Reactor cavity water injection system and top-mounted heat preservation module of reactor pressure vessel thereof

Abstract

A reactor cavity water injection system and a top-mounted heat preservation module (20) of a reactor pressure vessel thereof. The top-mounted heat preservation module (20) comprises a heat preservation assembly (21) and upper support structures (22); the heat preservation assembly (21) is provided with a heat preservation cavity for a reactor pressure vessel to be placed from the upper end; and the upper support structures (22) are disposed at the upper end of the heat preservation assembly (21) to be hung onto supports on the outer side. The heat preservation module (20) with the upper support structures (22) is prefabricated and assembled outside a nuclear island building and then hoisted as a whole to a reactor pit (10) for adjustment and fixation, and after being hoisted, the upper support structures (22) form a support at the upper end to hang the heat preservation module (20), thereby improving the stability of the heat preservation module (20). The mounting mode is simple and rapid, and the mounting and adjustment duration in the reactor pit (10) is shortened to be within one month, significantly improving the construction efficiency and improving the economy and competitiveness of the unit.

Description

Reactor cavity water injection system and its upper hanging insulation module for reactor pressure vessel Technical Field

[0001] The present invention relates to the field of nuclear power, and more particularly to a reactor cavity water injection system of a nuclear power plant and an upper-hanging thermal insulation module of a reactor pressure vessel thereof. Background Art

[0002] After a serious accident in a pressurized water reactor nuclear power plant, the reactor core will gradually melt and form a high-temperature molten pool at the lower head of the reactor pressure vessel. At this time, if the heat of the molten pool is not effectively dissipated, the high-temperature molten material will melt through the lower head and enter the reactor pit through the breach.

[0003] The high-temperature molten material reacts with the concrete in the reactor cavity, releasing a large amount of non-condensable gases (H2, CO2, CO, etc.). This will have two consequences for the containment:

[0004] a) The containment fails due to overpressure caused by the continuous accumulation of non-condensable gas, and radioactive materials enter the atmosphere;

[0005] b) The molten material melts through the base plate, and radioactive materials enter the foundation, contaminating the soil and groundwater.

[0006] The melt retention strategy is a post-core melt response measure and a hallmark of third-generation reactors. After a core melt accident occurs, the core cavity water injection system begins injecting water into the reactor cavity, cooling the exterior of the reactor pressure vessel to maintain its integrity, thereby retaining the core melt within the reactor pressure vessel.

[0007] The reactor pressure vessel insulation layer is an important part of the reactor cavity water injection system. It provides an annular cavity flow channel for the reactor cavity water injection system, allowing cooling water to enter the annular cavity flow channel from the bottom of the insulation layer to cool the reactor pressure vessel. The generated steam-water mixture is discharged from the exhaust port of the insulation pipe, thereby achieving the in-core retention of the core melt.

[0008] At present, the insulation layer of the reactor pressure vessel cylinder section of the reactor cavity water injection system used at home and abroad is fixed by supporting parts fixed on the reactor pit embedded parts, among which the flow channel liner is connected and fixed to the lateral support parts by bolts, and the lateral support parts are fixed to the reactor pit embedded parts by welding.

[0009] The shell insulation support solution requires welding and adjustment of the reactor pressure vessel insulation lateral supports after the delivery of the pit civil structure. Finally, the flow channel lining and insulation blocks are installed. Due to the large number of insulation lateral supports, the high installation precision, and the limited space, the insulation installation period in the pit generally exceeds six months.

[0010] Especially after adopting the open-top construction method, the RPV (reactor pressure vessel) insulation installation work is on the critical path, and the difficulty of risk prevention and control in terms of project progress and quality will be more prominent. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a reactor cavity water injection system and an upper-hanging insulation module for a reactor pressure vessel thereof in view of the above-mentioned defects of the prior art.

[0012] The technical solution adopted by the present invention to solve the technical problem is: constructing an upper-hanging insulation module for a reactor pressure vessel, comprising an insulation component and an upper support structure;

[0013] The insulation assembly is provided with an insulation cavity for the reactor pressure vessel to be placed from the upper end;

[0014] The upper support structure is arranged at the upper end of the heat preservation component to be hung on the outer support.

[0015] In some embodiments, the upper support structure includes a plurality of hanging ears provided outward from the upper end of the thermal insulation component; or, the upper support structure includes an annular hanging ring provided on the outer ring of the upper end of the thermal insulation component.

[0016] In some embodiments, the lower side of the upper support structure is a plane; or, the upper support structure is provided with rollers for support.

[0017] In some embodiments, the thermal insulation assembly includes a flow channel liner, and the flow channel liner includes a cylindrical body and a lower head located at the lower end of the cylindrical body.

[0018] In some embodiments, the thermal insulation module further includes a horizontal limiting structure provided at the bottom of the thermal insulation component to limit the horizontal displacement of the thermal insulation component.

[0019] In some embodiments, the horizontal limit structure includes a base and a plurality of horizontal limiters distributed around the bottom of the insulation component. The bottom of the stacking pit provides support for the base, and the horizontal limiters are connected to the base.

[0020] In some embodiments, a ring plate is provided at the upper end of the base along the bottom periphery of the thermal insulation component, and the horizontal limiter is mounted on the ring plate and abuts against the bottom outer ring of the flow channel lining.

[0021] In some embodiments, the insulation assembly includes an insulation layer located outside the flow channel liner.

[0022] In some embodiments, the outer wall of the flow channel lining is provided with an installation structure for installing the insulation layer.

[0023] In some embodiments, the mounting structure includes a plurality of annular support rings distributed axially on the outer wall surface of the flow channel lining.

[0024] In some embodiments, the thermal insulation layer includes several pieces, and at least one piece of the thermal insulation layer is provided between adjacent support rings.

[0025] In some embodiments, a gap is left between the thermal insulation layer and the flow channel lining.

[0026] In some embodiments, a water inlet is provided at the bottom of the thermal insulation component.

[0027] A nuclear power plant reactor cavity water injection system comprises the above-mentioned thermal insulation module.

[0028] In some embodiments, the reactor cavity water injection system includes a reactor pit, the thermal insulation module is arranged in the reactor pit, and the upper periphery of the reactor pit supports the upper support structure.

[0029] In some embodiments, a support pad is provided on the outer periphery of the upper end of the pit, and the upper support structure is arranged on the support pad.

[0030] In some embodiments, the thermal insulation module further includes a horizontal limiting structure provided at the bottom of the thermal insulation component to limit the horizontal displacement of the thermal insulation component.

[0031] In some embodiments, the horizontal limit structure includes a base and a plurality of horizontal limiters distributed around the bottom of the insulation component. The bottom of the stacking pit provides support for the base, and the horizontal limiters are connected to the base.

[0032] In some embodiments, a ring plate is provided at the upper end of the base along the periphery of the bottom of the thermal insulation component, and the horizontal limiter is mounted on the ring plate and abuts against the bottom outer ring of the thermal insulation component.

[0033] The implementation of the reactor cavity water injection system and the upper-hanging insulation module of the reactor pressure vessel of the present invention has the following beneficial effects: the integral insulation module with the upper support structure can be prefabricated and assembled outside the nuclear island plant, and then hoisted as a whole to the reactor pit for adjustment and fixation. After hoisting, the upper support structure forms a support at the upper end to hang the insulation module, thereby improving the stability of the insulation module. The installation method is simple and fast, and the installation and adjustment period in the reactor pit will be shortened to within one month, which significantly improves construction efficiency and enhances the economy and competitiveness of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0035] FIG1 is a schematic structural diagram of the assembled reactor pressure vessel and the top-mounted thermal insulation module of the reactor cavity water injection system in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0037] As shown in FIG1 , a nuclear power plant reactor cavity water injection system in a preferred embodiment of the present invention includes a reactor pit 10 and an insulation module 20 disposed in the reactor pit 10. The reactor pit 10 is a civil engineering structure, typically made of concrete, and is formed with a reactor hole 11 for placing the insulation module 20 therein.

[0038] The insulation module 20 is an integrated structure, requiring no fixed connection to the reactor pit 10. It can be hoisted into the reactor cavity 11 for support and positioning, significantly shortening the installation and adjustment period for the insulation module 20 at the reactor pit 10. After the insulation module 20 is installed, the reactor pressure vessel 30 can be hoisted and placed into the insulation module 20, with the upper end of the reactor pressure vessel 30 supported by the upper side of the reactor pit 10.

[0039] Preferably, the insulation module 20 is an upper-hanging insulation module 20, including an insulation component 21 and an upper support structure 22, so that the upper support structure 22 and the insulation component 21 are an integral structure, which can be prefabricated and installed in advance outside the nuclear island plant, and then hoisted as a whole into the reactor pit 10.

[0040] The insulation component 21 is provided with an insulation cavity for the reactor pressure vessel 30 to be placed from the top. In this embodiment, the insulation component 21 includes a flow channel lining 211 and an insulation layer 212 located on the outside of the flow channel lining 211. An insulation cavity is formed on the inner side of the flow channel lining 211 for the reactor pressure vessel 30 to be placed from the top, so that an annular flow channel is formed between the insulation component 21 of the insulation module 20 and the reactor pressure vessel 30.

[0041] The flow channel liner 211 comprises a cylindrical body 2111 and a lower head 2112 at the lower end of the cylindrical body 2111. The cylindrical body 2111 and the lower head 2112 are welded or assembled to form an integrated structure, facilitating overall lifting. The cylindrical body 2111 and the lower head 2112 are liner structures made of 304 stainless steel. The thickness is typically 10 mm, but can also be 8 mm, 12 mm, or 15 mm. The upper end of the flow channel liner 211 can be thickened to enhance the connection strength with the upper support structure 22.

[0042] The flow channel lining 211 can be mounted on the reactor pressure vessel 30 from the lower end. The insulation layer 212 is arranged on the outside of the flow channel lining 211. The insulation layer 212 is a metal reflective insulation layer whose main material is 304 stainless steel and can play a role in heat insulation.

[0043] The upper support structure 22 is provided at the upper end of the cylindrical body 2111 so as to be hung on the outer support. Specifically, in this embodiment, it can be hung on the upper side of the stacking pit 10 so that the stacking pit 10 supports the upper support structure 22 .

[0044] Preferably, an annular support pad 12 is provided around the upper periphery of the reactor pit 10. Alternatively, the support pad 12 may be block-shaped and distributed around the upper periphery of the reactor pit 10. The upper support structure 22 is mounted on the support pad 12 to facilitate mounting the insulation module 20 within the reactor pit 10. Simultaneously, the outer mounting platform 31 of the reactor pressure vessel 30 can also be mounted on the support pad 12, allowing the support pad 12 to simultaneously support the reactor pressure vessel 30 and the upper support structure 22.

[0045] The upper support structure 22 forms a support at the upper end to hang the thermal insulation module 20 , so that both upper ends of the thermal insulation module 20 are positioned, thereby improving the stability of the thermal insulation module 20 .

[0046] The insulation module 20 is supported by a top-mounted structure. Once placed in the reactor pit 10, it forms a ventilation space with the reactor pit 10. Furthermore, after the reactor pressure vessel 30 is placed within the insulation module 20, an annular flow channel is formed between the module and the reactor pressure vessel 30. The channel liner 211 is a cup-shaped structure with reinforced external supports to withstand loads and ensure channel integrity in the event of an accident.

[0047] A water inlet 2113 is provided at the bottom of the insulation assembly 21. In this embodiment, the water inlet 2113 is arranged on the insulation layer 212. Under accident conditions, water is injected into the reactor pit 10, so that the cooling water in the reactor pit 10 can enter the annular cavity flow channel from the lower end and submerge the reactor pressure vessel 30 from the bottom to the top, thereby cooling the reactor pressure vessel 30.

[0048] During normal operation, the insulation module 20 can play an insulation effect and reduce the heat loss of the reactor pressure vessel 30. When a core melt accident occurs, the core cavity water injection system starts to inject water into the reactor pit 10, and the cooling water enters the annular cavity flow channel formed between the insulation module 20 and the reactor pressure vessel 30 from the insulation module 20 to cool the reactor pressure vessel 30. The generated steam-water mixture is discharged from the exhaust port of the insulation pipe, thereby achieving the in-core retention of the core melt.

[0049] In some embodiments, the upper support structure 22 includes a plurality of ears arranged outward from the upper end of the cylindrical body 2111. The ears are evenly spaced around the outer periphery of the upper end of the cylindrical body 2111. The ears can be hung on the upper side of the support pad 12, allowing the support pad 12 to support the upper end of the insulation module 20, so that the insulation module 20 is hung on the support pad 12.

[0050] In other embodiments, the upper support structure 22 may also include an annular hanging ring arranged on the outer ring of the upper end of the cylindrical body 2111. The hanging ring can be hung on the upper side of the support pad 12, so that the support pad 12 supports the upper end of the insulation module 20, so that the insulation module 20 is hung on the support pad 12.

[0051] The upper support structure 22 can be connected to the cylindrical body 2111 by welding or locking. After being hung on the stack pit 10, it plays the role of hanging and supporting the thermal insulation module 20.

[0052] Preferably, the underside of the upper support structure 22 is a sliding surface. When the unit expands due to temperature rise, it is allowed to undergo a certain amount of radial thermal displacement on the upper flange surface of the support ring to absorb the radial expansion of the entire insulation module 20. In other embodiments, to allow the upper support structure 22 to adjust its position radially, a roller structure can be provided on the upper support structure 22 to roll radially during thermal expansion, absorbing the radial expansion of the entire insulation module 20. Furthermore, the lower end of the insulation module 20 is not fixed in the vertical direction, allowing the entire insulation module 20 to freely expand and contract in the vertical direction during thermal expansion.

[0053] In some embodiments, the outer wall of the flow channel liner 211 is provided with a mounting structure 213 for mounting the thermal insulation layer 212, facilitating the installation and fixation of the dispersed thermal insulation layer 212 on the outer side of the flow channel liner 211. The mounting structure 213 includes a plurality of annular support rings 2131 distributed axially on the outer wall of the flow channel liner 211. Each annular support ring 2131 is disposed along the outer circumferential wall of the flow channel liner 211 and is fixed by welding. On the one hand, it is used to mount and support the metal thermal insulation layer 212, and on the other hand, it serves to enhance the rigidity and strength of the cylindrical body 2111 and the lower head 2112 of the flow channel.

[0054] The support ring 2131 divides the outer side surface of the flow channel lining 211 into several blocks along the height direction. Furthermore, the insulation layer 212 includes several blocks, and one or more insulation layers 212 are arranged between adjacent support rings 2131. The insulation layer 212 can be installed piece by piece to facilitate control of the relative position between the insulation layer 212 and the flow channel lining 211.

[0055] Furthermore, after the insulation layer 212 is installed and secured, a certain gap is reserved between it and the flow channel lining plate 211 to accommodate circumferential thermal expansion differences and manufacturing and installation errors. The mounting structure 213 can also be a grid-like structure formed on the outer wall of the flow channel lining plate 211, or a plurality of ribs distributed circumferentially on the outer wall of the flow channel lining plate 211, dividing the outer surface of the flow channel lining plate 211 into several areas for the installation of the insulation layer 212.

[0056] In some embodiments, the insulation module 20 also includes a horizontal limiting structure 24 arranged at the bottom of the insulation component 21 to limit the horizontal displacement of the insulation component 21 at the bottom, which can limit the horizontal swing of the insulation module 20 under normal working conditions and earthquake conditions after being hung, thereby improving the stability of the insulation module 20.

[0057] Furthermore, the horizontal limit structure 24 includes a base 241 and a plurality of horizontal limiters 242 distributed around the bottom of the insulation component 21. The base 241 is placed at the bottom of the stacking pit 10, so that the bottom of the stacking pit 10 provides support for the base 241. The horizontal limiter 242 is connected to the base 241, so that the bottom of the insulation component 21 can obtain horizontal limit support from the horizontal limiter 242 in all circumferential directions, so that the horizontal limit in all directions is balanced.

[0058] Preferably, a ring plate is provided at the upper end of the base 241 along the periphery of the bottom of the thermal insulation assembly 21. The horizontal stopper 242 is fixed to the ring plate of the base 241 by bolts or other fasteners, abutting against the outer ring of the bottom of the thermal insulation assembly 21 to limit the horizontal position of the thermal insulation assembly 21. Of course, the ring plate can also be omitted, and the horizontal stopper 242 can be directly installed at the upper end of the base 241.

[0059] It is understandable that in other embodiments, the horizontal limiter 242 may also be provided at the bottom of the thermal insulation component 21 , and the horizontal position of the thermal insulation component 21 may be limited by the cooperation between the horizontal limiter 242 and the base 241 .

[0060] Typically, the number of the horizontal limiters 242 distributed in the circumferential direction is 4 to 8. A flow channel liner extension section is provided at the bottom of the lower head 2112 , and the horizontal limiters 242 are arranged circumferentially of the extension section.

[0061] In order to ensure the stable position of the horizontal limiter 242 and the insulation component 21, slots are provided on the outer wall of the extension section. Each horizontal limiter 242 corresponds to a slot, in which the horizontal limiter 242 can be embedded. In the hot state, there is theoretically zero clearance between the horizontal limiter 242 and the bottom surface of the slot, which can effectively limit the horizontal swing of the insulation module 20 under normal working conditions and earthquake conditions.

[0062] At the same time, a certain gap is reserved between the upper part of the horizontal limiter 242 and the extended section of the flow channel lining, so that when the entire insulation component 21 expands thermally, the insulation component 21 will expand in the vertical direction. The gap allows the insulation component 21 to freely expand and contract downward.

[0063] The integrated insulation module 20 structure eliminates the traditional on-site block-type welding support and replaces it with an integral support structure of the insulation component 21 and the upper support structure 22, realizing the decoupling of the insulation module from the civil structure, greatly simplifying the on-site pre-buried workload and interfaces, and realizing prefabrication and assembly outside the nuclear island plant, and then hoisting the entire unit to the reactor pit 10 for adjustment and fixation. The on-site installation work of the reactor pit 10 is optimized from the traditional "split installation" to "integral hoisting", and the installation and adjustment period in the reactor pit 10 will be shortened to within one month, which will significantly improve construction efficiency and enhance the economy and competitiveness of the unit.

[0064] It can be understood that the above technical features can be used in any combination without limitation.

[0065] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A top-mounted thermal insulation module for a reactor pressure vessel, characterized in that: It comprises a heat preservation component (21) and an upper support structure (22); The heat preservation assembly (21) is provided with a heat preservation cavity into which the reactor pressure vessel (30) is placed from the upper end; The upper support structure (22) is arranged at the upper end of the thermal insulation component (21) so as to be hung on an outer support.

2. The upper-hanging insulation module of the reactor pressure vessel according to claim 1, characterized in that: The upper support structure (22) comprises a plurality of hanging ears arranged outwardly from the upper end of the thermal insulation component (21); or, the upper support structure (22) comprises an annular hanging ring arranged on the outer ring of the upper end of the thermal insulation component (21).

3. The upper-hanging insulation module of the reactor pressure vessel according to claim 1 or 2, characterized in that: The lower side of the upper support structure (22) is a plane; or, the upper support structure (22) is provided with rollers for support.

4. The upper-hanging insulation module of the reactor pressure vessel according to claim 1, characterized in that: The heat-insulating component (21) comprises a flow channel lining plate (211), and the flow channel lining plate (211) comprises a cylindrical body (2111) and a lower sealing head (2112) located at the lower end of the cylindrical body (2111).

5. The upper-hanging insulation module of the reactor pressure vessel according to claim 4, characterized in that: The thermal insulation module (20) further comprises a horizontal limiting structure (24) arranged at the bottom of the thermal insulation component (21) to limit the horizontal displacement of the thermal insulation component (21).

6. The upper-hanging thermal insulation module of the reactor pressure vessel according to claim 5, characterized in that: The horizontal limit structure (24) comprises a base (241) and a plurality of horizontal limiters (242) distributed around the bottom of the thermal insulation component (21); the bottom of the stacking pit (10) provides support for the base (241), and the horizontal limiters (242) are connected to the base (241).

7. The upper-hanging thermal insulation module of the reactor pressure vessel according to claim 5 or 6, characterized in that: A ring plate is provided at the upper end of the base (241) along the periphery of the bottom of the thermal insulation component (21); the horizontal stopper (242) is mounted on the ring plate and abuts against the bottom outer ring of the flow channel lining plate (211).

8. The upper-hanging thermal insulation module of the reactor pressure vessel according to claim 4, characterized in that: The thermal insulation component (21) comprises a thermal insulation layer (212) located outside the flow channel lining plate (211); The outer wall of the flow channel lining plate (211) is provided with a mounting structure (213) for mounting the thermal insulation layer (212); The mounting structure (213) comprises a plurality of annular support rings (2131) distributed along the axial direction on the outer wall surface of the flow channel lining plate (211); The thermal insulation layer (212) comprises a plurality of pieces, and at least one piece of the thermal insulation layer (212) is arranged between adjacent support rings (2131); A gap is left between the thermal insulation layer (212) and the flow channel lining plate (211).

9. A reactor cavity water injection system, characterized in that: Comprising the thermal insulation module (20) according to any one of claims 1 to 8.

10. The reactor cavity water injection system according to claim 9, characterized in that: The reactor cavity water injection system comprises a reactor pit (10), the heat preservation module (20) is arranged in the reactor pit (10), and the upper periphery of the reactor pit (10) supports the upper support structure (22).

11. The reactor cavity water injection system according to claim 10, characterized in that: A support pad (12) is provided on the outer periphery of the upper end of the stack pit (10), and the upper support structure (22) is arranged on the support pad (12).

12. The reactor cavity water injection system according to claim 10, characterized in that: The thermal insulation module (20) further comprises a horizontal limiting structure (24) arranged at the bottom of the thermal insulation component (21) to limit the horizontal displacement of the thermal insulation component (21).

13. The reactor cavity water injection system according to claim 12, characterized in that: The horizontal limit structure (24) comprises a base (241) and a plurality of horizontal limiters (242) distributed around the bottom of the thermal insulation component (21); the bottom of the stacking pit (10) provides support for the base (241), and the horizontal limiters (242) are connected to the base (241).

14. The reactor cavity water injection system according to claim 13, characterized in that: The upper end of the base is provided with a ring plate along the periphery of the bottom of the thermal insulation component, and the horizontal stopper is mounted on the ring plate and abuts against the bottom outer ring of the thermal insulation component (21).

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