A high-safety and low-flow resistance reactor body structure and reactor system

Abstract

The present invention relates to the field of nuclear reactor technology, and in particular to a high-safety, low-resistance reactor body structure and a reactor system. The high-safety, low-resistance reactor body structure comprises: a reactor pressure vessel and an internal component arranged in the reactor pressure vessel; the reactor pressure vessel comprises a bottom head, and the bottom head has an arc-shaped inner wall; the internal component comprises a core support lower plate, the core is arranged on the core support lower plate, the core support lower plate is located on 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, and the through hole is a step 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 present invention solves the safety problem caused by the long time of submerging the core, which is not conducive to the heat extraction of the core, and solves the problem of large resistance caused by increasing the flow of the reactor body structure due to the increase of reactor power.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactors, and in particular to a high-safety and low-flow-resistance reactor body structure and a reactor system. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] A nuclear reactor is a device that starts, controls and maintains a nuclear fission or fusion chain reaction. Nuclear reactors have many uses, the most important of which is to generate heat energy, which can be used to heat water to generate steam and generate electricity instead of other fuels.

[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 in 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 core of the reactor. 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 time for submerging 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. Summary of the invention

[0005] In view of the deficiencies in the prior art, an embodiment of the present invention aims to provide a high-safety and low-flow resistance reactor body structure to solve the safety problems caused by long core flooding time and the disadvantage of core heat extraction.

[0006] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] A high-safety and low-flow-resistance reactor body structure, comprising: a reactor pressure vessel and an internal component arranged in the reactor pressure vessel; the reactor pressure vessel comprises a bottom head, the bottom head has an arc-shaped inner wall; the internal component comprises a core support lower plate, the core 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 a guide angle is arranged on the outer edge of the core support lower plate; the core support lower plate is provided with a through hole, the through hole is a step 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.

[0008] Preferably, the guide angle forms an equidistant or nearly equidistant flow channel with the arc-shaped inner wall of the reactor pressure vessel bottom head. The nearly equidistant flow channel means that the floating range of the flow channel width 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 provided with a reactor pressure vessel cylinder, a hanging basket cylinder and a core shroud in sequence 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 pressure vessel further comprises a top head, the top head is an integral structure, and the bottom head is an integral structure.

[0017] Preferably, an outlet pipe is provided on the reactor pressure vessel cylinder, 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 opening is a conical flow channel, and the conical flow channel adopts a conical surface of 5° to 15°.

[0019] An embodiment of the present invention also provides a reactor system, including a pump, a steam generator, and the high-safety, low-flow resistance reactor body structure as described above, wherein 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 pressure vessel, the outlet pipe of the 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] 1. The present invention adjusts the position of the lower plate of the core support to the lower side of the spherical center of the arc-shaped inner wall, which reduces 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 lower plate of the core support, which not only reduces the fluid resistance, but also enables the fluid flowing rapidly downward to turn quickly under the action of the flow channel, thereby improving the uniformity of the flow distribution at the core inlet. The gradually shrinking and expanding step holes on the lower plate of the core support form equal-section or nearly equal-section flow channels with the transition area of ​​the bottom head of the reactor pressure vessel under the coordination of the diversion angle, which can turn quickly under the action of the 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] 2. The present invention arranges the core support lower plate at the lower side of the spherical center of the arc-shaped inner wall, arranges a guide angle at 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 more uniform core inlet flow distribution performance.

[0023] 3. The present invention increases the thickness of the core shroud and the basket barrel, adjusts the water gap width 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, but also reduces the flow resistance in this area, thereby reducing the requirements for the power of the loop flow main pump, and at the same time 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.

[0024] Advantages of additional aspects of the present invention will be given in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 It is a schematic diagram of the existing reactor structure;

[0028] Figure 2 is a schematic diagram of the structure of a reactor body provided by an embodiment of the present invention;

[0029] Figure 3 is an enlarged view of the lower part of the reactor body structure provided by an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of a step hole provided by an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of an outlet pipe provided by an embodiment of the present invention;

[0032] Figure 6 is a schematic diagram of a top head provided by an embodiment of the present invention;

[0033] Figure 7 is a schematic diagram of a bottom head provided by an embodiment of the present invention;

[0034] In the figure: 1, reactor pressure vessel; 21, core; 22, core support lower plate; 221, diversion angle; 222, step hole; 222a, top hole; 222b, bottom hole; 23, core shroud; 3, bottom head; 31, arc inner wall sphere center; 4, neutron shielding plate; 5, hanging basket cylinder; 6, outlet pipe; 61, tapered mouth; 7, top head;

[0035] In order to show the positions of various parts, the distances or sizes between them are exaggerated and the schematic diagram is for reference only. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the present invention explicitly states otherwise, singular forms are also intended to include plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] Terminology explanation section: The terms "install", "connect", "connect", "fixed" and the like in the present invention should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; it can be an internal connection between two elements, or an interaction relationship between two elements. For ordinary technicians in this field, the specific meaning of the terms in the present invention can be understood according to the specific circumstances.

[0039] like Figure 1As shown in the figure, the main structure of the high-safety low-resistance reactor is mainly composed of the core, internal components, reactor pressure vessel, control rod drive mechanism and other equipment. The internal components are used to accommodate and support the core, the reactor pressure vessel is used to accommodate the internal components, the core and the internal coolant, and provide support for the control rod drive mechanism. The reactor pressure vessel is mainly composed of the top head, the cylinder and the bottom head.

[0040] The safety of nuclear power plant reactors has always been the focus of attention of all parties. In the traditional reactor structure, the reactor core is relatively high relative to the bottom of the reactor pressure vessel. The core is generally located about 750mm above the center of the reactor pressure vessel bottom head. Therefore, it is not conducive to external water injection into the core to discharge the reactor heat in a timely manner in the event of a serious accident.

[0041] The applicant encountered the following problems during the research and development process. If the position of the core is directly lowered, on the one hand, the fluid distribution in the reactor 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 of the reactor pressure vessel. Specifically:

[0042] 1. Impact on fluid distribution:

[0043] After lowering the core, the bottom space is reduced, which will cause the fluid in the reactor to not be able to fully flow and distribute after the bottom head of the reactor pressure vessel turns 180 degrees, making the flow distribution at the core inlet very uneven. The deviation of the flow distribution at the traditional core inlet is greater than 13%. If the core is lowered, the flow distribution deviation will be further increased. The uneven flow distribution at the core inlet further brings the following two major problems: ① It is not conducive to the full combustion of hundreds of fuel assemblies in the core at the same time. The fuel assemblies with low flow will limit the excessive combustion of the entire core, otherwise the fuel assemblies with low flow will easily burn out; ② The channel fluid with large flow will flow to the channel with small flow, which will increase the lateral flow of the fuel assemblies in the relevant channels, thereby causing greater vibration of the fuel rods, greatly increasing the risk of wear and damage of the fuel rods of the fuel assemblies.

[0044] 2. Influence on fluid flow resistance:

[0045] As the power of the unit exceeds 1350MWe, the reactor structure needs to be continuously enlarged to accommodate more fuel assemblies to generate heat, and more coolant is needed to cool the core. However, due to the current large-scale container forging manufacturing capacity, the outer diameter of the container that accommodates the reactor structure is limited. The unit power can only be increased by increasing the fluid flow rate in the reactor structure, which increases the resistance of the fluid in the reactor body structure. If the core position is lowered on this basis, the fluid space between the outer edge of the core support lower plate supporting the core and the bottom head of the reactor pressure vessel will become smaller, thereby greatly increasing the fluid resistance there, thereby affecting the overall flow resistance of the reactor structure, so that the reactor coolant main pump needs more power to overcome these increased flow resistances. The increase in the power of the reactor coolant main pump further brings the following problems: ① It brings great difficulties to the development of the main pump; ② It requires more power to drive the reactor coolant flow, which will consume more electricity.

[0046] Example 1

[0047] Based on the above problems, the present invention proposes a passive reactor body structure with high power, low flow resistance, high reliability and safety, such as Figure 2-Figure 7 As shown, it includes: a reactor pressure vessel 1 and an internal component arranged in the reactor pressure vessel 1; the reactor pressure vessel 1 includes a bottom head 3, and the bottom head 3 has an arc-shaped inner wall; the internal component includes a core support lower plate 22, the core 21 is arranged on the core support lower plate 22, the core support lower plate 22 is located at the lower side of the arc-shaped inner wall sphere center 31, and the outer edge of the support lower plate 22 is provided with a guide angle 221; the core support lower plate 22 is provided with a through hole, and the through hole is a step hole 222, including a top hole 222a on the upper side and a bottom hole 222b on the lower side, and the diameter of the bottom hole 222b is smaller than the diameter of the top hole 222a.

[0048] The main coolant fluid flow channels in the reactor are as follows Figure 2 As shown, the coolant is driven into the reactor pressure vessel 1 inlet pipe by the main pump, flows downward into the annular cavity between the reactor pressure vessel 1 cylinder and the 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), passes through the fuel assembly and the core upper plate into the upper chamber area, and then flows out of the reactor from the reactor pressure vessel 1 outlet pipe 6. When the core 21 melts, water is injected into the interior through the pipe on the reactor pressure vessel 1 cylinder, and the core 21 is submerged by the water injection to achieve core cooling.

[0049] The present invention adjusts the position of the core support lower plate 22 to the lower side of the spherical center of the arc-shaped inner wall, thereby reducing the space under the core 21 and 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.

[0050] On this basis, the outer edge of the core support lower plate 22 is provided with a flow guide angle 221, so that the outer contour of the core support lower plate 22 and the arc-shaped inner wall of the bottom head 3 of the reactor pressure vessel 1 form an equidistant or 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 core inlet. Among them, the nearly equidistant flow channel means that the floating range of the flow channel width does not exceed 100mm. For example, if the vertical distance between the flow guide angle and the arc-shaped inner wall of the bottom head at a certain point is 300mm, then the width between the flow guide angle and the arc-shaped inner wall of the bottom head in the entire flow channel shall not exceed 200-400mm. When the flow channel cross section suddenly shrinks or expands, due to the effect of inertia, obvious vortices will be generated at the mainstream and the mutation point, and the formed vortex 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 channel by setting the water flow holes of the core support lower plate 22 as stepped holes 222 that are smaller at the bottom and larger at the top. Through flow field analysis, it can be seen that the gradually shrinking and expanding stepped holes 222, in cooperation with the guide angle 221, make the vortex of the peripheral water flow holes of the core 21 less, and then more fluid flows into the peripheral water flow holes of the core 21, so that the flow distribution effect of the peripheral water flow holes of the core 21 is better.

[0051] The present invention arranges the core support lower plate 22 at the lower side of the sphere center of the arc inner wall, arranges the guide angle 221 at the outer edge of the core support lower plate 22, and arranges the stepped hole 222 with a smaller bottom and a larger top on the core support lower plate 22. Through the coordination of the three, under the condition of improving safety, the fluid resistance in the reactor pressure vessel 1 is not only reduced, but also the core 21 has a relatively uniform core inlet flow distribution. Under the condition that the flow resistance of the reactor body structure and the core inlet flow distribution performance meet the requirements, the reactor core 21 is as low as possible relative to the bottom head 3 of the reactor pressure vessel 1.

[0052] like Figure 3 As shown, the distance between the top surface of the core support lower plate 22 and the arc-shaped inner wall sphere center 31 is 0-300 mm. Further preferably, the distance between the top surface of the core support lower plate 22 and the arc-shaped inner wall sphere center 31 is about 250 mm. By placing the top surface of the core support lower plate 22 below the sphere center of the bottom head 3 of the reactor pressure vessel 1, it is beneficial to reduce the time required for external water injection to submerge the core 21 when the core 21 is melted, thereby improving the reactor's ability to resist severe accidents.

[0053] The guide angle 221 is a cone angle or an arc angle, the lower diameter of the cone angle is smaller than the upper diameter, 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 set to be a flow channel with equal or nearly equal cross-sections, and the slope of the tangent point between the two is not greater than 30°, that is, Figure 3 The angle between the inclined surface of the middle guide angle 221 and the tangent of the corresponding position point on the arc is not greater than 30°. In this way, the coolant can flow smoothly and the pressure drop change can be reduced. The three-dimensional flow field analysis shows that the flow distribution deviation of the core inlet of 193 fuel assemblies is less than 6%. The setting of the guide angle 221 can not only reduce the flow resistance in this area, but also facilitate the uniformity of the flow distribution at the core inlet. When the outer contour of the lower end of the internal component adopts a guide angle 221 of 5° to 10°, it is more beneficial to the flow distribution at the core inlet. 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.

[0054] like Figure 4 As shown, the diameter of the bottom hole 222b of the through hole ranges from 38 to 64 mm, and the diameter of the top hole 222a is greater than or equal to 70 mm. The core support lower plate 22 adopts a step-shaped coolant flow hole to achieve gradual contraction and expansion of the flow channel. The diameter of the bottom hole 222b ranges from 38 to 64 mm. A too small diameter will affect fuel safety, and a too large diameter will reduce the core heat exchange effect.

[0055] like Figure 1 As shown, conventional reactors generally limit the neutron radiation dose received by the reactor pressure vessel 1 during its life cycle by setting a neutron shielding plate 4 on the outer wall of the hanging basket cylinder 5. The neutron shielding plate 4 is installed on the outer wall of the hanging basket cylinder 5, covering the height of the entire core 21 area, and is used to limit the radiation dose received by the reactor pressure vessel 1 from fast neutrons generated by the core 21 when the reactor is running, thereby reducing the adverse irradiation effects on the reactor pressure vessel 1.

[0056] The neutron shielding plate 4 is generally installed on the outer wall of the hanging basket cylinder 5 by bolts. The bolts are exposed to stress corrosion cracking caused by long-term neutron irradiation of the reactor core 21 due to long-term fast neutron irradiation. At the same time, since the outer wall of the hanging basket cylinder 5 is in the high flow rate area of ​​the reactor coolant, the neutron shielding plate 4 is arranged on the outer wall of the hanging basket cylinder 5, which not only increases the fluid resistance in the area, but also increases the risk of failure of the neutron shielding plate 4 and related parts.

[0057] Based on this, the reactor body structure of the present invention is as follows Figure 2As shown, the pressure vessel 1 cylinder, the hanging basket cylinder 5 and the core shroud 23 are arranged in sequence from the outside to the inside, and no neutron shielding plate 4 is arranged between the pressure vessel 1 cylinder and the hanging basket cylinder 5.

[0058] The thickness of the core shroud 23 of a conventional reactor is generally 20mm to 25mm, the minimum water gap between the core shroud 23 and the basket barrel 5 is 80mm to 100mm, and the thickness of the basket barrel 5 is about 50mm. The applicant conducted thermal hydraulic analysis, shielding analysis, reactor physics analysis, and structural thermal-solid-fluid multi-physics field coupling analysis, and finally carried out flow-induced vibration analysis and experimental verification of the internal components of the reactor, adjusted 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, and then eliminated the neutron shielding plate 4.

[0059] Specifically, 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.

[0060] The wall thickness of the core shroud 23 is increased from the traditional 20mm to 25mm to 30mm to 100mm, so that the thermal neutrons emitted from the core 21 will be absorbed by the thicker core shroud 23, and more fast neutrons will be slowed down into thermal neutrons. The minimum water gap width between the core shroud 23 and the hanging basket cylinder 5 is adjusted to 30mm to 60mm, so that the neutrons (hot, fast) coming out of the core shroud 23 are further slowed down, and the neutrons can be better absorbed by the hanging basket cylinder 5. By increasing the wall thickness of the hanging basket cylinder 5 by 10mm to 40mm, thermal neutrons can be better absorbed, thereby reducing the irradiation dose of the reactor pressure vessel 1.

[0061] The reactor physical shielding analysis confirmed that the reactor pressure vessel 1 can have a design life of 60 years even without the neutron shielding plate 4 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 basket cylinder 5 is 60 mm thick, the neutron injection 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.

[0062] 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 4 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 requirement 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 components inside the reactor.

[0063] In addition, after a serious accident in which the core 21 melts, retaining the molten material in the vessel by cooling the outer wall of the bottom head 3 of the reactor pressure vessel 1 (IVR) is an important mitigation measure for serious accidents in nuclear power plants. It was first implemented in the transformation of the Loviisa power plant. At present, research on IVR measures has been carried out, but more attention has been paid to the research work on the molten pool of the bottom head 3 of the pressure vessel 1 and the external molten reception. There are few studies on the participation of the weight of the reactor structure metal in IVR. When the core 21 melts and collapses to the bottom head 3 to form a layered molten pool, the metal layer on the upper layer of the molten pool has a large heat flux density due to its small mass and thin thickness, forming a thermal focusing effect. When the thickness of the metal layer is relatively small, it will pose a huge threat to the integrity of the reactor pressure vessel 1. When the core 21 melts, the weight of the heat-conducting metal participating in the accident is relatively small, which is not conducive to the heat extraction of the core 21 under severe accidents.

[0064] 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.

[0065] The top head 7 and the bottom head 3 of the existing reactor pressure vessel 1 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 1 head welds and poses a risk of stress corrosion cracking of the welds, reducing the reliability and safety of the reactor.

[0066] Based on this, the top head 7 and the bottom head 3 of the pressure vessel 1 described in the present invention are both integrated structures. Figure 6 , Figure 7 As shown, the top head 7 and the bottom head 3 of the reactor pressure vessel 1 are designed in an integrated manner, and the related structures are forged as a whole, so as to achieve zero welds at the pressure-bearing boundaries of the above components, eliminate the risk of stress corrosion cracking of the pressure boundary welds, and thus improve the reliability of the pressure vessel 1. At the same time, the number of in-service inspections of the reactor pressure vessel welds and the dose of personnel can be reduced.

[0067] like Figure 5 As shown, 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, and the inner side of the tapered opening 61 ( Figure 5 The diameter of the right side is larger than the outer side ( Figure 5 The tapered opening 61 is a conical flow passage, and the conical flow passage adopts a conical surface of 5° to 15°.

[0068] 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° cone 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.

[0069] The beneficial effects of the present invention are as follows:

[0070] First, ① the core shroud and basket cylinder are set with appropriate thickness for the internal components of the reactor. At the same time, the water gap width between the core shroud and the basket cylinder, and between the basket cylinder and the pressure vessel is adjusted. The neutron shielding plate is removed from the outside of the basket cylinder to reduce the fluid resistance in the annular cavity area.

[0071] ② The transition area between the outer edge of the lower core support plate and the bottom head of the reactor pressure vessel is set to be an equal-section or nearly equal-section flow channel to reduce the fluid resistance in the transition area between the lower end of the internal components and the bottom head of the pressure vessel.

[0072] ③ The lower plate of the core support adopts step-shaped coolant flow holes to achieve gradual contraction and expansion of the flow channel, thereby reducing the fluid resistance of the lower plate of the core support.

[0073] ④ The outlet pipe of the pressure vessel adopts a tapered interface to reduce the fluid resistance in the outlet pipe area.

[0074] Through the above improvements ①②③④, the fluid resistance of the reactor structure can be effectively reduced. Calculations show that it can be reduced by 30%. This 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 of a nuclear power unit (60 years), it can generate an additional revenue of RMB 483 million.

[0075] Secondly, ① the top and bottom heads of the reactor pressure vessel 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 dosage of personnel.

[0076] ② The neutron shielding plates and hundreds of bolts on the outer wall of the hanging basket cylinder are eliminated, which not only reduces the flow resistance in this area, but also avoids the stress corrosion fracture of the bolts in the core area caused by long-term neutron irradiation.

[0077] ③ The outer edge of the lower plate of the core support is set with a guide angle and the cross-sectional or near-sectional flow channel and flow distribution device of equal section in the transition zone of the bottom head of the reactor pressure vessel, so that the flow distribution performance of the core inlet reaches the international leading level, thereby greatly reducing the wear and damage of the core (fuel assembly) caused by the uneven distribution of the core inlet flow.

[0078] Through the above improvements ①②③, the reliability of the reactor structure is greatly improved.

[0079] Finally, ① the reactor core should be placed as low as possible relative to the bottom head of the reactor pressure vessel. This will facilitate the time required for external water injection to submerge the core when the core is melted, thereby improving the reactor's ability to resist severe accidents.

[0080] ② Appropriately increasing the weight of the core shroud, basket cylinder and core support lower plate can effectively improve the core heat extraction from the reactor pressure vessel under severe accident conditions (core melting).

[0081] Through the above improvements ①②, the safety of the reactor structure under severe accident conditions has been greatly improved, thereby improving the safety of the entire nuclear power plant.

[0082] Example 2

[0083] Based on the high-safety and low-flow resistance reactor structure of Example 1, this example proposes a reactor system, wherein the reactor structure contains fuel assemblies, internal components, a reactor pressure vessel, a control rod drive mechanism, and an integrated top assembly. A coolant of water or boron-containing water is pumped into the reactor pressure vessel of the reactor structure, flows through the fuel assembly, where heat energy is absorbed, and enters the steam generator, where the heat is transferred to the loop coolant on the other side. Then, the reactor coolant returns to the pump through the pipeline, thereby completing a loop system cycle.

[0084] Since the above reactor body structure has the above technical effects, please refer to the above embodiment 1 for the technical effects of the reactor system using the reactor body structure.

[0085] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A high-safety and low-flow resistance reactor structure. It is characterized in that include: A reactor pressure vessel and a reactor internal component arranged in the reactor pressure vessel; The reactor pressure vessel comprises a bottom head having an arc-shaped inner wall; The internal component comprises a core support lower plate, the core is arranged on the core support lower plate, the core support lower plate is located at the lower side of the arc 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 step 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 guide angle and the arc-shaped inner wall of the bottom head form an equidistant or nearly equidistant flow channel, the angle between the outer wall of the guide angle and the tangent of the corresponding position point on the arc-shaped inner wall of the bottom head is not greater than 30°, the guide angle is a cone 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°.

2. The high-safety and low-flow-resistance reactor body structure according to claim 1, It is characterized in that The nearly equidistant flow channels refer to flow channel widths having a floating range that does not exceed 100 mm.

3. The high-safety and low-flow-resistance 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.

4. The high-safety and low-flow-resistance reactor body structure according to claim 3, 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.

5. The high-safety and low-flow-resistance 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.

6. The high-safety and low-flow-resistance 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.

7. The high-safety and low-flow-resistance reactor body structure according to claim 6, 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.

8. The high-safety and low-flow-resistance reactor body structure according to claim 7, 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.

9. The high-safety and low-flow-resistance 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.

10. The high-safety and low-flow-resistance reactor body structure according to claim 6, It is characterized in that An outlet pipe is arranged on the reactor pressure vessel cylinder, and 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.

11. The high-safety and low-flow-resistance reactor body structure according to claim 10, 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°.

12. A reactor system, It is characterized in that It comprises a pump, a steam generator and a high-safety, low-flow-resistance reactor body structure as described in any one of claims 1 to 11, wherein 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 further connected to the inlet of the pump.

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