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

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority of the Chinese patent application No. 202310709542.5, filed on June 14, 2023 and entitled 'TIigh-safety and iow-flow resistance Reactor body structure and Reactor system”, which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present invention relates to the field of nuclear reactor technology, and in particular to a reactor body structure and a reactor system. BACKGROUND

[0003] A nuclear reactor mainly includes a core, a reactor pressure vessel and reactor internals. The reactor pressure vessel includes a cylinder, a top head and a bottom head. The core is arranged in the reactor internals in the reactor pressure vessel . In the event of a serious accident occurs in the core, a safety injection system outside the reactor is designed to activate and inject boron-containing water into the reactor to submerge the core of the reactor. In existing nuclear reactor body structure, the core is located at a relatively high position from the bottom head of the reactor pressure vessel, that is to say, the space below the core is relatively large. Therefore, a large amount of boron-containing water is required to submerge the core, which takes a long time. This hinders the dissipation of heat from the core in a serious accident, thereby reducing the safety of the reactor. SUMMARY

[0004] In view of the shortcomings in the prior art, the present invention provides a reactor body structure that is both highly safety and has low-flow resistance so as to solve the safety problems caused by the long time taken to submerge the core, which is not conducive to the conduction of heat from the core.

[0005] A first aspect of the present invention provides a reactor body structure, including: a reactor pressure vessel, which includes a bottom head having an arc-shaped inner wall; reactor internals, which are arranged in the reactor pressure vessel and include a core supporting lower-plate; and a core, which is arranged on the core supporting lower-plate, wherein the core supporting lower-plate is located on a lower side of a sphere center of the arc-shaped inner wall, and an outer edge of the core supporting lower-plate is provided with a flow guide comer; and the core supporting lower-plate is provided with a through hole, which is a step hole and includes a top hole on upper side and a bottom hole on lower side, and a diameter of the bottom hole is sm aller than that of the top hole.

[0006] Preferably, the flow guide corner and the arc-shaped inner wall of the bottom head form an equidistant or nearly equidistant flow channel, and a floating range of a flow channel width of the nearly equidistant flow channel does not exceed 100 mm.

[0007] Preferably, the flow guide corner is a cone corner or an arc comer, a lower diameter of the cone corner is smaller than its upper diameter, and an angle between an outer wall of the cone comer and a vertical direction is between 5° and 10°.

[0008] Preferably, the top surface of the core supporting lower-plate is located between 0 and 300 mm below sphere center of the arc-shaped inner wall.

[0009] Preferably, the distance between the top surface of the core supporting lower-plate and the sphere center of the arc-shaped inner wall is 250 mm.

[0010] Preferably, the diameter of the bottom hole of the through hole is in a range from 38 to 64 mm. 10011] Preferably, 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 arranged between the reactor pressure vessel cylinder and the hanging basket cylinder.

[0012] Preferably, a thickness of the hanging basket cylinder is between 60 and 90 mm, a thickness of the core shroud is between 30 and 100 mm, and a gap between the hanging basket cylinder and the core shroud is between 30 and 60 mm.

[0013] 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.

[0014] Preferably, the reactor pressure vessel further includes a top head, the top head has an integral structure, and the bottom head has an integral structure.

[0015] Preferably, an outlet pipe is provided on the reactor pressure vessel, an inner side of the outlet pipe is provided with a tapered opening, and an inner diameter of the tapered opening is larger than an outer diameter thereof.

[0016] Preferably, the tapered opening is a conical flow channel winch has a conical surface of 5° to 15°. 10017] A 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 having an arc-shaped inner wall; reactor internals, which are arranged in the reactor pressure vessel and include a core supporting lower-plate; and a core, which is arranged on the core supporting lower-plate, wherein the core supporting lower-plate is located on a lower side of a sphere center of the arc-shaped inner wall, and an outer edge of the core supporting lower-plate is provided with a flow guide corner: the core supporting lower-plate is provided with a through hole, which is a step hole and includes a top hole on upper side and a bottom hole on lower side, and a diameter of the bottom hole is smaller than that of the top hole; and the reactor pressure vessel has an inlet pipe and an outlet pipe, an outlet of the pump is communicated with the inlet pipe of the reactor pressure vessel, the outlet pipe of the reactor pressure vessel is communicated with the steam generator, and the steam generator is communicated with an inlet of the pump,

[0018] One or more technical solutions provided in embodiments of the present invention have at least the following technical effects or advantages:

[0019] According to the present invention, the position of the core supporting lower-plate is adjusted to the lower side of the sphere center of the arc-shaped inner wall, which reduces the time required for external water injection to submerge the core when the core melts, thereby improving safety. On this basis, the flow guide corner is provided at the outer edge of the core supporting lower-plate, 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 hole on the core supporting lower-plate forms a flow channel of equal or nearly equal cross-section with the transition area of the bottom head of the reactor pressure vessel under the coordination of the flow guide comer, which enables the fluid to turn quickly under the action of the flow channel, so that more fluid flows into flow holes at the periphery of the core, and the flow distribution effect of the flow holes at the periphery of the core is better.

[0020] According to the present invention, the core supporting lower-plate is arranged at the lower side of the sphere center of the arc-shaped inner wall, the flow guide corner is provided at the outer edge of the core supporting lower-plate, the step holes that are small at the bottom and large at the top are provided on the core supporting lower-plate, and the coordination of above three components not only reduces the fluid resistance in the reactor pressure vessel, but also make the core have a more uniform core inlet flow distribution performance, while improving the safety.

[0021] According to the present invention, the thicknesses of the core shroud and the hanging basket cylinder are increased, while the width of the water gap between the core shroud and the hanging basket cylinder is adjusted and the neutron shielding plate on the outer wall of the hanging basket cylinder is eliminated, which not only increases the flow area of the flow channel on the outer vvaH of the hanging basket cylinder, but also reduces the flow resistance in this area, thereby reducing the requirement for the power of the main pump for the loop flow; and at the same time, which avoids the problem of stress corrosion cracking of the bolts in the core area caused by long-term neutron irradiation, thereby improving the reliability of the reactor internals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to illustrate the technical solutions of the embodiments of the present application more clearly, the accompanying drawing to be used in the embodiments of the present application will be briefly introduced below.

[0023] FIG. 1 is a schematic diagram of a reactor body structure in the prior art;

[0024] FIG. 2 is a schematic diagram of a reactor body structure according to a specific embodiment of the present invention;

[0025] FIG. 3 is a partial enlarged view of the bottom head position of the reactor body structure according to a specific embodiment of the present invention ;

[0026] FIG. 4 is a partial enlarged view of a core supporting lower-plate according to a specific embodiment of the present invention;

[0027] FIG. 5 is a partial enlarged view' of an outlet pipe according to a specific embodiment of the present invention;

[0028] FIG. 6 is a schematic diagram of a top head according to a specific embodiment of the present invention;

[0029] FIG. / is a schematic diagram of a bottom head according to a specific embodiment of the present invention; and

[0030] FIG. 8 is a schematic diagram of a reactor system according to a specific embodiment of the present invention.

[0031] Reference signs: 100- Reactor body structure; 1- Reactor pressure vessel; 2- Reactor internals; 21- Core; 22-Core supporting lower-plate; 221- Flow guide comer; 222- Step hole; 222a- Top hole; 222b-Bottom hole; 23- Core shroud; 24- Core upper-plate; 3- Bottom head; 31- Sphere center of arcshaped inner wall; 32- Arc-shaped inner wall; 5- Hanging basket cylinder; 6- Outlet pipe; 61-Tapered opening; 7- Top head; 8- Inlet pipe; 9- Cylinder; 300- Reactor system; 301- Pump; 302- Steam generator. DETAILED DESCRIPTION

[0032] In order to better understand the technical solutions of the present application, the embodiments of the present application will be described in detail below in conjunction with the accom panying drawin gs.

[0033] FIG. 1 is a schematic diagram of a reactor body structure 200 in the prior art.

[0034] As shown in FIG. 1, the reactor body structure 200 in the prior art is mainly composed of a core 201, reactor internals 202, a reactor pressure vessel 203, a control rod drive mechanism 204 and other apparatuses. The reactor internals 202 are used to accommodate and support the core 201, and the reactor pressure vessel 203 is used to accommodate the reactor internals 202, the core 201 and the internal coolant, and provide support for the control rod drive mechanism 204. The reactor pressure vessel 203 is mainly composed of a top head 2031, a cylinder 2032, and a bottom head 2.033.

[0035] The reactor body structure 200 is provided with the cylinder 2032 of the reactor pressure vessel 203, a hanging basket cylinder 205 and a core shroud 206 in sequence from outside to inside, and a neutron shielding plate 207 is provided on the outer wall of the hanging basket cylinder 205.

[0036] The safety of reactors in nuclear power plants has always been a key concern for everyone involved. In the conventional reactor body structure 200, the reactor core 201 is relatively high with respect to the bottom head 2033 of the reactor pressure vessel 203. The core 201 is generally located about 750 mm above the sphere center of the bottom head 2033 of the reactor pressure vessel 203. Therefore, it is not conducive to externally injecting water into the core 201 to submerge the core 201 for a short time and to timely discharge the heat from the reactor in a case of a serious accident.

[0037] The applicant encountered the following problem during the research and development process: if the position of the core 201 is directly lowered, on 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.

[0038] In terms of fluid distribution, the bottom space is reduced after the core 201 is lowered, so that the fluid in the reactor cannot fully flow and cannot be fully distributed after the bottom head 2033 of the reactor pressure vessel turns 180 degrees, making the flow distribution at the inlet of the core 201 very uneven. The deviation of the flow distribution at the inlet of the traditional core 201 is greater than 13%, and if the core 201 is lowered, the deviation of the flow' distribution will be further increased. The uneven flow distribution at the inlet of the core 201 further brings the following two major problems: 1) it is not conducive to the simultaneous full combustion of hundreds of fuel assemblies in the core, and the fuel assemblies with low flow will limit the efficient combustion of the entire core 201, otherwise the fuel assemblies with low-flow will easily bum out; 2) the fluid will flow from channels with large flow to channels with small flow', which will increase the cross flow of the fuel assemblies in the relevant channels, thereby causing the vibration of larger fuel rods, and greatly increasing the risk of abrasion and damage of the fuel rods of the fuel assemblies. 10039] In terms of fluid flow resistance, as the unit power exceeds 1350M'We, the reactor body-structure is required to be continuously enlarged to accommodate more fuel assemblies to generate heat, and more coolant is needed to cool the core 201. However, due to the current capacity for manufacturing forgings of a large-scale container, the outer diameter of the container accommodating the reactor structure is limited, while the unit power can only be increased by increasing the fluid flow in the reactor structure, which brings greater resistance to the fluid in the reactor body structure 200. If the position of the core 201 is further lowered on this basis, the fluid space between the outer edge of the core supporting lower-plate supporting the core 201 and the bottom head 2033 of the reactor pressure vessel will become smaller, thereby greatly increasing the fluid resistance at this location and affecting the overall flow resistance of the reactor structure, so that the main pump for coolant of the reactor needs more power to overcome the increased flow resistance. The increase in the power of the main pump for coolant of the reactor further brings the following problems: 1) it brings great difficulties to the development of the main pump; 2) it requires more power to dri ve the coolant in the reactor to flow, which will consume more electricity.

[0040] 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.

[0041] FIG. 2 is a schematic diagram of a reactor body structure 100 according to a specific embodiment of the present invention.

[0042] As shown in FIG. 2, the reactor body structure 100 of this embodiment includes a core 21, a reactor pressure vessel 1 and reactor internals 2.

[0043] The reactor pressure vessel 1 is used to accommodate the reactor internals 2, the core 21 and the internal coolant (not shown). The reactor pressure vessel 1 includes a top head 7, a cylinder 9 and a bottom head 3. The bottom head 3 has an arc-shaped inner wall 32, The reactor pressure vessel 1 is provided with an inlet pipe 8 and an outlet pipe 6. The coolant fluid enters through the inlet pipe 8 and flows out through the outlet pipe 6. The reactor internals 2 include a core supporting lower-plate 22, and the core 21 is arranged on the core supporting lower-plate 22.

[0044] The reactor body structure 100 is provided with a cylinder 9 of the reactor pressure vessel 1, a hanging basket cylinder 5 and a core shroud 23 in sequence from outside to inside. The hanging basket cylinder 5 carries the core 21, and the interior of the core shroud 23 is provided with a core component such as a fuel assembly (not shown).

[0045] The main flow path for the coolant fluid in the reactor is shown by the bold arrow in FIG. 2: driven by the main pump, the coolant enters the reactor pressure vessel 1 through the inlet pipe 8, 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 I, flows upward through the flow' holes (i.e., through holes) of the core supporting lower-plate 22 and then enters the core 21 (fuel assemblies), passes through the fuel assemblies and the core upper-plate 24 to enter the upper chamber area, and then flows out of the reactor body structure 100 through the outlet pipe 6 of the reactor pressure vessel 1. When the core 21 melts, water is injected into the interior of the core 21 through the direct safety-injection inlet pipe (not shown) on the cylinder 9 of the reactor pressure vessel 1, and the core 21 is submerged by the injected water and cooled down.

[0046] FIG. 3 is a partially enlarged view of the bottom head 3 of the reactor body structure 100 according to a specific embodiment of the present invention.

[0047] As shown in FIG. 3, the arc-shaped inner wall 32 of the bottom head 3 has a sphere center 31, the core supporting lower-plate 22 is located at the lower side of the sphere center 31 of the arc-shaped inner wall 32, and a flow guide comer 221 is provided at the outer edge of the core supporting lower-plate 22. The core supporting lower-plate 22 is provided with a through hole 22.2 which is a step hole.

[0048] In the present invention, the position of the core supporting lower-plate 22 is adjusted to the lower side of the sphere center 31 of the arc-shaped inner wall 32, so that the space on the lower side of the core 21 is reduced and the time required for external water injection to submerge the core 21 when the core 21 melts is shortened, thereby improving the capability of the reactor of resisting severe accidents and improving safety.

[0049] On this basis, the flow guide corner 221 is provided at the outer edge of the core supporting lower-plate 22, so that the outer contour of the core supporting lotver-plate 22 and the arc-shaped 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 flow holes on the outer edge of the core supporting lower-plate 22, thereby improving the uniformity of flow' distribution at the inlet of the core 21.

[0050] The equidistant flow channel means that the curvature of the flow guide corner 221 is the same as that of the arc-shaped inner wall 32, so that the distances in the width direction of the flow channel formed between the core supporting lower-plate 22 and the arc-shaped inner wall 32 are equal: and the nearly equidistant flow channel means that the floating range of the width of the flow channel formed between the flow guide corner 221 of the core supporting lower-plate 22 and the arc-shaped inner wall 32 does not exceed 100 mm. For example, if a vertical distance between the flow guide corner 221 and the arc-shaped inner wall 32 of the bottom head 3 at a certain position is 300 mm, then the width between the flow guide comer 221 and the arc-shaped inner wall 32 on the entire flow channel shall not exceed 200 to 400 mm.

[0051] When the cross section of the flow channel suddenly shrinks or expands, due to the effect of inertia, obvious vortices will be generated between the main flow channel and the point of sudden change, and the formed vortices will in turn cause the pressure around the point of sudden change to drop sharply, thereby increasing the flow resistance. In the present invention, the flow resistance of the main flow channel is reduced by setting the flow holes of the core supporting 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 flow' guide corner 221, reduce the vortices at the flow holes at the periphery of the core 21, so that more fluid, flows into the through holes 222 at the periphery of the core 21, and the flow distribution effect of the through holes 222 at the periphery of the core 21 is better.

[0052] According to the present invention, the core supporting lower-plate 22 is arranged at the lower side of the sphere center 31 of the arc-shaped inner wall 32, the flow guide corner 221 is provided at the outer edge of the core supporting lower-plate 22, the through holes 222 that are small at the bottom and large at the top are provided on the core supporting lower-plate 22, and the coordination of above three components not only reduces the fluid resistance in the reactor pressure vessel 1, but also make the core 21 have relatively uniform core 21 inlet flow distribution, while improving the safety. In the case that the flow resistance of the reactor body structure 100 and the flov,' distribution performance of the core inlet meet the requirements, the height of the reactor core 21 relative to the bottom head 3 of the reactor pressure vessel 1 is adjusted as low as possible.

[0053] As shown in FIG. 3, the distance between the top surface of the core supporting lower-plate 22 and the sphere center 31 of the arc-shaped inner wall 32 is between 0 and 300 mm. Preferably, the distance between the top surface of the core supporting lower-plate 22 and the sphere center 31 of the arc-shaped inner wall 32 is about 250 mm. By placing the top surface of the core supporting lower-plate 22 below the sphere center 31 of the bottom head 3, it is benefi cial to shortening of the time required for extern al water injection to submerge the core 21 when the core 21 melts, thereby improving the capability of the reactor for resisting severe accidents.

[0054] In an embodiment, the flow guide corner 221 is a cone comer or an arc comer, the lower diameter of the cone corner is smaller than the upper diameter thereof, and the angle between the outer wall of the cone corner and the vertical direction is between 5° and 10°. The outer contour of the lower end of the core supporting imvenpklc 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, and the tangent point slope therebetween is not greater than 30°, that is, the angle between the inclined surface of the flow guide corner 221 and a tangent line at a point of the corresponding position on the arc as shown in FIG. 3 is not greater than 30°. In this way, the coolant can flow smoothly to reduce the change of pressure drop. The three-dimensional flow field analysis shows that the deviation of the core inlet flow distribution of 193 fuel assemblies is less than 6%. The arrangement of the flow guide comer 221 can not only reduce the flow resistance in this area, but also facilitate the uniformity of the core inlet flow' distribution. When the outer contour of the lower end of the reactor internals is implemented as the flow’ guide corner 221 of 5° to 10°, it is more beneficial to the core inlet flow distribution. Furthermore, the difference between the flow guide corner 221 in the present invention and a common chamfer should be noted: the function of the flow guide comer 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 common chamfer is to remove burrs and achieve aesthetic appearance.

[0055] FIG. 4 is a partially enlarged view of the core supporting lower-plate 22 according to a specific embodiment of the present invention.

[0056] As shown in FIG. 4, the through hole 222 includes 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.

[0057] As shown in FIG. 4, the diameter of the bottom hole 222b of the through hole is in a range of 38 to 64 mm, and the diameter of the shown top hole 222a is greater than or equal to 70 mm. The core supporting lower-plate 22 is implemented as a step-shaped coolant flow hole to achieve gradual shrinking and expanding of the flow’ channel. The diameter of the bottom hole 222b ranges from 38 to 64 mm, a diameter that is too small will affect fuel safety, and a diameter that is too large will reduce the core heat exchange effect.

[0058] As shown in FIG. 1, in the prior art, conventional reactors generally limit the neutron radiation dose received by the reactor pressure vessel 203 during its sendee life by means of arranging a neutron shielding plate 207 on the outer wall of the hanging basket cylinder 205. The neutron shielding plate 207 is installed on the outer wall of the hanging basket cylinder 205 to cover the entire height area of the core 201 for limiting the radiation dose received by the reactor pressure vessel 203 from fast neutrons generated by the core 201 during the operation of the reactor, thereby reducing the adverse irradiation effects on the reactor pressure vessel 203,

[0059] The neutron shielding plate 207 is generally installed on the outer wall of the hanging basket cylinder 205 by bolts. The bolts in this area are exposed to stress corrosion cracking caused by long-term neutron irradiation due to the long-term irradiation of fast neutrons from the reactor core 201, At the same time, since the outer wall of the hanging basket cylinder 205 is in the high flow rate area of the reactor coolant, arranging the neutron shielding plate 207 on the outer wall of the hanging basket cylinder 205 not only increases the fluid resistance in this area, but also increases the risk of failure of the neutron shielding plate 207 and related parts.

[0060] In order to solve the problem that the neutron shielding plate 207 increases fluid resistance and the risk of failure of the neutron shielding plate 207 and related parts, 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 in sequence from outside to inside with water gaps 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.

[0061] The thickness of the core shroud 206 of a conventional reactor is generally between 20 mm and 25 mm, the minimum water gap between the core shroud 206 and the hanging basket cylinder 205 is between 80 mm and 100 mm, and the thickness of the hanging basket cylinder 205 is about 50 mm. The applicant adjusted the thickness of the core shroud 23, the gap between the core shroud 23 and the hanging basket cylinder 5, and the thickness of the hanging basket cylinder 5 by conducting thermal hydraulic analysis, shielding analysis, reactor physics analysis, and structural thermal solid flow multi-physics field coupling analysis, so that the neutron shielding plate is canceled.

[0062] In an embodiment, the thickness of the hanging basket cylinder 5 is between 60 and 90 mm, the thickness of the core shroud 23 is between 30 and 100 mm, and the gap between the hanging basket cylinder 5 and the core shroud 23 is between 30 and 60 mm,

[0063] The wall thickness of the core shroud 23 is increased from the traditional range of 20 mm to 25 mm to a range of 30 mm to 100 mm, 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 moderated into thermal neutrons. The width of the minimum water gap between the core shroud 23 and the hanging basket cylinder 5 is adjusted into a range of 30 mm to 60 mm, so that the neutrons (thermal, fast) from the core shroud 23 are further moderated to be better absorbed by the hanging basket cylinder 5. By increasing the wall thickness of the hanging basket cylinder 5 by 10 mm to 40 mm, thermal neutrons can be better absorbed, thereby reducing the irradiation dose of the reactor pressure vessel 1.

[0064] Preferably, the thickness of the hanging basket cylinder 5 is 60 mm, the thickness of the core shroud 23 is 30 mm, and the gap between the hanging basket cylinder 5 and the core shroud 23 is 40 mm. Through the reactor physical shielding analysis, it is confirmed that the reactor pressure vessel 1 can have a design life of 60 years even if no neutron shielding plate is provided on the outer wall of the hanging basket cylinder 5, When the wall thickness of the core shroud 23 is 30 mm, the width of the minimum water gap between the core shroud 23 and the hanging basket cylinder 5 is 40 mm, and when the thickness of the hanging basket cylinder 5 is 60 mm, the neutron injection at the end of the life of the reactor pressure vessel 1 is 2.82 x E+19 n / cm\ which is about half of that of the conventional reactor body structure.

[0065] In the present invention, the thicknesses of the core shroud 23 and the hanging basket cylinder 5 are increased, the width of the water gap between the core shroud 23 and the hanging basket cylinder 5 is adjusted, and the neutron shielding plate on the outer wall of the hanging basket cylinder 5 is canceled, which not only increases the flow area of the flow channel and reduces the flo w resistance in this area, thereby reducing the requirement for the power of the main pump for the loop flow, but also avoids the problem of stress corrosion cracking of the bolts in the area of core 21 caused by long-term neutron irradiation, thereby improving the reliabi lity of the reactor internals 2.

[0066] In addition, in a case of a serious accident in which the core 21 melts, an important mitigation measure for serious accidents of nuclear power plants is to cool the outer wall of the bottom head 3 of the reactor pressure vessel 1 for retention of the molten material in the vessel (IVR), which 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 melt reception, and there is less research on the participation of the metal weight of the reactor body structure 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 metal participating in the accident heat-conducting is relatively small, which is not conducive to the heat conduction of the core 21 in a serious accident.

[0067] In the present invention, the heat conduction of the core 21 from the bottom head .3 of the reactor pressure vessel 1 under severe accident conditions (melting of the core 21) can be effectively improved by increasing the weight of the core shroud 23 and the hanging basket cylinder 5.

[0068] FIG. 5 is a partially enlarged view of an outlet pipe 6 according to a specific embodiment of the present invention.

[0069] As shown in FIG. 5, the reactor pressure vessel 1 is provided with the outlet pipe 6, the inner side of the outlet pipe 6 has a tapered opening 61, and the diameter at the inner side (the side close to the inside of the reactor pressure vessel 1, i.e., the right side in FIG. 5) of the tapered opening 61 is larger than that at the outer side (the left side in FIG. 5) thereof. The tapered opening 61 is a conical flow channel, and the conical flow channel is implemented with a conical surface of 5° to 15°.

[0070] The outlet pipe 6 of the reactor pressure vessel 1 in the present invention is implemented as a tapered interface, and the internal flow channel of the outlet pipe 6 is implemented 'with a conical surface of 5° ~15°, which on one hand can increase the diameter of the outlet pipe 6 of the reactor internals to reduce the flow resistance of the outlet pipe 6 of the reactor internals, and on the other hand can achieve the gradual changing of the outlet pipe 6 of the pressure vessel 1 to reduce the flow resistance.

[0071] The top head and bottom head of the existing reactor pressure vessel are formed by welding multiple forgings, which poses a risk of stress corrosion cracking, increases the inservice inspection time of the head weld seams of the reactor pressure vessel and poses a risk of stress corrosion cracking of the weld seams, thereby reducing the reliability and safety of the reactor.

[0072] Based on this, both the top head 7 and the bottom head 3 of the pressure vessel 1 according to the present invention have integrated structures.

[0073] FIG. 6 is a schematic diagram of the top head 7 according to a specific embodiment of the present invention, and FIG. 7 is a schematic diagram of the bottom head 3 according to a specific embodiment of th e present in vention.

[0074] As shown in FIG. 6 and FIG. 7, the top head 7 and the bottom head 3 of the reactor pressure vessel 1 are designed in an integrated manner, and related structures are forged as a whole, so as to achieve zero weld seam at the pressure-bearing boundaries of the above-mentioned components, eliminate the risk of stress corrosion cracking of the weld seams as the pressure boundaries, and thus improve the reliability of the pressure vessel 1. At the same time, the inspection number of in-service weld seams of the reactor pressure vessel 1 and the radiation dose received by personnel can be reduced.

[0075] In the above-mentioned embodiments of the present invention, multiple beneficial effects can be achieved through the combination and improvement of respective embodiments.

[0076] First, 1) the core shroud 23 arid the hanging basket cylinder 5 of appropriate thicknesses are provided for the reactor internals 2, the widths of the water gap between the core shroud 23 and the hanging basket cylinder 5 and of the water gap between the hanging basket cylinder 5 and the reactor pressure vessel 1 are adjusted, and the neutron shielding plate is removed from the outside of the hanging basket cylinder 5, so as to reduce the fluid resistance in the annular cavity area;

[0077] 2) the transition area between the outer edge of the core supporting lower-plate 22 and the bottom head 3 of the reactor pressure vessel 1 is arranged to be a flow channel with equal or nearly equal cross-section, so as to reduce the fluid resistance at the lower end of the reactor internals 2 and the transition area of the bottom head 3;

[0078] 3) the core supporting lower-plate 22 is provided with step-shaped coolant flow' holes, so as to achieve gradual shrinking and expanding of the flow channel, thereby reducing the fluid resistance of the core supporting lower-plate 22; and

[0079] 4) the outlet pipe 6 of the pressure vessel is provided with a tapered interface, so as to reduce the fluid resistance in the area of the outlet pipe 6.

[0080] Through the above improvements I), 2), 3) and 4), the fluid resistance of the reactor body structure 100 can be effectively reduced by 30% as shown in calculation, which not only reduces the difficulty of developing the main pump, but also reduces the power of the main pump by 2300Kw. It is estimated that within the lifetime of a nuclear power unit (60 years), an additional revenue of RMB 483 million can be generated.

[0081] Secondly, 1) the top head 7 and bottom head 3 of the reactor pressure vessel is in an integrated design, and the core measurement tube seat and top cover of the pressure vessel are integrally forged, in this way, the related structures are integrally forged to achieve zero weld seam at the pressure-bearing boundaries of the above-mentioned components, which not only reduces the risk of stress corrosion cracking of the weld seams at the pressure boundaries, but also reduces the inspection number of in-service weld seams of the reactor pressure vessel and the radiation dose received by personnel;

[0082] 2) the neutron shielding plate and hundreds of bolts are canceled from the outer wall of the hanging basket cylinder 5, which not only reduces the flow' resistance in this area, but also avoids the problem of stress corrosion cracking of the bolts in the area of the core 21 caused by long-term neutron irradiation; and

[0083] 3) the outer edge of the core supporting lower-plate 22 is provided w'ith the flow' guide corner 221, which forms a flow channel of equal or nearly equal cross-section with the transition area of the bottom head 3 of the reactor pressure vessel to be used as a flow' distribution device, so that the core inlet flow distribution performance reaches the international leading level, thereby greatly reducing the abrasion and damage of the core 21 (fuel assembly) caused by the uneven core inlet flow distribution.

[0084] The reliability of the reactor body structure 100 is greatly improved through the above-mentioned improvements 1), 2) and 3).

[0085] Finally, 1) the reactor core 21 is placed as low as possible relative to the bottom head 3 of the reactor pressure vessel, which is beneficial to the time required for external water injection to submerge the core 21 when the core 21 melts, thereby improving the capability of the reactor to resist severe accidents; and

[0086] 2) by properly increasing the weight of the core shroud 23, the hanging basket cylinder 5 and the core supporting lower-plate 22, the heat conduction of the core 21 from the reactor pressure vessel 1 under severe accident (core melting) conditions can be effectively improved.

[0087] 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.

[0088] FIG. 8 is a schematic diagram of a reactor system 300 according to a specific embodiment of the present invention.

[0089] As shown in FIG. 8, 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.

[0090] The reactor body structure 100 includes the reactor pressure vessel 1, which has the inlet pipe 8 and the outlet pipe 6. The outlet of the pump is communicated with the inlet pipe 8 of the reactor pressure vessel 1, and the outlet pipe 6 of the reactor pressure vessel 1 is communicated with the steam generator which is in turn communicated with the inlet of the pump.

[0091] In the reactor system, water or boron-containing water coolant is pumped into the reactor pressure vessel 1 of the reactor body structure 100 by the pump 301, flows through the fuel assembly, where the heat energy is absorbed, and enters the steam generator 302, where the heat is transferred to the loop coolant on the other side, then the reactor coolant returns to the pump 301 through the pipeline, thus completing the cycle of the first loop system.

[0092] The above are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

What is claimed is:

1. A reactor body structure, comprising:a reactor pressure vessel, which comprises a bottom head having an arc-shaped inner wall;reactor internals, which are arranged in the reactor pressure vessel and comprise a core supporting lower-plate; anda core, which is arranged on the core supporting lower-plate, whereinthe core supporting lower-plate is located on a lower side of a sphere center of the arcshaped inner wall, and an outer edge of the core supporting lower-plate is provided with a flow guide comer; andthe core supporting lower-plate is provided with a through hole, which is a step hole and comprises a top hole on upper side and a bottom hole on lower side, and a diameter of the bottom hole is smaller than that of the top hole.

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

3. The reactor body structure according to claim 2, wherein the flow guide comer is a cone corner or an arc corner, a lower diameter of the cone corner is smaller than its upper diameter, and an angle between an outer wall of the cone corner and a vertical direction is between 5° and 10°.

4. The reactor body structure according to claim 1, wherein the top surface of the core supporting lower-plate is located between 0 and 300 mm below the sphere center of the arcshaped inner wall.

5. The reactor body structure according to claim 4, wherein the distance between the top surface of the core supporting lower-plate and the sphere center of the arc-shaped inner wall is 250 mm.

6. The reactor body structure according to claim 1, wherein the diameter of the bottom hole of the through hole is in a range from 38 to 64 mm.

7. The reactor body structure according to claim 1, wherein 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 arranged between the reactor pressure vessel cylinder and the hanging basket cylinder.

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

9. The reactor body structure according to claim 8, wherein 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, wherein the reactor pressure vessel further comprises a top head, the top head has an integral structure, and the bottom head has an integral structure.

11. The reactor body structure according to claim 1, wherein an outlet pipe is provided on the reactor pressure vessel, an inner side of the outlet pipe is provided with a tapered opening, and an inner diameter of the tapered opening is larger than an outer diameter thereof.

12. The reactor body structure according to claim 11, wherein the tapered opening is a conical flow channel which has a conical surface of 5° to 15°.

13. A reactor system, comprising a pump, a steam generator and a reactor body structure, the reactor body structure comprising:a reactor pressure vessel, which comprises a bottom head having an arc-shaped inner wall;reactor internals, which are arranged in the reactor pressure vessel and comprise a core supporting lower-plate; anda core, which is arranged on the core supporting lower-plate, whereinthe core supporting lower-plate is located on a lower side of a sphere center of the arcshaped inner wall, and an outer edge of the core supporting lower-plate is provided with a flow guide comer;the core supporting lower-plate is provided with a through hole, which is a step hole and comprises a top hole on upper side and a bottom hole on lower side, and a diameter of the bottom hole is smaller than that of the top hole; andthe reactor pressure vessel has an inlet pipe and an outlet pipe, an outlet of the pump is communicated with the inlet pipe of the reactor pressure vessel, the outlet pipe of the reactor pressure vessel is communicated with the steam generator, and the steam generator is communicated with an inlet of the pump.

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