Method for cutting the inner plate of a nuclear reactor containment vessel

Abstract

The present invention provides a method for cutting the internal plates of a nuclear reactor containment vessel, which allows for easy cutting of the internal plates of the reactor containment vessel when dismantling equipment inside the reactor containment vessel, such as internal structures. [Solution] A method for cutting an internal plate of a reactor containment vessel that constitutes the internal structure of a nuclear reactor, wherein the internal plate of the reactor containment vessel has a plurality of through holes that penetrate in the thickness direction and are arranged in a grid pattern when viewed from the thickness direction, and the method includes the step of cutting the internal plate of the reactor containment vessel such that a cutting blade that moves in a straight line passes through the plurality of through holes arranged in a grid pattern.

Description

Technical Field

[0001] This disclosure relates to a method for cutting the inner plate of a reactor containment vessel.

Background Art

[0002] Patent Document 1 discloses a technique for disassembling the in-vessel structures in a reactor vessel in the water stored in a working pool and removing the disassembled in-vessel structures from the working pool, regarding a method for decommissioning a nuclear power plant.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, a nuclear power plant as described in Patent Document 1 has large inner plates of a reactor containment vessel, such as an upper core support plate, an upper core plate, a lower core support plate, a lower core plate, etc., which have a circular contour and constitute the equipment inside the reactor containment vessel. When decommissioning a nuclear power plant, it is necessary to cut these inner plates of the reactor containment vessel, store them in a container for radioactive waste, and then remove them. However, when cutting such large inner plates of the reactor containment vessel, it is necessary to consider that the cutting thickness changes due to differences in plate thickness caused by cavities and shapes. If an inexperienced operator performs the cutting, there are problems such as an increase in working time and an increase in the required power of the cutting tool.

[0005] This disclosure has been made in view of the above circumstances, and provides a method for cutting the inner plate of a reactor containment vessel that can easily cut the inner plate of the reactor containment vessel when disassembling the in-vessel structures.

Means for Solving the Problems

[0006] To address the above issues, the following configuration will be adopted. According to a first aspect of the present disclosure, a method for cutting an internal plate of a reactor containment vessel is a method for cutting an internal plate of a reactor containment vessel that constitutes an internal structure of a reactor, wherein the internal plate of the reactor containment vessel has a plurality of through holes that penetrate in the thickness direction and are arranged in a grid pattern when viewed from the thickness direction, and the method includes the step of cutting the internal plate of the reactor containment vessel such that a linearly advancing cutting blade passes through the plurality of through holes arranged in a grid pattern in a row. [Effects of the Invention]

[0007] According to this disclosure, the internal plates of the reactor containment vessel can be easily cut when dismantling the internal structures of the reactor. [Brief explanation of the drawing]

[0008] [Figure 1] This is a longitudinal cross-sectional view showing a pressurized water reactor, which is the reactor to be dismantled according to this embodiment. [Figure 2] This is a schematic diagram showing a pressurized water reactor, with water stored inside and its reactor vessel lid removed, positioned inside a pool within the reactor building according to the embodiment. [Figure 3] This is a perspective view showing the upper core structure according to the embodiment. [Figure 4] This is a perspective view of a portion of the upper core support plate according to the first embodiment, with parts of it disassembled. [Figure 5] This is a flowchart of the method for cutting the inner plate of the reactor containment vessel in the first embodiment. [Figure 6] This is a plan view showing the cutting line of the upper core support plate body in the first embodiment. [Figure 7] This is a side view showing the schematic configuration of a cutting device equipped with a cutting blade according to the first embodiment. [Figure 8] This is a plan view of the upper core plate in the second embodiment. [Figure 9] This is a side view of the fuel assembly guide pins and orifice fixed to the upper core plate body. [Figure 10]This is a perspective view showing the orifice of the upper reactor core plate as it is fixed to the upper reactor core plate body. [Modes for carrying out the invention]

[0009] Next, a method for cutting the internal plates of a reactor containment vessel according to the first embodiment of this disclosure will be described with reference to the drawings. (nuclear reactor) Figure 1 is a longitudinal cross-sectional view showing a pressurized water reactor, which is the reactor to be dismantled according to this embodiment. The reactor is a pressurized water reactor (PWR) that uses light water as a reactor coolant and neutron moderator to create high-temperature, high-pressure water that does not boil throughout the entire core 7, sends this high-temperature, high-pressure water to a steam generator to generate steam through heat exchange, and sends this steam to a turbine generator to generate electricity.

[0010] Figure 2 is a schematic diagram showing a pressurized water reactor, with water stored inside and the reactor vessel lid removed, positioned within the reactor building pool according to the embodiment. As shown in Figure 2, the pressurized water reactor 1 is located within the reactor building pool 100. The reactor building pool 100 has a space where cooling water (water) can be stored. In this embodiment, the reactor building pool 100 has a first cavity 110 in which the pressurized water reactor 1 is located, and a second cavity 120 located adjacent to the first cavity 110. The first cavity 110 has a first floor surface 111 in which workers can walk. The second cavity 120 has a second floor surface 121 that is recessed from the first floor surface 111. That is, the second floor surface 121 is located vertically Dv below the first floor surface 111. As a result, the second cavity 120 is formed as a space that is recessed vertically Dv lower than the first cavity 110.

[0011] As shown in Figures 1 and 2, the pressurized water reactor 1 of this embodiment comprises a reactor vessel 2, a control rod drive unit 3, an upper core structure 5, and a lower core structure 6.

[0012] The reactor vessel 2 has a reactor vessel main body 21 and a reactor vessel head 22 (upper plenum), so that the in-vessel structure can be inserted therein. The reactor vessel 2 is disposed inside a hole formed to be recessed with respect to the first floor surface 111. The reactor vessel 2 is disposed in a state where a part thereof (specifically, the reactor vessel head 22) protrudes from the first floor surface 111.

[0013] The upper part of the reactor vessel main body 21 can be opened by removing the reactor vessel head 22. The lower part of the reactor vessel main body 21 has a cylindrical shape closed by a lower plenum having a hemispherical shape. An inlet nozzle 23 (inlet plenum) for supplying light water (coolant) as primary cooling water (water) and an outlet nozzle 24 (outlet plenum) for discharging the light water are formed in the upper part of the reactor vessel main body 21. Further, a water injection nozzle (water injection plenum; not shown) is formed in the reactor vessel main body 21 separately from the inlet nozzle 23 and the outlet nozzle 24.

[0014] The reactor vessel head 22 is attached to the upper part of the reactor vessel main body 21. The reactor vessel head 22 is fixedly attached to the reactor vessel main body 21 so as to be openable and closable by a plurality of stud bolts and nuts (not shown).

[0015] FIG. 3 is a perspective view showing an upper core structure according to the embodiment. The upper core structure 5 is disposed inside the reactor vessel 2. The upper core structure 5 can be withdrawn from the reactor vessel main body 21 by being moved upward in the vertical direction Dv with respect to the reactor vessel main body 21. As shown in FIG. 3, the upper core structure 5 of the present embodiment has at least an upper core plate 51, an upper core support plate 52, upper core support columns 53, guide tubes 55, and a water level gauge support tube 57. Note that the upper core structure 5 is not limited to having only the above structure. For example, the upper core structure 5 may have other components (all not shown) such as a mixer and a thermocouple lead-out tube.

[0016] The upper core plate 51 is disposed at a distance below the upper core support plate 52 in the vertical direction Dv. The upper core plate 51 has a disk shape with a number of through holes. A control rod cluster drive shaft 45 (see FIG. 1) capable of gripping the control rod cluster 4 is inserted through a part of the plurality of through holes of the upper core plate 51.

[0017] The upper core support plate 52 is disposed at a distance above the upper core plate 51 in the vertical direction Dv. As shown in FIGS. 1 and 2, the upper core support plate 52 is fixed to the reactor vessel body 21 above the inlet nozzle 23 and the outlet nozzle 24 in the vertical direction Dv inside the reactor vessel body 21.

[0018] As shown in FIG. 3, the upper core support plate 52 exemplified in this embodiment is formed in a disk shape larger than the upper core plate 51. A plurality of through holes 54 (see FIG. 4) are formed in the upper core support plate 52 at the same positions as a part of the through holes formed in the upper core plate 51 when viewed from the vertical direction Dv. A guide tube 55 and a water level gauge support tube 57 are inserted through the through holes 54 of the upper core support plate 52. Also, as shown in FIG. 2, the upper surface of the upper core support plate 52 of this embodiment is disposed at the same height as the first floor surface 111 in the vertical direction Dv when the upper core structure 5 is disposed in the reactor vessel 2.

[0019] As shown in FIG. 3, the plurality of upper core support columns 53 connect the upper core support plate 52 and the upper core plate 51. The plurality of upper core support columns 53 extend in the vertical direction Dv and extend linearly. The upper end of the upper core support column 53 is fixed to the upper core support plate 52. The lower end of the upper core support column 53 is fixed to the upper core plate 51. The plurality of upper core support columns 53 are arranged so as not to overlap with the guide tube 55 and the water level gauge support tube 57 when viewed from the vertical direction Dv.

[0020] The guide tube 55 is fixed to the upper core support plate 52, inserted through the through-hole 54 of the upper core support plate 52. The guide tube 55 guides the vertical movement Dv of the control rod cluster drive shaft 45 (see Figure 1) for driving the control rod cluster 4. The control rod cluster drive shaft 45 is inserted through the inside of the guide tube 55. The guide tube 55 is made of, for example, stainless steel. The guide tube 55 is inserted from above in the vertical direction Dv into the through-hole 54 of the upper core support plate 52 and the through-hole 54 of the upper core plate 51. The lower end of the guide tube 55 is connected to the upper core plate 51.

[0021] As shown in Figures 1 and 2, the lower core structure 6 is located inside the reactor vessel 2. Many of the components of the lower core structure 6 are positioned below the upper core structure 5 in the vertical direction Dv. The lower core structure 6 can be removed from the reactor vessel body 21 by moving it above the upper core structure 5 in the vertical direction Dv. The lower core structure 6 is separable from the upper core structure 5 inside the reactor vessel body 21. The lower core structure 6 in this embodiment includes a core tank 61, a lower core plate 62, and a lower core support plate 63. However, the lower core structure 6 does not have only the structure described above. The lower core structure 6 may have other components such as a thermal shield (not shown), a baffle plate (not shown), and a lower instrumentation guide tube (not shown).

[0022] The core vessel 61 is formed to extend vertically downward in the direction Dv from the upper core support plate 52. The core vessel 61 is positioned with a predetermined gap between it and the inner wall surface of the reactor vessel body 21. The core vessel 61 is connected to the upper core plate 51.

[0023] The lower core plate 62 is connected to the lower part of the core tank 61. The lower core plate 62 has a disc shape and numerous through-holes. Lower instrumentation guide tubes (not shown) are inserted through the through-holes in the lower core plate 62. The core 7 is formed by the upper core plate 51, the core tank 61, and the lower core plate 62.

[0024] The reactor core 7 contains numerous fuel assemblies 71. Each fuel assembly 71 is composed of numerous fuel rods bundled together in a grid pattern by a support grid.

[0025] The lower core support plate 63 is positioned below the lower core plate 62 in the vertical direction Dv. The lower core support plate 63 is located near the lower mirror and is fixed to the reactor vessel body 21. The lower core support plate 63 is disc-shaped and has numerous through holes.

[0026] (Upper core support plate) Figure 4 is a perspective view showing a portion of the upper core support plate according to the first embodiment, with parts disassembled. As shown in Figure 4, the upper core support plate 52 comprises an upper core support plate body (internal plate body) 52a and accessories 52b. The upper core support plate body 52a is plate-shaped. Furthermore, the outline of this upper core support plate body 52a as viewed from the plate thickness direction Dt is circular. The upper core support plate body 52a has a plurality of through holes 54 that penetrate in the plate thickness direction Dt, and these multiple through holes 54 are arranged in a grid pattern as viewed from the plate thickness direction Dt.

[0027] Multiple through-holes 54 formed in the upper core support plate body 52a are formed in the thickness direction Dt of the upper core support plate body 52a to allow guide tubes 55, water level gauge support pipes 57 (see Figure 3), etc., to pass through. In this embodiment, the multiple through-holes 54 through which the guide tubes 55 pass and the multiple through-holes 54 through which the water level gauge support pipes 57 pass are all circular and have the same inner diameter. The thickness of the upper core support plate body 52a can be exemplified as about 100 mm. Note that the inner diameters of the multiple through-holes 54 are not limited to being the same.

[0028] The multiple through-holes 54 form a grid pattern, arranged in a first direction D1 perpendicular to the plate thickness direction Dt of the upper core support plate body 52a, and in a second direction D2 perpendicular to both the plate thickness direction Dt and the first direction D1. More specifically, the first row L11 to the nth row L1n (n=7 in this embodiment), consisting of multiple through-holes 54 arranged linearly in the first direction D1, are arranged at intervals in the second direction D2. Of the multiple through-holes 54 constituting these first row L11 to the nth row L1n, the first through-holes 54 in the first direction D1 are located at the same position in the first direction D1, and the second through-holes 54 in the first direction D1 are located at the same position in the first direction D1. Similarly, the third to the nth through-holes 54 in the first direction D1 are located at the same position in the first direction D1. In other words, the first through-hole 54 in the first direction D1 forms a linear row L21 in the second direction D2, and the second through-hole 54 in the first direction D1 forms a linear row L22 in the second direction D2. Similarly, up to the nth through-hole 54, a linear row L2n (n=7 in this embodiment) forms in the second direction D2. Multiple through-holes 54 are arranged in a grid pattern in this manner. Furthermore, in this embodiment, the arrangement is a grid pattern of a rectangular shape in plan view with n rows having the same number of through-holes 54 in both the first direction D1 and the second direction D2, with the through-holes 54 at the four corners of the rectangular shape in plan view omitted. Note that Figure 4 illustrates the case where there are up to 7 rows in both the first direction D1 and the second direction D2, but the number of rows is not limited to these.

[0029] (Accessories) The accessory 52b protrudes from the upper core support plate body 52a in the thickness direction Dt. The upper core support plate 52 in this embodiment includes a cover 52b1 and a reinforcing beam 52b2 as accessories 52b. Both the cover 52b1 and the reinforcing beam 52b2 are detachably fixed to the upper core support plate body 52a by fastening members (not shown) such as bolts.

[0030] (lid) The lid 52b1 is attached to and closes off unused through-holes 54 formed in the upper core support plate body 52a that are not used for inserting guide tubes 55 or water level gauge support pipes 57, etc. The lid 52b1 is sized to be able to close each of the through holes 54. The lid 52b1 of this embodiment is rectangular when viewed from the plate thickness direction Dt. The lid 52b1 of this embodiment also has a plate-shaped lid body and circular protrusions that protrude from the lid body and fit into the through holes 54. The four rectangular corners of the lid 52b1 of this embodiment are fixed to the upper core support plate body 52a by fastening members (not shown) such as bolts. The fastening members (not shown) that fix the lid 52b1 of this embodiment also have anti-rotation and anti-detachment parts (not shown) made by welding or the like.

[0031] In this embodiment, the lid 52b1 is attached to the third to fifth through-holes 54 located in the center of the second row L12 and the sixth row (n-1 row) L16, and to the second and sixth through-holes 54 in the third row L13 to the fifth row (n-2 row) L15, respectively, among the multiple through-holes 54 forming the first row L11 to the seventh row (n-th row) L17. Note that the number of rows of multiple through-holes 54 formed in the upper core support plate body 52a, the number of through-holes 54 in each row, and the positions of the through-holes 54 to which the lid 52b1 is attached are examples and are not limited to the above configuration.

[0032] (Reinforcement beam) The reinforcing beam 52b2 is a member that reinforces the upper core support plate body 52a. In this embodiment, the reinforcing beam 52b2 has a grid-like structure when viewed from the plate thickness direction Dt. Furthermore, the reinforcing beam 52b2 extends perpendicularly from one surface of the upper core support plate body 52a in the plate thickness direction Dt. The reinforcing beam 52b2 has one central frame portion 56 and four outer frame portions 58. The central frame portion 56 is formed in a hollow rectangular shape when viewed from the plate thickness direction Dt. The multiple outer frame portions 58 are formed to protrude from the central frame portion in the first direction D1 and the second direction D2, respectively. In other words, the outer frame portions 58 protrude outward from each of the four sides of the central frame portion 56 and together with each of the four sides of the central frame portion 56 form a hollow rectangular portion. In this embodiment, the reinforcing beam 52b2 is fixed to the upper core support plate body 52a by a plurality of fastening members (not shown), such as bolts. Furthermore, the fastening member (not shown) that secures the reinforcing beam 52b2 in this embodiment has a rotation-preventing and detachment-preventing portion (not shown) made by welding or the like, similar to the fastening member that secures the cover 52b1 described above.

[0033] (Method for cutting the inner plates of the reactor containment vessel) Figure 5 is a flowchart of the method for cutting the inner plate of the reactor containment vessel in the first embodiment of this disclosure. As shown in Figure 5, the method S10 for cutting the reactor containment vessel inner plate in this first embodiment includes a step S11 for determining the radioactivity level of the reactor containment vessel inner plate, a step S12 for determining a waste container according to the radioactivity level, and a step S13 for cutting the reactor containment vessel inner plate. In this embodiment, the method S10 for cutting the reactor containment vessel inner plate will be explained using the case where the upper core support plate 52 is cut as the reactor containment vessel inner plate as an example. Before performing the method S10 for cutting the reactor containment vessel inner plate, the reactor containment vessel inner plate is removed from the reactor vessel. Various methods can be applied to remove the reactor containment vessel inner plate from the reactor vessel.

[0034] In step S11, which determines the radioactivity level of the reactor containment vessel inner plate, the radioactivity level of the upper core support plate 52 is determined. Here, the radioactivity level of the upper core support plate 52 may be the radioactivity level measured by a measuring instrument, or it may be the radioactivity level obtained by simulation or calculation. Also, for example, if the radioactivity level of a single upper core support plate 52 differs depending on the location, the radioactivity level with the highest value may be used.

[0035] In step S12, which determines the waste container according to the radioactivity level, the waste container is determined according to the radioactivity level obtained in step S11. The waste container (not shown) tends to have a smaller internal storage space as the radioactivity level of the waste it contains increases, requiring a thicker wall. In other words, determining the waste container according to the radioactivity level determines the upper limit of the size of the contents that can be contained within the container.

[0036] In step S13, which involves cutting the inner plate of the reactor containment vessel, the cutting blade 91 (see Figure 7), which moves in a straight line, cuts the upper core support plate 52 by passing through a plurality of through holes 54 arranged in a grid-like row. In step S13 of cutting the reactor containment vessel inner plate in this embodiment, the upper core support plate 52 is cut after removing the attachments 52b from the upper core support plate body 52a. In other words, in step S13 of this embodiment, since at least the lid 52b1 and the reinforcing beam 52b2 are attached to the upper core support plate body 52a as attachments 52b, the lid 52b1 and the reinforcing beam 52b2 are removed from the upper core support plate body 52a, respectively.

[0037] To remove the lid 52b1 and the reinforcing beam 52b2 from the upper core support plate body 52a, the fastening members (not shown) must first be removed. Specifically, the anti-rotation and anti-loosening mechanisms of all fastening members that secure the lid 52b1 and the reinforcing beam 52b2 must be released. For example, to release the anti-rotation and anti-loosening mechanisms that are welded, one method is to remove the welded parts of the anti-rotation and anti-loosening mechanisms using tools such as a disc grinder or rotary cutter. By releasing these anti-rotation and anti-loosening mechanisms, the fastening members can be rotated in the direction of release. In this state, the fastening members can be removed using a tool such as a wrench. An example of the order in which the lid 52b1 and the reinforcing beam 52b2 are removed is to detach the upper core support plate body 52a from the reinforcing beam 52b2, and then remove the lid 52b1 from the upper core support plate body 52a. If the fastening members are stuck and cannot be rotated due to seizing or other reasons, the fastening can be released by removing the heads of the fastening members.

[0038] Figure 6 is a plan view showing the cutting line of the upper core support plate body in the first embodiment of the present disclosure. As shown in Figures 5 and 6, in step S13, which cuts the inner plate of the reactor containment vessel, a linear cutting line 80 is further set on the upper core support plate body 52a, passing through multiple through holes 54. Here, the cutting line 80 is a straight line indicating the position where the cutting blade 91 passes when cutting the upper core support plate body 52a. In this embodiment, two types of cutting lines 80 are set: a first cutting line 81 and a second cutting line 82. Multiple first cutting lines 81 are set extending in the first direction D1 and spaced apart in the second direction D2. Multiple second cutting lines 82 are set extending in the second direction D2 and spaced apart in the first direction D1.

[0039] Each of the above-mentioned cutting lines 80 is a straight line passing through a plurality of through holes 54 arranged in a grid-like row. In step S13 of cutting the inner plate of the reactor containment vessel in this embodiment, the number of first cutting lines 81 and the spacing of the first cutting lines 81 in the second direction D2, and the number of second cutting lines 82 and the spacing of the second cutting lines 82 in the first direction D1 are determined so that the size of each of the plurality of cut pieces obtained by cutting the upper core support plate body 52a is such that it can be contained in a waste container according to the radioactivity level.

[0040] In this embodiment, an example is shown in which two first cutting lines 81 and two second cutting lines 82 perpendicular to the two first cutting lines 81 are set. The two first cutting lines 81 divide the area on the upper core support plate body 52a into three parts in the second direction D2, and the two second cutting lines 82 divide the area on the upper core support plate body 52a into three parts in the first direction D1. By setting these two first cutting lines 81 and two second cutting lines 82, the upper core support plate body 52a in this embodiment is divided into nine areas. Each of these nine divided areas is sized to fit within the waste container storage space determined in step S12.

[0041] Furthermore, at least one of the first cutting line 81 and the second cutting line 82 is set to pass through the center of the multiple through holes 54 through which it passes. In this embodiment, the case in which both the first cutting line 81 and the second cutting line 82 pass through the center of the through holes 54 is shown. In this embodiment, the case in which the first cutting line 81 passes through rows L12 and L16 of the through holes 54 and the second cutting line 82 passes through rows L22 and L26 of the through holes 54 is illustrated, but the rows of through holes 54 through which the cutting line 80 passes are not limited to these rows.

[0042] In step S13, which involves cutting the inner plate of the reactor containment vessel, the inner plate body is further cut along the first cutting line 81 and the second cutting line 82 using a cutting blade.

[0043] Figure 7 is a side view showing a schematic configuration of a cutting device equipped with a cutting blade in a first embodiment of the present disclosure. As shown in Figure 7, the cutting device 90 comprises at least a cutting blade 91, a frame 92, and a turntable 93. The cutting blade 91 is a circular saw blade (also called a carbide-tipped saw blade) capable of cutting the metal upper core support plate 52, and is rotatable by an electric motor or engine (not shown). The frame 92 supports the cutting blade 91 so that it can move up, down, left, and right. The frame 92 in this embodiment is a so-called gate-type frame and comprises a pair of column sections 92a and a beam section 92b that spans between these column sections 92a.

[0044] The beam section 92b supports the cutting blade 91 so that it can move horizontally in the direction Dh1 along the beam section 92b between the column sections 92a. The pair of column sections 92a support the beam section 92b so that it can be displaced vertically, and are also capable of sliding parallel to the horizontal direction perpendicular to the direction in which the beam section 92b extends (in other words, the horizontal direction Dh1). The turntable 93 is positioned between the pair of column sections 92a and below the beam section 92b. The turntable 93 is rotatable around a rotation axis O1 extending in the vertical direction Dv. The turntable 93 in this embodiment has a planar upper surface extending horizontally, and an internal plate body such as the upper core support plate body 52a can be placed on this upper surface of the turntable 93 in an orientation where the plate thickness direction Dt is in the vertical direction.

[0045] In step S13 of cutting the inner plate of the reactor containment vessel in this embodiment, for example, the cutting device 90 is installed on the first floor surface 111 or the like in the reactor building pool 100, and the upper core support plate body 52a is placed on the turntable 93 of the cutting device 90. Then, the upper core support plate 52 placed on the turntable 93 is cut with the cutting blade 91. An example of the cutting procedure with the cutting blade 91 is to cut the upper core support plate body 52a in a straight line passing through one of the multiple first cutting lines 81 and second cutting lines 82, and then rotate the turntable 93 by 90° to cut the upper core support plate body 52a in a straight line passing through the other of the multiple first cutting lines 81 and second cutting lines 82. The cut pieces (not shown) of the upper core support plate body 52a are stored in a waste container in the reactor building pool 100 and transported out of the reactor building pool 100.

[0046] (Effects and Benefits) The method for cutting the reactor containment vessel inner plate of the first embodiment described above includes a step S13 for cutting the reactor containment vessel inner plate, in which a cutting blade 91 that moves in a straight line cuts the upper core support plate body 52a so as to pass through a plurality of through holes 54 arranged in a grid-like row. This allows for a reduction in the effective cutting length of the upper core support plate 52 (upper core support plate body 52a) when cutting it using a cutting blade 91 that moves in a straight line. As a result, the load on the cutting blade 91 and the power required for cutting are reduced, and the time required for the cutting operation is shortened. Consequently, the upper core support plate 52 can be cut easily.

[0047] Furthermore, in the method for cutting the reactor containment vessel inner plate of the first embodiment described above, the upper core support plate body 52a is cut after the attachment 52b is removed from the upper core support plate body 52a in step S13 for cutting the reactor containment vessel inner plate. As a result, compared to the case where the upper core support plate body 52a and the attachments 52b are cut simultaneously, the thickness of the object to be cut by the cutting blade 91 can be reduced, thereby further reducing the load on the cutting blade 91 and the power required for cutting.

[0048] Furthermore, in the method for cutting the inner plate of the reactor containment vessel according to the first embodiment described above, the upper core support plate body 52a is cut so as to pass through the through hole 54 from which the lid 52b1 has been removed. This reduces the load on the cutting blade 91 and the power required for cutting compared to cutting the lid 52b1. It also shortens the time required for the cutting operation. Therefore, it improves the flexibility in selecting the cutting position, making it easier to cut than when the lid 52b1 is not removed.

[0049] Furthermore, in the method for cutting the inner plate of the reactor containment vessel according to the first embodiment described above, a plurality of first cutting lines 81 and a plurality of second cutting lines 82 are set as straight cutting lines 80 passing through a plurality of through holes 54, and the upper core support plate body 52a is cut along the first cutting lines 81 and the second cutting lines 82 with a cutting blade 91. This makes it possible to easily standardize the size of the multiple cut pieces formed by cutting the upper core support plate 52, while suppressing the complex shape of the cutting line 80.

[0050] Furthermore, in the method for cutting the inner plate of the reactor containment vessel according to the first embodiment described above, at least one of the first cutting line 81 and the second cutting line 82 passes through the center of the plurality of through holes 54. As a result, on the cutting line 80 that passes through the center of the multiple through holes 54, among the first cutting line 81 and the second cutting line 82, the distance between adjacent through holes 54 can be shortened. Therefore, the effective cutting length of the upper core support plate 52 can be further shortened.

[0051] Furthermore, the method for cutting the reactor containment vessel inner plate of the first embodiment described above includes a step S11 for determining the radioactivity level of the reactor containment vessel inner plate and a step S12 for determining a waste container according to the radioactivity level. In the step S13 for cutting the reactor containment vessel inner plate, the number of first cutting lines 81 and the spacing of the first cutting lines 81 in the second direction D2, and the number of second cutting lines 82 and the spacing of the second cutting lines 82 in the first direction D1 are determined so that the size of the cut piece after cutting the upper core support plate 52 is such that it can be accommodated in a waste container according to the radioactivity level. The space required for waste containers to hold radioactive waste tends to decrease as the radioactivity level of the waste increases. Therefore, by determining the first cutting line 81 and the second cutting line 82 as described above, the upper core support plate 52 can be easily cut, and the size of the cut pieces after cutting can be adjusted to the dimensions of the waste container according to the radioactivity level without requiring specialized skills.

[0052] (Second embodiment) Next, a method for cutting the reactor containment vessel inner plate in a second embodiment of this disclosure will be described with reference to the drawings. This second embodiment differs in that the reactor containment vessel inner plate is the upper core plate. Therefore, the same reference numerals are used for the same parts as in the first embodiment described above, and redundant explanations are omitted.

[0053] Figure 8 is a plan view of the upper core plate in a second embodiment of the present disclosure. Figure 9 is a side view of the fuel assembly guide pins and orifice fixed to the upper core plate body. Figure 10 is a perspective view showing the orifice of the upper core plate fixed to the upper core plate body. (Upper core plate) In the method for cutting the reactor containment vessel inner plate in the second embodiment, the upper core plate 51 is cut as the reactor containment vessel inner plate, which is an internal structure of the reactor. As shown in Figures 8 to 10, the upper core plate 51 comprises an upper core plate body (internal plate body) 51a and an accessory 51b. The upper core plate body 51a of this second embodiment is plate-shaped, similar to the upper core support plate body 52a described above. Furthermore, the contour of this upper core plate body 51a as viewed from the plate thickness direction Dt is circular. The upper core plate body 51a has a plurality of through holes 59 that penetrate in the plate thickness direction Dt. These plurality of through holes 59 are arranged in a grid pattern as viewed from the plate thickness direction Dt.

[0054] The multiple through-holes 59 formed in the upper core plate body 51a include at least two through-holes 59: one for passing control rod cluster drive shafts 45, etc., through the plate thickness direction Dt of the upper core plate body 51a, and another for circulating coolant (light water) in the plate thickness direction Dt. In the second embodiment, the shape of the multiple through-holes 59 as viewed from the plate thickness direction Dt is circular. The thickness of the upper core plate body 51a can be approximately 40 mm. The multiple through-holes 59 formed in the upper core plate body 51a may be a mixture of circular and rectangular shapes.

[0055] The multiple through-holes 59 form a grid pattern, arranged in a first direction D1 perpendicular to the thickness direction Dt of the upper core plate body 51a, and in a second direction D2 perpendicular to both the thickness direction Dt and the first direction D1. More specifically, similar to the first embodiment, the first to nth rows (n=13 in this embodiment), each consisting of multiple through-holes 59 arranged linearly in the first direction D1, are spaced apart in the second direction D2. The number of through-holes 59 constituting these first to nth rows is greater in the rows closer to the center of the upper core plate body 51a in the second direction D2 than in the rows further from the center. Furthermore, the through-holes 59 constituting the first to nth rows arranged in the first direction D1 form the first to nth rows (n=13 in this embodiment) arranged linearly in the second direction D2. Furthermore, the multiple through-holes 59 formed in the upper core plate body 51a of the second embodiment are arranged to be 90 degrees rotationally symmetric with respect to the center of the upper core plate body 51a. Although Figure 8 illustrates a case where there are up to 13 rows in both the first direction D1 and the second direction D2, the number of rows is not limited to this.

[0056] (Accessories) As shown in Figures 9 and 10, the attachment 51b protrudes from the upper core plate body 51a in the thickness direction Dt. The upper core plate 51 of the second embodiment includes at least a fuel assembly guide pin 51b1 and an orifice 51b2 as attachments 51b. In addition to the fuel assembly guide pin 51b1 and the orifice 51b2, the attachment 51b may also include a cylindrical mixer (not shown) extending from the upper core plate body 51a toward the upper core support plate 52.

[0057] As shown in Figure 9, the fuel assembly guide pins 51b1 are formed in a columnar shape that protrudes from the upper core plate body 51a in the thickness direction Dt and tapers to a point. The fuel assembly guide pins 51b1 have the function of guiding the fuel assemblies 71 and are fixed around each of the multiple through holes 59. In this embodiment, multiple fuel assembly guide pins 51b1 (for example, four) are provided for each through hole 59, and the arrangement of these multiple fuel assembly guide pins 51b1 is rotationally symmetrical with respect to the center of the through hole 59. In this embodiment, the fuel assembly guide pins 51b1 are attached to the upper core plate body 51a by a combination of methods such as shrink fitting, heat fitting, screw fastening, and welding to prevent rotation. In other words, the mounting structure of the fuel assembly guide pins 51b1 in this embodiment is such that it is difficult to attach or detach them from the upper core plate body 51a using only hand tools.

[0058] As shown in Figures 9 and 10, the orifice 51b2 protrudes from the upper core plate body 51a in one direction in the thickness direction Dt. In this embodiment, the orifice 51b2 protrudes in the opposite direction to the fuel assembly guide pin 51b1 in the thickness direction Dt. The orifice 51b2 is formed in a ring shape extending in the thickness direction Dt. In other words, the orifice 51b2 has an orifice hole 69 that communicates with a through hole 59 formed in the upper core plate body 51a in the thickness direction Dt. The orifice 51b2 is attached to the upper core plate body 51a so as to surround the through holes 59 through which the coolant (light water) flows, and limits the amount of coolant passing through the through holes 59 to a predetermined amount. These orifices 51b2 are attached to some of the through holes 59 through which the coolant flows, for example. Note that the orifice 51b2 is not limited to the shape shown in Figure 10. For example, the upper core plate body 51a may contain a mixture of orifices of different shapes.

[0059] As shown in Figure 10, the orifice 51b2 in this embodiment is detachably fixed to the upper core plate body 51a by fastening members 68 such as bolts. The orifice 51b2 in this embodiment also has a rotation-prevention and detachment-prevention part (not shown) that prevents the fastening members 68 from rotating and coming loose by welding or the like. When removing the orifice 51b2 from the upper core plate body 51a, the rotation-prevention and detachment-prevention part is released (removed) with a tool, and then the fastening member is rotated and loosened with a tool such as a wrench. In this way, the orifice 51b2 can be removed from the upper core plate body 51a more easily than the fuel assembly guide pin 51b1.

[0060] (Method for cutting the inner plates of the reactor containment vessel) Next, the method for cutting the inner plate of the reactor containment vessel in the second embodiment will be explained with reference to Figure 5. As shown in Figure 5, the method S20 for cutting the reactor containment vessel inner plate in this second embodiment includes a step S21 for determining the radioactivity level of the reactor containment vessel inner plate, a step S22 for determining a waste container according to the radioactivity level, and a step S23 for cutting the reactor containment vessel inner plate. In the method S20 for cutting the reactor containment vessel inner plate, the upper core plate 51 is cut as the reactor containment vessel inner plate. Before performing the method S20 for cutting the reactor containment vessel inner plate, the upper core plate 51 is removed from the reactor vessel 2. Various methods can be applied to remove the upper core plate 51 from the reactor vessel 2.

[0061] In step S21, which determines the radioactivity level of the reactor containment vessel inner plate, the radioactivity level of the upper core plate 51 is determined. Here, the radioactivity level of the upper core plate 51 may be the radioactivity level measured by a measuring instrument, as in the case of the upper core support plate 52 in the first embodiment, or it may be the radioactivity level obtained by simulation or calculation. Also, for example, if the radioactivity level of a single upper core plate 51 differs depending on the location, the radioactivity level with the highest value may be used.

[0062] In step S22, which determines the waste container according to the radioactivity level, the waste container is determined according to the radioactivity level obtained in step S21. In other words, the upper limit of the size of the contents that can be contained in the waste container according to the radioactivity level is determined.

[0063] In step S23, which involves cutting the inner plate of the reactor containment vessel, a cutting blade 91 that moves in a straight line cuts the upper core plate 51 so as to pass through a plurality of through holes 59 arranged in a grid-like row. In this embodiment, step S23, which involves cutting the inner plate of the reactor containment vessel, is performed with water filling the first cavity 110 and the second cavity 120 (see Figure 2) in the reactor building pool 100, with the upper core plate 51 placed in the water, and with waste containers placed in the air inside the reactor building pool 100.

[0064] In the second embodiment, step S23, which involves cutting the inner plate of the reactor containment vessel, the upper core plate 51 is cut after removing the attachment 51b, which can be easily removed from the upper core plate body 51a, from the upper core plate body 51a. In step S23 of the second embodiment, at least the orifice 51b2 of the attachment 51b is removed from the upper core plate body 51a, and the upper core plate body 51a is cut without removing the fuel assembly guide pin 51b1.

[0065] To remove the orifice 51b2 from the upper core plate body 51a, as in the first embodiment described above, a tool such as a disc grinder or rotary cutter is used to release the anti-rotation and anti-loosening mechanisms (not shown) of all fastening members 68 that secure the orifice 51b2. Then, the fastening members 68 are removed using a tool such as a wrench. If the fastening members 68 are stuck and cannot be turned due to seizing or the like, the fastening by the fastening members 68 may be released by removing the head (not shown) of the fastening member 68.

[0066] In step S23, which cuts the inner plate of the reactor containment vessel, a linear cutting line 180 is further set in the upper core plate body 51a that passes through a plurality of through holes 59. As shown in Figure 8, in the second embodiment, similar to the first embodiment, two types of cutting lines 180 are set: a first cutting line 181 and a second cutting line 182. Multiple first cutting lines 181 are set extending in the first direction D1 and spaced apart in the second direction D2. Multiple second cutting lines 182 are set extending in the second direction D2 and spaced apart in the first direction D1.

[0067] Each of the above-mentioned cutting lines 180 is a straight line passing through a plurality of through holes 59 arranged in a grid-like row. In the process S23 of cutting the reactor containment vessel inner plate of the second embodiment, similar to the first embodiment, the number of first cutting lines 181 and the spacing of the first cutting lines 181 in the second direction D2, and the number of second cutting lines 182 and the spacing of the second cutting lines 182 in the first direction D1 are determined so that the size of each of the plurality of cut pieces obtained by cutting the upper core plate body 51a is such that it can be accommodated in a waste container according to the radioactivity level.

[0068] In the second embodiment, similar to the first embodiment, an example is shown in which two first cutting lines 181 and two second cutting lines 182 perpendicular to the two first cutting lines 181 are set. The two first cutting lines 181 divide the area on the upper core plate body 51a into three parts in the second direction D2, and the two second cutting lines 182 divide the area on the upper core plate body 51a into three parts in the first direction D1. By setting these two first cutting lines 181 and two second cutting lines 182, the upper core plate body 51a in this embodiment is divided into nine areas. The size of all nine of these divided areas is such that they can be accommodated in the waste container storage space determined in step S12.

[0069] In the second embodiment, the first cutting line 181 and the second cutting line 182 are set to be straight lines that pass through multiple through holes 59 and through positions where the fuel assembly guide pins 51b1, which are attachments 51b that have not been removed from the upper core plate body 51a, are not located. In other words, the first cutting line 181 and the second cutting line 182 extend to avoid the fuel assembly guide pins 51b1. For example, if there are attachments 51b that cannot be removed from the upper core plate body 51a in addition to the fuel assembly guide pins 51b1, it is preferable to set the first cutting line 181 and the second cutting line 182 to pass through positions where none of the attachments 51b are located. Furthermore, it is preferable to set the first cutting line 181 and the second cutting line 182 to pass through positions close to the center of the multiple through holes 59, within a range that does not interfere with the attachments 51b. In the second embodiment, the positions through which the first cutting line 181 and the second cutting line 182 pass take priority over avoiding the attachment 51b, as they pass through multiple through holes 59.

[0070] In step S23, which cuts the inner plate of the reactor containment vessel, the inner plate body 51a is further cut so that the cutting blade 91 passes through the first cutting line 181 and the second cutting line 182. The cutting device 90 equipped with the cutting blade 91 is the cutting device 90 exemplified in the first embodiment.

[0071] (Effects and Benefits) The method for cutting the reactor containment vessel inner plate of the second embodiment described above includes a step S23 for cutting the reactor containment vessel inner plate, in which a cutting blade 91 that moves in a straight line cuts the upper core plate 51 so as to pass through a plurality of through holes 59 arranged in a grid-like row. This allows for a reduction in the effective cutting length of the upper core plate 51 when cutting it using a linearly moving cutting blade 91. As a result, the load on the cutting blade 91 and the power required for cutting are reduced, and the time required for the cutting operation is shortened. Consequently, the upper core plate 51 can be cut easily.

[0072] Furthermore, in the method for cutting the inner plate of the reactor containment vessel of the second embodiment, a plurality of first cutting lines 181 and a plurality of second cutting lines 182 are set as straight cutting lines 180 passing through a plurality of through holes 59, and the upper core plate 51 is cut along the first cutting lines 181 and the second cutting lines 182 with a cutting blade 91. This makes it possible to easily standardize the size of the multiple cut pieces formed by cutting the upper core plate 51, while suppressing the complex shape of the cutting line 180.

[0073] Furthermore, the method for cutting the inner plate of the reactor containment vessel of the second embodiment includes a step S21 for determining the radioactivity level of the inner plate of the reactor containment vessel, and a step S22 for determining a waste container according to the radioactivity level. In the step S23 for cutting the inner plate of the reactor containment vessel, the number of first cutting lines 181 and the spacing of the first cutting lines 181 in the second direction D2, and the number of second cutting lines 182 and the spacing of the second cutting lines 182 in the first direction D1 are determined so that the size of the cut piece after cutting the upper core plate 51 is such that it can be accommodated in a waste container according to the radioactivity level. This allows the upper core plate 51 to be easily cut, and the size of the cut pieces can be adjusted to the dimensions of waste containers according to the radioactivity level without requiring specialized skills.

[0074] Furthermore, in the method for cutting the reactor containment vessel inner plate of the second embodiment, in step S23 for cutting the reactor containment vessel inner plate, the easily removable orifice 51b2 of the attachments 51b is removed from the upper core plate body 51a before the upper core plate body 51a is cut. As a result, compared to cutting the orifice 51b2 together with the upper core plate body 51a, the thickness of the material to be cut by the cutting blade 91 can be reduced, thus further reducing the load on the cutting blade 91 and the power required for cutting.

[0075] Furthermore, in the method for cutting the inner plate of the reactor containment vessel according to the second embodiment described above, the cutting blade 91, which moves in a straight line, cuts the upper core plate body 51a by passing through a plurality of through holes 59 arranged in a grid-like row, and also passing through positions where fuel assembly guide pins 51b1 are not located. This reduces the load on the cutting blade 91 and the power required for cutting, compared to cutting the fuel assembly guide pins 51b1 together with the upper core plate body 51a. Furthermore, it shortens the time required for the cutting operation.

[0076] (Other embodiments) This disclosure is not limited to the configurations of the embodiments described above, and design modifications are possible without departing from the gist of the disclosure. For example, in the embodiments described above, the cases in which the upper core support plate 52 and the upper core plate 51 are cut as internal plates of the reactor containment vessel were explained. However, the internal plates of the reactor containment vessel are not limited to the upper core support plate 52 and the upper core plate 51. For example, the method can also be applied when cutting plate-shaped members having multiple through holes, such as the lower core plate 62, the lower core support plate 63, and the rectifier plate. Furthermore, although plate-shaped members provided inside the reactor vessel 2 were given as examples of internal plates of the reactor containment vessel, the internal plates of the reactor containment vessel can be any plate-shaped member that constitutes equipment inside the reactor containment vessel, and are not limited to plate-shaped members provided inside the reactor vessel 2. Other examples of internal plates of the reactor containment vessel include the heater support plate of the pressurizer and the tube sheet and tube support plate of the steam generator.

[0077] Furthermore, in the first embodiment described above, the first cutting line 81 and the second cutting line 82 were set on the premise that the attachment 52b would be removed, and the upper core support plate body 52a was cut with the cutting blade 91. However, some of the lids 52b1 may be cut together with the upper core support plate body 52a by the cutting blade 91.

[0078] Similarly, in the second embodiment described above, the first cutting line 181 and the second cutting line 182 were set while avoiding the attachments 51b, and the upper core plate body 51a was cut with the cutting blade 91. However, some orifices 51b2 and some fuel assembly guide pins 51b1 may be cut together with the upper core plate body 51a by the cutting blade 91. Furthermore, the upper core plate body 51a may be cut with the cutting blade 91 after all attachments 51b, including the fuel assembly guide pins 51b1, have been removed from the upper core plate body 51a.

[0079] Furthermore, although the above embodiments have described the case in which mutually orthogonal first cutting lines 81,181 and second cutting lines 82,182 are set, it is not limited to the case in which the first cutting lines 81,181 and the second cutting lines 82,182 are orthogonal. Also, although two types of cutting lines, the first cutting line 81,181 and the second cutting line 82,182, are set, other straight cutting lines may also be set in addition to the first cutting line 81,181 and the second cutting line 82,182.

[0080] <Note> The method for cutting the inner plate of the reactor containment vessel described in the embodiment can be understood, for example, as follows.

[0081] (1) According to the first embodiment, the method for cutting the internal plates of a reactor containment vessel is a method for cutting the internal plates of a reactor containment vessel that constitute the internal structure of a reactor, wherein the internal plates 51, 52, 62, 63 of the reactor containment vessel have a plurality of through holes 54, 59 that penetrate in the thickness direction Dt and are arranged in a grid pattern when viewed from the thickness direction Dt, and the method includes steps S13 and S23 of cutting the internal plates of the reactor containment vessel such that a linearly advancing cutting blade 91 passes through the plurality of through holes 54, 59 arranged in a grid pattern in a row. Examples of internal plates for a reactor containment vessel include the upper core support plate, upper core plate, lower core support plate, lower core plate, and baffle plate.

[0082] This allows for a reduction in the effective cutting length of the reactor containment vessel inner plates 51, 52, 62, and 63 when cutting them using a linearly moving cutting blade 91. As a result, the load on the cutting blade 91 and the power required for cutting are reduced, and the time required for the cutting operation is shortened. Consequently, the reactor containment vessel inner plates 51, 52, 62, and 63 can be easily cut.

[0083] (2) According to the second embodiment, the method for cutting the reactor containment vessel internal plate is the method for cutting the reactor containment vessel internal plate of (1), wherein the reactor containment vessel internal plates 51, 52, 62, 63 include internal plate bodies 51a, 52a having a plurality of through holes 54, 59, and accessories 51b, 52b that protrude from the internal plate bodies 51a, 52a in the plate thickness direction Dt and are detachably fixed to the internal plate bodies 51a, 52a, and in the step of cutting the reactor containment vessel internal plate, the accessories 51b, 52b are removed from the internal plate bodies 51a, 52a, and then the internal plate bodies 51a, 52a are cut. Examples of accessories that can be detachably fixed to the internal panel include a lid, reinforcing beams, and orifices.

[0084] As a result, compared to the case where the reactor containment vessel inner plates 51, 52, 62, 63 and the accessories 51b, 52b are cut simultaneously, the thickness of the material to be cut by the cutting blade 91 can be reduced, thereby further reducing the load on the cutting blade 91 and the power required for cutting.

[0085] (3) According to the third aspect, the method for cutting the reactor containment vessel inner plate is the method for cutting the reactor containment vessel inner plate of (1), wherein the reactor containment vessel inner plates 51, 52, 62, 63 comprise an inner plate body 51a, 52a having a plurality of through holes 54, 59, and an attachment 51b, 52b protruding from the inner plate body 51a, 52a in the plate thickness direction Dt, and in the step of cutting the reactor containment vessel inner plate, the cutting blade 91, which moves in a straight line, cuts the inner plate body 51a, 52a by passing through a plurality of through holes 54, 59 arranged in a grid-like row, and passing through positions where the attachments 51b, 52b are not located.

[0086] This reduces the load on the cutting blade 91 and the power required for cutting compared to cutting the lid 52b1. It also shortens the time required for the cutting operation. Therefore, it allows for greater flexibility in the cutting position compared to when the lid 52b1 is not removed.

[0087] (4) According to the fourth aspect, the method for cutting the reactor containment vessel inner plate is any one of the methods for cutting the reactor containment vessel inner plate from (1) to (3), wherein the accessory 52b is a lid 52b1 that closes the through hole 59, and in the step of cutting the reactor containment vessel inner plate, the inner plate bodies 51a, 52a are cut so that they pass through the through hole 54 from which the lid 52b1 has been removed.

[0088] This reduces the load on the cutting blade 91 and the power required for cutting compared to cutting the lid 52b1. It also shortens the time required for the cutting operation. Therefore, it allows for greater flexibility in the cutting position compared to when the lid 52b1 is not removed.

[0089] (5) According to the fifth embodiment, the method for cutting the internal plate of the reactor containment vessel is one of the methods for cutting the internal plate of the reactor containment vessel of (1) to (4), wherein the plurality of through holes 54, 59 are arranged in a grid shape in a first direction D1 perpendicular to the plate thickness direction Dt and a second direction D2 perpendicular to the plate thickness direction Dt and the first direction D1, and in the step of cutting the internal plate of the reactor containment vessel, a plurality of first cutting lines 81, 181 extending in the first direction D1 and spaced apart in the second direction D2 and a plurality of second cutting lines 82, 182 extending in the second direction D2 and spaced apart in the first direction D1 are set as linear cutting lines 80, 180 passing through the plurality of through holes 54, 59, and the internal plate of the reactor containment vessel 51, 52 is cut along the first cutting lines 81, 181 and the second cutting lines 82, 182 with the cutting blade 91.

[0090] This makes it possible to easily standardize the size of the multiple cut pieces formed by cutting the reactor containment vessel inner plates 51, 52, 62, and 63, while suppressing the complex shape of the cutting lines 80 and 180.

[0091] (6) According to the sixth aspect, the method for cutting the internal plate of the reactor containment vessel is the method for cutting the internal plate of the reactor containment vessel of (5), wherein in the step of cutting the internal plate of the reactor containment vessel, two first cutting lines 81, 181 and two second cutting lines 82, 182 which are perpendicular to the two first cutting lines 81, 181, respectively are set.

[0092] This allows the reactor containment vessel inner plates 51, 52, 62, and 63 to be cut with fewer cutting steps while maintaining a consistent size of cut pieces.

[0093] (7) According to the seventh aspect, the method for cutting the inner plate of the reactor containment vessel is the method for cutting the inner plate of the reactor containment vessel according to (5) or (6), wherein at least one of the first cutting lines 81, 181 and the second cutting lines 82, 182 passes through the centers of the plurality of through holes 54, 59.

[0094] As a result, on the cutting lines 80, 180 that pass through the centers of the multiple through holes 54, 59, among the first cutting lines 81, 181 and the second cutting lines 82, 182, the distance between adjacent through holes 54, 59 can be shortened. Therefore, the effective cutting length of the internal plate bodies 51a, 52a can be further shortened.

[0095] (8) According to the eighth aspect, a method for cutting the internal plates of a reactor containment vessel is a method for cutting the internal plates of a reactor containment vessel, which includes steps S11 and S21 for determining the radioactivity level of the internal plates 51, 52, 62, and 63 of the reactor containment vessel, and steps S12 and S22 for determining a waste container according to the radioactivity level, wherein in steps S13 and S23 for cutting the internal plates of the reactor containment vessel, the number of first cutting lines 81, 181 and the spacing between the first cutting lines 81, 181 in the second direction D2, and the number of second cutting lines 82, 182 and the spacing between the second cutting lines 82, 182 in the first direction D1 are determined so that the size of the cut pieces after cutting the internal plates 51, 52, 62, and 63 of the reactor containment vessel are such that they can be accommodated in the waste container according to the radioactivity level.

[0096] This makes it possible to easily cut the internal plates 51, 52, 62, and 63 of the reactor containment vessel, while also allowing the size of the cut pieces to be adjusted to the dimensions of waste containers according to the radioactivity level without requiring specialized skills. [Explanation of symbols]

[0097] 1… Pressurized water reactor 2…Reactor vessel 3…Control rod drive mechanism 4…Control rod cluster 5…Upper core structure 6…Lower core structure 7…Core 21…Reactor vessel 22...Reactor vessel lid 23... Inlet nozzle 24…Outlet nozzle 25… Housing 41... Control rods 45...Control rod cluster drive shaft 51…Upper core plate (internal plate of the reactor containment vessel) 51a... Upper core plate body (internal plate body) 51b, 52b... Accessories 51b... Accessories 51b1…Fuel assembly guide pin 51b2... Orifice 52…Upper core support plate (internal plate of the reactor containment vessel) 52a... Upper core support plate body (internal plate body) 52b...Accessories 52b1…Lid 52b2…Reinforcement beam 53… Upper core support column 54, 59… Through holes 55... Guide tube 56…Central frame section 57…Water level gauge support pipe 58...Outer frame section 61…Core tank 62…Lower core plate (internal plate of the reactor containment vessel) 63…Lower core support plate (internal plate of the reactor containment vessel) 68… Fastening member 69… Orifice hole 71…Fuel assembly 80,180…cutting line 81,181…First cutting line 82,182…Second cutting line 90...Cutting device 91...Cutting blade 92...frame 93... Turntable 100... Reactor building pool 110... First Cavity 111...First floor 120...Second cavity 121…Second floor surface

Claims

1. A method for cutting an internal plate of a reactor containment vessel, which constitutes equipment inside the reactor containment vessel, The reactor containment vessel inner plate has multiple through holes that penetrate in the thickness direction and are arranged in a grid pattern when viewed from the thickness direction, A method for cutting the inner plate of a reactor containment vessel, comprising the step of cutting the inner plate of the reactor containment vessel such that a cutting blade moving in a straight line passes through a plurality of through holes arranged in a grid-like row.

2. The reactor containment vessel inner plate comprises an inner plate body having a plurality of through holes, and an accessory that protrudes from the inner plate body in the thickness direction and is detachably fixed to the inner plate body, In the process of cutting the reactor containment vessel inner plate, the attachments are removed from the inner plate body before the inner plate body is cut. The method for cutting the inner plate of a reactor containment vessel according to claim 1.

3. The reactor containment vessel inner plate comprises an inner plate body having a plurality of through holes, and an attachment protruding from the inner plate body in the thickness direction, In the process of cutting the inner plate of the reactor containment vessel, the cutting blade, which moves in a straight line, cuts the inner plate body by passing through a plurality of through holes arranged in a grid-like row and passing through positions where no attachments are placed. The method for cutting the inner plate of a reactor containment vessel according to claim 1.

4. The aforementioned accessory is a cover that closes the through hole, In the process of cutting the internal plate of the reactor containment vessel, the internal plate body is cut so as to pass through the through hole from which the lid has been removed. The method for cutting the inner plate of a reactor containment vessel according to claim 3.

5. The multiple through holes are arranged in a grid pattern, with a first direction perpendicular to the plate thickness direction and a second direction perpendicular to both the plate thickness direction and the first direction. In the process of cutting the inner plate of the reactor containment vessel, a plurality of first cutting lines extending in the first direction and spaced apart in the second direction, and a plurality of second cutting lines extending in the second direction and spaced apart in the first direction are set as straight cutting lines passing through a plurality of through holes, and the inner plate of the reactor containment vessel is cut along the first cutting lines and the second cutting lines with the cutting blade. The method for cutting the inner plate of a reactor containment vessel according to claim 1.

6. In the process of cutting the inner plate of the reactor containment vessel, two first cutting lines and two second cutting lines perpendicular to the two first cutting lines are set. The method for cutting the inner plate of a reactor containment vessel according to claim 5.

7. At least one of the first cutting line and the second cutting line passes through the center of the plurality of through holes. The method for cutting the inner plate of a reactor containment vessel according to claim 5.

8. A step of determining the radioactivity level of the inner plate of the reactor containment vessel, The process includes determining a waste container according to the radioactivity level, In the process of cutting the inner plate of the reactor containment vessel, The number of first cutting lines and the spacing between them in the second direction, and the number of second cutting lines and the spacing between them in the first direction, are determined so that the size of the cut pieces after cutting the inner plate of the reactor containment vessel is such that they can be contained in the waste container according to the radioactivity level. The method for cutting the inner plate of a reactor containment vessel according to claim 5.

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