Reactor body structure and reactor system

Abstract

A reactor body structure and a reactor system. The reactor body structure (100) comprises: a reactor pressure vessel (1), the reactor pressure vessel (1) comprising a bottom closure head (3), and the bottom closure head (3) having an arc-shaped inner wall (32); a reactor internal (2), the reactor internal (2) comprising a reactor core supporting lower plate (22); and a reactor core (21), the reactor core (21) being arranged on the reactor core supporting lower plate (22); wherein the reactor core supporting lower plate (22) is located on the lower side of the center of sphere of the arc-shaped inner wall (32), and the outer edge of the reactor core supporting lower plate (22) is provided with a flow guide corner (221); the reactor core supporting lower plate (22) is provided with through holes (222), the through holes (222) are stepped holes and each comprise a top hole (222a) in the upper side and a bottom hole (222b) in the lower side, and the diameter of the bottom hole (222b) is smaller than that of the top hole (222a).

Description

Reactor body structure and reactor system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310709542.5, filed on June 14, 2023, entitled “A High-Safety, Low-Flow-Resistance Reactor Body Structure and Reactor System,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of nuclear reactors, and in particular to a reactor body structure and a reactor system. Background Art

[0004] A nuclear reactor mainly includes a core, a reactor pressure vessel, and internal components. The reactor pressure vessel includes a cylinder, a top head, and a bottom head. The core is arranged in the internal components inside the reactor pressure vessel. When a serious accident occurs in the core, a safety injection system outside the reactor needs to be put into operation to inject boron-containing water into the reactor to submerge the reactor core. In the existing nuclear reactor structure, the core is located at a relatively high distance from the bottom head of the reactor pressure vessel, that is, the space at the bottom of the core is relatively large. Therefore, a large amount of boron-containing water is required to submerge the core. The submergence time of the core is long, which is not conducive to the removal of heat from the core in a serious accident, thereby reducing the safety of the reactor.

[0005] Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention provides a high-safety and low-flow resistance reactor body structure to solve the safety problems caused by long core flooding time and the inconvenience of core heat dissipation.

[0007] A first aspect of the present invention provides a reactor body structure, comprising: a reactor pressure vessel, comprising a bottom head, the bottom head having an arc-shaped inner wall; an internal component placed in the reactor pressure vessel, the internal component comprising a core support lower plate; a core, which is arranged on the core support lower plate; wherein the core support lower plate is located on the lower side of the center of the arc-shaped inner wall, and a guide angle is provided on the outer edge of the core support lower plate; the core support lower plate is provided with a through hole, which is a stepped hole, comprising a top hole on the upper side and a bottom hole on the lower side, and the diameter of the bottom hole is smaller than the diameter of the top hole.

[0008] Preferably, the guide angle and the arc-shaped inner wall of the bottom head form an equidistant or nearly equidistant flow channel, and the floating range of the flow channel width of the nearly equidistant flow channel does not exceed 100 mm.

[0009] Preferably, the guide angle is a cone angle or an arc angle, the lower diameter of the cone angle is smaller than the upper diameter, and the angle between the outer wall of the cone angle and the vertical direction is 5° to 10°.

[0010] Preferably, the distance between the top surface of the core support lower plate and the center of the arc-shaped inner wall is 0 to 300 mm.

[0011] Preferably, the distance between the top surface of the core support lower plate and the center of the arc-shaped inner wall is 250 mm.

[0012] Preferably, the diameter of the bottom hole of the through hole ranges from 38 to 64 mm.

[0013] Preferably, the reactor body structure is sequentially provided with a reactor pressure vessel cylinder, a hanging basket cylinder and a core shroud from the outside to the inside, and no neutron shielding plate is provided between the reactor pressure vessel cylinder and the hanging basket cylinder.

[0014] Preferably, the thickness of the hanging basket cylinder is 60-90 mm, the thickness of the core shroud is 30-100 mm, and the gap between the hanging basket cylinder and the core shroud is 30-60 mm.

[0015] Preferably, the thickness of the hanging basket cylinder is 60 mm, the thickness of the core shroud is 30 mm, and the gap between the hanging basket cylinder and the core shroud is 40 mm.

[0016] Preferably, the reactor pressure vessel further includes a top head, the top head is an integral structure, and the bottom head is an integral structure.

[0017] Preferably, the reactor pressure vessel is provided with an outlet pipe, the inner side of the outlet pipe has a tapered opening, and the inner diameter of the tapered opening is larger than the outer diameter.

[0018] Preferably, the tapered port is a tapered flow channel, and the tapered flow channel adopts a 5° to 15° cone surface.

[0019] The second aspect of the present invention provides a reactor system, including a pump, a steam generator and a reactor body structure, the reactor body structure including: a reactor pressure vessel, which includes a bottom head, the bottom head having an arc-shaped inner wall; an in-core component, which is placed in the reactor pressure vessel, the in-core component including a core support lower plate; a core, which is arranged on the core support lower plate; the core support lower plate is located on the lower side of the center of the arc-shaped inner wall, and the outer edge of the core support lower plate is provided with a guide angle; the core support lower plate is provided with a through hole, which is a stepped hole, including a top hole on the upper side and a bottom hole on the lower side, and the diameter of the bottom hole is smaller than the diameter of the top hole; the reactor pressure vessel has an inlet pipe and an outlet pipe, the outlet of the pump is connected to the inlet pipe of the reactor pressure vessel, the outlet pipe of the reactor pressure vessel is connected to the steam generator, and the steam generator is connected to the inlet of the pump.

[0020] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0021] The present invention adjusts the position of the core support lower plate to the lower side of the spherical center of the arc-shaped inner wall, reducing the time required for external water injection to submerge the core when the core is melted, thereby improving safety. On this basis, a diversion angle is set at the outer edge of the core support lower plate, which not only reduces the fluid resistance, but also enables the fluid flowing rapidly downward to quickly turn under the action of this flow channel, thereby improving the uniformity of the flow distribution at the core inlet. The gradually shrinking and expanding step holes on the core support lower plate form a flow channel of equal cross-section or nearly equal cross-section with the transition area of ​​the bottom head of the reactor pressure vessel under the cooperation of the diversion angle, which can quickly turn under the action of this flow channel, so that more fluid flows into the water holes outside the core, making the flow distribution effect of the water holes outside the core better.

[0022] The present invention arranges the core support lower plate on the lower side of the spherical center of the arc-shaped inner wall, arranges a guide angle on the outer edge of the core support lower plate, and arranges a stepped hole with a smaller bottom and a larger top on the core support lower plate. Through the coordination of the three, the fluid resistance in the reactor pressure vessel is reduced while improving safety, and the core has a relatively uniform core inlet flow distribution performance.

[0023] The present invention increases the thickness of the core shroud and the basket barrel, adjusts the width of the water gap between the core shroud and the basket barrel, and eliminates the neutron shielding plate on the outer wall of the basket barrel. This not only increases the flow area of ​​the flow channel on the outer wall of the basket barrel and reduces the flow resistance in this area, thereby reducing the requirements for the power of the loop flow main pump, but also avoids the stress corrosion fracture problem of the bolts in the core area caused by long-term neutron irradiation, thereby improving the reliability of the components inside the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application.

[0025] FIG1 is a schematic diagram of the structure of a reactor body in the prior art;

[0026] FIG2 is a schematic diagram of a reactor body structure according to a specific embodiment of the present invention;

[0027] FIG3 is a partial enlarged view of the bottom head position of the reactor body structure according to a specific embodiment of the present invention;

[0028] FIG4 is a partial enlarged view of a core support lower plate according to a specific embodiment of the present invention;

[0029] FIG5 is a partial enlarged view of an outlet pipe according to a specific embodiment of the present invention;

[0030] FIG6 is a schematic diagram of a top head according to a specific embodiment of the present invention;

[0031] FIG7 is a schematic diagram of a bottom head according to a specific embodiment of the present invention;

[0032] FIG8 is a schematic diagram of a reactor system according to a specific embodiment of the present invention.

[0033] Figure numerals: 100 - reactor structure; 1 - reactor pressure vessel; 2 - reactor internal components; 21 - core; 22 - core support lower plate; 221 - diversion angle; 222 - stepped hole; 222a - top hole; 222b - bottom hole; 23 - core shroud; 24 - core upper plate; 3 - bottom head; 31 - arcuate inner wall sphere center; 32 - arcuate inner wall; 5 - hanging basket cylinder; 6 - outlet pipe; 61 - tapered mouth; 7 - top head; 8 - inlet pipe; 9 - cylinder; 300 - reactor system; 301 - pump; 302 - steam generator. DETAILED DESCRIPTION

[0034] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0035] FIG1 is a schematic diagram of a reactor body structure 200 in the prior art.

[0036] As shown in Figure 1, the conventional reactor structure 200 primarily consists of a core 201, internals 202, a reactor pressure vessel 203, a control rod drive mechanism 204, and other components. The internals 202 house and support the core 201. The reactor pressure vessel 203 houses the internals 202, the core 201, and the internal coolant, and provides support for the control rod drive mechanism 204. The reactor pressure vessel 203 primarily consists of a top head 2031, a barrel 2032, and a bottom head 2033.

[0037] The reactor body structure 200 is provided with a cylinder 2032 of a reactor pressure vessel 203 , a hanging basket cylinder 205 and a core shroud 206 in sequence from the outside to the inside. A neutron shielding plate 207 is provided on the outer wall of the hanging basket cylinder 205 .

[0038] The safety of nuclear power plant reactors has always been a key concern. In a conventional reactor structure 200, the reactor core 201 is relatively high relative to the bottom head 2033 of the reactor pressure vessel 203. The core 201 is typically located approximately 750 mm above the center of the bottom head 2033 of the reactor pressure vessel 203. This makes it difficult to inject water into the core 201 for a short period of time in the event of a serious accident, thereby preventing the timely removal of heat from the reactor.

[0039] The applicant encountered the following problems during the research and development process: if the position of the core 201 is directly lowered, on the one hand, the fluid distribution at the core inlet will be uneven, and on the other hand, the fluid flow resistance will be increased, especially the flow resistance in the area of ​​the bottom head 2033 of the reactor pressure vessel 203.

[0040] In terms of fluid distribution, lowering the core 201 reduces the bottom space, which in turn prevents the fluid in the reactor from fully flowing and distributing after turning 180 degrees at the reactor pressure vessel bottom head 2033. This results in very uneven flow distribution at the core 201 inlet. The deviation in flow distribution at the inlet of a conventional core 201 is greater than 13%. Lowering the core 201 further increases the deviation. This uneven flow distribution at the core 201 inlet further leads to the following two major problems: 1) It is not conducive to the simultaneous and full combustion of hundreds of fuel assemblies in the core. Fuel assemblies with low flow rates will limit the efficient combustion of the entire core 201, otherwise these fuel assemblies will easily burn out; 2) Fluid in channels with high flow rates will flow into channels with low flow rates, which will increase the lateral flow of the fuel assemblies in the corresponding channels, causing greater vibration of the fuel rods and greatly increasing the risk of wear and damage to the fuel rods in the fuel assemblies.

[0041] In terms of fluid flow resistance, as the unit's electrical power exceeds 1350 MWe, the reactor structure must continue to grow to accommodate more fuel assemblies to generate heat, while also requiring more coolant to cool the core 201. However, due to current limitations in the manufacturing capacity of large-scale vessel forgings, the outer diameter of the vessel housing the reactor structure is limited. The only way to increase the unit's power is to increase the fluid flow within the reactor structure, which creates even greater resistance for the fluid within the reactor body structure 200. Further lowering the core 201 would reduce the fluid space between the outer edge of the core support lower plate supporting the core 201 and the reactor pressure vessel bottom head 2033, significantly increasing the fluid resistance there. This, in turn, affects the overall flow resistance of the reactor structure and requires a higher power for the reactor coolant main pump to overcome this increased flow resistance. Increasing the power of the reactor coolant main pump further presents the following problems: ① It creates significant difficulties in the development of the main pump; ② The higher power required to drive the reactor coolant flow consumes more electricity.

[0042] Based on the above problems, the present invention proposes a passive reactor body structure and a reactor system with high power, low flow resistance, high reliability and safety.

[0043] FIG2 is a schematic diagram of a reactor body structure 100 according to a specific embodiment of the present invention.

[0044] As shown in FIG2 , the reactor main structure 100 of this embodiment includes a core 21 , a reactor pressure vessel 1 , and reactor internals 2 .

[0045] The reactor pressure vessel 1 is used to accommodate the reactor internals 2, the reactor core 21, and the internal coolant (not shown). The reactor pressure vessel 1 includes a top head 7, a barrel 9, and a bottom head 3. The bottom head 3 has a curved inner wall 32. The reactor pressure vessel 1 is provided with an inlet nozzle 8 and an outlet nozzle 6. The coolant fluid enters through the inlet nozzle 8 and flows out through the outlet nozzle 6. The reactor internals 2 include a core support lower plate 22, on which the core 21 is mounted.

[0046] The reactor body structure 100 is provided with the cylinder 9 of the reactor pressure vessel 1, the basket cylinder 5 and the core shroud 23 from the outside to the inside. The basket cylinder 5 carries the core 21, and the core shroud 23 is provided with core components such as fuel assemblies (not shown).

[0047] The main coolant fluid flow path in the reactor is shown by the thick arrow in Figure 2. Driven by the main pump, the coolant is input into the reactor pressure vessel 1 from the inlet pipe 8. The coolant flows downward into the annular cavity between the cylinder 9 of the reactor pressure vessel 1 and the hanging basket cylinder 5, turns 180 degrees through the bottom head 3 of the reactor pressure vessel 1, flows upward through the water flow holes (i.e., through-holes) of the core support lower plate 22, and then enters the core 21 (fuel assembly). After passing through the fuel assembly and the core upper plate 24, it enters the upper chamber area and then flows out of the reactor body structure 100 from the outlet pipe 6 of the reactor pressure vessel 1. When the core 21 melts, water is injected into the interior through the direct injection inlet pipe (not shown) on the cylinder 9 of the reactor pressure vessel 1. The core 21 is cooled by the water injection to submerge the core 21.

[0048] FIG3 is a partial enlarged view of the bottom head 3 of the reactor body structure 100 according to a specific embodiment of the present invention.

[0049] As shown in Figure 3, the arc-shaped inner wall 32 of the bottom head 3 has a spherical center 31, the core support lower plate 22 is located on the lower side of the spherical center 31 of the arc-shaped inner wall 32, and the outer edge of the core support lower plate 22 is provided with a guide angle 221; the core support lower plate 22 is provided with a through hole 222, and the through hole 222 is a stepped hole.

[0050] The present invention adjusts the position of the core support lower plate 22 to the lower side of the spherical center 31 of the arc-shaped inner wall 32, thereby reducing the space under the core 21 and shortening the time required for external water injection to submerge the core 21 when the core 21 melts, thereby improving the reactor's ability to resist severe accidents and improving safety.

[0051] On this basis, a guide angle 221 is set at the outer edge of the core support lower plate 22, so that the outer contour of the core support lower plate 22 and the curved inner wall 32 of the bottom head 3 of the reactor pressure vessel 1 form an equidistant flow channel or a nearly equidistant flow channel, which not only widens the flow area of ​​the fluid in this area and reduces the fluid resistance in the reactor pressure vessel 1, but also enables the fluid flowing downward rapidly to turn quickly under the action of the flow channel, so that more fluid flows to the water flow holes on the outer edge of the core support lower plate 22, thereby improving the uniformity of the flow distribution at the inlet of the core 21.

[0052] An equidistant flow channel refers to a flow channel with the same curvature as the curved inner wall 32, ensuring that the width of the flow channel formed between the core support lower plate 22 and the curved inner wall 32 is equal. A near-equidistant flow channel refers to a flow channel with a width that fluctuates within 100 mm between the flow channel angle 221 and the curved inner wall 32 of the core support lower plate 22. For example, if the vertical distance between the flow channel angle 221 and the curved inner wall 32 of the bottom head 3 at a certain point is 300 mm, the width of the flow channel between the flow channel angle 221 and the curved inner wall 32 must not exceed 200 to 400 mm.

[0053] When the cross section of the flow channel suddenly shrinks or expands, due to the effect of inertia, obvious vortices will be generated in the mainstream and the mutation point, and the formed vortices will cause the pressure around the mutation point to drop sharply, thereby increasing the flow resistance. The present invention reduces the flow resistance of the main flow channel by setting the water flow holes of the core support lower plate 22 as through holes 222 that are small at the bottom and large at the top. Through flow field analysis, it can be seen that the gradually shrinking and expanding through holes 222, in conjunction with the guide angle 221, make the vortices in the water flow holes outside the core 21 less, and then more fluid flows into the through holes 222 outside the core 21, so that the flow distribution effect of the through holes 222 outside the core 21 is better.

[0054] The present invention arranges the core support lower plate 22 below the spherical center 31 of the arc-shaped inner wall 32, provides a flow guide angle 221 at the outer edge of the core support lower plate 22, and provides a through hole 222 with a smaller bottom and larger top on the core support lower plate 22. Through the coordination of these three features, the fluid resistance within the reactor pressure vessel 1 is reduced while improving safety, and the core 21 has a relatively uniform flow distribution at the core 21 inlet. As long as the flow resistance of the reactor body structure 100 and the core inlet flow distribution performance meet the requirements, the height of the reactor core 21 relative to the bottom head 3 of the reactor pressure vessel 1 is minimized.

[0055] As shown in Figure 3, the distance between the top surface of the core support lower plate 22 and the spherical center 31 of the curved inner wall 32 is 0-300 mm. Preferably, the distance between the top surface of the core support lower plate 22 and the spherical center 31 of the curved inner wall 32 is approximately 250 mm. Placing the top surface of the core support lower plate 22 below the spherical center 31 of the bottom head 3 shortens the time required for external water injection to submerge the core 21 during a melt, thereby improving the reactor's ability to withstand severe accidents.

[0056] In one embodiment, the flow guide angle 221 is a conical angle or an arc angle. The lower diameter of the cone angle is smaller than the upper diameter, and the angle between the outer wall of the cone angle and the vertical direction is 5° to 10°. The outer contour of the lower end of the core support lower plate 22 and the transition area of ​​the bottom head 3 of the reactor pressure vessel 1 are arranged to form an equidistant or nearly equidistant flow channel. The slope of the tangent point between the two is no greater than 30°. That is, as shown in Figure 3, the angle between the inclined surface of the flow guide angle 221 and the tangent line at the corresponding point on the arc is no greater than 30°. This ensures smooth coolant flow and reduces pressure drop variations. Three-dimensional flow field analysis shows that the core inlet flow distribution deviation of 193 fuel assemblies is less than 6%. The setting of the flow guide angle 221 not only reduces the flow resistance in this area but also promotes uniformity of the core inlet flow distribution. When the outer contour of the lower end of the internals adopts a flow guide angle 221 of 5° to 10°, the core inlet flow distribution is more favorable. Moreover, the difference between the guide angle 221 in the present invention and the ordinary chamfer should be distinguished. The function of the guide angle 221 in the present invention is to reduce the flow resistance and improve the uniformity of the core inlet distribution, while the function of the ordinary chamfer is to remove burrs and make it beautiful.

[0057] FIG4 is a partially enlarged view of the core support lower plate 22 according to a specific embodiment of the present invention.

[0058] As shown in FIG. 4 , the through hole 222 includes a top hole 222 a on the upper side and a bottom hole 222 b on the lower side. The diameter of the bottom hole 222 b is smaller than that of the top hole 222 a .

[0059] As shown in Figure 4, the diameter of the bottom hole 222b of the through-hole ranges from 38 to 64 mm, while the diameter of the top hole 222a is greater than or equal to 70 mm. The core support lower plate 22 utilizes stepped coolant flow holes to achieve a gradually converging and expanding flow path. The diameter of the bottom hole 222b ranges from 38 to 64 mm. A smaller diameter will affect fuel safety, while a larger diameter will reduce the core heat exchange effect.

[0060] As shown in Figure 1, conventional reactors generally limit the neutron radiation dose to the reactor pressure vessel 203 during its lifetime by installing neutron shielding panels 207 on the outer wall of the basket cylinder 205. Neutron shielding panels 207 are installed on the outer wall of the basket cylinder 205, covering the entire height of the core 201. They are used to limit the radiation dose to the reactor pressure vessel 203 from fast neutrons generated by the core 201 during reactor operation, thereby reducing adverse irradiation effects on the reactor pressure vessel 203.

[0061] Neutron shielding plates 207 are typically bolted to the outer wall of the basket cylinder 205. These bolts are subject to stress corrosion cracking caused by long-term neutron exposure to the reactor core 201. Furthermore, because the outer wall of the basket cylinder 205 is located in an area with high reactor coolant flow rates, installing neutron shielding plates 207 on this outer wall not only increases fluid resistance in this area but also increases the risk of failure of the neutron shielding plates 207 and related components.

[0062] In order to solve the problem of increased fluid resistance caused by the neutron shielding plate 207 and the risk of failure of the neutron shielding plate 207 and related components, in a specific embodiment of the present invention, the reactor body structure 100 is provided with a reactor pressure vessel cylinder 9, a hanging basket cylinder 5 and a core shroud 23 from the outside to the inside, and a water gap therebetween, and the neutron moderation and shielding effect of metal and water is utilized, so that no neutron shielding plate is provided between the reactor pressure vessel cylinder 9 and the hanging basket cylinder 5.

[0063] The core shroud 206 of a conventional reactor is generally 20mm to 25mm thick, the minimum water gap between the core shroud 206 and the basket barrel 205 is 80mm to 100mm, and the basket barrel 205 is approximately 50mm thick. The applicant conducted thermal-hydraulic analysis, shielding analysis, reactor physics analysis, and structural thermal-solid-fluid multi-physics coupling analysis to adjust the thickness of the core shroud 23, the gap between the core shroud 23 and the basket barrel 5, and the thickness of the basket barrel 5, thereby eliminating the neutron shielding plate.

[0064] In one embodiment, the thickness of the hanging basket cylinder 5 is 60-90 mm, the thickness of the core shroud 23 is 30-100 mm, and the gap between the hanging basket cylinder 5 and the core shroud 23 is 30-60 mm.

[0065] The wall thickness of the core shroud 23 is increased from the traditional 20mm to 25mm to 30mm to 100mm. This allows thermal neutrons emitted from the core 21 to be absorbed by the thicker core shroud 23, while also slowing down more fast neutrons into thermal neutrons. The minimum water gap width between the core shroud 23 and the basket cylinder 5 is adjusted to 30mm to 60mm, further slowing down the neutrons (thermal, fast) emitted from the core shroud 23 and enabling them to be better absorbed by the basket cylinder 5. Increasing the wall thickness of the basket cylinder 5 by 10mm to 40mm can better absorb thermal neutrons, thereby reducing the irradiation dose of the reactor pressure vessel 1.

[0066] Preferably, the thickness of the basket cylinder 5 is 60 mm, the thickness of the core shroud 23 is 30 mm, and the gap between the basket cylinder 5 and the core shroud 23 is 40 mm. Reactor physical shielding analysis confirms that the reactor pressure vessel 1 can have a design life of 60 years even without neutron shielding plates on the outer wall of the basket cylinder 5. When the core shroud 23 has a wall thickness of 30 mm, the minimum water gap width between the core shroud 23 and the basket cylinder 5 is 40 mm, and the thickness of the basket cylinder 5 is 60 mm, the neutron flux at the end of the life of the reactor pressure vessel 1 is 2.82×E+19n / cm 2 , which is about half of the traditional reactor structure.

[0067] The present invention increases the thickness of the core shroud 23 and the basket barrel 5, adjusts the water gap width between the core shroud 23 and the basket barrel 5, and eliminates the neutron shielding plate on the outer wall of the basket barrel 5. This not only increases the flow area of ​​the flow channel and reduces the flow resistance in this area, thereby reducing the requirements for the power of the loop flow main pump, but also avoids the stress corrosion fracture problem of the bolts in the core 21 area caused by long-term neutron irradiation, thereby improving the reliability of the in-core components 2.

[0068] Furthermore, after a severe accident involving a core 21 melt, retaining the melt within the vessel (IVR) by cooling the outer wall of the reactor pressure vessel 1's bottom head 3 is an important mitigation measure for severe nuclear power plant accidents. This was first implemented at the Loviisa power plant, and research on IVR measures is currently underway. However, much attention has been focused on the molten pool in the pressure vessel 1's bottom head 3 and external melt reception, with limited research on the contribution of reactor structural metal weight to IVR. When the core 21 melts and collapses into the bottom head 3, forming a layered molten pool, the metal layer above the molten pool, due to its low mass and thin thickness, has a high heat flux density, creating a thermal focusing effect. When the metal layer is relatively thin, this poses a significant threat to the integrity of the reactor pressure vessel 1. The relatively low weight of the heat-conducting metal involved in the accident during the core 21 melt is detrimental to heat removal from the core 21 in the event of a severe accident.

[0069] The present invention can effectively improve the heat of the core 21 from being conducted away from the bottom head 3 of the reactor pressure vessel 1 under severe accident conditions (melting of the core 21) by increasing the weight of the core shroud 23 and the hanging basket cylinder 5.

[0070] FIG5 is a partial enlarged view of the outlet pipe 6 according to a specific embodiment of the present invention.

[0071] As shown in Figure 5 , the reactor pressure vessel 1 is provided with an outlet pipe 6 . The inner side of the outlet pipe 6 has a tapered opening 61 . The inner diameter of the tapered opening 61 (the side closer to the interior of the reactor pressure vessel 1, i.e., the right side in Figure 5 ) is larger than the outer diameter (the left side in Figure 5 ). The tapered opening 61 is a tapered flow channel with a taper of 5° to 15°.

[0072] The outlet pipe 6 of the reactor pressure vessel 1 in the present invention adopts a tapered interface, and the internal flow channel of the outlet pipe 6 adopts a 5° to 15° conical surface. On the one hand, the diameter of the outlet pipe 6 of the in-core component can be increased to reduce the flow resistance of the outlet pipe 6 of the in-core component. On the other hand, the outlet pipe 6 of the pressure vessel 1 can be gradually changed to reduce the flow resistance.

[0073] The existing reactor pressure vessel top and bottom heads are welded from multiple forgings, which poses a risk of stress corrosion cracking. This increases the in-service inspection time of the reactor pressure vessel head welds and poses a risk of stress corrosion cracking of the welds, reducing the reliability and safety of the reactor.

[0074] Based on this, the top head 7 and the bottom head 3 of the pressure vessel 1 in the present invention are both integrated structures.

[0075] FIG6 is a schematic diagram of a top head 7 according to a specific embodiment of the present invention, and FIG7 is a schematic diagram of a bottom head 3 according to a specific embodiment of the present invention.

[0076] As shown in Figures 6 and 7, the top and bottom heads 7 and 3 of the reactor pressure vessel 1 are integrated, with the related structures forged as a whole. This achieves zero welds at the pressure-bearing boundaries of these components, eliminating the risk of stress corrosion cracking in pressure boundary welds and thus improving the reliability of the pressure vessel 1. This also reduces the number of in-service inspections of the reactor pressure vessel 1's welds and the doses required by personnel.

[0077] In the above embodiments of the present invention, multiple beneficial effects can be achieved through the combination and improvement of various embodiments.

[0078] First, ① the core shroud 23 and the basket cylinder 5 of appropriate thickness are set for the in-core component 2. At the same time, the water gap widths between the core shroud 23 and the basket cylinder 5, and between the basket cylinder 5 and the reactor pressure vessel 1 are adjusted. The neutron shielding plate setting on the outside of the basket cylinder 5 is cancelled to reduce the fluid resistance in the annular cavity area.

[0079] ② The transition area between the outer edge of the core support lower plate 22 and the bottom head 3 of the reactor pressure vessel 1 is set to a flow channel with equal or nearly equal cross-section to reduce the fluid resistance in the transition area between the lower end of the internal component 2 and the bottom head 3.

[0080] ③ The core support lower plate 22 adopts stepped coolant flow holes to achieve gradual contraction and expansion of the flow channel, thereby reducing the fluid resistance of the core support lower plate 22.

[0081] ④ The pressure vessel outlet pipe 6 adopts a tapered interface to reduce the fluid resistance in the outlet pipe 6 area.

[0082] Through the above improvements ①②③④, the fluid resistance of the reactor body structure 100 can be effectively reduced. Calculations show a 30% reduction, which not only reduces the difficulty of developing the main pump, but also reduces the main pump power by 2300Kw. It is estimated that during the life cycle of a nuclear power unit (60 years), an additional revenue of RMB 483 million can be generated.

[0083] Secondly, ① the reactor pressure vessel top head 7 and bottom head 3 adopt an integrated design, the stacking tube seat and the pressure vessel top cover are forged as a whole, and the relevant structures are forged as a whole to achieve zero welds at the pressure-bearing boundaries of the above-mentioned components, which not only reduces the risk of stress corrosion cracking of the pressure boundary welds, but also reduces the number of in-service inspections of the reactor pressure vessel welds and the personnel dose.

[0084] ② The neutron shielding plate and hundreds of bolts are removed from the outer wall of the basket cylinder 5, which not only reduces the flow resistance in this area, but also avoids the stress corrosion cracking problem of the bolts in the core 21 area caused by long-term neutron irradiation.

[0085] ③ A guide angle 221 is provided on the outer edge of the core support lower plate 22 and is used with equal-section or near-section flow channels and a flow distribution device in the transition zone of the reactor pressure vessel bottom head 3, so that the core inlet flow distribution performance reaches the international leading level, thereby greatly reducing the wear and damage of the core 21 (fuel assembly) caused by uneven core inlet flow distribution.

[0086] Through the above improvements ①②③, the reliability of the reactor body structure 100 is greatly improved.

[0087] Finally, ① the reactor core 21 is positioned as low as possible relative to the reactor pressure vessel bottom head 3, which facilitates the time required for external water injection to submerge the core 21 when the core 21 melts, thereby improving the reactor's ability to resist severe accidents.

[0088] ② Properly increasing the weight of the core shroud 23, the hanging basket cylinder 5 and the core support lower plate 22 can effectively improve the heat of the core 21 from the reactor pressure vessel 1 under severe accident conditions (core melting).

[0089] Through the above improvements ① and ②, the safety of the reactor body structure 100 under severe accident conditions is greatly improved, thereby improving the safety of the entire nuclear power plant.

[0090] FIG8 is a schematic diagram of a reactor system 300 according to a specific embodiment of the present invention.

[0091] As shown in FIG8 , the reactor system 300 of this embodiment includes a pump 301 , a steam generator 302 , and the reactor body structure 100 of the above-mentioned embodiment.

[0092] The reactor body structure 100 includes a reactor pressure vessel 1, which has an inlet pipe 8 and an outlet pipe 6. The outlet of the pump is connected to the inlet pipe 8 of the reactor pressure vessel 1, and the outlet pipe 6 of the reactor pressure vessel 1 is connected to the steam generator, which is in turn connected to the inlet of the pump.

[0093] In the reactor system, water or boron-containing water coolant is pumped into the reactor pressure vessel 1 of the reactor main structure 100 by pump 301. It flows through the fuel assemblies, where heat is absorbed, and then enters the steam generator 302, where it transfers heat to the other side of the loop coolant. The reactor coolant then returns to the pump 301 through a pipeline, completing the primary system cycle.

[0094] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A reactor body structure, It is characterized in that include: A reactor pressure vessel, comprising a bottom head having an arc-shaped inner wall; An internal component is placed in the reactor pressure vessel, and the internal component includes a core support lower plate; A core, which is arranged on the core support lower plate; in, The core support lower plate is located at the lower side of the arc-shaped inner wall sphere center, and the outer edge of the core support lower plate is provided with a guide angle; The core support lower plate is provided with a through hole, which is a stepped hole including a top hole on the upper side and a bottom hole on the lower side, and a diameter of the bottom hole is smaller than a diameter of the top hole.

2. The reactor body structure according to claim 1, It is characterized in that The guide angle and the arc-shaped inner wall of the bottom head form an equidistant or nearly equidistant flow channel, and the floating range of the flow channel width of the nearly equidistant flow channel does not exceed 100 mm.

3. The reactor body structure according to claim 2, It is characterized in that The guide angle is a cone angle or an arc angle, the lower diameter of the cone angle is smaller than the upper diameter, and the angle between the outer wall of the cone angle and the vertical direction is 5° to 10°.

4. The reactor body structure according to claim 1, It is characterized in that The distance between the top surface of the core support lower plate and the center of the arc-shaped inner wall is 0 to 300 mm.

5. The reactor body structure according to claim 4, It is characterized in that The distance between the top surface of the core support lower plate and the center of the arc-shaped inner wall is 250 mm.

6. The reactor body structure according to claim 1, It is characterized in that The diameter of the bottom hole of the through hole ranges from 38 to 64 mm.

7. The reactor body structure according to claim 1, It is characterized in that The reactor body structure is provided with a reactor pressure vessel cylinder, a hanging basket cylinder and a core shroud in sequence from outside to inside, and no neutron shielding plate is provided between the reactor pressure vessel cylinder and the hanging basket cylinder.

8. The reactor body structure according to claim 7, It is characterized in that The thickness of the hanging basket cylinder is 60-90 mm, the thickness of the core shroud is 30-100 mm, and the gap between the hanging basket cylinder and the core shroud is 30-60 mm.

9. The reactor body structure according to claim 8, It is characterized in that The thickness of the hanging basket cylinder is 60 mm, the thickness of the core shroud is 30 mm, and the gap between the hanging basket cylinder and the core shroud is 40 mm.

10. The reactor body structure according to claim 1, It is characterized in that The reactor pressure vessel further comprises a top head, the top head is an integral structure, and the bottom head is an integral structure.

11. The reactor body structure according to claim 1, It is characterized in that The reactor pressure vessel is provided with an outlet pipe, the inner side of the outlet pipe has a tapered opening, and the inner diameter of the tapered opening is greater than the outer diameter.

12. The reactor body structure according to claim 11, It is characterized in that The tapered opening is a conical flow channel, and the conical flow channel adopts a conical surface of 5° to 15°.

13. A reactor system, It is characterized in that Including pumps, steam generators and reactor structure, The reactor body structure comprises: A reactor pressure vessel, comprising a bottom head having an arc-shaped inner wall; An internal component is placed in the reactor pressure vessel, and the internal component includes a core support lower plate; A core, which is arranged on the core support lower plate; The core support lower plate is located at the lower side of the arc-shaped inner wall sphere center, and the outer edge of the core support lower plate is provided with a guide angle; The core support lower plate is provided with a through hole, the through hole is a stepped hole, including a top hole on the upper side and a bottom hole on the lower side, and the diameter of the bottom hole is smaller than the diameter of the top hole; The reactor pressure vessel has an inlet pipe and an outlet pipe, the outlet of the pump is connected to the inlet pipe of the reactor pressure vessel, the outlet pipe of the reactor pressure vessel is connected to the steam generator, and the steam generator is connected to the inlet of the pump.

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