[0034] Additionally, in the water supply valve insert of the localization device body, according to the invention, a temperature sensor (21) is installed on the inner surface (14e) of the second plate (14), which makes it possible to monitor the thermal state of the KPV insert (4), to determine the moment of opening of the KPV (4) and the beginning of water flow through the KPV (4) (by a sharp decrease in temperature when the KPV is opened).

[0035] Additionally, in the insert of the water supply valve of the body of the melt localization device, according to the invention, the first compartment (7) and the second compartment (8) are connected by a first plate (13), in which at least one third opening (15) is made, the profile of which corresponds to the profile of the second compartment (8), and a second plate (14), in which at least one fourth opening (16) is made, the profile of which corresponds to the profile of the third compartment (9), which makes it possible to ensure the manufacturability of the insert due to the use of standard design elements.

[0036] Brief description of the drawings

[0037] Fig. 1 shows a sectional view of the housing of a localization device with water supply valves, made in accordance with the claimed invention.

[0038] Fig. 2 shows a fragment in section of the ULR housing with an installed water supply valve and insert. >

[0039] Fig. 3 shows the front view of the KPV insert.

[0040] Fig. 4 shows a side sectional view of a preferred embodiment of the KPV insert, made in accordance with the claimed invention.

[0041] Fig. 5 shows a side view of a preferred embodiment of the KPV insert, made in accordance with the claimed invention.

[0042] Fig. 6 (a) - (c) show the manufacturing options for the plate installed from the side of the internal space of the ULR housing.

[0043] Embodiments of the invention •

[0044] As shown in Figs. 1 - 6, the melt localization device body comprises an outer shell (1) and an inner shell (2) forming a container in the form of a crucible. Thermal protection (3) is installed in the upper part of the melt localization device body. Thermal protection (3) is installed on the inner side of the inner shell (2). Water supply valves (4) are also installed in the upper part of the melt localization device body. Each KPV (4) is designed in such a way that it comprises a horizontal section (5) and a vertical section (6). The horizontal section (5) passes through an opening (1a) made in the outer shell (1), an opening (2a) made in the inner shell (2) and an opening (3a) made in the thermal protection (3). The vertical section (6) of the KPV (4) is located outside the outer shell (1). An insert is installed in the opening (3a) of the thermal protection (3). The insert has a first compartment (7), inside of which a second compartment (8), at least one third compartment (9), and a fourth compartment (10) are located.The fourth section (10) is connected to the second section (8) through the first opening (11). The third section (9) is connected to the fourth section (10) through one second opening (12). On one side of the insert facing the inner casing (2), the first section (7) and the second section (8) are connected by a first plate (13). A third opening (15) is made in the plate (13) intended for connecting the horizontal section (5) of the water supply valve (4) with the second section (8). The KPV insert (4) can be installed with the plate (13) adjoining the inner casing (2) of the ULR housing, with a gap from the inner casing (2) and through a gasket. Various options for installing the plate (13) of the KPV insert (4) in relation to the inner shell (2) of the ULR body make it possible to establish a time delay by providing direct or indirect thermophysical interactions between the KPV insert (4) and the ULR body.On the other side of the insert KPV (4), facing the inner space of the LM catcher body, the first compartment (7), the second compartment (8) and the third compartment (9) are connected by a second plate (14), in which at least one fourth opening (16) is made, intended for connecting the fourth compartment (9) with the inner space of the LM catcher body. The insert KPV (4) of the LM catcher body comprises the first compartment (7). Inside the first compartment (7) there is a second compartment (8), as well as at least one third compartment (9), a fourth compartment (10). The fourth compartment (10) is connected to the second compartment (8) through the first opening (11). At least one third compartment (9) is connected to the fourth compartment (10) through at least one second opening (12).On one side, facing the inner shell (2), the first compartment (7) and the second compartment (8) are connected by a first plate (13), in which a third opening (15) is made, intended for connecting the horizontal section (5) of the CPV (4) with the second compartment (8). On the other side, facing the inner space of the LM catcher housing, the first compartment (7), the second compartment (8), the third compartment (9) are connected by a second plate (14), in which at least one fourth opening (16) is made, intended for connecting the fourth compartment (9) with the inner space of the LM catcher housing. The cavities between the first plate (13), the second plate (14), the first compartment (7), the second compartment (8), the third compartment (9), the fourth compartment (10) of the water supply valve (4) insert can be filled with heat-insulating and / or heat-conducting material (17).

[0045] Additionally, rods (18) can be installed in the KPV insert (4) along the perimeter of the second compartment (8) in such a way that the first end (18a) of each rod (18) is connected to the outer surface (8a) of the wall of the second compartment (8), and the second end (186) is made with a gap from the inner surface (7a) of the wall of the first compartment (7), as well as a second group of rods (19) connecting the first plate (13) and the second plate (14). In total, the presence of heat-insulating and / or heat-conducting material (17) and rods (18), (19) makes it possible to ensure the actuation of the KPV (4) at a time specified by calculations, elapsed from the moment of corium entry into the CCLR body, and to increase the strength of the KPV insert (4) due to the adhesion of the heat-conducting and / or heat-insulating material to them. The second plate (14) of the KPV insert (4) can be made in the form of an octagon with ribs (14a), which are connected to the said plate (14) by means of welded joints (20).The ribs (14a) are installed in such a way that their ends (146) protrude beyond the edges (14b).

[0046] In one embodiment of the invention, the plate (14) can be made in the form of a monolithic circle.

[0047] In another embodiment of the invention, the plate D (14) can be made in the form of a circle with ribs (14g). The ribs (14g) are made by milling the plate (14).

[0048] In the plate (14) grooves (14d) can be made that coincide with the end surfaces (76), (7v) of the first section (7) and the second section (8). In this case, the plate (14) is placed on the end surfaces (76), (7v) for the purpose of fixing it.

[0049] The first section (7), the second section (8), the third section (9), the fourth section (10) can be made in various forms, with the preferred option being the form of cylindrical tubes. The use of cylindrical tubes allows for high technological efficiency in the manufacture of sections (7), (8), (9), (10) due to the simplicity of manufacturing the said elements.

[0050] A temperature sensor (21) can be installed on the inner surface (14e) of the second plate (14). The temperature sensor (21) allows monitoring the thermal state of the KPV insert (4), determining the time of opening of the KPV (4) and the beginning of water flow through the KPV (4) (by a sharp decrease in temperature when opening the KPV).

[0051] The first section (7) and the second section (8) are connected by the first plate (13), in which an opening (15) is made, the profile of which corresponds to the profile of the second section (8), and the second plate (14), in which at least one opening (16) is made, the profile of which corresponds to the profile of the third section (9). Making openings (15), (16) in plates (13), (14) with an identical profile simplifies the process of manufacturing and installing the KPV insert (4) in the ULR body.

[0052] When the corium enters the CCLR body, the process of intensive heating of the CCLR structures begins. The KPV insert (4) is heated by radiation from the surface of the corium located in the CCLR body, located below the KPV insert (4). When the temperature in the second compartment (8) of the KPV insert (4) reaches the temperature corresponding to the opening temperature of the KPV (4), the KPV actuator (cover) is triggered and water (steam-water mixture) enters the second compartment (8) through the KPV (4), then the water enters the corium in the CCLR body through the third compartment (10) and the fourth compartment (11).

[0053] Thus, the use of the KPV insert (4) of the declared design allows for the guaranteed flow of cooling water into the ULR housing at a specified time, determined by calculations.

[0054] It should be obvious to an ordinary person skilled in the art that specific embodiments of the melt localization device housing and the melt localization device housing water supply valve insert are described for illustrative purposes, while various modifications are permissible that do not go beyond the scope of legal protection of the claimed invention.

Claims

Invention formula 1. A melt localization device housing comprising an outer shell (1) and an inner shell (2) forming a crucible-shaped container intended for receiving the melt, thermal protection (3) installed in the upper part of the housing on the inside of the inner shell (2), water supply valves (4) installed in the upper part of the housing, each of which comprises a horizontal section (5) installed through an opening (1a) in the outer shell (1), an opening (2a) in the inner shell (2), an opening (3a) in the thermal protection (3), and a vertical section (6) installed outside the outer shell (1), characterized in that an insert is installed in the opening (3a) of the thermal protection (3), comprising a first compartment (7), inside of which a second compartment (8), at least one third compartment (9), and a fourth compartment (10) are located, wherein the third compartment (9) and the fourth compartment (10) are located in such a way that the fourth compartment (10) is connected to the second compartment (8) through the first opening (I), at least,one third compartment (9) is connected to the fourth compartment (10) through at least one second opening (12), on one side the first compartment (7) and the second compartment (8) are connected by a first plate (13) in which a third opening (15) is made, intended for connecting the horizontal section (5) of the water supply valve (4) with the second compartment (8), on the other side the first compartment (7), the second compartment (8), the third compartment (9) are connected by a second plate (14) in which at least one fourth opening (16) is made, intended for connecting the fourth compartment (9) with the internal space of the melt localization device housing.

2. The body of the melt localization device according to item 1, characterized in that the insert is installed in such a way that the first plate (13) adjoins the inner shell (2) of the body of the melt localization device.

3. The body of the melt localization device according to item 1, characterized in that the insert is installed in such a way that the first plate (13) is positioned with a gap from the inner shell (2) of the body of the melt localization device.

4. The body of the melt localization device according to item 1, characterized in that the first plate (13) of the insert is installed from the inner shell (2) of the body of the melt localization device through a gasket.

5. An insert for a water supply valve of a melt localization device housing, characterized in that it comprises a first compartment (7), inside which a second compartment (8), at least one third compartment (9), a fourth compartment (10) are placed, wherein the third compartment (9) and the fourth compartment (10) are placed in such a way that the fourth compartment (10) is connected to the second compartment (8) through the first opening (I), at least one third compartment (9) is connected to the fourth compartment (10) through at least one second opening (12), on one side the first compartment (7) and the second compartment (8) are connected by a first plate (13), in which a third opening (15) is made, intended for connecting the horizontal section (5) of the water supply valve (4) to the second compartment (8), on the other side the first compartment (7), the second compartment (8), the third compartment (9) are connected by a second plate (14), in which at least one fourth opening (16) is made,designed to connect the fourth compartment (9) with the internal space of the melt localization device body, 6. The water supply valve insert of the melt localization device body according to item 5, characterized in that the cavities limited by the first plate (13), the second plate (14), the walls of the first compartment (7), the second compartment (8), the third compartment (9), the fourth compartment (10) of the water supply valve insert (4) are filled with heat-insulating and / or heat-conducting material (17).

7. The insert of the water supply valve of the melt localization device body according to item 5 or item 6, characterized in that it additionally comprises a first group of rods (18) installed along the perimeter of the second compartment (8), wherein the first end (18a) of each rod (18) is connected to the outer surface (8a) of the wall of the second compartment (8), and the second end (186) is made with a gap (18b) from the inner surface (7a) of the wall of the first compartment (7), as well as a second group of rods (19) connecting the first plate (13) and the second plate (14).

8. An insert for the water supply valve of the melt localization device body according to item 5 or item 6 or item 7, characterized in that the second plate (14) is made in the form of an octagon with ribs (14a) connected to the second plate (14) by means of welded joints (20), and the ends (146) of the ribs (14a) protrude beyond the edges (14b) of the second plate (14).

9. An insert for the water supply valve of the melt localization device body according to item 5 or item 6 or item 7, characterized in that the second plate (14) is made in the form of a monolithic circle.

10. An insert for the water supply valve of the melt localization device body according to item 5 or item 6 or item 7, characterized in that the second plate (14) is made in the form of a monolithic circle with ribs (14g) made by milling.

11. The insert of the water supply valve of the melt localization device body according to item 8 or item 9 or item 10, characterized in that the second plate (14) has central grooves (14d) and peripheral grooves (14d), and is installed with said grooves against the end surfaces (76), (86) of the first compartment (7) and the second compartment (8).

12. An insert for the water supply valve of the melt localization device body according to item 5, characterized in that the first compartment (7), the second compartment (8), the third compartment (9), and the fourth compartment (10) are made in the form of cylindrical tubes.

13. An insert for the water supply valve of the melt localization device body according to item 5, characterized in that a temperature sensor (21) is installed on the inner surface (14e) of the second plate (14).

14. The insert of the water supply valve of the melt localization device body according to item 5, characterized in that the first compartment (7) and the second compartment (8) are connected by a first plate (13), in which at least one third opening (15) is made, the profile of which corresponds to the profile of the second compartment. (8), and a second plate (14), in which at least one is made 16 the fourth hole (16), the profile of which corresponds to the profile of the third compartment (9). 17

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