A large-scale fast reactor low-pressure containment system

Abstract

The present invention belongs to the technical field of nuclear power plant containments, and particularly relates to a large fast reactor low-pressure containment system, which system includes a low-pressure containment system and a ventilation and filtration system; the low-pressure containment system is used to contain radioactive substances during operation and accident conditions, ensure the airtightness of the containment boundary, and conduct in-core nuclide closed decay in the initial stage of the accident; the ventilation and filtration system is used to filter and discharge radioactive substances after the decay of short-lived nuclides in the later stage of the accident, and maintain the radioactive levels inside the plant and in the environment at low levels. Through the coupling of the ventilation and filtration system and the low-pressure containment system, the system of the present invention can meet the airtightness requirements of the containment under severe accident conditions, and at the same time meet the economic requirements for the construction of the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power plant containments, and particularly relates to a large fast reactor low-pressure containment system. Background Art

[0002] The design of the containment is carried out based on the accident conditions of the design basis, and it is necessary to ensure that radioactive substances are completely sealed under accident conditions to prevent leakage to the external environment. The design basis of the pressurized water reactor containment is the design basis accident condition, and it needs to withstand the maximum internal pressure and temperature generated by the design basis accident (such as the loss of coolant accident). Under the design basis accident (such as the loss of coolant accident) condition of the pressurized water reactor nuclear power plant, a large amount of high-temperature and high-pressure radioactive substances are generated, mainly a mixture of water vapor, inert gas, iodine / cesium isotopes combined with aerosol, etc. The peak pressure inside the containment usually reaches the order of 0.4 - 0.5 MPa. The design of the pressurized water nuclear power plant containment is a mature design type in China. The design requirements for the airtightness and strength of the containment are high. It is a fully steel-lined design type. For local penetration items, the personnel gate adopts a double-channel personnel air lock design, and the cable penetration adopts electrical penetrators. A prestressing system is designed and installed in the containment structure wall. The construction technology is complex and the cost is high.

[0003] Even in the severe accident (the design basis accident of the containment) condition, the amount of radioactive substances generated by the liquid metal sodium-cooled fast reactor is less than that of the pressurized water reactor. The main substances are a mixture of inert gas and sodium aerosol, etc. The peak pressure inside the containment is in the order of kilopascals. The containment has airtightness design requirements and no strength design requirements. The BN series units are not designed with containments. The design pressure of the large liquid metal sodium-cooled fast reactor containment is low, but the types and quantities of items penetrating the containment boundary are numerous. The free volume of the large liquid metal sodium-cooled fast reactor containment is large, which is 2 - 3 times that of the pressurized water reactor nuclear power plant, and the number of cable penetrations and pipe penetrations is also more than that of the pressurized water reactor. If a similar design to the pressurized water reactor nuclear power plant is adopted, the construction cost of the containment will increase significantly, which has an adverse impact on reducing the construction cost.

[0004] In addition, considering the increasingly high requirements for nuclear safety in the future, the structural strength design of the containment should use the most severe accident (HCDA accident) that can be imagined in the fast reactor as the design input to ensure the integrity of the containment structure under any working conditions. In terms of the source term, the maximum core damage accident that can be considered in the safety analysis report is used as the input. The design basis of the fast reactor containment is core melting under severe accident conditions, and it needs to withstand the transient shock wave and high-temperature load generated by the severe accident of the hypothetical core disassembly.

[0005] Therefore, how to ensure that any radioactive release of the liquid metal sodium-cooled fast reactor to the environment under severe accident conditions is maintained at a reasonably achievable and as low as possible level, while being able to meet the airtightness requirements and the economic requirements for the construction of the unit is an urgent problem to be solved in this field. Summary of the Invention

[0006] The object of the present invention is to provide a large fast reactor low-pressure containment system. Through the coupling of the ventilation and filtration system with the low-pressure containment system, the nuclides in the containment can be enclosed and decayed at the initial stage of the accident. After the short-lived nuclides decay, the ventilation and filtration system is used for filtration and discharge to maintain the radioactive levels in the plant and the environment at a low level. It can meet the airtightness requirements of the containment under severe accident conditions and at the same time meet the economic requirements for the construction of the unit.

[0007] Technical solution for achieving the object of the present invention:

[0008] A large fast reactor low-pressure containment system includes a low-pressure containment system and a ventilation and filtration system; the low-pressure containment system is used for containing radioactive substances and ensuring the airtightness of the containment boundary under operating conditions and accident conditions, and for enclosing and decaying nuclides in the containment at the initial stage of the accident; the ventilation and filtration system is used for filtering and discharging radioactive substances after the short-lived nuclides decay in the later stage of the accident to maintain the radioactive levels in the plant and the environment at a low level; the low-pressure containment system includes a containment; the containment includes a reactor hall, a reactor pit, an in-plant transportation barrel installation well for new components, and boundary items; the outer boundary connecting the reactor hall, the reactor pit, and the in-plant transportation barrel installation well for new components forms the containment boundary; the boundary items are hermetically connected to the concrete structure at the junction of the containment boundary.

[0009] Further, the reactor hall, the reactor pit, and the in-plant transportation barrel installation well for new components are all non-prestressed concrete structures. The entire reactor pit is provided with a steel lining, the top of the reactor hall is provided with steel formwork, the bottom plate of the reactor hall is provided with a steel lining, and the nuclear island paint is applied to the concrete walls around the reactor hall to form a nuclear island paint coating on the concrete structure of the containment boundary; the entire in-plant transportation barrel installation well for new components is coated with nuclear island paint to form a nuclear island paint coating on the concrete structure of the containment boundary.

[0010] Further, the low-pressure containment system further includes a core melt collector, and a main container is provided in the reactor pit, and a core melt collector is provided at the bottom inside the main container.

[0011] Further, the low-pressure containment system further includes a sodium leakage receiving and suppressing tray, and a sodium leakage receiving and suppressing tray is provided at the bottom of the reactor pit.

[0012] Further, the low-pressure containment system further includes a reactor top protection cover, and the reactor top protection cover is provided on the top of the main container.

[0013] Further, the reactor hall is provided on the reactor pit, the reactor hall is communicated with the reactor pit to form a mushroom-shaped structure, the in-plant transportation barrel installation well for new components is provided under the bottom plate of the reactor hall, and the reactor hall, the reactor pit, and the in-plant transportation barrel installation well for new components are connected to form a sealed structure.

[0014] Furthermore, the boundary items include: pipes, mechanical penetrations, cable penetrations, personnel access passages, equipment access passages, fuel transfer passages, and containment boundary cover plates that constitute the extended part of the containment; the pipes, mechanical penetrations, cable penetrations, personnel access passages, equipment access passages, fuel transfer passages, and containment boundary cover plates that constitute the extended part of the containment are respectively arranged on the containment boundary.

[0015] Furthermore, an equipment access passage is opened on the wall of the reactor hall near the bottom plate, and a personnel access passage is opened on the installation well of the transport barrel in the new component factory and the wall of the reactor hall; pipes, mechanical penetrations and cable penetrations constituting the extension of the containment are arranged on the wall of the reactor hall; containment isolation valves are installed upstream and downstream of the mechanical penetrations respectively; a fuel transfer channel and a containment boundary cover are opened on the bottom plate of the reactor hall.

[0016] Furthermore, the cable penetration is sealed and connected to the concrete structure at the boundary of the containment shell by means of cable plugging and sealing; the cable penetration comprises an embedded casing and a cable, the embedded casing is placed in the concrete structure at the boundary of the containment shell, the cables are arranged in the embedded casing at intervals, gaps are formed between the cables and between the cables and the embedded casings, high-density silicone sealant is filled in the gaps, so that the embedded casing with the cable is sealed and plugged; fire-resistant silicone sealant is coated on the junction of the embedded casing and the concrete structure at the boundary of the containment shell and on the surface of the high-density silicone sealant.

[0017] Furthermore, the mechanical penetration is placed in the concrete structure of the containment boundary, and a wing ring is provided on the outer periphery of the mechanical penetration, which extends into the concrete structure of the containment boundary. The junction between the mechanical penetration and the concrete structure of the containment boundary is first coated with polysulfide rubber, and then the polysulfide rubber is covered with metal foil for overlap, and then nuclear island paint is coated on the metal foil to form a nuclear island paint coating. The nuclear island paint coating covers from the junction of the mechanical penetration and the concrete structure of the containment boundary to the overlap of the nuclear island paint coating with the concrete structure of the containment boundary.

[0018] Furthermore, the boundary door frames of the personnel entrance and exit passages and the equipment entrance and exit passages are fitly connected to the concrete structure of the containment boundary. At the junction of the boundary door frame and the concrete structure of the containment boundary, polysulfide rubber chamfering is first used, and then nuclear island paint is applied to form a nuclear island paint coating. The nuclear island paint coating covers from the junction of the boundary door frame and the concrete structure of the containment boundary to the overlap of the nuclear island paint coating with the concrete structure of the containment boundary.

[0019] Furthermore, the containment boundary cover plate is provided with a double - seal ring and meets the conditions for single - body sealing test; during the power plant installation and commissioning stage, the containment boundary cover plate is movable; after the power plant installation and commissioning are completed, the unused containment boundary cover plate is welded to the steel cladding of the reactor hall floor, and 100% penetrant inspection is carried out on the surface of the welded seam; a gate valve is provided at the junction of the fuel transfer channel and the steel cladding of the reactor hall floor, and the fuel transfer channel is connected or closed by controlling the opening and closing of the gate valve.

[0020] Furthermore, the ventilation and filtration system includes a supply air pipeline, an exhaust air pipeline, a high - efficiency filter, an exhaust air fan, an exhaust chimney, an exhaust isolation valve, a supply air isolation valve, and a supply air fan; supply air pipelines are respectively provided between the top shield and the reactor hall, and between the reactor pit and the reactor hall. The inlet of the supply air pipeline is located outside the reactor hall, the first outlet of the supply air pipeline is located in the top shield, and the second outlet of the supply air pipeline is located in the reactor pit; a supply air isolation valve and a supply air fan are provided on the supply air pipeline; an exhaust chimney is provided outside the reactor hall, an exhaust air pipeline is provided between the reactor pit and the exhaust chimney, the outlet of the exhaust air pipeline is connected to the inlet of the exhaust chimney, and the inlet of the exhaust air pipeline communicates with the reactor pit; an exhaust isolation valve, a high - efficiency filter, and an exhaust air fan are provided on the exhaust air pipeline.

[0021] The beneficial technical effects of the present invention are as follows:

[0022] 1. The large - scale fast reactor low - pressure containment system provided by the present invention can play a sealing role under severe accident conditions, prevent radioactive substances from leaking into the environment, and can also withstand the impacts of external natural disasters and human events.

[0023] 2. The large - scale fast reactor low - pressure containment system provided by the present invention, through the coupling of the post - accident ventilation and filtration system and the low - pressure containment system, ensures that any radioactive release from the sodium - cooled fast reactor to the environment is maintained at as low a level as reasonably achievable, does not exceed the regulatory emission limit of radioactive release under operating conditions, and does not exceed the acceptable limit of radioactive release under accident conditions.

[0024] 3. In the large - scale fast reactor low - pressure containment system provided by the present invention, the containment (including the reactor hall, reactor pit, and installation well for new component in - plant transport barrels) adopts a non - prestressed concrete wall, effectively reducing the construction cost.

[0025] 4. The large - scale fast reactor low - pressure containment system provided by the present invention coats nuclear island paint at the junction of the non - prestressed concrete wall and the items passing through the wall to seal the micro - cracks of the concrete, ensuring that the nuclear island paint coating remains intact, adherent, and resistant to sodium or alkaline substances after combustion under severe accident load tension, meeting the airtightness requirements of the containment.

[0026] 5. In a large fast reactor low-pressure containment system provided by the present invention, as a barrier, the containment can envelope radioactive substances and avoid adverse effects on the external environment due to low-level discharge.

[0027] 6. In a large fast reactor low-pressure containment system provided by the present invention, by providing a sodium leakage receiving and suppressing tray at the bottom of the reactor pit, it can collect and extinguish sodium fires in the reactor pit, ensuring the integrity of the main vessel and the integrity of the containment boundary.

[0028] 7. In a large fast reactor low-pressure containment system provided by the present invention, by providing a core melt collector at the inner bottom of the main vessel, after 100% core melting under severe accident conditions, the molten fuel will be completely collected and cooled, ensuring that most radioactive substances are contained inside the main vessel and avoiding large sodium fires after the main vessel melts through.

[0029] 8. In a large fast reactor low-pressure containment system provided by the present invention, by adopting a specific sealing connection method for the items passing through the containment boundary (including embedded parts, boundary doors, mechanical penetrations, and cable penetrations), it can not only ensure the sealing performance of the containment but also facilitate construction, with good economy.

[0030] 9. In a large fast reactor low-pressure containment system provided by the present invention, by using a cable plugging and sealing method to seal and connect the cable penetrations with the concrete structure of the containment boundary, arranging multiple cables in a staggered and spaced manner, and using silicone sealant to plug the cable gaps, it can ensure the sealing and waterproofing of the cable penetration position under severe accident conditions, while avoiding damage to the control signals of the cables and saving economic costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of a large fast reactor low-pressure containment system provided by the present invention;

[0032] Figure 2 is a front view and a top-down sectional view of the junction between the embedded parts and the concrete structure of the containment boundary in a large fast reactor low-pressure containment system provided by the present invention;

[0033] Figure 3 is a sectional view of the junction between the mechanical penetration and the concrete structure of the containment boundary in a large fast reactor low-pressure containment system provided by the present invention;

[0034] Figure 4 is a top-down sectional view of the junction between the boundary door and the concrete structure of the containment boundary in a large fast reactor low-pressure containment system provided by the present invention;

[0035] Figure 5Cross-sectional view of the junction between the cable penetrator and the concrete structure at the containment boundary in a large fast reactor low-pressure containment system provided by the present invention.

[0036] In the figure: 1, reactor core; 2, core melt collector; 3, main vessel; 4, sodium leakage receiving and suppressing tray; 5, reactor top shield; 6, reactor hall; 7, reactor pit; 8, installation well for in-plant transport barrel of new components; 9, pipes forming the extended part of the containment; 10, containment isolation valve; 11, mechanical penetrator; 12, cable penetrator; 13, personnel access passage; 14, equipment access passage; 15, fuel transfer passage; 16, containment; 17, containment boundary cover plate; 18, high-efficiency filter; 19, exhaust fan; 20, exhaust chimney; 21, exhaust isolation valve; 22, supply air isolation valve; 23, supply air fan; 31, embedded part; 32, nuclear island paint coating; 33, metal foil; 34, wing ring; 35, polysulfide rubber; 36, wall; 37, door frame; 38, embedded casing; 39, fireproof silicone sealant; 40, cable; 41, high-density silicone sealant. Detailed implementation manners

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] A large fast reactor low-pressure containment system provided by the present invention includes a low-pressure containment system and a ventilation and filtration system; the low-pressure containment system is used to contain radioactive substances under operating conditions and accident conditions, ensure the airtightness of the containment boundary, and conduct in-containment nuclide sealing and decay in the initial stage of the accident; the ventilation and filtration system is used to filter and discharge radioactive substances after the decay of short-lived nuclides in the later stage of the accident, and maintain the radioactive levels in the plant and the environment at a low level.

[0039] As Figure 1 shown, the low-pressure containment system includes a containment 16, a core melt collector 2, a sodium leakage receiving and suppressing tray 4, and a reactor top shield 5.

[0040] The containment 16 includes a containment structure and containment subsystems and facilities required to perform their functions under specific accidents. The containment 16 is not designed with a prestressing system, has no strength test requirements, but has airtightness test requirements. The containment structure is a reinforced concrete structure with a square arch roof.

[0041] The containment structure includes the reactor hall 6, the reactor pit 7, and the installation well 8 for the transportation bucket inside the new component factory. The reactor hall 6 is located on the reactor pit 7, and the reactor hall 6 is connected to the reactor pit 7 to form a mushroom-shaped structure. The installation well 8 for the transportation bucket inside the new component factory is located under the floor of the reactor hall 6. The reactor hall 6, the reactor pit 7, and the installation well 8 for the transportation bucket inside the new component factory are connected to form a sealed structure. The outer boundaries where the reactor hall 6, the reactor pit 7, and the installation well 8 for the transportation bucket inside the new component factory are connected (i.e., the top, walls, and floor of the reactor hall 6, the walls and floor of the reactor pit 7, and the outer wall of the installation well 8 for the transportation bucket inside the new component factory) form the containment boundary.

[0042] The reactor hall 6, the reactor pit 7, and the installation well 8 for the transportation bucket inside the new component factory are all non-prestressed concrete structures. The top of the reactor hall 6 is provided with steel formwork, and the floor of the reactor hall 6 is provided with a steel cladding, which can withstand the high-temperature sodium fire in the hall and ensure the normal functions such as the integrity and airtightness of the containment boundary at the location. The nuclear island paint with high adhesion, high elasticity, high tensile strength, and alkali resistance is painted on the concrete walls around the reactor hall 6 to form a nuclear island paint coating on the concrete structure of the containment boundary, sealing the concrete microcracks and ensuring that the nuclear island paint coating remains intact, adherent, and resistant to sodium or alkaline substances after combustion under severe accident loads. The entire reactor pit 7 is provided with a steel cladding, and a sodium leakage receiving and suppressing tray 4 is provided at the bottom of the reactor pit 7 for collecting and extinguishing the sodium fire in the reactor pit, ensuring the integrity of the primary container and the integrity of the containment boundary. The entire installation well 8 for the transportation bucket inside the new component factory is coated with nuclear island paint to form a nuclear island paint coating on the concrete structure of the containment boundary, sealing the concrete microcracks and ensuring that the nuclear island paint coating remains intact, adherent, and resistant to sodium or alkaline substances after combustion under severe accident loads.

[0043] The primary container 3 is located in the reactor pit 7. A reactor top shield 5 is provided at the top of the primary container 3 to prevent the radioactive substances leaked from the primary container 3 from leaking into the reactor hall 6. A core melt collector 2 is provided at the bottom inside the primary container 3 to ensure that after 100% of the core melts, the molten fuel will be completely collected and cooled. Therefore, when a severe accident occurs and the core melts, there is no need to consider the large-scale sodium fire after the primary container 3 melts through. Most of the radioactive substances are contained inside the primary container 3. Only a small amount of primary loop sodium needs to enter the reactor top shield 5 through the top of the primary container and leak into the inside of the containment 16. As a barrier, the containment envelopes the radioactive substances to avoid the adverse effects on the external environment due to low-level discharge and achieve the purpose of the closed decay of radionuclides inside the containment at the initial stage of the accident.

[0044] The containment system and facilities, i.e., the boundary items, include the pipes 9, mechanical penetrations 11, cable penetrations 12, personnel access channels 13, equipment access channels 14, fuel transfer channels 15, and containment boundary covers 17 that form the extended part of the containment. The pipes 9, mechanical penetrations 11, cable penetrations 12, personnel access channels 13, equipment access channels 14, fuel transfer channels 15, and containment boundary covers 17 that form the extended part of the containment are respectively arranged on the containment boundary and are hermetically connected to the concrete structure at the junction of the containment boundary.

[0045] In a specific embodiment, an equipment access channel 14 is opened on the wall near the bottom plate in the reactor hall 6, and personnel access channels 13 are opened at multiple heights on the wall of the reactor hall 6 and in the installation well 8 for the in-plant transport barrel of new components; pipes 9, mechanical penetrations 11, and cable penetrations 12 that form the extended part of the containment are provided on the wall of the reactor hall 6; containment isolation valves 10 are respectively installed upstream and downstream of the mechanical penetrations 11; a fuel transfer channel 15 is opened on the bottom plate of the reactor hall 6, and a containment boundary cover 17 is provided.

[0046] Considering the large volume of the large fast reactor containment 16 and the large number of wall-piercing boundary items, applying nuclear island paint to the concrete wall and the junction of the wall-piercing boundary items and the wall can seal the microcracks of the concrete, ensure the integrity of the concrete wall, and meet the airtightness requirements of the containment. The factors affecting the leakage rate of the containment include: containment isolation valves 10, mechanical penetrations 11, cable penetrations 12, personnel access channels 13, equipment access channels 14, fuel transfer channels 15, containment boundary covers 17, walls, etc.

[0047] The personnel access channels 13, equipment access channels 14, fuel transfer channels 15, and containment boundary covers 17 need to withstand the high-temperature airtightness test in the sodium fire environment under severe accident conditions.

[0048] During the installation and commissioning stage of the power plant, the containment boundary cover 17 is designed to be movable and is provided with a double-seal ring, i.e., a pressure port, and has the condition for single-body airtightness testing. For the infrequently used containment boundary covers 17, after the installation and commissioning of the power plant are completed, they can be changed to a welding method to connect the containment boundary cover 17 to the steel cladding of the bottom plate of the reactor hall 6, and 100% penetrant inspection is carried out on the surface of the welded seam.

[0049] A gate valve is provided at the junction of the fuel transfer channel 15 and the steel cladding of the bottom plate of the reactor hall 6. By controlling the opening and closing of the gate valve, the fuel transfer channel 15 is connected or closed. The gate valve is connected to the steel cladding of the bottom plate of the reactor hall 6 by welding.

[0050] The embedded parts 31 of the concrete structure at the containment boundary (the reactor hall wall) are used for welding and fixing supports, etc. They are pre-embedded in the concrete structure in advance. The sealing connection method at the junction is as follows Figure 2 as shown. Apply nuclear island paint to the periphery of the embedded part 31 to form a nuclear island paint coating 32. The nuclear island paint coating 32 smoothly transitions at the junction between the embedded part 31 and the concrete structure at the containment boundary. The nuclear island paint coating 32 covers from the junction between the embedded part 31 and the concrete structure at the containment boundary to overlap with the nuclear island paint coating of the concrete structure at the containment boundary, and the boundary of the nuclear island paint coating 32 gradually fades.

[0051] The sealing connection method at the junction between the mechanical penetration 11 and the concrete structure at the containment boundary (the reactor hall wall) is as follows Figure 3 as shown. The mechanical penetration 11 is placed in the concrete structure at the containment boundary (i.e., the wall 36). A wing ring 34 is provided on the outer periphery of the mechanical penetration 11. The wing ring 34 is inserted into the concrete structure at the containment boundary (i.e., the wall 36) to increase the fixing strength of the mechanical penetration 11. Before pouring the concrete structure at the containment boundary (i.e., the wall 36), a hole is left using the mechanical penetration 11 with the wing ring 34. At the junction between the mechanical penetration 11 and the concrete structure at the containment boundary, first apply polysulfide rubber 35, then cover it with a metal foil 33 for overlapping, and then apply nuclear island paint on the metal foil 33 to form a nuclear island paint coating 32. The nuclear island paint coating 32 covers from the junction between the mechanical penetration 11 and the concrete structure at the containment boundary to overlap with the nuclear island paint coating of the concrete structure at the containment boundary.

[0052] The sealing connection method at the junction between the pipe 9 forming the extended part of the containment and the concrete structure at the containment boundary is the same as that at the junction between the mechanical penetration 11 and the concrete structure at the containment boundary, as follows Figure 3 as shown.

[0053] In a specific embodiment, the metal foil can be foil materials such as tin foil and aluminum foil.

[0054] The sealing connection method at the junction between the boundary doors of the personnel access passage 13 and the equipment access passage 14 and the concrete structure at the containment boundary (the wall of the installation well for the in-plant transport barrel in the new component factory, the reactor hall wall) is as follows Figure 4 as shown. The boundary door frame 37 is fitted and connected to the concrete structure at the containment boundary (i.e., the wall 36). At the junction between the boundary door frame 37 and the concrete structure at the containment boundary (i.e., the wall 36), first chamfer with polysulfide rubber 35, and then apply nuclear island paint to form a nuclear island paint coating 32. The nuclear island paint coating 32 covers from the junction between the boundary door frame 37 and the concrete structure at the containment boundary to overlap with the nuclear island paint coating of the concrete structure at the containment boundary.

[0055] The cable penetrator 12 is hermetically connected to the concrete structure (the reactor hall wall) at the containment boundary by means of cable plugging and sealing. The hermetic connection method is as Figure 5 shown. The cable penetrator 12 includes a pre-embedded sleeve 38 and a cable 40. The pre-embedded sleeve 38 is placed in the concrete structure (i.e., the wall 36) at the containment boundary. The cables 40 are arranged at intervals in the pre-embedded sleeve 38. Gaps are formed between the cables 40 and between the cables 40 and the pre-embedded sleeve 38. High-density silicone sealant 41 is filled in the gaps, so that the pre-embedded sleeve 38 arranged with the cables 40 forms a sealed plug; Fireproof silicone sealant 39 is coated on the surface of the joint between the pre-embedded sleeve 38 and the concrete structure (i.e., the wall 36) at the containment boundary and the high-density silicone sealant 41. Before the wall 36 is poured, holes are left using the pre-embedded sleeve 38. Before cable plugging, the cables 40 are first arranged in a staggered and spaced manner in the holes of the pre-embedded sleeve 38, and sufficient gaps are left between the cables 40 and between the cables 40 and the pre-embedded sleeve 38. Then, the high-density silicone sealant 41 is used to fully fill all the gaps in the holes; Finally, the fireproof silicone sealant 39 is used to coat the surface of the joint between the pre-embedded sleeve 38 and the wall 36 and the high-density silicone sealant 41.

[0056] As Figure 1 shown, the ventilation and filtration system includes a supply air pipeline, an exhaust air pipeline, a high-efficiency filter 18, an exhaust air fan 19, an exhaust chimney 20, an exhaust isolation valve 21, a supply air isolation valve 22, and a supply air fan 23.

[0057] A supply air pipeline is provided between the top shield 5 of the reactor and the reactor hall 6 and between the reactor pit 7 and the reactor hall 6 respectively. The inlet of the supply air pipeline is arranged outside the reactor hall 6. The first outlet of the supply air pipeline is arranged in the top shield 5 of the reactor, and the second outlet of the supply air pipeline is arranged in the reactor pit 7; Since the reactor hall 6 and the reactor pit 7 are connected, the reactor hall 6 and the reactor pit 7 can be supplied with air simultaneously through the second outlet of the supply air pipeline arranged in the reactor pit 7; A supply air isolation valve 22 and a supply air fan 23 are provided on the supply air pipeline. The supply air isolation valve 22 is arranged inside the reactor hall 6, and the supply air fan 23 is arranged outside the reactor hall 6.

[0058] There is an exhaust chimney 20 outside the reactor hall 6. An exhaust pipeline is provided between the reactor pit 7 and the exhaust chimney 20. The outlet of the exhaust pipeline is connected to the inlet of the exhaust chimney 20, and the inlet of the exhaust pipeline is communicated with the reactor pit 7. Since the reactor hall 6 and the reactor pit 7 are connected, radioactive substances in both the reactor hall 6 and the reactor pit 7 can be discharged simultaneously through the inlet of the exhaust pipeline (the top shield 5 is not the last shielding layer, and the exhaust is mainly to prevent the low-level discharge through the last shielding layer of the reactor hall 6, so no exhaust pipeline is provided inside the top shield 5); an exhaust isolation valve 21, a high-efficiency filter 18, and an exhaust fan 19 are provided on the exhaust pipeline. The exhaust isolation valve 21 is provided outside the reactor pit 7, and the high-efficiency filter 18 and the exhaust fan 19 are provided outside the reactor hall 6 or outside the reactor pit 7 to filter radioactive aerosols through the high-efficiency filter 18.

[0059] The sealing connection method at the concrete structure junction of the supply pipeline, exhaust pipeline and the containment boundary is the same as that at the concrete structure junction of the mechanical penetrator 11 and the containment boundary, as Figure 3 shown.

[0060] In the later stage of the accident, post-accident ventilation filtration is started. The exhaust isolation valve 21 and the supply isolation valve 22 are opened, and the exhaust fan 19 and the supply fan 23 are operated. After filtering radioactive sodium aerosols and fission products, they are discharged through the high-level exhaust chimney 20 to minimize the radioactive consequences to the environment. The post-accident ventilation filtration system of the containment ensures the controllable discharge of radioactive substances, maintains a slightly negative pressure in the later stage of the containment accident, and filters radioactive sodium aerosols, fission product aerosols, etc. inside the containment.

[0061] The present invention has been described in detail above in conjunction with the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present invention. The content not described in detail in the present invention can all adopt the prior art.

Claims

1. A large fast reactor low-pressure containment system, characterized in that, It includes a low-pressure containment system and a ventilation and filtration system; the low-pressure containment system is used to contain radioactive substances during normal operation and accident conditions, ensure the airtightness of the containment boundary, and conduct in-containment nuclide sealed decay in the initial stage of the accident; the ventilation and filtration system is used to filter and discharge radioactive substances after the decay of short-lived nuclides in the later stage of the accident, and maintain the radioactive levels in the plant and the environment at a low level; the low-pressure containment system includes a containment (16); the containment (16) includes a reactor hall (6), a reactor pit (7), an in-plant transportation barrel installation well for new components (8), and boundary items; the outer boundaries connecting the reactor hall (6), the reactor pit (7), and the in-plant transportation barrel installation well for new components (8) form the containment boundary; the boundary items are hermetically connected to the concrete structure at the junction of the containment boundary. The reactor hall (6), the reactor pit (7), and the in-plant transportation barrel installation well for new components (8) are all non-prestressed concrete structures. The reactor pit (7) is entirely covered with steel cladding, the top of the reactor hall (6) is provided with steel formwork, the bottom plate of the reactor hall (6) is covered with steel cladding, and the nuclear island paint is applied to the concrete walls around the reactor hall (6) to form a nuclear island paint coating on the concrete structure of the containment boundary; the in-plant transportation barrel installation well for new components (8) is entirely coated with nuclear island paint to form a nuclear island paint coating on the concrete structure of the containment boundary. The boundary items include: pipes (9), mechanical penetrations (11), cable penetrations (12), personnel access channels (13), equipment access channels (14), fuel transfer channels (15), and containment boundary covers (17) that form extended parts of the containment. The pipes (9), mechanical penetrations (11), cable penetrations (12), personnel access channels (13), equipment access channels (14), fuel transfer channels (15), and containment boundary covers (17) that form extended parts of the containment are respectively arranged on the containment boundary. The mechanical penetration (11) is placed in the concrete structure of the containment boundary. A wing ring (34) is provided on the outer periphery of the mechanical penetration (11), and the wing ring (34) extends into the concrete structure of the containment boundary. At the junction of the mechanical penetration (11) and the concrete structure of the containment boundary, polysulfide rubber (35) is first coated, then a metal foil (33) is covered on the polysulfide rubber (35) for lapping, and then nuclear island paint is coated on the metal foil (33) to form a nuclear island paint coating (32). The nuclear island paint coating (32) covers from the junction of the mechanical penetration (11) and the concrete structure of the containment boundary to overlap with the nuclear island paint coating on the concrete structure of the containment boundary. The boundary door frames (37) of the personnel access channel (13) and the equipment access channel (14) are fitted and connected to the concrete structure of the containment boundary. At the junction of the boundary door frame (37) and the concrete structure of the containment boundary, polysulfide rubber (35) is first used for chamfering, and then nuclear island paint is coated to form a nuclear island paint coating (32). The nuclear island paint coating (32) covers from the junction of the boundary door frame (37) and the concrete structure of the containment boundary to overlap with the nuclear island paint coating on the concrete structure of the containment boundary.

2. The large fast reactor low-pressure containment system according to claim 1, characterized in that The low-pressure containment system further includes a core melt collector (2). A main vessel (3) is provided in the reactor pit (7), and the core melt collector (2) is provided at the inner bottom of the main vessel (3).

3. A large fast reactor low-pressure containment system according to claim 1, characterized in that, The low-pressure containment system further includes a sodium leakage receiving and suppressing tray (4). The sodium leakage receiving and suppressing tray (4) is provided at the bottom of the reactor pit (7).

4. A large fast reactor low-pressure containment system according to claim 1, characterized in that, The low-pressure containment system further includes a reactor top shield (5). The reactor top shield (5) is provided at the top of the main vessel (3).

5. A large fast reactor low-pressure containment system according to claim 1, characterized in that, The reactor hall (6) is provided above the reactor pit (7). The reactor hall (6) communicates with the reactor pit (7) to form a mushroom-shaped structure. The installation well (8) for the in-plant transport cask of new components is provided under the floor slab of the reactor hall (6). The reactor hall (6), the reactor pit (7), and the installation well (8) for the in-plant transport cask of new components are connected to form a sealed structure.

6. The large fast reactor low-pressure containment system according to claim 1, characterized in that, An equipment access passage (14) is opened on the wall of the reactor hall (6) near the floor slab. A personnel access passage (13) is opened on the wall of the installation well (8) for the in-plant transport cask of new components and the reactor hall (6). Pipes (9), mechanical penetrations (11), and cable penetrations (12) that form an extension of the containment are provided on the wall of the reactor hall (6). Safety containment isolation valves (10) are installed respectively upstream and downstream of the mechanical penetration (11). A fuel transfer passage (15) is opened on the floor slab of the reactor hall (6), and a containment boundary cover plate (17) is provided.

7. A large fast reactor low-pressure containment system according to claim 1, characterized in that, The cable penetration (12) is sealed and connected to the concrete structure of the containment boundary by means of cable plugging and sealing. The cable penetration (12) includes a pre-embedded sleeve (38) and cables (40). The pre-embedded sleeve (38) is placed in the concrete structure of the containment boundary. The cables (40) are arranged at intervals in the pre-embedded sleeve (38). Gaps are formed between the cables (40) and between the cables (40) and the pre-embedded sleeve (38). High-density silicone sealant (41) is filled in the gaps so that the pre-embedded sleeve (38) arranged with the cables (40) forms a sealed plug. Fireproof silicone sealant (39) is coated on the surface at the junction of the pre-embedded sleeve (38) and the concrete structure of the containment boundary and on the surface of the high-density silicone sealant (41).

8. A large fast reactor low-pressure containment system according to claim 1, characterized in that, The containment boundary cover plate (17) is provided with a double-seal ring and has the condition for single-body sealing test. During the installation and commissioning stage of the power plant, the containment boundary cover plate (17) is movable. After the installation and commissioning of the power plant are completed, the infrequently used containment boundary cover plate (17) is welded to the steel clad surface of the floor slab of the reactor hall (6), and 100% penetrant inspection is carried out on the surface of the welded seam. A gate valve is provided at the junction of the fuel transfer passage (15) and the steel clad surface of the floor slab of the reactor hall (6). By controlling the opening and closing of the gate valve, the fuel transfer passage (15) is connected or closed.

9. A large fast reactor low-pressure containment system according to claim 1, characterized in that The ventilation and filtration system includes a supply air pipeline, an exhaust air pipeline, a high-efficiency filter (18), an exhaust air fan (19), an exhaust chimney (20), an exhaust isolation valve (21), a supply air isolation valve (22), and a supply air fan (23); a supply air pipeline is provided between the top shield (5) and the reactor hall (6), and between the reactor pit (7) and the reactor hall (6). The inlet of the supply air pipeline is located outside the reactor hall (6), the first outlet of the supply air pipeline is located in the top shield (5), and the second outlet of the supply air pipeline is located in the reactor pit (7); a supply air isolation valve (22) and a supply air fan (23) are provided on the supply air pipeline; an exhaust chimney (20) is provided outside the reactor hall (6), an exhaust air pipeline is provided between the reactor pit (7) and the exhaust chimney (20), the outlet of the exhaust air pipeline is connected to the inlet of the exhaust chimney (20), and the inlet of the exhaust air pipeline communicates with the reactor pit (7); an exhaust isolation valve (21), a high-efficiency filter (18), and an exhaust air fan (19) are provided on the exhaust air pipeline.

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