Integral nuclear reactor with heavy liquid metal coolant

Abstract

A monolithic nuclear reactor with a heavy liquid metal coolant, comprising a reactor housing (9) closed with a cover (1) and having a bottom cavity (16) formed by an isolation structure connected to the cover (1), a core, at least one primary circuit circulation pump (21), at least one heat exchanger, and a plug (25); the primary loop circulating pump is positioned in a circulating pump shell (2), and the circulating pump shell is connected with the cover (1); the heat exchanger is located in a heat exchanger shell (20), the heat exchanger shell is connected with the cover (1), and the heat exchanger is used for removing heat from the heavy liquid metal coolant to the secondary circuit coolant. The isolation structure adopts an annular element (11) fixed on the reactor shell (9); the reactor core shell (3) is inserted on the guide shell of the annular element and is connected with the cover (1) of the reactor; the reactor internal device (8) comprises a plurality of channels limiting the circulation of the coolant, connected to each other and fixed to the periphery of the cover (1) of the reactor; the bottom end of the heat exchanger shell (20) is arranged above the annular element (11); furthermore, the bottom end of the housing (2) of the circulation pump (21) penetrates into the bottom cavity (16) through an opening in the annular element (11). According to the invention, the degree of freedom of longitudinal and radial movement of each structural component element of the nuclear reactor relative to each other in the heating and cooling process is ensured, so that the corrosion resistance and required friction performance of the material are improved, and the speed of a coolant at a bottom cavity and a reactor core inlet is balanced; and the fuel assembly is reliably fixed when floating abnormally without influencing temperature expansion, so that the operation safety and reliability of the nuclear reactor are improved.

Description

Technical Field

[0001] The present invention relates to the field of nuclear energy, and in particular to a nuclear reactor with a heavy liquid metal coolant. More particularly, the present invention relates to a shell device of an integral nuclear reactor with a heavy liquid metal coolant. Background Art

[0002] The first characteristic of the integral nuclear reactor is that it has no primary circuit coolant pipes. In addition to the core, the reactor shell also contains all the main equipment for discharging the core heat to the secondary circuit coolant. In addition, the integral nuclear reactor also includes the reactivity control mechanism required for power control and system equipment for monitoring the coolant temperature and flow at various points of the circuit. All these equipment are basically located on the reactor shell or connected to it. The chain fission reaction that maintains and accompanies the migration of neutrons and radiation in the core is accompanied by heat release, both in the core and in the reflectors and surrounding structures. The heat removal of the core elements and the structural elements arranged in the nuclear reactor shell requires the organization of circulation and the distribution of the coolant flow so that the temperature of the structural elements does not exceed the permissible value. For this purpose, pipes, channels, and throttling devices are provided in the reactor structures to ensure the distribution of the coolant flow required for cooling.

[0003] Important devices installed in the reactor shell include components around the core and components that perform the function of neutron reflectors, and radiation protection devices, which provide neutron and radiation absorption. Under the condition that all adverse factors are fully effective, the radiation protection devices also reduce the negative impact of neutron and radiation absorption on some components in the reactor that must ensure the integrity of the structural parts and working performance.

[0004] All housing devices and metal structures should be securely fixed. At the same time, nuclear reactor equipment with heavy liquid metal coolant operates under temperature gradients of up to hundreds of degrees. The temperature differences associated with the different elongation rates or size changes of structural components at different temperatures can be very large. Without a special structural solution to ensure the freedom of movement of the different components when heated and cooled, very large stresses may occur, limiting the service life of the structural components or causing them to be damaged.

[0005] Therefore, there is an urgent need to develop structures that can prevent or reduce the mechanical influence of components on each other when the temperature gradient is large, and also to eliminate the uncontrolled or accidental escape of coolant through the gaps, which are necessary to ensure the freedom of thermal expansion of the structural components. The latter important task is more complicated because the reactor is a large device, and even when assembled in the cold state, it is necessary to have the gaps required to compensate for production errors.

[0006] Another important feature of reactors with heavy liquid metal coolants is that the density of all structural and radiation protection materials is actually lower than the density of the coolant. Therefore, when using equipment to fix structural components and related reactor internal devices to the bottom or side walls of the shell, tensile stresses will appear due to the influence of buoyancy on these components. Tensile stresses in structural components and welds are the most dangerous from the perspective of stress corrosion development.

[0007] When manufacturing reactor shell structural parts and connecting the reactor internal devices to the shell, it is priority to conduct compressive stress testing on the detachable and non-detachable joints of the structural components, which is also an important technical task.

[0008] An integral nuclear reactor with a heavy liquid metal coolant has been disclosed (US10699816, international patent numbers G21C 1 / 03, G21C 1 / 32, G21C 5 / 02, G21C 15 / 06, published on June 30, 2020), comprising a reactor shell, a hot catcher located above the core, and a cold catcher surrounding the hot catcher and separated by an isolation structure, wherein a primary fluid circulates in the cold catcher, in particular a heavy liquid metal coolant. The reactor comprises at least one heat exchanger, in particular a steam generator, in order to remove heat from the heavy liquid metal coolant by means of a secondary fluid, in particular water. The isolation structure comprises a bottom element and a top element, the bottom element being arranged around the core, and the top element being arranged above the core. The top element has a smaller radial distance relative to the bottom element and is connected to the bottom element by a connecting element. The connecting element is provided with an opening through which a vertical channel passes so as to be connected to one or more heat exchangers, which are arranged between the top region of the isolation structure and the reactor shell and are used to receive heavy liquid metal coolant from the core. The connecting element and the top element of the isolation structure form a core limiter, specifically a radial limiter in the inactive top region of the fuel unit.

[0009] The isolation structure also has a complex-shaped shell, which is fixed to the reactor cover by brackets. However, in this case, the bottom of the shell is not fixed, which is an obvious disadvantage. If the core installed in the shell is large and heavy, this structural solution will increase the load in the bracket fixing area, which is particularly dangerous when subjected to earthquake loads.

[0010] Also disclosed is an integral nuclear reactor with heavy liquid metal coolant (RU2756231, international patent number: G21C1 / 00, published on September 28, 2021), comprising a reactor shell with a bottom cavity, a core, a hot cavity, a top cavity and a heat exchanger. The hot cavity is arranged above the core, comprising: a hot cavity shell, which is substantially cylindrical and has a heat discharge pipe for discharging hot coolant from the core to the heat exchanger; and a plug, wherein the heat discharge pipe is flushed from the outside with cold coolant from the outlet of the heat exchanger. The hot cavity shell comprises an inner shell and at least one auxiliary shell, which is provided with a gap on the outside, is concentric with the inner shell, and forms at least one hot cavity channel. Each heat discharge pipe comprises an inner shell and at least one auxiliary shell, which is provided with a gap on the outside, is concentric with the inner shell, and forms at least one tube channel, at least one hot cavity channel and at least one tube channel are connected to the outlet of the heat exchanger so as to guide the cold coolant to these channels.

[0011] The invention reduces the thermal load of the heat chamber components, mainly the thermal load of the entire shell of the heat chamber and the heat coolant heat exhaust pipe, including adjusting and reducing the temperature gradient generated in the above components, thereby increasing the service life of these components. However, the design and production process of the heat exhaust pipe and the heat chamber are complex, making it difficult to achieve the above results.

[0012] A reactor with a heavy liquid metal coolant is also disclosed (JP2022097583, international patent numbers: G21D1 / 02, G21C1 / 02, G21C13 / 00, G21C15 / 02, published on June 30, 2022), comprising a shell closed by a lid, a core is arranged in the shell, a hot collector located above the core, a cold collector surrounding the hot collector and separated by a separation structure, and a primary fluid is arranged in the cold collector for cooling the core. The reactor is also provided with a heat exchanger, a primary fluid inlet is arranged at the bottom of the heat exchanger, and a surrounding discharge hole is arranged near the free liquid surface of the primary fluid in the cold collector. The discharge hole is arranged in the middle position relative to the tube bundle, partially protruding from the free liquid surface in the cold collector, and the primary fluid is added through auxiliary equipment to establish a negative pressure in the gas of the heat exchanger relative to the gas in the container. The heat exchanger is convexly arranged, and its discharge hole is arranged near the free liquid surface of the primary fluid to minimize the movement of the primary fluid when the secondary fluid in the heat exchanger is accidentally discharged.

[0013] Since there is no structural solution to ensure the freedom of movement of the different components of the reactor when heated and cooled, these components of the reactor are subjected to very large stresses, which limits the service life of the structural parts or causes them to be damaged, making the reliability of the disclosed nuclear reactor low.

[0014] A reactor with a heavy liquid metal coolant is also disclosed (US20180061513, International Patent Numbers: G21C1 / 03, G21C15 / 14, G21C1 / 32, G21C5 / 02, published on June 30, 2020), which is consistent with the technical solution of the present invention in terms of the maximum number of essential features and can be regarded as a prototype. The nuclear reactor prototype includes a reactor shell closed by a lid, in which a core well, a heat collector located above the core and a bottom cavity separated by an isolation structure are provided, and a primary fluid circulation is provided in the bottom cavity for cooling the core. The reactor also includes at least one heat exchanger fixed to its lid, in particular a steam generator, for removing heat from the primary fluid by a secondary fluid. The isolation structure includes a bottom element and a top element, the bottom element is arranged around the core, and the top element is arranged above the core. The top element has a smaller radial distance than the bottom element and is connected to the bottom element by a connecting element, which is made of plastic or the like. The connecting element is provided with an opening through which a vertical channel passes so as to be connected to one or more heat exchangers, which are arranged between the top region of the isolation structure and the reactor shell and are used to receive the primary hot fluid from the core. The connecting element and the top element of the isolation structure form a core limiter, specifically a radial limiter in the inactive top region of the fuel unit.

[0015] The known nuclear reactor prototype has insufficient reliability due to the fact that, as the different elements of the reactor structure have no freedom of movement when heated and cooled, tensile stresses are generated in the structural elements due to the buoyancy force, which have a density lower than that of the liquid metal coolant, and, due to the coolant cavity provided in the reactor shell and the very low coolant velocity, areas of poor coolant movement are formed, which lead to corrosion damage due to poor monitoring of the coolant quality. Summary of the invention

[0016] The object of the present invention is to develop a nuclear reactor, in particular a nuclear reactor with a heavy liquid metal coolant, which improves the operational safety and reliability of the nuclear reactor by ensuring the freedom of longitudinal and radial movement of the structural components of the nuclear reactor relative to each other during assembly, heating and cooling, improving the corrosion resistance and required friction properties of the contact materials, balancing the speed of the coolant at the bottom cavity and the core inlet, and ensuring a controlled and limited compression force that ensures that the fuel assemblies are reliably fixed during abnormal floating without affecting temperature expansion.

[0017] By solving the above problems, the present invention can achieve the following technical effects:

[0018] - provide freedom of longitudinal and radial movement of the different elements relative to each other during heating and cooling, without which the coolant could escape uncontrolled or accidentally through the gaps, thereby reducing the cooling reliability of the reactor equipment and generating very large stresses, which in turn limit the service life of the structural parts or cause their destruction;

[0019] - Improve the corrosion resistance and required friction properties of the material;

[0020] - equalizing the coolant velocity at the bottom cavity and the core inlet, which is very important to ensure reliable cooling and safety of the components;

[0021] - Ensure that the fuel assembly is securely fixed during abnormal floating without affecting temperature expansion by limiting the compressive force;

[0022] - Improve the operational safety and reliability of the reactor.

[0023] In order to solve the above problems, the present invention provides a nuclear reactor with heavy liquid metal coolant, comprising: a reactor shell, a core, at least one primary loop circulation pump, at least one heat exchanger, and a plug, wherein the reactor shell is closed by a cover and has a bottom cavity formed by an isolation structure connected to the cover; the primary loop circulation pump is located in the circulation pump shell, and the circulation pump shell is connected to the cover; the heat exchanger is located in the heat exchanger shell, and the heat exchanger shell is connected to the cover, and the heat exchanger is used to remove heat from the heavy liquid metal coolant to the secondary loop coolant. Its novelty lies in that the isolation structure adopts an annular element fixed to the reactor shell; the core shell is inserted on the guide shell of the annular element and connected to the cover of the reactor; the internal device of the reactor includes a plurality of channels for limiting the circulation of the coolant, the plurality of channels are interconnected and fixed to the periphery of the cover of the reactor; the bottom end of the heat exchanger shell is arranged above the annular element; and the bottom end of the circulation pump shell penetrates into the bottom cavity through the opening in the annular element.

[0024] The bottom of the core shell may be provided with a support plate, in which a fuel assembly (FA) with a control and protection system (CPS) channel and a reflector unit are fixed.

[0025] In the reactor plug, the end of the control and protection system channel may be tapered, and its inner surface contacts the head of the fuel assembly.

[0026] A diaphragm may be provided below the top in the plug, to which the control and protection system passage is connected using an elastic bellows joint, and the elastic bellows joint limits stress transmitted to the head of the fuel assembly.

[0027] An auxiliary annular element with a smaller diameter may be provided below the annular element. The auxiliary annular element is provided with at least one opening. An annular collector is formed between the annular element and the auxiliary annular element. The inlet of the annular collector is connected to the outlet of the circulation pump, and the outlet is connected to the bottom chamber.

[0028] A heat sink may be provided below the auxiliary annular element, the heat sink being fixed to the bottom of the reactor shell for guiding the coolant from the periphery of the bottom cavity to its center. Preferably, in order to balance the azimuth distribution of the flow, an opening for ensuring the azimuth is provided in the heat sink.

[0029] An annular groove may be provided in the circulating pump housing, and at least one piston sealing ring may be provided in the annular groove. When the circulating pump housing moves radially, the sealing ring may move radially and cover the gap between the circulating pump housing and the annular element.

[0030] An annular groove may be provided in the core shell, and at least one piston sealing ring may be provided in the annular groove. When the core shell moves radially, the sealing ring may move radially and cover the gap between the core shell and the annular element.

[0031] The piston sealing ring can be made of high-strength gray cast iron containing lamellar graphite and a silicon content of not less than 1%, or corrosion-resistant stainless steel.

[0032] Each shell is rigidly connected to the reactor cover by means of detachable or non-detachable joints. The most important equipment is located in these shells, and the reactor can be inspected, repaired or replaced during operation. The required openings are provided in the above shells to realize the circulation of coolant. When heated or cooled, the above shells can move freely in the longitudinal direction, and special sliding seals are provided at the places where they cooperate with other elements of the structure so as not to affect such movement.

[0033] Thus, for example, circulating pumps, steam generators or heat exchangers between primary and secondary circuits, core support structures, extractable parts of the core and radial reflectors and plugs above the core may be extractable elements of the reactor structure.

[0034] The main part of the reactor internal device, including pipes and coolant guide channels, is combined into an assembly structure and connected to the reactor cover. In this case, all stresses generated by the buoyancy of the coolant with a density higher than that of the structural member are guided from bottom to top and finally transmitted to the reactor cover. Considering that most of the reactor internal device is located and fixed on the reactor cover, including the circulation pump with a transmission device, the regulating mechanism transmission device, the introduction chamber and the outlet chamber, the steam or heat exchanger pipe, the external radiation protection device and other elements, the stresses generated by the Archimedean buoyancy are largely compensated by the weight of these devices, which is beneficial to the working performance of the cover. In this case, the internal elements that do not belong to the core elements are preferably fixed around the reactor cover, which is beneficial to reduce the bending moment and improve the working performance of the cover.

[0035] For coolant flow guide elements, it should be ensured that only the minimum number necessary is fixed to the bottom of the reactor, and the elements are provided with interfaces with the shell to arrange the core and pumps. The interface is equipped with seals to ensure that the shell can move freely longitudinally and only produce limited radial movement, while maintaining tightness or significantly limiting overflow.

[0036] It is necessary to compensate for dimensional tolerances and temperature expansion during production to determine the allowable radial movement value in the seal. In this case, large radial movement of the reactor is impossible, because large movement will cause danger when external conditions significantly affect the reactor, such as earthquakes. The seal can be selected from the existing technical solutions disclosed in the field, but the piston seal is the most preferred material. In this case, the gray cast iron grade material containing layered graphite is the most preferred material. The content of silicon and layered graphite inclusions in this grade of cast iron is (1-3) weight percent, which improves the corrosion resistance and required friction properties of the seal material; when the pressure difference is not large, a labyrinth seal can be used. By using the methods disclosed in the field for hydraulic calculations, it can be determined whether a labyrinth seal can be used, but the calculated leakage value must be determined separately when the specific implementation project is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is illustrated by the following drawings:

[0038] Figure 1 A projection diagram of a nuclear reactor having a heavy liquid metal cooler is shown, including a partial cross-section;

[0039] Figure 2 A cross-sectional view showing the interface between the end of the control and protection system channel and the head of the fuel assembly;

[0040] Figure 3 A cross-sectional view showing the elements that secure the control and protection system channel to the middle support plate of the plug;

[0041] Figure 4 shows a cross-sectional view of a seal unit with a self-mounting seat;

[0042] Figure 5 Shows Figure 4 an enlarged view of unit G shown in ; and

[0043] Figure 6 An embodiment is shown in which the seal unit is provided in a removable joint in the extractable and non-extractable elements of the housing, for example Figure 1 The unit E shown: embodiment A is a rectangular sealing ring; embodiment B is a wire sealing ring; embodiment C is a labyrinth sealing ring.

[0044] The following reference numerals are used to indicate components in the drawings:

[0045] 1: Reactor cover;

[0046] 2: Circulation pump housing;

[0047] 3: end shell;

[0048] 4: Circulation pump housing sealing unit;

[0049] 5: Core well sealing unit;

[0050] 6: triangle iron;

[0051] 7: Coolant channel;

[0052] 8: Reactor internal device;

[0053] 9: Reactor shell;

[0054] 10: bottom;

[0055] 11: Ring element;

[0056] 12: Reactor core well shell;

[0057] 13: Core well sealing unit;

[0058] 14: Connect the shell;

[0059] 15: auxiliary annular element;

[0060] 16: bottom cavity;

[0061] 17: Guide triangle iron;

[0062] 18: Shell;

[0063] 19: supporting flange;

[0064] 20: A housing for arranging a steam generator or a heat exchanger module between the primary circuit and the secondary circuit;

[0065] 21: primary loop circulation pump;

[0066] 22: core well support plate;

[0067] 23: fuel assembly;

[0068] 24: reflector;

[0069] 25: Reactor plug;

[0070] 26: Flange;

[0071] 27: Control and protection system transmission device;

[0072] 28: Control and protection system inside the plug;

[0073] 29: Control and protection system channel terminal;

[0074] 30: fuel assembly head;

[0075] 31: middle support plate of the plug;

[0076] 32: Corrugated unit for the control and protection system channel in the plug;

[0077] 33: Seal unit self-mounting seat;

[0078] 34: Assemble the joint;

[0079] 35: bottom of mounting base;

[0080] 36: Install the seat ring;

[0081] 37: Pin;

[0082] 38: Sealing ring;

[0083] 39: Pressing circle;

[0084] 40: Coolant overflow hole;

[0085] 41: Piston sealing ring;

[0086] 42: Iron wire sealing ring;

[0087] 43: Circulation pump transmission device;

[0088] 44: Rectangular sealing ring. DETAILED DESCRIPTION

[0089] Figure 1 A nuclear reactor with a heavy liquid metal coolant is schematically shown.

[0090] The cover 1 of the reactor shell 9 includes a shell 2 of a circulating pump 21 and a core well shell 12 with an end shell 3, on which the sealing units 4 and 5 of the circulating pump shell 2 and the end shell 3 are arranged. A fixing element for connection is also arranged in the reactor cover 1, such as a triangular iron 6 of the reactor internal device 8. Preferably, the triangular iron 6 is connected to the periphery of the reactor cover 1. The elements of the shell internal device 8 are arranged between the reactor cover 1 and the annular element 11, and they are assembled into a unified structure, which may include a thermal protection or radiation protection device (not shown in the figure), a coolant channel, for example, the coolant channel 7 is connected to the catcher above the core shell, and is used to set the heat exchanger shell 20 or other elements disclosed in the art. The elements of the reactor internal device 8 are assembled into an assembly unit, and then formed into an assembly unit with the cover 1, and connected to the reactor shell 9. On the element for supplying coolant to the core from the primary loop circulation pump 21 of the belt drive 43, a bottom 10 is formed, which cooperates with other elements of the structure via sliding and detachable joints, and the main loads it is subjected to include the weight of the coolant and the pressure difference between different areas of the circuit. The annular element 11 is sealed and connected to the bottom 10. A connecting shell 14 is arranged in the annular element 11 along the inner ring, and the connecting shell includes an end shell 3, in which a sealing unit 13 and a joint with the core well shell 12 are arranged. An opening and a sealing unit 4 are provided in the annular element 11 for aligning with the shell 2 of the circulation pump 21. Using the connecting shell 14, an auxiliary annular element 15 is connected to the annular element 11, so that an annular cavity is formed between the annular element 11 and the auxiliary annular element 15, and the liquid from the circulation pump 21 flows into the annular cavity, where it is redistributed and discharged to the bottom cavity 16 through the periphery of the annular cavity. The coolant flowing out of the annular cavity can pass through the annular gap, such as Figure 1As shown, for example, it flows out through a hole system (not shown in the figure), so that the coolant flow is more evenly distributed in the azimuth. In order to balance the velocity field, the guide triangle 17 can be connected to the annular element 15. Therefore, the velocity of the coolant at the entrance of the bottom cavity 16 is balanced, and an additional technical effect is achieved, which is very important for ensuring reliable cooling and safety of the components. In the triangle 17, an overflow hole 40 can be provided to improve the balance of the velocity. The assembly unit of the cover 1 is connected to the assembly unit of the internal device of the reactor, and then connected to the outer shell 18 of the reactor shell 9, which is first connected to the bottom 10 to form a reactor shell assembly. In this case, the reactor shell assembly is supported on the supporting structure of the reactor well by a support flange 19, and the support flange is provided on the reactor cover 1. A shell 20 for arranging a steam generator or a heat exchanger module between the primary circuit and the secondary circuit is provided in the reactor shell assembly, and a circulating pump 21 is fixed on the reactor cover 1. The heat exchange surface of the heat exchanger and the fixing unit for fixing it to the reactor cover are not shown in the figure and can have different embodiments known in the art. The weight load and buoyancy of the part of the above-mentioned element immersed in the coolant are transmitted to the reactor cover 1 from multiple directions. The core support plate (shroud) 22 is fixed to the end shell 3, and the fuel assembly 23 and the reflector element 24 are fixed in the end shell in turn. Finally, stresses in multiple directions act on the above-mentioned elements 23, 24. To a large extent, the downward gravity and the upward buoyancy compensate each other, and the final stress is transmitted to the shell 3, 12 and the reactor cover 1. The isolation structure assembled by the shell 3 and 12 can be in the form of an assembly element, or it can be divided into additional assemblies along the height while maintaining the sealing of the connection. This solution can solve the technical problems related to the selection of different materials according to the height of the isolation structure, for example, when the conditions of use of the materials are very different. A reactor plug 25 with a flange 26 is provided on the reactor cover 1, and a transmission device 27 of the control and protection system mechanism is provided on the plug. The resulting force is transmitted to the reactor cover 1 similarly to the previous case.

[0091] Therefore, the present invention eliminates the stress transmission from the core elements, the reactor internal devices or the equipment on the bottom 10 of the reactor shell 9 in principle. Accordingly, the important equipment is not connected to the reactor bottom 10, and the accidents caused by the rupture of such joints and the uncontrolled floating of various equipment or reactor elements are also prevented. The overall weight load of the core, the reactor internal devices 8, the plug 25 and other elements of the reactor is compensated by the Archimedean buoyancy and transmitted from bottom to top to the cover 1. The circulating pump 21 with the transmission device 43 and the control and protection system transmission device 27 are respectively arranged on the reactor cover 1 and the plug 25, and the additional loads from them are compensated by the priority effect of buoyancy. By compressing the fuel assembly 23 with the control and protection system channel 28 in the plug 25, when the fuel assembly 23 is fixed in the core well support plate 22 by the lower handle, it is ensured that the fuel assembly 23 can be reliably fixed when it is not floating normally, which is very important for safety. In this case, the compression should be limited and cannot affect the temperature expansion.

[0092] The bottom of the control and protection system channel 28 in the plug 25 is provided with an end 29 with a conical surface, along which the end 29 is matched with the head 30 of the fuel assembly 23 ( Figure 2 The end 29 of the control and protection system channel 28 is fixed to the middle support plate 31 of the plug 25 through the bellows unit 32, so that the control and protection system channel 28 can move vertically within the movement range of the bellows, which is connected to the middle support plate 31 ( Figure 3 ).

[0093] Coolant leaks in the seal unit must be limited in order to reliably cool the core and the reactor internals 8. In this case, freedom of thermal expansion and ease of assembly should be ensured, which is also an important task considering the very large dimensions of the nuclear reactor installation. When the maximum load of the seal unit and the pressure difference between the booster chamber of the circulating pump 21 and the rest of the circuit are large, it is preferred to use a seal unit with a self-mounting seat 33, such as Figure 4 and Figure 5 As shown. The mounting seat 33 has an assembly joint 34 connected to the bottom 35 of the mounting seat 33, which is used to assemble the mounting seat 33 and the mounting seat ring 36 and ensure that the two operate together. The mounting seat and the mounting seat ring are matched along a spherical surface with a radius R, and the center of the circular surface is located on the axis of the mounting seat ring 36. In order to limit movement, four pins 37 are used to fix the mounting seat ring 36 along mutually perpendicular axes. The entire unit assembly is fixed in the annular element 11, and the sealing ring 38 and the pressure ring 39 are used to prevent axial movement and leakage. The sealing ring and the pressure ring are welded to the annular element 11 in turn. Gap δ( Figure 5) ensures that the unit seal can be moved horizontally without damage. The size of the required gap is related to the process tolerance, production and assembly accuracy of large and extra-long equipment of the reactor, and is determined by dimensional engineering calculations known in the art. The extractable housing 2 of the pump well is sealed along the inner surface of the mounting seat ring 36 by a piston seal 41, which is preferably made of gray cast iron containing lamellar graphite.

[0094] For large diameter removable joints, for example, the joints between the annular shell 3 of the core well and the corresponding fixed seal unit, it is preferred to use Figure 6 In this case, preferably, a rectangular seal ring 44 similar to the piston seal ring 41, a wire seal ring 42 ( Figure 6 , embodiment B) or labyrinth seal 43 ( Figure 6 , Example C).

[0095] Finally, the metal structural parts of the reactor cover mainly operate under compressive stress conditions. The bottom of the reactor shell is unloaded through the joints with the core support structure. The internal devices of the reactor and the detachable elements of the reactor are unloaded through temperature expansion and can move longitudinally freely and independently while maintaining the sealing of the mating area, which is beneficial to the working performance and safety of the structural parts.

Claims

1. An integral nuclear reactor with a heavy liquid metal coolant, comprising a reactor shell, a core, at least one primary loop circulation pump, at least one heat exchanger, and a plug, wherein the reactor shell is closed by a cover and has a bottom cavity formed by an isolation structure connected to the cover; The primary loop circulation pump has a circulation pump housing, and the circulation pump housing is connected to the cover; the heat exchanger is located in the heat exchanger housing, and the heat exchanger housing is connected to the cover, and the heat exchanger is used to discharge heat from the heavy liquid metal coolant to the secondary loop coolant, characterized in that: The isolation structure adopts an annular element fixed to the reactor shell; the core shell is inserted into the guide shell of the annular element and connected to the cover of the reactor; the reactor internal device includes a plurality of channels for limiting the circulation of coolant, and the plurality of channels are connected to each other and fixed to the periphery of the cover of the reactor; The bottom end of the heat exchanger housing is arranged above the annular element; and the bottom end of the circulation pump housing penetrates into the bottom cavity through the opening in the annular element.

2. The nuclear reactor according to claim 1, characterized in that: The isolation structure is made of heterogeneous materials and has detachable joints of various heights.

3. The nuclear reactor according to claim 1, characterized in that: A support plate is provided in the end element of the isolation structure, and a fuel assembly (FA) with a control and protection system (CPS) channel and a reflector unit are fixed in the support plate.

4. The nuclear reactor according to claim 1, characterized in that: In the plug of the reactor, the end of the control and protection system channel is tapered, and its inner surface contacts the head of the fuel assembly.

5. The nuclear reactor according to claim 1, characterized in that: A partition is provided below the top in the plug, a control and protection system channel is connected to the partition by an elastic bellows joint, and the elastic bellows joint limits stress transmitted to the head of the fuel assembly.

6. The nuclear reactor according to claim 1, characterized in that: An auxiliary annular element with a smaller diameter is provided below the annular element, and at least one opening is provided in the auxiliary annular element. An annular collector is formed between the annular element and the auxiliary annular element, and the inlet of the annular collector is connected to the outlet of the circulating pump, and its outlet is connected to the bottom cavity.

7. The nuclear reactor according to claim 5, characterized in that: A heat sink is provided below the auxiliary annular element and is fixed to the bottom of the reactor shell for guiding the coolant from the periphery of the bottom cavity to the center thereof.

8. The nuclear reactor according to claim 1, characterized in that An annular groove is provided in the circulation pump housing, and at least one piston sealing ring is provided in the annular groove. When the circulation pump housing moves radially, the sealing ring can move radially and cover the gap between the circulation pump housing and the annular element.

9. The nuclear reactor according to claim 1, characterized in that: An annular groove is provided in the core shell, and at least one piston sealing ring is provided in the annular groove. When the core shell moves radially, the sealing ring can move radially and cover the gap between the core shell and the annular element.

10. A nuclear reactor according to claims 8 and 9, characterised in that The piston sealing ring is made of high-strength gray cast iron or corrosion-resistant stainless steel containing layered graphite and a silicon content of not less than (1-3) weight percent.

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