Steel containment shell of low-power reactor

Abstract

FIELD: containment shells; nuclear power plants.SUBSTANCE: invention relates to a steel containment shell for a low-power reactor. The shell contains first, second and third sections connected to each other by means of ribs and rings. First section (2) and second section (5) are connected by first annular welded joint (26) made between the ends of first section (2) and second section (5), second section (5) and third section (10) with dome (14) are connected by second annular welded joint (27). Inside the first section, a cooling medium tank is installed, resting on a flange. Second section (5), intended for installation above first section (2), has first neck (19), intended for forming main airlock (17), as well as second neck (20), intended for forming emergency airlock (23), wherein on the outer surface of second section (5) bypass pipeline (30) is placed between second neck (20) and second ring (8) of second section (5). In dome (14) there is third neck (15), closed by lid (29).EFFECT: minimization of the release of radioactive fission products into the premises of a nuclear power plant and into the environment during normal operation and during various accidents of the reactor installation under conditions of external influences, including seismic ones.8 cl, 6 dwg

Description

[0001] The invention relates to the field of nuclear energy, in particular, to systems that ensure the safety of nuclear power plants (NPP) with low-power nuclear reactors, and can be used during the operation of a nuclear reactor in the following modes: during normal operation, during disruption of normal operation, during design basis accidents, during beyond-design basis accidents without destruction of the core of a nuclear reactor, and during severe beyond-design basis accidents leading to destruction of the core of a nuclear reactor.

[0002] In all these modes, the steel containment vessel serves as a hermetically sealed barrier between the reactor and other areas of the SNPP, ensuring the containment of solid, liquid, and gaseous radioactive fission products within its internal volume for the time required to implement emergency response measures at the SNPP. During normal operation, the steel containment vessel maintains a slight vacuum within its internal volume, which houses the reactor unit, preventing the ingress of low-level radioactive condensate, aerosols, gases, and vapors into the SNPP areas.

[0003] The greatest radiation hazard is posed by design basis accidents associated with the destruction of the pipelines of the first or second circuit of the reactor plant, beyond design basis accidents without destruction of the core associated with non-design basis multiple failures of equipment, as well as severe beyond design basis accidents with meltdown of the core, which can occur with multiple failures of the core cooling systems.

[0004] In such accidents, solid, liquid and gaseous radioactive fission products are released from the reactor facility into the interior of the SNPP and then beyond the SNPP into the environment.

[0005] To prevent this phenomenon and minimize the spread of radioactive fission products throughout the SNPP premises, it is necessary to localize solid, liquid, and gaseous radioactive fission products in a concentrated volume located around the small nuclear reactor until the completion of emergency response measures. This ensures the containment, gradual cooling, and condensation of radioactive fission products in the gas and vapor phases, as aerosols, and in liquid and solid form. This function is performed by the steel containment shell of the small nuclear reactor, which prevents (minimizes) the entry of radioactive fission products into the SNPP premises, thereby protecting the population and the environment from radiation exposure during accidents involving the small nuclear reactor.

[0006] The primary factor ensuring the operational reliability of a small-power reactor is the strength and stability of the steel containment vessel against seismic and external impacts during normal operation, operational disturbances, design-basis accidents, beyond-design-basis accidents without core destruction, and severe beyond-design-basis accidents. In all these situations, loss of strength and stability of the steel containment vessel can lead to a breach of containment and the release of radioactive fission products into the internal volumes of the SNPP's building structures and the environment.

[0007] The second factor ensuring the operational reliability of a small-power reactor is the strength and resistance of the steel containment vessel to internal pressures of up to 1 MPa and temperatures of up to 350°C, during design-basis accidents, beyond-design-basis accidents without destruction of the nuclear reactor core, and during severe beyond-design-basis accidents. These parameters are necessary to reduce and seal leaks in the reactor facility's primary and secondary circuit pipelines located within the steel containment vessel (within the accident containment zone). In all these processes, loss of strength and stability of the steel containment vessel can lead to a breach of containment and the release of radioactive fission products into the SNPP's structural components and the environment.

[0008] The third factor ensuring the operational reliability of a low-power reactor is the tightness of the steel containment vessel during normal operation, during operational disturbances, during design basis accidents, during beyond-design basis accidents without destruction of the nuclear reactor core, and during severe beyond-design basis accidents. In all these processes, the tightness of the primary and emergency airlocks, the tightness of the main connector, and the tightness of the pipeline and cable penetrations through the steel containment vessel are key to ensuring the reliable containment of radioactive fission products within the steel containment vessel.

[0009] The fourth factor ensuring the operational reliability of a low-power reactor is access to the interior of the steel containment vessel, which has a small internal volume due to the limited spread of radioactive fission products and the need to maintain a vacuum during normal operation. Access to the steel containment vessel during reactor operation is provided through the main and emergency airlocks. During refueling, access is also provided through the main connector in the steel containment vessel, allowing the use of large-scale equipment for refueling the core, maintenance, and repair.

[0010] The technical field knows of low-power reactor designs with a containment vessel located in the reactor's vicinity. Typically, a low-power reactor is installed in a reactor shaft, and the containment vessel is formed by the walls and bottom of the reactor building's containment structure, constructed of concrete or reinforced concrete. The disadvantages of these containment vessel designs include low strength and resistance to seismic and external impacts, as well as the lack of mechanisms to ensure a leak-proof seal under various operating conditions.

[0011] A protective shell is known [1] which comprises an internal steel lining which is in air (gas) contact with an internal cavity of the protective shell intended to accommodate radioactive material; an external steel lining which forms an intermediate layer with the internal lining, said intermediate layer having a cavity for filling; a concrete shell placed outside the lining and intended to protect the outer layer of the lining; the cavity is filled with a phase change material which ensures restoration of the protective shell.

[0012] The disadvantage of this design is its low strength and seismic resistance, due to the lack of mechanisms to ensure the relative movement of the elements under external influences. Furthermore, if the pipelines supplying and discharging phase-change material are damaged, the process of ensuring the containment shell's tightness cannot be achieved.

[0013] A protective shell [2] for a low-power nuclear reactor is known, which has a nuclear reactor, a protective shell in which the nuclear reactor is placed, wherein the protective shell contains several active and passive heat removal systems that are switched on and off taking into account the temperature in the protective shell. The claimed design is characterized in that the reactor vessel (20) is placed in an underground pit (60). The pit (60) contains a protective shell (62) in which the reactor vessel (20) is installed. A barrier zone (64) is formed around and below the protective shell (62) of the reactor vessel (20). Side support elements (66) and lower support elements (68) can extend from the side walls and the bottom of the protective shell (62) into the barrier zone (64). The side support elements (66) and the lower support elements (68) ensure the dissipation of thermal energy from the reactor body (20) into the barrier zone (64) and to the ground.The indicated numerical designations are used in patent US 10460844 (B2) [2] and are not used to disclose the features of the claimed invention.

[0014] The disadvantage of this design is its low strength and seismic resistance, due to the lack of mechanisms to ensure the relative movement of the elements under external influences. Furthermore, concrete failure due to seismic and external influences could lead to the destruction of the supporting elements that act as heat-removal mechanisms, the destruction of the reactor vessel, and the release of radioactive substances beyond the containment.

[0015] The technical result of the claimed invention consists in minimizing (eliminating) the release of radioactive fission products into the premises of the SNPP and into the environment during normal operation and during various accidents of the reactor installation under conditions of seismic and external impacts on the building structures of the SNPP, as well as in increasing the manufacturability of the equipment of the steel protective shell of the SNPP low-power reactor.

[0016] The tasks that the claimed invention is aimed at solving are the localization of radioactive fission products inside a steel protective shell at pressures of up to 1 MPa and temperatures of up to 350°C (2 times higher than the pressure and temperature of localization inside sealed shells for high-power reactors) under various states of the reactor installation under conditions of seismic and external impacts on the building structures of the SNPP.

[0017] The set tasks are solved due to the fact that the steel protective shell (1) of a low-power reactor, according to the invention, contains a first section (2) with a bottom (13), a second section (5), a third section (10) with a dome (14), a bypass pipeline (30), a tank (28) of a cooling medium, wherein the first section (2) with a bottom (13), intended for installation on a base (22), has first ribs (3), connected to a first ring (4), wherein said first ribs (3) and the first ring (4) are located on the outer surface of the first section (2), in the upper part of the inner surface of the first section (2) a flange (21) is made, intended to support a tank (28) of a cooling medium, installed inside the first section (2), the second section (5), intended for installation above the first section (2), has a first neck (19), intended to form the main airlock (17), the second neck (20), designed to form an emergency airlock (23), the second ribs (6), the third ribs (7),a second ring (8), a third ring (9), wherein the second ribs (6) and the second ring (8) are installed in the lower part of the second section (5) and are connected to each other, wherein the third ribs (7) and the third ring (9) are installed in the upper part of the second section (5) and are connected to each other, a third section (10) with a dome (14), intended for installation above the second section (5), has fourth ribs (11), a fourth ring (12), wherein the fourth ribs (11) and the fourth ring (12) are installed in the lower part of the third section (10) and are connected to each other, a third neck (15) is made in the dome (14) of the third section (10), wherein the third neck (15) is closed by a lid (29), the first section (2) and the second section (5) are connected by a first annular welded joint (26), made between the ends of the first section (2) and the second section (5), the second section (5) and the third section (10) are connected by a second annular welded joint (27),the bypass pipeline (30) is located on the outer surface of the second section (5) between the second neck (20) and the second ring (8) of the second section (5).,

[0018] One essential feature of the claimed invention is the presence of a flange (21) in the upper part of the inner surface of the first section, which makes it possible to secure the tank (28) of the cooling medium to the elements of the steel protective shell (1) and, thereby, increase the strength and seismic resistance of the steel protective shell (1).

[0019] Another essential feature of the claimed invention is that the first section (2), the second section (5), the third section (10) are connected by means of rings (4), (8), (9), (12) and annular welded joints (26), (27), which increases the contact area between the first, second, third sections and increases the strength of the steel protective shell structure.

[0020] Another essential feature of the claimed invention is that on the outer surface of the bottom (13), the first section (2), the second section (5), the third section (10) there are installed supporting vertical ribs (3), (6), (7), (11), which are connected to the rings (4), (8), (9), (12), respectively, which makes it possible to increase the strength of the steel protective shell at the joints of the sections (2), (5), (10).

[0021] Another essential feature of the claimed invention is the presence of a tank (28) for the cooling medium, installed inside the first section (2) and supported by a flange (21), which makes it possible to reduce the power of radioactive radiation acting from the active zone on the equipment located around the reactor, on the steel protective shell, on the shaft and on the personnel of the SNPP. In addition, the presence of a tank (28) for the cooling medium makes it possible to maintain the temperature regime in said tank (28) by absorbing the heat released in this tank (28) under the influence of radioactive radiation, and the heat coming from the side of the thermally insulated reactor vessel, which, accordingly, maintains the strength characteristics of the equipment surrounding the reactor within the specified design limits.The presence of the tank (28) ensures the absorption of the "reverse" re-radiation acting from the equipment into the tank (28) both during reflection and during the formation of secondary isotopes in the equipment located near the reactor, including the steel protective shell. The presence of the flange (21), on which the tank (28) is installed, on which (the tank), in turn, the low-power reactor is installed, the active zone of which is located inside the tank (28), ensures the transfer of the load from the reactor to the tank (28), and the tank (28) transfers the entire load to the flange (21) of the first section (2).

[0022] Another essential feature of the claimed invention is the presence of a bypass pipeline (30), which is located on the outer surface of the second section (5) between the second neck (20) and the second ring (8) of the second section (5), which makes it possible to equalize the pressure in the steel protective shell in the event of an accident.

[0023] Another significant invention of the claimed invention is the presence of necks (19), (20), (15) intended for the installation of equipment that provides access to the internal space of the steel protective shell (1), which makes it possible to increase the manufacturability of the equipment.

[0024] Additionally, in the steel protective shell (1) of the low-power reactor, according to the invention, the equipment room (16) is formed from the floor level of the main airlock (17) of the second section (5) to the cover (29) of the third section (10), which makes it possible to increase the manufacturability of the equipment by ensuring guaranteed access of personnel to the internal space of the steel protective shell (1).

[0025] Additionally, in the steel protective shell (1) of the low-power reactor, according to the invention, the reactor room (18) is formed from the bottom (13) of the first section (2) to the floor level of the main airlock (17), which makes it possible to increase the manufacturability of the equipment by ensuring guaranteed access of personnel to the internal space of the steel protective shell (1).

[0026] Additionally, in the steel protective shell (1) of the low-power reactor, according to the invention, the tank (28) of the cooling medium is made of metal, which makes it possible to form a metal-water barrier, which makes it possible to reduce the power of radioactive radiation acting from the active zone on the equipment located around the reactor, on the steel protective shell, on the shaft and on the personnel of the SNPP.

[0027] Additionally, in the steel protective shell (1), according to the invention, longitudinal radial ribs (33) are installed on the outer sides of the main gateway (17) and the emergency gateway (23), which makes it possible to ensure the strength of the gateways (17), (23) in the event of impact loads by distributing the impact energy to the said ribs (33).

[0028] Additionally, in the steel protective shell (1) of the low-power reactor, according to the invention, the cover (29) is made in the shape of a circle, on the inner side of which radial ribs (34) are installed, which makes it possible to ensure the strength of the cover (29) in the event of impact loads by distributing the impact energy to the said ribs (34).

[0029] Additionally, in the steel protective shell (1) of a low-power reactor, according to the invention, the first ribs (3), second ribs (6), third ribs (7), fourth ribs (11) are installed vertically along the circumference of sections (2), (5), (10) with equal gaps, which makes it possible to increase the strength of the steel protective shell structure when exposed to impact and seismic loads by distributing impact effects throughout the entire structure, rather than in localized places.

[0030] Additionally, in the steel protective shell (1) of the low-power reactor, according to the invention, the equipment room (16) and the reactor room (18) are separated from each other by a biological protection flooring (32), which makes it possible to ensure the physical separation of the rooms (16) and (18), which are on the same level with the floor (31) of the emergency lock (23).

[0031] Fig. 1 shows a steel protective shell made in accordance with the claimed invention.

[0032] Fig. 2 shows a sectional view of a steel protective shell made in accordance with the claimed invention.

[0033] Fig. 3 shows a steel protective shell made in accordance with the claimed invention.

[0034] Fig. 4 shows a steel protective shell without a lid, made in accordance with the claimed invention.

[0035] Fig. 5 shows the first section of a steel protective shell made in accordance with the claimed invention.

[0036] Fig. 6 shows a sectional view of a steel protective shell with an installed tank (28) for a cooling medium, made in accordance with the claimed invention.

[0037] Fig. 1-6 shows a steel protective shell (1). The steel protective shell (1) is placed in a reactor shaft with a floor (24) and vertical walls (25). The steel protective shell (1) of a low-power reactor is made of three sections: the first section (2), the second section (5), and the third section (10). The first section (2) is made with a bottom (13) and is installed on a base (22) located in the floor (24) of the reactor shaft. The second section (5) is installed on top of the first section (2), and the third section (10) is installed on top of the second section (5). A dome (14) is installed on the second section. A third neck (15) is made in the dome (14), into which a cover (29) is installed.

[0038] The first section (2) with the bottom (13) is designed to be installed on the base (22). First ribs (3) are installed on the outside of the first section (2) and the bottom (13). These first ribs (3) are connected to the first ring (4). A flange (21) is formed in the upper part of the inner surface of the first section (2). The flange (21) is designed to support the tank (28) of the cooling medium installed inside the first section (2).

[0039] The second section (5) is designed to be installed above the first section (2). The second section (5) has a first neck (19) designed to form the main airlock (17), as well as a second neck (20) designed to form the emergency airlock (23). The second ribs (6), third ribs (7), second ring (8), third ring (9) are installed outside the second section (5). The second ribs (6) and the second ring (8) are installed at the bottom of the second section (5) and are connected to each other. The third ribs (7) and the third ring (9) are installed at the top of the second section (5) and are connected to each other.

[0040] The third section (10) with a dome (14) is designed to be installed above the second section (5). The fourth ribs (11) and the fourth ring (12) are installed at the bottom of the third section (10), which are connected to each other. A third neck (15) is formed in the dome (14) of the third section (10), and the third neck (15) is closed with a lid (29).

[0041] The first section (2) and the second section (5) are connected by a first annular welded joint (26) made between the ends of the first section (2) and the second section (5). The second section (5) and the third section (10) are connected by a second annular welded joint (27). The bypass pipeline (30) is located on the outer surface of the second section (5) between the second neck (20) and the second ring (8) of the second section (5).

[0042] The equipment room (16) is formed from the floor level of the main airlock (17) of the second section (5) to the cover (29) of the third section (10). The reactor room (18) is formed from the bottom (13) of the first section (2) to the floor level of the main airlock (17). A tank (28) for the cooling medium is installed inside the first section (2). The tank (28) for the cooling medium can be made of metal. Longitudinal radial ribs (33) are installed on the outer sides of the main airlock (17) and the emergency airlock (23). The cover (29) is made in the shape of a circle, on the inner side of which radial ribs (34) are installed. The first ribs (3), second ribs (6), third ribs (7), fourth ribs (11) are installed vertically along the circumference of sections (2), (5), (10) with equal gaps.

[0043] The main airlock (17) and the emergency airlock (23) are used to provide access during normal operation to the inside of the steel containment shell (1) in the equipment room (16). During scheduled preventive maintenance, access to the equipment room (16) is additionally provided through the third neck (15) of the dome (14) after removing the cover (29). There is no access to the reactor room (18). A tank (28) is installed in the reactor room (18), in which a low-power reactor is installed. In the event of emergency situations or accidents associated with leaks in the primary or secondary circuit pipelines, the coolant or working fluid can enter the interior of the steel containment shell (1) either in the reactor room (18) or in the equipment room (16), which causes an increase in pressure and temperature in the room where the coolant or working fluid enters.The equipment room (16) and the reactor room (18) are separated from each other by a biological protection flooring (32), which provides physical separation of rooms (16) and (18) and is located practically at the same level with the floor (31) of the emergency airlock (23). To equalize the pressure between the equipment room (16) and the reactor room (18), a bypass pipeline (30) is installed, ensuring equalization of pressure between rooms (16) and (18) in the event of abnormal operating conditions and accidents.

[0044] Thus, the use of a steel protective shell allows for the localization of radioactive fission products inside the steel protective shell at pressures up to 1 MPa and temperatures up to 350°C under various states of the reactor facility under conditions of seismic and external impacts on the building structures of the SNPP.

[0045] Sources of information:

[0046] 1. PRC Application CN 119560188 A, IPC G21C13 / 093; G21C13 / 028; priority dated 11 / 18 / 2024;

[0047] 2. US Patent US 10460844 B2, IPC G21C1 / 32; G21C13 / 02; G21C15 / 18; priority dated 05 / 09 / 2017.

Claims

1. A steel containment shell (1) for a low-power reactor, characterized in that it comprises a first section (2) with a bottom (13), a second section (5), a third section (10) with a dome (14), a bypass pipeline (30), a tank (28) for a cooling medium, wherein the first section (2) with a bottom (13), intended for installation on a base (22), has first ribs (3) connected to a first ring (4), wherein said first ribs (3) and the first ring (4) are located on the outer surface of the first section (2), in the upper part of the inner surface of the first section (2) there is a flange (21) intended to support a tank (28) for a cooling medium installed inside the first section (2), the second section (5), intended for installation above the first section (2), has a first neck (19), intended to form a main airlock (17), a second neck (20), intended to form an emergency airlock (23), second ribs (6), third ribs (7), second ring (8), third ring (9),wherein the second ribs (6) and the second ring (8) are installed in the lower part of the second section (5) and are connected to each other, wherein the third ribs (7) and the third ring (9) are installed in the upper part of the second section (5) and are connected to each other, the third section (10) with a dome (14), intended for installation above the second section (5), has fourth ribs (11), a fourth ring (12), wherein the fourth ribs (11) and the fourth ring (12) are installed in the lower part of the third section (10) and are connected to each other, a third neck (15) is made in the dome (14) of the third section (10), wherein the third neck (15) is closed by a cover (29), the first section (2) and the second section (5) are connected by a first annular welded joint (26), made between the ends of the first section (2) and the second section (5), the second section (5) and the third section (10) is connected by a second annular welded joint (27),the bypass pipeline (30) is located on the outer surface of the second section (5) between the second neck (20) and the second ring (8) of the second section (5)., 2. A steel protective shell (1) of a low-power reactor according to paragraph 1, characterized in that the equipment room (16) is formed from the floor level of the main airlock (17) of the second section (5) to the cover (29) of the third section (10).

3. A steel protective shell (1) of a low-power reactor according to paragraph 1, characterized in that the reactor room (18) is formed from the bottom (13) of the first section (2) to the floor level of the main airlock (17).

4. A steel protective shell (1) of a low-power reactor according to paragraph 1, characterized in that the tank (28) of the cooling medium is made of metal.

5. A steel protective shell (1) of a low-power reactor according to paragraph 1, characterized in that longitudinal radial ribs (33) are installed on the outer sides of the main airlock (17) and the emergency airlock (23).

6. A steel protective shell (1) for a low-power reactor according to paragraph 1, characterized in that the cover (29) is made in the shape of a circle, on the inner side of which radial ribs (34) are installed.

7. A steel protective shell (1) of a low-power reactor according to paragraph 1, characterized in that the first ribs (3), second ribs (6), third ribs (7), fourth ribs (11) are installed vertically along the circumference of sections (2), (5), (10) with equal gaps.

8. A steel protective shell (1) of a low-power reactor according to paragraphs 2 and 3, characterized in that the equipment room (16) and the reactor room (18) are separated from each other by a biological protection flooring (32).

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