KR100423814B1 - Reactor Vessel Internal Structure Having an Integrated Inner Barrel Assembly Component - Google Patents

Abstract

The present invention relates to a reactor internal structure in a PWR reactor, and in the conventional reactor, a combined rod supporting a bundle of fuel control rods (230) due to random random turbulent loads and seismic loads due to the flow rate toward the reactor vessel outlet direction ( The weld of 21) was structurally weak. In particular, due to the increase in reactor heat output and the increase in safety stop criterion selected during design, it was difficult to support the existing design, which could not guarantee the safety of the reactor internal structure.

In the present invention, by adding the inner cylinder 520 to the outside of the bundle 230 of the nuclear fuel control rod wraps constituting the upper guide structure assembly 110 located on the inner structure of the reactor, the control rod guide support 590 was integrated. In addition, by introducing the inner cylinder 520 to change the transmission path of the seismic load from the outside to distribute the seismic load was able to increase the structural integrity of the reactor internal structure, and to protect the vertical movement of the reactor control rods. As a result, it was possible to safely design the reactor internal structure of the improved pressurized water reactor with increased heat output and 50% increase in safety stop criterion.

Description

Reactor Vessel Internal Structure Having an Integrated Inner Barrel Assembly Component

The present invention relates to a pressurized water reactor reactor vessel, and more specifically, to increase the structural integrity of the upper guide structure assembly of the reactor inner structure, and to install a cylindrical container outside the bundle of nuclear fuel control rod wrap to ensure the safe operation of the reactor Integrates with the control rod guide support, welds the nuclear fuel control rod envelopment bundle and the cylindrical vessel by welding, and the control rod guide support is an integral internal cylindrical assembly structure having an internal cylindrical bundle which is an integral structure welded to the upper guide assembly assembly flange. It relates to the internal structure.

The reactor internal structure of the LWR nuclear power plant supports nuclear reactor core fuel in the reactor pressure vessel and controls the flow of coolant.

The upper guide structure assembly 11 of the internal structure of the conventional reactor vessel 10, as shown in Figures 5a, 5b and 6, the upper guide structure cylinder 51 and the nuclear fuel control rod wrap 23 and the control rod guide support It consists of three connecting strips 24 for fixing the support 22 and the fuel control rod wrap 23. The upper guide structure assembly 11, as shown in Figure 2a, of the fuel assembly 12 Align the top and maintain the control rod spacing while supporting the transverse direction, by pressing the upper end of the nuclear fuel assembly 12 during operation of the nuclear power plant to prevent the nuclear fuel assembly 12 from escaping from the critical position, the reactor vessel (10 Protect the control rod from the effects of coolant transverse flow in the upper region of

In addition, as shown in Figures 2a, 5a and 5b, the upper guide structure assembly 11, the nuclear fuel control rod encapsulation 23 and the control rod guide support support 22 is separated, the upper guide structure support plate 53 and The upper portion of the nuclear fuel control rod bundle 23 is welded to the coupling rod, and the flange 31 of the control rod guide supporter 22 and the upper flange 26 of the upper guide structure cylinder 51 are fastened as bolts / nuts. In this case, reference numeral 17 shown in FIG. 2A is a reactor vessel support, 10 is a reactor vessel, 18 is a reactor vessel flange, and 13 is a core support cylinder. 15 is the lower support structure. In addition, reference numeral 25 shown in Fig. 5b is a connection strip seam.

In addition, the reactor coolant flow occurs through the control rod guide tube bundle 14 through the control rod guide tube bundle 14 due to the excessive thermal hydraulic load due to the flow having severe turbulence characteristics to the reactor vessel outlet nozzle. The load is transmitted to the bundle 23 to enclose the nuclear fuel control rod along the coupling rod 21. Further, the control rod guide tube bundle 14, the fuel alignment plate 55, and the insertion tube 56 When the weight of the force and the force pressing the nuclear fuel is dynamically interacted to form a load in the same direction, a large load acts on the coupling rod 21 and the nuclear fuel control rod wrap bundle (23).

Due to the above reasons, a large amount of welding is required at the load transmission part, and a stress tends to be excessively applied at the welding part of the connecting device, particularly at the welding part of the coupling rod 21.

Therefore, in the case of the next generation reactor, which is an improved pressurized water reactor in which the heat output is increased and the safety stop criterion is increased by 50%, the existing method of the nuclear fuel control rod enclosing bundle of the upper guide structure due to excessive stress is generated in the load transfer welding site. Structural health does not meet the requirements, and may also pose a risk to the structural safety of the reactor's internal structure during operation, resulting in increased probability of damaging the nuclear fuel, the core of the reactor.

Thus, the present invention was invented to improve the problems described above, in the present invention, in the pressurized water reactor reactor, the fuel control rod encapsulation described above maintains a function of safely guiding the control rod for controlling the reactivity of the nuclear fuel. Increasing heat output and earthquake load safety standard by 50% in one state, and integrated internal cylindrical assembly structure to maintain the structure and shape of the reactor internal structural components to maintain soundness in normal and abnormal operation conditions. Its purpose is to provide internal reactor structures with

Another object of the present invention is to improve the structure and shape of the assembly of the upper guide structure to ensure the integrity of the fuel control rod enclosed bundles for random random turbulent load due to the flow rate through the fuel control rod guide tube bundle to the reactor outlet nozzle. To design.

Another objective is to design a bundle of nuclear fuel control rods so as to minimize the stress at each welded site by minimizing the stress at each welded site.

Another objective is to ensure structural integrity of the fuel control rod guide tube bundles by minimizing the initial working stresses on the fuel control rod guide tube bundles caused by the self-weight of the reactor internal structure and the vertical or horizontal seismic loads on the reactor internal structures. In other words, the top guide structure assembly structure of the reactor internal structure is designed to safely perform alignment at the top of the fuel assembly and maintain the fuel assembly transverse support capacity.

1 is a cross-sectional view of the entire internal structure of the reactor subject to the present invention.

2 is a schematic diagram of a load transfer path of an internal reactor structure;

(a) is a schematic diagram of an existing reactor internal structure.

(b) is a schematic diagram of the reactor internal structure of the present invention.

Figure 3 is an upper guide structure aggregate structure comprising the inventors of the inner cylinder assembly.

4 is a simplified modeling of the load transfer path of the reactor internal structure

Figures 5a and 5b is a cross-sectional view of the existing upper guide structure assembly and the nuclear fuel control rods enclosed in the upper guide structure assembly wrapped and tube cross-sectional view.

Figure 6 is a perspective view of the control rod guide support of the existing fuel control rod wrap bundle.

Explanation of symbols on the main parts of the drawings

100: reactor vessel 110: the upper guide structure assembly

120: nuclear fuel assembly 130: core support

140: control rod guide tube bundle 150: reactor vessel inlet nozzle

160: reactor vessel outlet nozzle 170: reactor vessel support

180: reactor vessel flange 191: control rod extension shaft

105: lower support structure 230: bundle of nuclear fuel control rods

260: flange 510: upper guide structure cylinder 520: inner cylinder 530: upper guide structure support plate 540: control rod guide tube 550: fuel alignment plate 580: U-shaped guide tube 590: control rod guide support

In order to achieve the above object, the present invention is a pressurized light-water reactor having a large heat output of a nuclear power plant and a high safety stop reference earthquake load, and supports a nuclear fuel assembly that is a reactor core in a reactor vessel, and controls coolant flow. Aligning the top of the fuel assembly in the reactor internal structure, supporting the fuel assembly in the transverse direction, maintaining the spacing of the control rod, and pressing the top of the fuel assembly during operation, the fuel assembly is displaced from its position in the event of a serious accident And an upper guide structure assembly which functions to protect the control rod from the force caused by the transverse flow of coolant in the upper region. An inner cylinder assembly incorporating the vessel and the existing control rod guide support holder by placing a cylindrical container on the outside of the bundle to increase the fuel control rod bundle and structural integrity; Remains in the form of a plate on top of the inner cylindrical assembly to support the reactor control rod extension shaft from the side, and the plate is perforated to allow a plurality of reactor control rods to pass through, and is welded in the circumferential direction on the flange of the upper guide structure assembly. A control rod guide supporter that is part of the cylindrical assembly; A bundle of nuclear fuel control rods, which is a honeycomb-shaped welding structure that serves to maintain thermal equilibrium by passing a bypass flow flowing over the reactor vessel, and serves as a control rod guide; An upper guide cylinder which is external to the inner cylinder assembly and supports the fuel alignment plate and the fuel control rod guide tube bundle and transmits the load through the reactor vessel flange; Each fuel control rod consists of a bundle of fuel control rod guide tubes that guide the movement vertically against the coolant outlet flow.

Hereinafter, embodiments of the present invention, functions and implementation methods thereof will be described in detail.

1 is a cross-sectional view of the entire internal structure of the reactor according to the present invention. The reactor assembly supports the nuclear fuel assembly 120 which is the core of the reactor in the reactor vessel 100, and the nuclear fuel assembly of the reactor internal structure having a function of controlling coolant flow. Align the top of the 120, support the fuel assembly 120 in the transverse direction, maintain the spacing of the control rod, and press the top of the fuel assembly 120 during operation, the fuel assembly 120 in a serious accident from the position It is composed of an upper guide structure assembly 110 to prevent the departure, and to function to protect the control rod from the force caused by the lateral flow of coolant in the upper region.

In addition, as shown in Figure 2b and 3, the nuclear fuel control rod wrapped bundle 230 and the inner cylinder 520 to the outside of the nuclear fuel control rod wrapped bundle 230 to increase the structural integrity, the container and the existing control rod guide It forms an inner cylinder assembly incorporating a support support (see 22. FIG. 2A), and remains in the form of a plate above the inner cylinder assembly to support the reactor control rod extension shaft (191. FIG. 1) from the side, and the plate has a plurality of reactor control rods. It is made of a control rod guide support 590, which is a part of the inner cylindrical assembly that is drilled to pass through and welded circumferentially on the upper guide structure assembly flange 260.

And, a hole is drilled to maintain the thermal equilibrium by passing the bypass flow flowing in the reactor vessel, nuclear fuel control rod wrapped bundles 230, which is a honeycomb-shaped welding structure that serves as a control rod guide; An upper guide structure cylinder 510 which is outside the inner cylinder assembly and supports the fuel alignment plate 550 and the fuel control rod guide tube bundle 140 and passes a load through the reactor vessel flange 180; Each fuel control rod consists of a nuclear fuel control rod guide tube bundle 140 for guiding movement vertically in response to coolant outlet flow.

Figure 2b is a simplified diagram of the transmission path of earthquake loads transmitted from the nuclear power plant building through the reactor vessel support 170 through the reactor vessel flange 180 to the reactor internal structure.

In the improved pressurized water reactor, the design of the comprehensive site applied building structure is designed to increase the safety stop standard earthquake load by 50% to strengthen the seismic response capacity of nuclear power plants and to be applied to the ground as well as sand-based soil. Adopted. Therefore, the safety stop criteria earthquake load increased by 50%, but the effect of earthquake load on the reactor internal structure is more than 50%.

Therefore, it is necessary to design a reactor internal structure that can sufficiently withstand an increased seismic load, and in particular, a new structure of a bundle 230 of nuclear fuel control rods vulnerable to dynamic loads is required.

The transmission path of the vertical and horizontal movement of the earthquake load is transmitted from the bottom of the building to the support vessel support flange 170 through the reactor vessel flange 180 to the core support cylinder 130 flange and the upper guide assembly assembly 110 flange. In this case, it supports the total load of the internal structure and the load is transmitted in two directions.

One passage is passed through the core support barrel 130 to the lower support structure 105, the fuel assembly 120 is placed on the lower support structure, the control rod guide tube bundle 140 above the fuel assembly 120. When the fuel assembly 120 is moved upward, the load is transmitted to the control rod guide tube bundle 140 by the behavior of the nuclear fuel assembly 120, and the transferred load is The final load is delivered to the bundle 230 through the upper guide structure support plate, which is the bottom plate of the upper guide structure assembly 110.

Another path is finally reached to the bundle 230 by passing through the inner cylinder 520 through the upper guide structure assembly 110, flange 260, past the upper guide structure support plate and wrap the nuclear fuel control rod.

Nuclear fuel control rod wrap bundle 230 is vulnerable to dynamic load as the end point structure of the dynamic behavior by earthquake load.

Therefore, the conventional structure of the bundle of nuclear fuel control rods 230, referring to Figure 5 (a) and Figure 5 (b), uses a combination method in two ways. One is to combine the welding rod and the upper and upper guide structure support plate (53) with a bundle of honeycomb-shaped nuclear fuel control rod wrapped with a coupling rod (21) and the nuclear fuel control rod wrapped bundle (23) with three connecting strips (24) It is a method of strengthening rigidity by tying. In the state of the existing coupling state, there may be a tendency that excessive stress is applied in the welding portion of the coupling rod 21, and the fuel control rod is wrapped around the nuclear fuel control rod. There is no number.

Therefore, in the present invention, as shown in Figure 2b, the core support cylinder 130, the lower support structure 105, the nuclear fuel assembly 120, and the input load through the control rod guide tube bundle 140 and the upper guide structure assembly ( A structure of unifying two input load paths of the input load transmitted through the lower portion of 110) into one input load path is designed as shown in FIG. 3.

In addition, the load transfer paths and the working loads acting on the bundle 230 and the control rod guide tube bundle 140 in a nuclear fuel control rod wrapped in terms of thermal hydraulic load are as follows. As indicated by the arrow in the path, the coolant enters the four reactor vessel inlet nozzles 150 and enters the lower portion of the reactor vessel along the downward flow path between the reactor vessel 100 and the core support cylinder 130, and again the lower support structure ( When passing through 105, the temperature rises by the fuel reaction heat while passing through the fuel assembly 120, and exits through the two reactor vessel outlet nozzles 160 through the control rod guide tube bundle 140. It causes severe turbulent flow while passing through the control rod guide tube bundle 140, and an irregular load is applied to the control rod guide tube 540, which causes the fuel alignment plate 550 and Excessive stress is applied to the connection with the upper guide structure support plate 530. In particular, a large force is applied when the coolant rapidly exits to the reactor vessel outlet nozzle 160 due to a virtual pipe rupture that is considered in design, and a bundle of nuclear fuel and the fuel control rods of the upper guide structure (230. FIG. 2B). Due to the coolant flow as described above, the structure of the bundle 230 and the coupling rod (21 of FIG. 2A) may be impaired in the integrity of the fuel control rods, thereby unifying the load transfer path for reducing the seismic load. To make the structure as shown in Figure 4

In addition, the weight of the control rod guide tube bundle 140 on the upper guide structure support plate 530 acts in the downward direction, and additionally the load by the bundle of nuclear fuel control rods (230, see FIG. 2B) is upward. The upper guide structure support plate 530 is acted on. Therefore, the initial load on the upper guide structure support plate 530 results in a large act, which makes it difficult to secure the stress margin required in the design. This problem can also be alleviated by adopting the unified structure of the load transmission path described above as shown in FIG.

The impact of the seismic load transfer path and the thermal hydraulic load as seen in FIG. 2b finally reaches the bundle 230 of nuclear fuel control rods so that the fuel rods are tightly enclosed in the welding rod (21 in FIG. 2a). In order to reduce the stress and reduce the excessive initial load at the upper guide structure support plate 530 and the control rod guide tube 540 by the weight of the nuclear fuel control rod bundle (230) to devise a structure having a unified load transfer path It is the core of the present invention.

The structure of the reactor superstructure assembly having a unified load transfer path designed in the present invention is as follows. First, the existing connection band 24 and the control rod guide support 22 as shown in FIG. 5A and 5B installed to give rigidity of the bundle of nuclear fuel control rods 230 are integrated as shown in FIG. 520), the outermost plate of the bundle of nuclear fuel control rods (230, see FIG. 2B) is welded to the inner cylinder 520 by adding a U-shaped guide tube 580, and separated from the upper guide structure support plate In addition, as shown in FIG. 2A, the existing control rod guide support 22 is bolted to the upper guide structure assembly flange 16 at a portion thereof and does not act as a load transfer path, as shown in FIG. 2B. A flange was placed on the entire circumference of the housing and welded to the flange 260 of the upper guide structure assembly to increase rigidity and use it as a main load transfer path. Also, as shown in FIGS. 2B and 3, the upper guide structure supporting plate 530 ) To remove the coupling rod (21 in Fig. 2a) that surround the nuclear fuel rod connecting the sheaf (230) of the load transmission block as giving a clearance between the upper guide structure support plate 530 and fuel rod wrapped bundles (230). The schematic diagram considering the load transfer path as described above was configured as shown in FIG.

In addition, the bypass flow rate in the reactor vessel near the upper guide structure assembly is small, and this flow rate causes the fluid-controlled vibration of the bundle 230 to enclose the fuel control rod, so that the local crack is likely to occur. In order to reduce the occurrence of vibration directly on the control rod bundle 230, there is no flow hole in the inner cylinder 520, the fuel control rod wrap bundle 230 is a hole to make the heat transfer by the micro bypass flow smoothly Put it.

As shown in FIG. 4, the structure of the structure due to the unification of the load transfer path and the structural change of the inner cylindrical assembly 230 + 520 + 590 is illustrated in FIG. 4, the fuel control rod wrap bundle 230. Control rod guide support (590), which is coupled to the upper guide structure assembly and acts under the final dynamic load of the reactor internal structure, acting as an inner cylinder (520) and a conventional control rod guide support in the reactor vessel. And it is directly connected to the inner cylindrical assembly (230 + 520 + 590) consisting of the U-shaped guide tube 580, low-frequency dynamic behavior occurs, it can also reduce the stress concentration at each weld site of the nuclear fuel control rod wrap.

As described above, the present invention is a top of a conventional reactor internal structure having structural weaknesses of a welding rod welded portion supporting a bundle of nuclear fuel control rods due to a random random turbulent load and an earthquake load caused by a coolant flow in a PWR reactor internal structure. Guide Structure Aggregate Structure Integral structure designed to unify load transfer paths to relieve the stress on the welded joint of the fuel control rod bundle, and to maintain the integrity of the reactor under normal and abnormal operation conditions. Designed to maintain the structure and shape of the components, it ensures the integrity of the bundle to enclose the fuel control rods and minimizes the initial working stress on the fuel control rod guide tube bundles, resulting in increased heat output and a 50% increase in the safety stop reference earthquake. Pressure The structural integrity of the internal structure channel reactor was able to be obtained.

Therefore, the present invention is a very useful technology to increase the safety of the nuclear power plant by improving the structural integrity of the reactor inner structure supporting the nuclear fuel, which is a core component of the nuclear power plant.

Claims (3)

The nuclear fuel assembly 120 is installed through the upper guide structure support plate 530 on the upper side of the control rod guide tube bundle 140 in a state in which the core support cylinder 130 is installed in the receiving space of the reactor vessel 100. In the upper guide structure assembly 110 of the reactor vessel (100), in addition to the pressing, the nuclear fuel control rods enclosed with a plurality of nuclear fuel control rods 230 is installed in the inner space of the body, The inner cylinder 520 and the upper end of the inner cylinder 520 for absorbing the load transferred from the reactor vessel flange 180 to the core support cylinder 130 while accommodating the nuclear fuel control rod wrapped bundle 230 is provided with a nuclear fuel control rod The control rod guide support for guiding the support 590 is attached by welding and integrated, and the outermost plate of the nuclear fuel control rod wrapped bundle 230 is welded with the inner wall of the inner cylinder 520 wrapped around the nuclear fuel control rod wrapped bundle 230 Reactor internal structure having an integrated internal cylindrical aggregate structure, characterized in that a plurality of U-shaped guide tube 580 is formed between the upper and lower guide structure supporting plate 530 to form a gap for blocking load transfer. delete delete