Method of dismantling core internals

Abstract

To provide a method of dismantling core internals, which improves workability of dismantling work of core internals.SOLUTION: A method of dismantling core internals for dismantling a reactor vessel representing a reactor internal consisting of former plates fixed to an inner circumferential wall of a cylindrical reactor vessel body and baffle plates fixed to inner sides of the former plates, the method involving cutting the reactor vessel while the reactor vessel body, former plates, and baffle plates are assembled together.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for dismantling reactor internals, which involves cutting reactor internals arranged inside a reactor vessel. [Background technology]

[0002] In a nuclear power plant, a containment vessel is erected on solid ground such as bedrock, and a nuclear reactor is disposed inside the containment vessel. The reactor is configured by disposing of reactor internals such as fuel inside the reactor vessel. When a nuclear reactor is to be disposed of, the reactor internals are removed from inside the reactor vessel and cut into predetermined sizes. One example of a technique for cutting reactor internals is described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2987070 Summary of the Invention [Problem to be solved by the invention]

[0004] The core barrel, which is a reactor internal structure, is constructed by fixing a former plate to the inner peripheral wall of the cylindrical core barrel body and fixing a baffle plate to the inside of the former plate. The former plate is fixed to the inner peripheral wall of the core barrel body with multiple bolts, and the baffle plate is fixed to the former plate with multiple bolts. Therefore, when dismantling the core barrel, the bolts on the former plate are loosened to remove the baffle plate, and the bolts on the core barrel body are loosened to remove the former plate, and then the core barrel body is cut to a specified size. This poses a problem in that the dismantling of the core barrel takes a long time.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a method for dismantling reactor internal structures that improves the workability of dismantling reactor internal structures. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the method of dismantling reactor internal structures disclosed herein involves dismantling a reactor core vessel as an internal structure, which is constructed by fixing a former plate to the inner peripheral wall of a cylindrical reactor core vessel body and fixing a baffle plate to the inside of the former plate, and cutting the reactor core vessel body, the former plate, and the baffle plate while they are assembled together. [Effects of the Invention]

[0007] According to the method for dismantling reactor internal structures of the present disclosure, it is possible to improve the workability of dismantling reactor internal structures. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a longitudinal cross-sectional view showing a pressurized water reactor. [Figure 2] FIG. 2 is a schematic plan view showing the core barrel as a reactor internal structure. [Figure 3] FIG. 3 is a schematic plan view showing the main parts of the core barrel. [Figure 4] FIG. 4 is a schematic vertical cross-sectional view showing the core barrel. [Figure 5] FIG. 5 is a schematic perspective view showing the connection structure of the core barrel. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a cut state of the core barrel. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0010] <Pressurized water reactor> FIG. 1 is a longitudinal cross-sectional view showing a pressurized water reactor.

[0011] Although not shown, the nuclear power plant has a nuclear reactor and a steam generator arranged in a reactor containment vessel, and a steam turbine power generation facility. The nuclear reactor in this embodiment is a pressurized water reactor (PWR). However, the nuclear reactor may be any type of nuclear reactor, such as a boiling water reactor (BWR) or a fast breeder reactor (FBR).

[0012] As shown in FIG. 1, in a pressurized water reactor 10, a reactor vessel 11 is composed of a reactor vessel main body 12 and a reactor vessel lid 13 attached to the top so that reactor internals can be inserted inside, and the reactor vessel lid 13 is fixed to the reactor vessel main body 12 by a plurality of stud bolts 14 and nuts 15 so that it can be opened and closed.

[0013] The reactor vessel body 12 has a cylindrical shape that is open at the top and closed at the bottom, forming a hemispherical shape, and is provided with an inlet nozzle 16 at the top for supplying light water as primary coolant and an outlet nozzle 17 for discharging the light water. A core barrel 18 is disposed inside the reactor vessel body 12, and its upper part is supported by the inner wall surface of the reactor vessel body 12. An upper core support plate 19 is disposed inside the reactor vessel body 12, and its upper part is supported by the upper part of the core barrel 18. An upper core plate 20 is suspended and supported from the upper core support plate 19 by a plurality of core support rods 21.

[0014] A lower core support plate 22 is supported below the core barrel 18, and the outer periphery of the lower core support plate 22 is positioned and supported by positioning members 23 on the inner wall surface of the reactor vessel body 12. A lower core plate 24 is supported below the core barrel 18. A core 25 is formed by arranging a large number of fuel assemblies 26, and a large number of control rods 27 are arranged inside, and the control rods 27 are insertable into the fuel assemblies 26. A large number of control rod cluster guide tubes 28 are fixed to the upper core support plate 19, and the control rods 27 can be inserted therein. The reactor vessel lid 13 is hemispherical, and a control rod drive mechanism 29 is arranged therein. A plurality of control rod cluster drive shafts 30 are inserted into the control rod cluster guide tubes 28, and the control rods 27 are connected to the lower ends thereof. The control rod drive mechanism 29 controls the reactor power by inserting and withdrawing each control rod 27 into and from the core 25.

[0015] Furthermore, a detector guide device 31 is disposed inside the reactor vessel 11. The detector guide device 31 guides a neutron flux detector (not shown) from an instrumentation nozzle 32 on the reactor vessel lid 13 to the core 25 (fuel assemblies 26) through a guide member 33. The neutron flux detector can measure the neutron level and distribution (neutron flux). Specifically, the detector guide device 31 guides the neutron flux detector (not shown) from the instrumentation nozzle 32 on the reactor vessel lid 13 to the core 25 (fuel assemblies 26) through the guide member 33 and a guide thimble (not shown) fixed to the lower end of the guide member 33.

[0016] <Core tank> Figure 2 is a schematic plan view showing the core barrel as a reactor internal structure, Figure 3 is a schematic plan view showing the main parts of the core barrel, Figure 4 is a schematic longitudinal cross-sectional view showing the core barrel, and Figure 5 is a schematic oblique view showing the connecting structure of the core barrel.

[0017] As shown in FIGS. 2 to 5, the core barrel 18 as a reactor internal structure has a core barrel main body 51, a former plate 52, and a baffle plate 53.

[0018] The core barrel body 51 is cylindrical. The former plates 52 are ring-shaped and provided in multiple numbers. The outer peripheral surface of the former plate 52 is nearly circular and the inner peripheral surface is jagged. That is, the inner peripheral surface of the former plate 52 is perpendicular to the horizontal plane and is formed by two surfaces 52a, 52b that are perpendicular to each other. The outer diameter of the former plate 52 is the same as or slightly smaller than the inner diameter of the core barrel body 51. The baffle plates 53 are rectangular and provided in multiple numbers.

[0019] A former plate 52 is arranged inside the core barrel body 51. Multiple former plates 52 are arranged at intervals in the axial direction of the core barrel body 51. The former plate 52 is fixed by multiple first bolts 61 with its outer circumferential surface in contact with the inner circumferential surface of the core barrel body 51. The multiple first bolts 61 penetrate the core barrel body 51 from the outer circumferential surface side and screw into the former plate 52. The multiple first bolts 61 are arranged at intervals in the circumferential direction of the core barrel body 51 and the former plate 52.

[0020] The plurality of baffle plates 53 are arranged inside the former plate 52. The plurality of baffle plates 53 are arranged along the axial direction and fixed by a plurality of second bolts 62 while in contact with the surfaces 52a and 52b of the former plate 52.

[0021] The core barrel main body 51 and the former plate 52 are connected by first bolts 61, and the former plate 52 and the baffle plate 53 are connected by second bolts 62. A plurality of fuel assemblies 26 are arranged inside the core barrel 18. The fuel assemblies 26 are arranged adjacent to the baffle plate 53. The baffle plate 53 divides the flow of coolant leading to the fuel assemblies 26.

[0022] <Method of dismantling reactor internals> FIG. 6 is a schematic cross-sectional view showing a cut state of the core barrel.

[0023] 1, the reactor vessel lid 13 is removed from the reactor vessel main body 12, and the reactor internals such as the reactor core 25 are carried out from inside. The reactor internals include the core barrel 18.

[0024] The core barrel 18 is in a state in which the core barrel main body 51 and the former plates 52 are connected by first bolts 61, and the former plates 52 and the baffle plates 53 are connected by second bolts 62. In the method for dismantling the reactor internals in this embodiment, as shown in Figures 3 and 4, the core barrel main body 51, the former plates 52, and the baffle plates 53 are cut while they are assembled together.

[0025] At this time, cutting is performed at positions other than the positions of the plurality of first bolts and the plurality of second bolts from the upper side of the core barrel 18. The cutting method is mechanical cutting, but gas cutting, laser cutting, or the like may also be used.

[0026] Specifically, first, with the core barrel body 51, former plates 52, and baffle plates 53 assembled as a single unit, the core barrel 18 is cut into a ring shape at the horizontal cutting position L1. As shown in Fig. 6, the cut piece 18a of the core layer 18 is ring-shaped, and the cut pieces 51A, 52A, and 53A of the core barrel body 51, former plates 52, and baffle plates 53 are connected by first bolts 61 and second bolts 62.

[0027] 3 and 6, the cut piece 18a of the core layer 18 is cut in the axial direction at vertical cutting positions L2. A plurality of vertical cutting positions L2 are provided at intervals in the circumferential direction. At this time, the cutting is performed at positions other than the positions of the plurality of first bolts and the plurality of second bolts.

[0028] In the above description, the core barrel 18 is cut into a ring shape and then cut along the axial direction, but the core barrel 18 may also be cut along the axial direction and then cut along the horizontal direction.

[0029] [Effects of this embodiment] The first aspect of the method for dismantling reactor internal structures involves dismantling a reactor core vessel 18 as a reactor internal structure, which is configured by fixing a former plate 52 to the inner peripheral wall of a cylindrical reactor core vessel main body 51 and fixing a baffle plate 53 to the inside of the former plate 52, and cutting the reactor core vessel main body 51, the former plate 52, and the baffle plate 53 while they are assembled together.

[0030] According to the method for dismantling reactor internal structures relating to the first aspect, there is no need to dismantle the core vessel body 51, the former plate 52, and the baffle plate 53 in advance, thereby improving the workability of the dismantling work of the core layer 18 as a reactor internal structure.

[0031] The method for dismantling reactor internals according to the second embodiment is the method for dismantling reactor internals according to the first embodiment, further comprising the steps of: fastening a former plate 52 to the inner peripheral wall of the core barrel body 51 with a plurality of first bolts 61; fastening a baffle plate 53 to the inside of the former plate 52 with a plurality of second bolts 62; and cutting the former plate at a position other than the positions of the first bolts 61 and the second bolts 62. This eliminates the need to cut the first bolts 61 and the second bolts 62, thereby suppressing the generation of fine waste.

[0032] The method for dismantling reactor internals according to the third embodiment is the method for dismantling reactor internals according to the first or second embodiment, and further includes cutting the core barrel body 51 into ring shapes. This allows the core layer 18 to be dismantled efficiently.

[0033] The method for dismantling reactor internals according to the fourth aspect is the method for dismantling reactor internals according to any one of the first to third aspects, and further includes cutting the core barrel body 51 along the axial direction. This allows the core layer 18 to be dismantled efficiently.

[0034] The method for dismantling reactor internals according to the fifth aspect is the method for dismantling reactor internals according to any one of the first to fourth aspects, and further comprises cutting the core barrel body 51 into a ring shape and then cutting it along the axial direction, thereby enabling the core layer 18 to be dismantled efficiently.

[0035] In the above embodiment, the core barrel 18 is cut horizontally or axially, but it may be cut obliquely. [Explanation of symbols]

[0036] 10 Pressurized Water Reactor 11 Reactor vessel 12 Reactor vessel body 13 Reactor vessel lid 18 Core tank (core internal structure) 19 Upper core support plate 20 Upper core plate 21 Core support rod 25 reactor core 26 Fuel assembly 51 Core vessel body 52 Forma board 53 Baffle plate 61 First Bolt 62 Second bolt

Claims

1. A method for dismantling a reactor internals structure, comprising dismantling a reactor internals structure comprising a core barrel having a cylindrical core barrel body, a former plate fixed to an inner peripheral wall portion of the core barrel body, and a baffle plate fixed inside the former plate, the method comprising: The core barrel body, the former plate, and the baffle plate are cut in a state where they are integrally assembled. Methods for dismantling reactor internal structures.

2. the former plate is fixed to the inner peripheral wall portion of the core barrel body by a plurality of first bolts, the baffle plate is fixed to the inside of the former plate by a plurality of second bolts, and the former plate is cut at a position other than the positions of the first bolts and the second bolts; The method for dismantling reactor internal structures according to claim 1.

3. cutting the core barrel body into a ring shape; 3. The method for dismantling reactor internal structures according to claim 1 or 2.

4. cutting the core barrel body along the axial direction; 3. The method for dismantling reactor internal structures according to claim 1 or 2.

5. cutting the core barrel body into a ring shape and then cutting it along the axial direction; 3. The method for dismantling reactor internal structures according to claim 1 or 2.

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