JP2013228376A - Reactor control rod and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor control rod in which rear surfaces of welding portions among a tie rod and sheaths are easily inspected.SOLUTION: A handle 5 is welded to an upper end of a tie rod 2, and a lower support member 6 is welded to a lower end of the tie rod 2. Sheaths 4 having U-shaped cross sections are individually welded to the tie rod 2 in four directions, to the handle 5 and to the lower support member 6. A plurality of hafnium members 7A and 7B are disposed inside the sheaths 4. A tab 12A and a tab 12B formed at both end portions of each sheath 4 are disposed offset from each other in an axial direction of the tie rod 2. A tab 13A of the tie rod 2 opposite to each tab 12A is welded to each tab 12A, and a tab 13B of the tie rod 2 opposite to each tab 12B is welded to each tab 12B. A rear surface of each welding portion between the tab 12A and the tab 13A is opposite to each of openings 15A formed among the tie rod 2 and the sheaths 4, and a rear surface of each welding portion between the tab 12B and the tab 13B is opposite to each of openings 15 formed among the tie rod 2 and the sheaths 4.

Description

  The present invention relates to a nuclear reactor control rod and a method for manufacturing the same, and more particularly to a nuclear reactor control rod suitable for application to a boiling water reactor and a method for manufacturing the same.

  The control rod used in the boiling water reactor has a cross shape in cross section, and controls the reactor power by being taken in and out of the core loaded with fuel assemblies during the operation of the reactor. All control rods are withdrawn from the core at the end of the operating cycle.

  An example of the control rod is described in JP-A-9-61576. In this control rod, a flat hafnium cylindrical body, which is a neutron absorbing material, is arranged in a sheath constituting the blade. Two hafnium cylinders are present in the axial direction of the control rod. Japanese Patent Application Laid-Open No. 9-61576 describes the manufacture of the control rod as follows.

  A handle is attached to the upper end of the tie rod. The handle has a handle body and an upper tongue extending downward from the handle body. A lower support member having a lower support member main body and a lower tongue-shaped portion extending upward from the lower support member main body is attached to a lower end portion of the tie rod. An assembly of the handle, the tie rod and the lower support member is referred to as a frame.

  The upper tongue of the handle is inserted into the upper end of the upper hafnium cylinder, and the upper hafnium cylinder is fixed to the upper tongue with a pin. The lower tongue of the lower support member is inserted into the lower end of the lower hafnium cylinder, and the lower hafnium cylinder is fixed to the lower tongue by a pin. A plurality of upper hafnium cylinders attached to the upper tongue and a plurality of lower hafnium cylinders attached to the lower tongue are inserted into a stainless steel sheath having a U-shaped cross section. Is done. Thereafter, the upper end, lower end and side ends of the sheath are welded to the handle, the lower support member and the tie rod, respectively. A plurality of tabs (projections) are formed in the axial direction of the control rod at the side end of the sheath, and these tabs are welded to the tie rod. One blade is formed by the sheath and the plurality of hafnium cylinders. The control rod has four blades extending in all directions from the tie rod.

  As a technique for imparting compressive residual stress to a structural member, water jet peening (see, for example, Japanese Patent No. 3162104), laser peening (see, for example, Japanese Patent Laid-Open No. 7-246483) and wire peening (for example, in Japanese Patent Laid-Open No. 6-26483). No. 155172) is known.

JP-A-9-61576 Japanese Patent No. 3162104 Japanese Patent Application Laid-Open No. 7-246483 JP-A-6-155172

  In the control rod described in Japanese Patent Laid-Open No. 9-61576, a plurality of tabs and tie rods formed at the side end portions of the sheath are joined by welding. In the welded portion between the sheath tab and the tie rod, the region of the fusion zone formed on the opposite side of the heat input side is called the back wave.

  In general, it is preferable that the sheath and the tie rod are melted and joined together at the welded portion of the sheath and the tie rod. That is, it is preferable that no defects such as poor fusion occur in the back wave portion. In order to ensure the reliability of the quality of the control rod, it is required that it can be easily inspected that there is no defect in the back wave portion. Further, if a defect is detected by inspection, it is preferable that the repair can be easily performed.

  In the control rod described in Japanese Patent Laid-Open No. 9-61576, the back wave of the welded portion between the sheath and the tie rod is blocked by the sheath constituting the blade after welding, and inspection such as appearance observation cannot be performed.

  An object of the present invention is to provide a control rod for a nuclear reactor that can easily inspect the back surface of a welded portion between a tie rod and a sheath, and a method for manufacturing the same.

A feature of the present invention that achieves the above-described object is that a plurality of sheaths each having a U-shaped cross section and having end portions on both sides joined to a tie rod by welding and extending in four directions from the tie rod, and the respective sheaths A neutron absorbing member disposed inside,
A plurality of first projecting portions projecting toward the tie rod are formed on a first side end portion which is one side end portion of both side end portions of the sheath, and the other side end of the both side end portions is formed. A plurality of second projecting portions projecting toward the tie rod are formed at the second side end portion which is a portion,
The plurality of first protrusions are arranged so as to be shifted from the plurality of second protrusions in the axial direction of the tie rod,
The back surface of the first protrusion and the first welded portion of the tie rod are opposed to the second opening formed between the second protrusions adjacent in the axial direction of the tie rod between the tie rod and the second side end. And
The back surface of the second protrusion and the second welded portion of the tie rod are opposed to a first opening formed between the first protrusions adjacent in the axial direction of the tie rod between the tie rod and the first side end. There is in being.

  The plurality of first protrusions are arranged so as to be shifted with respect to the plurality of second protrusions in the axial direction of the tie rod, and the back surfaces of the first protrusion and the first welded portion of the tie rod are connected to the tie rod and the second side end. Since it faces the second opening formed between the second protrusions adjacent in the axial direction of the tie rod between the parts, the back surface of the first welded part can be easily inspected through the second opening. be able to. Further, the back surface of the second protrusion and the second welded portion of the tie rod are formed in a first opening formed between the first protrusions adjacent in the axial direction of the tie rod between the tie rod and the first side end. Since they are opposed to each other, the back surface of the second welded portion can be easily inspected through the first opening.

  According to the present invention, in the reactor control rod, the back surface of the welded portion between the tie rod and the sheath can be easily inspected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a reactor control rod according to embodiment 1, which is a preferred embodiment of the present invention. It is AA sectional drawing of FIG. FIG. 2 is an enlarged view of a welded portion between a tie rod and a sheath of the nuclear reactor control rod shown in FIG. 1. It is OO sectional drawing of FIG. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG. It is DD sectional drawing of FIG. It is explanatory drawing which shows the state which grind | polishes the back surface of the welding part of a tie rod shown in FIG. 5 and FIG. 6 with a grinding stone. It is explanatory drawing which shows the grinding wheel which grind | polishes the back surface of the welding part of a tie rod and a sheath. It is explanatory drawing which shows the state in which the abrasive grain is couple | bonded with the soft binder in the grinding wheel. FIG. 4 is an explanatory diagram showing a process in which compressive residual stress is generated on the sheath surface due to heat generation; (A) is an explanatory diagram showing the heat generation process; (B) is an explanatory diagram showing a contraction process after heat generation; It is explanatory drawing which shows the state in which a tensile residual stress generate | occur | produces on the surface and a compressive residual stress is provided. FIG. 5 is an explanatory diagram showing a process in which compressive residual stress is generated on the sheath surface by plastic deformation, (A) is an explanatory diagram showing a state in which the sheath surface is plastically deformed, and (B) is a compressive residual stress applied to the sheath surface by plastic deformation. It is explanatory drawing which shows the state performed. It is an enlarged view which shows the welding part of the tie rod of a conventional nuclear reactor control rod, and a sheath. It is EE sectional drawing of FIG. It is explanatory drawing which shows the state which has performed the shot peening on the back surface of the welding part of the tie rod of the nuclear reactor control rod of Example 2 which is another Example of this invention, and a sheath. It is an enlarged view of the welding part of the tie rod and sheath of the control rod for reactors of Example 3 which is another Example of this invention. It is a cross-sectional view of the welding part of the tie rod and sheath of the control rod for reactors of Example 4 which is another Example of this invention. It is a cross-sectional view of the welding part of the other tie rod and sheath of the control rod for reactors of Example 4 shown in FIG. It is an enlarged view of the welding part of the tie rod and sheath of the control rod for reactors of Example 5 which is another Example of this invention. It is FF sectional drawing of FIG. It is GG sectional drawing of FIG. It is HH sectional drawing of FIG. It is II sectional drawing of FIG. It is a block diagram of the water jet peening apparatus which constructs water jet peening to the welding part of the tie rod and sheath of the control rod for reactors of Example 6 which is another Example of this invention. It is explanatory drawing which shows the state which is implementing the water jet peening on the back surface of the welding part of the tie rod of the nuclear reactor control rod of Example 6 which is another Example of this invention, and a sheath. It is explanatory drawing which shows the state which is constructing | assembling the laser peening on the back surface of the welding part of the tie rod of the nuclear reactor control rod of Example 7 which is another Example of this invention, and a sheath. It is a block diagram of the rod peening apparatus which constructs a rod peening to the welding part of the tie rod and sheath of the control rod for reactors of Example 8 which is another Example of this invention. It is explanatory drawing which shows the state which is constructing | attaching the rod peening on the back surface of the welding part of the tie rod and sheath of the control rod for reactors of Example 8 which is another Example of this invention. It is a block diagram of the crushing apparatus which constructs crushing to the welding part of the tie rod and sheath of the control rod for reactors of Example 9 which is another Example of this invention. It is explanatory drawing which shows the state which is crushing by the steel ball on the back surface of the tie rod of the control rod for reactors of Example 9 which is another Example of this invention, and the welding part of a sheath. It is explanatory drawing which shows the state which is crushing with the roller on the back surface of the welding part of the tie rod and sheath of the control rod for reactors of Example 9 which is another Example of this invention.

  Examples of the present invention will be described below.

  A control rod for a nuclear reactor according to embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS. The control rod 1 of the present embodiment is a control rod used in a boiling water reactor.

  The control rod 1 of the present embodiment has a cross-shaped cross section, and a tie rod 2 is disposed at the axial center. The control rod 1 has four blades 3 extending from the tie rod 2 in all directions. The handle 5 is attached to the upper end portion of the tie rod 2, and the lower support member 6 is attached to the lower end portion of the tie rod 2. The lower support member 6 is a lower support plate (or a drop speed limiter).

  In one blade 3, each blade 3 includes a sheath 4 having a U-shaped cross section, and hafnium members 7A and 7B which are flat cylindrical bodies and are neutron absorbing members. The sheath 4 is made of stainless steel (SUS304, SUS316L, etc.). The upper end of the sheath 4 is welded to the handle 5, and the lower end of the sheath 4 is welded to the lower support member 6.

  A plurality of tabs (projections) 12 are formed at both ends of the U-shaped sheath 4 at predetermined intervals in the axial direction of the tie rod 2. The tabs 12 are part of the sheath 4 and are formed at the opposing side end portions of the U-shaped sheath 4, respectively, and projecting toward the tie rod 2 side. A plurality of tabs 12 formed at one side end of the sheath 4 in the axial direction of the tie rod 2 and a plurality of tabs 12 formed at the other side end of the sheath 4 in the axial direction. Each position in is different. That is, the position of the former tab 12 (tab 12A shown in FIG. 3) in the axial direction of the tie rod 2 and the position of the latter tab 12 (tab 12B shown in FIG. 3) in the axial direction of the tie rod 2 Is shifted in the axial direction. Thereby, the latter tabs 12B do not exist in the axial positions of the tie rods 2 of the former tabs 12A, and the former tabs 12B do not exist in the axial positions of the tie rods 2 of the latter tabs 12B. Each tab 12A does not exist.

  Each tab 12A protruding from the tie rod 2 toward each tab 12A at one side end of the sheath 4 at the same position in the axial direction of the tie rod 2 of each tab 12A formed at one side end of the sheath 4 A plurality of tabs 13 (tabs 13 </ b> A shown in FIG. 3) opposite to the tie rod 2 are formed. Each tab 12B formed at the other side end of the sheath 4 protrudes from the tie rod 2 toward the tab 12B at the other side end of the sheath 4 at the same position in the axial direction of the tie rod 2. A plurality of tabs 13 (tabs 13B shown in FIG. 3) facing the tabs 12B are formed on the tie rod 2. The thickness of each tab 13A and the thickness of each tab 13B are substantially the same as the thickness of the sheath 4.

  In one blade 3, each tab 12 A at one side end of the sheath 4 is welded to each tab 13 A formed on the tie rod 2, and each tab 12 B at the other side end of the sheath 4 is welded to the tie rod 2. It welds to each tab 13B formed in this. The welded portion 14A is a welded portion between the tab 12A and the tab 13A, and the welded portion 14B is a welded portion between the tab 12B and the tab 13B (see FIGS. 3 and 4). The upper end of the sheath 4 and the handle 5 and the lower end of the sheath 4 and the lower support member 6 are also joined by welding.

  An opening 15 elongated in the axial direction of the tie rod 2 is formed between one side end of the tie rod 2 and the sheath 4 between the tabs 12A and 13A adjacent in the axial direction of the tie rod 2. An opening 15A elongated in the axial direction of the tie rod 2 is formed between one side end of the tie rod 2 and the sheath 4 between the tabs 12B and 13B adjacent in the axial direction of the tie rod 2. The weld 14A is opposed to the opening 15A (see FIGS. 2 and 5), and the weld 14B is opposed to the opening 15 (see FIG. 6). In the DD cross section of the tie rod 2 in FIG. 3, an opening is formed between each end of the tie rod 2 and the sheath 4, and a protrusion 19 that protrudes toward the sheath 4 is formed on the tie rod 2. In the portion where the tabs 13 </ b> A and 13 </ b> B are present, the protruding portion 19 is not formed on the tie rod 2.

  Two hafnium members 7A and two hafnium members 7B are arranged in a space formed in the sheath 4 of one blade 2. The hafnium member 7A is located above the hafnium member 7B, and the axial lengths thereof are the same. A tongue 8A formed at the lower end of the handle 5 is inserted into the upper end of the hafnium member 7A. In this state, the upper end of the hafnium member 7A is attached to the tongue 8A with a pin 9A. A tongue-like portion 8B formed at the upper end portion of the lower support member 6 is inserted into the lower end portion of the hafnium member 7B. In this state, the lower end portion of the hafnium member 7B is attached to the tongue-like portion 8B with a pin 9B. As a result, the upper end portion of the hafnium member 7A is attached to the handle 5, and the hafnium member 7B is attached to the lower support member 6. During operation of the boiling water reactor, even if the hafnium members 7A and 7B attached to the tongues 8A and 8B are thermally expanded, the lower end of the hafnium member 7A and the upper end of the hafnium member 7B are not in contact with each other. A gap (not shown) is formed between the lower end of the hafnium member 7A and the upper end of the hafnium member 7B.

  A plurality of openings 10 are formed in the sheath 4, and a plurality of openings 11 are also formed in the hafnium members 7A and 7B.

  The remaining three blades 2 have the same configuration as the blade 2 described above.

  The control rod 1 is disposed in a reactor pressure vessel of a boiling water reactor, and a control rod drive mechanism (not shown) is provided in a core loaded with a plurality of fuel assemblies in order to control the reactor power. In and out. The control rod 1 is connected to a control rod driving device provided at the bottom of the reactor pressure vessel by a connector 18 provided at the lower end of the lower support member 6. The control rod driving device performs an operation of inserting the control rod 1 into the core and an operation of extracting the control rod 1 from the core. Cooling water flowing in the reactor pressure vessel flows into the sheath 4 from a part of the openings 10 formed in the sheath 4, and gaps formed between the hafnium members 7 </ b> A and 7 </ b> B and the inner surface of the sheath 4. The hafnium members 7A and 7B are cooled while rising. The cooling water that has flowed into the sheath 4 flows out of the sheath 4 from another opening 10 (in particular, the opening 10 located at the upper end).

  A part of the cooling water flowing into the sheath 4 flows into the hafnium member 7B through the small-diameter opening 11 provided in the hafnium member 7B, rises in the hafnium members 7B and 7A, and forms the hafnium member 7A. It flows out of the hafnium member 7A through the small-diameter opening 11 formed. In this way, the cooling water flows into the hafnium members (neutron absorbing members) 7B and 7A, thereby cooling the hafnium members.

  The production of the control rod 1 of this embodiment will be described.

  First, the handle 5 having a cross-shaped cross section has a cross-shaped cross section at the upper end of the tie rod 2 in which a plurality of tabs 13A and a plurality of tabs 13B are formed in the axial direction as described above. The lower support member 6 is attached to the lower end of the tie rod 2 by welding. Then, the upper end part of each hafnium member 7A of a flat cylindrical body is attached to each upper tongue part 8A formed in the handle 5 by the pin 9A. Furthermore, the lower end part of each hafnium member 7B of a flat cylindrical body is attached to each lower tongue-like part 8B formed on the lower support member 6 by a pin 9B. Two hafnium members 7A and two hafnium members 7B are arranged from the tie rod 2 in the four directions. A single sheath 4 having a U-shaped cross section is arranged so that tabs 12A and 12B formed at both ends of the sheath 4 face the tie plate 2 side, and the sheath 4 faces the tie rod 2. To move. By this movement of the sheath 4, two hafnium members 7 </ b> A and two hafnium members 7 </ b> B are arranged in the sheath 4, and each tab 12 </ b> A formed on one sheath 4 is formed on the tie rod 2. Each tab 13A is abutted, and each tab 12B is abutted to each tab 13B formed on the tie rod 2. Similarly, the remaining three sheaths 4 are abutted against the tabs 13A and 13B formed on the tie rod 2, respectively. In each sheath 4 and tie rod 2, the butted tabs 12A and 13A are welded, and the butted tabs 12B and 13B are welded. In this way, the four sheaths 4 are welded to the tie rod 2.

  After the welding of all the tabs 8 existing in the axial direction of the tie rod 2 and the tie rod 2, that is, the welding of the sheath 4 and the tie rod 2, the upper end of each sheath 4 and the handle 5, and the lower end of each sheath 4 The lower support member 6 is welded.

  After the welding of the sheath 4, the tie rod 2, the handle 5, and the lower support member 6 is finished, the appearance inspection of the welded portion 14A of the tab 12A and the tab 13A and the welded portion 14B of the tab 12B and the tab 13B is performed. The appearance inspection of these welded portions is performed not only on the front side but also on the back side of the welded portion 14A through the opening 15A and on the backside of the welded portion 14B through the opening 15 respectively. Since the welded portions 14A and 14B are arranged so as to be shifted from each other in the axial direction of the tie rod 2, the back surface of the welded portion 14A faces the opening portion 15A, and further, the back surface of the welded portion 14B faces the opening portion 15. The appearance inspection of the back side of each of the welds 14A and 14B can be easily performed. In the appearance inspection of these welds, the presence or absence of defects such as cracks in the welds is visually observed. When there is no defect in each welded portion 14A and 14B, the back surface of each welded portion 14A, the back surface of each of tabs 12A and 13A connected to welded portion 14A, and the back surface of each welded portion 14B, The back surfaces of the tabs 12B and 13B connected to the welded portion 14B are polished.

  This polishing will be described with reference to FIGS. 8, 9, and 10. FIG. A polishing grindstone 20 attached to the rotary drive head 21 is used for polishing each of the above locations. Polishing of the back surface of the welded portion between the tab of the tie rod 2 and the tab of the sheath 4 will be described by taking the welded portion 14B as an example (see FIG. 8). The polishing grindstone 20 attached to the rotary drive head 21 is inserted into the sheath 4 through the opening 15 and brought into contact with the back surface of the welded portion 14B. In this state, the rotation drive head 21 is rotated to rotate the polishing grindstone 20 in the direction of the arrow (see FIG. 9). The grinding wheel 20 polishes the back surface of the welded portion 14B while rotating. As shown in FIG. 10, the polishing grindstone 20 is configured by combining a large number of abrasive grains 22 with a soft binder 23. As the binder 2, paper, cloth, sponge-shaped material, or brush-shaped material is used. By using a sponge-shaped material, a thin disk-shaped grinding wheel can be formed. In this embodiment, the back surface of the welded portion 14B is polished by the polishing grindstone 20 using a sponge-shaped material as the binder 23. Polishing by the polishing grindstone 20 is performed on the widths of the tab 12B and the tab 13B in the axial direction of the tie rod 2. Polishing of the welded portion 14B is also performed on the front side of the welded portion 14B. By the polishing using the polishing grindstone 20, the back surfaces of the welded portion 14B, the tab 12B and the tab 13B and their surfaces are plastically deformed and generate heat (see FIG. 10).

  When a defect such as a crack is found on the back surface of the welded portion 14B by visual inspection, the welded portion 14B including this defect is scraped off from the backside and the front surface of the welded portion 14B, and then the welded portion is welded again. Fill the shaved parts. Thereafter, the appearance inspection is performed again, and when no defect is detected by this inspection, the back surface and the surface of the re-welded welded portion 14B are polished by the polishing grindstone 20 as described above.

  By polishing the welds 14A and 14B and the back and front surfaces in the vicinity of these welds using the polishing grindstone 20, compressive residual stress can be applied to the polished back and front surfaces. The reason why compressive residual stress is applied to the back and front surfaces of the polished welds 14A and 14B and the like will be described below with reference to FIGS.

  The surface processing mechanism of the welded portion 14A (or welded portion 14B) by the grinding wheel 20 is based on the process in which the abrasive grains 22 hit and crush the surface of the welded portion 14A (or welded portion 14B), and the grinding wheel 20 rotates. This is considered to be a combination of processes in which the abrasive grains 22 scrape the surface of the welded portion 14A (or the welded portion 14B). Through these processes, plastic deformation occurs on the surface of the welded portion 14A (or welded portion 14B) and heat is generated.

  The surface (rear surface and front surface) of the welded portion 14A (or the welded portion 14B) polished by the polishing grindstone 20 generates heat (see FIG. 11A). When heat is generated, the surface of the welded portion 14A (or welded portion 14B) tends to shrink during the cooling process, but is restrained by the material inside the welded portion 14A (or welded portion 14B) (FIG. 11B). reference). For this reason, tensile residual stress is generated on the surface of the welded portion 14A (or welded portion 14B) (see FIG. 11C). On the other hand, when the surface of welded portion 14A (or welded portion 14B) is plastically deformed by crushing with abrasive grains 22 (see FIG. 12A), the surface tends to be stretched, but is restrained by the internal material. Therefore, compressive residual stress is generated on the surface of welded portion 14A (or welded portion 14B) (see FIG. 12A).

  In the surface processing of the welded portion 14A (or welded portion 14B) by polishing, the plastic deformation due to the process of hitting and crushing the surface is larger than the influence of heat generation, so the surface of the welded portion 14A (or welded portion 14B) Residual stress changes to compressive residual stress.

  Even when the surfaces (rear surface and front surface) of the tab 12A and the tab 13A (or tabs 12B and 13B) near the welded portion 14A (or the welded portion 14B) are polished, the above phenomenon occurs, and compressive residual stress is generated on the surface. Occur.

  By applying compressive residual stress to the welded portion 14A of the tab 12A and the tab 13A (or the welded portion 14B of the tab 12B and the tab 13B) and the surface thereof (the back surface and the front surface) as described above, The occurrence and development of stress corrosion cracking from the steel can be suppressed.

  By carrying out the polishing described above, the surface of the welded portion 14A (or welded portion 14B) and the boundary between the welded portion 14A and the tabs 12A and 13A (or the respective bordered portions of the welded portion 14B and the tabs 12B and 13B). ), Even if a minute crack is generated, the crack can be deleted.

  The difference between the control rod 1 of the present embodiment described above and the conventional control rod described in Japanese Patent Application Laid-Open No. 9-61576 is shown in FIGS. 13 and 14 showing the tie rod and sheath welds of this conventional control rod. Based on In this conventional control rod, tabs 16 facing each other are formed at both end portions of the U-shaped sheath 4. The tabs 16 formed at both end portions of the sheath 4 exist at the same position in the axial direction of the tie rod 2 and face each other (see FIG. 14). The tabs 16 formed at both end portions of the sheath 4 are joined to the tie rod 2 by welding. The welded portion 17 is a welded portion between the tab 16 and the tie rod 2. Between the tabs 16 adjacent in the axial direction of the tie rod 2, an opening 15B is formed between the tie rod 2 and the sheath.

  In order to weld the welding target members having different thicknesses, such as the tabs 16 formed on the tie rod 2 and the sheath 4 in the conventional control rod, the joint portions (tie rods 2 and the sheath 4 of the respective welding target members) are used. It is necessary to melt the joint portion of the tab 16). At this time, since it is necessary to sufficiently dissolve the tie rod 2 which is a thick member to be welded, the welding heat input becomes large. When the welding heat input is large, the high temperature region in the member to be welded becomes wide in the welding process. In a region where the temperature of each member to be welded is high during the welding process, tensile stress is generated when the entire region returns to room temperature. For this reason, the area | region where the tensile residual stress in the tie rod 2 is distributed becomes wide.

  On the other hand, in the control rod 1 of the present embodiment, the tab 13A formed on the tie rod 2 is substantially the same as the thickness of the sheath 4 and the sheath 12A formed on the sheath, and the sheath 4 formed on the tie rod 2. The amount of heat input for melting the tab 13B and the sheath 12B, which is substantially the same as the thickness, was formed on the tie rod 2 and the sheath 4 in the conventional control rod described in JP-A-9-61576. Compared with the welding of the tab 16, it becomes very small. For this reason, the area | region where the tensile stress generate | occur | produces in the control rod 1 can be restrained narrowly compared with the above-mentioned conventional control rod. The tensile residual stress is a driving force that causes a crack to develop when a crack occurs in the weld. In the control rod 1 of the present embodiment, since the region where the tensile residual stress is generated can be narrowed, even if a crack is generated, the progress can be made smaller than that of the conventional control rod.

  In the conventional control rod described in Japanese Patent Laid-Open No. 9-61576, the tabs 16 formed on both side ends of the sheath 4 having a U-shaped cross section are formed on the tie rod 2 as described above. It exists at the same position in the axial direction. As a result, the tabs 16 formed at both end portions of the sheath 4 and the respective welded portions 17 of the tie rod 2 are also present at the same position in the axial direction of the tie rod 2. In the conventional control rod, the back wave of the welded portion 17 between one tab 16 and the tie rod 2 of the two tabs 16 that are formed on both end portions of the sheath 4 and are opposed to each other is generated. It is obstructed by other tabs 16 and cannot be visually inspected. Similarly, the back wave of the welded portion 17 between the latter other tab 16 of the two tabs 16 and the tie rod 2 is blocked by the former one of the two tabs 16 for visual inspection. I can't. That is, it is difficult to observe the presence or absence of a welding defect in the back wave portion of the welded portion 17 by visual inspection. On the other hand, in the control rod 1 of the present embodiment, as described above, the appearance inspection of the back wave portion of the welded part 14A is performed through the opening 15A facing the back wave of the welded part 14A, and the back wave part of the welded part 14B. These visual inspections can be easily carried out through the openings 15 facing the back waves of the welded portions 14B. For this reason, the presence or absence of defects such as cracks in the back wave portion of the welded portion 14A and the back wave portion of the welded portion 14B can be easily confirmed visually.

  In the control rod 1 of the present embodiment, as described above, the back wave portion of the welded portion 14A is opposed to the opening portion 15A. Therefore, the polishing grindstone 20 is brought into contact with the back wave portion of the welded portion 14A through the opening portion 15A. The back surface of each of the tabs 12A and 13A in the vicinity of the back wave portion and the back wave portion can be polished. Thereby, compressive residual stress can be provided to the back surface of the welded portion 14A and the back surfaces of the tabs 12A and 13A near the welded portion 14A. It is possible to suppress the occurrence of stress corrosion cracks on the back surface of the welded portion 14A and the back surfaces of the tabs 12A and 13A. Moreover, in the control rod 1, since the back wave part of the welding part 14B has opposed the opening part 15, the rotary grindstone 20 can be made to contact the back wave part of the welding part 14B through the opening part 15, and the back wave part The back surface of each of the portions and the tabs 12B and 13B near the back wave portion can be polished. Thereby, compressive residual stress can be provided to the back surface of the welded portion 14B and the back surfaces of the tabs 12B and 13B near the welded portion 14B. It is possible to suppress the occurrence of stress corrosion cracks on the back surface of the welded portion 14B and the back surfaces of the tabs 12B and 13B. On the other hand, in the conventional control rod, the tabs 16 formed at both ends of the sheath 4 having a U-shaped cross section are opposed to each other. The back-wave part of can not be polished. For this reason, compressive residual stress cannot be applied to the back surface of the welded portion 17.

  A control rod according to embodiment 2, which is another embodiment of the present invention, will be described with reference to FIG. The control rod 1B of the present embodiment is a control rod used in a boiling water reactor.

  The control rod 1B of the present embodiment has the same hardware configuration as the control rod 1 of the first embodiment. The control rod 1B includes a weld 14A between the control rod 1, a tab 13A formed on the tie rod 2 and a tab 12A formed on the sheath 4, and a tab 13B formed on the tie rod 2 and a tab formed on the sheath 4. The method of applying compressive residual stress to the back surface of each welded portion 14B with 12B is different. In the control rod 1, the compressive residual stress is applied to the back surfaces of the welded portions 14A and 14B by polishing using a grinding wheel 20, but in the control rod 1B, each of the welded portions 14A and 14B is shot by shot peening. A compressive residual stress is applied to the back surface.

  The control rod 1B is manufactured in the same manner as the control rod 1 except for the step of applying compressive residual stress. In the manufacturing process of the control rod 1B, when it is determined in the appearance inspection of the respective back wave portions of the welds 14A and 14B that there is no defect in the back wave portions, the respective back waves of the weld portions 14A and 14B. , And shot peening is performed on the back surfaces of the tabs 12A, 13A, 12B and 13B existing in the vicinity of the respective back waves.

  This shot peening will be described by taking construction on the welded portion 14B as an example. The injection nozzle 30 connected to the fine particle supply pipe 31 for supplying the fine metal particles 32 used for shot peening is inserted into the opening 15 facing the welded portion 14B, and the welded portion 14B and the tabs 12B and 13B are respectively Opposite the back. A known method is applied to shot peening. In this shot peening, a large number of fine metal particles 32 supplied from the fine particle supply pipe 31 are directed from the injection nozzle 30 toward the back surfaces of the welded portion 14B and the tabs 12B and 13B, which are the target surfaces of the shot peening. Jetting and colliding with these surfaces at high speed. Compressive residual stress is applied to those surfaces on which the injected metal granules 32 collide. Compressive residual stress can be applied to the welded portion 14A and the back surfaces of the tabs 12A and 13A by inserting the injection nozzle 30 into the opening 15A.

  Also in the present embodiment, each effect generated in the first embodiment can be obtained.

  A control rod according to embodiment 3, which is another embodiment of the present invention, will be described with reference to FIG. The control rod 1C of the present embodiment is a control rod used in a boiling water reactor.

  The control rod 1C of the present embodiment has a semicircular opening 25A having a width larger than the width of the opening 15 in the horizontal direction at a portion of the control rod 1 facing the back surface of the welded portion 14A of the opening 15A. Further, a semicircular opening 25 having a width larger than the width of the opening 15 in the horizontal direction is formed in a portion of the opening 15 facing the back surface of the welded portion 14B. The opening 25A faces the back surface of the welded portion 14A and communicates with the opening 15A. The opening 25 faces the back surface of the welded part 14 </ b> B and communicates with the opening 15. The other structure of the control rod 1C is the same as that of the control rod 1.

  The openings 25 and 25 </ b> A function as openings through which cooling water flows, in the same manner as the openings 10 formed in the sheath 4.

  In the present embodiment, each effect produced in the first embodiment can be obtained. The width of the opening 25 in the direction perpendicular to the axis of the tie rod 2 is wider than the width of the opening 15 in the direction perpendicular to the axis of the tie rod 2 and is orthogonal to the axis of the tie rod 2 of the opening 25A. Since the width of the opening 15A is wider than that of the opening 15A in the direction perpendicular to the axis of the tie rod 2, the appearance inspection of the back wave portion of the weld 14A through the opening 25A and the weld 14B through the opening 25 are performed. The appearance inspection of the back wave portion of can be performed more easily. Further, the insertion into the openings 25 and 25A of the polishing grindstone 20 or the injection nozzle 30 is facilitated due to the wide width, and the application of compressive residual stress to the vicinity of the back surfaces of the welds 14B and 14A is facilitated.

  The control rod of Example 4 which is another Example of this invention is demonstrated using FIG. 17 and FIG. The control rod 1D of the present embodiment is a control rod used in a boiling water reactor.

  The control rod 1D of this embodiment has a configuration in which the tabs 13A and 13B formed on the tie rod 2 in the control rod 1 are deleted, and the tabs 12A and 12B formed on both ends of the sheath 4 are welded to the tie rod 2, respectively. . Other configurations of the control rod 1D are the same as those of the control rod 1.

  The tab 12A and the tab 12B respectively formed at both end portions of the sheath 4 having a U-shaped cross section are displaced from each other in the axial direction of the tie rod 2 in the same manner as the control rod 1. The tab 12A is placed on a stepped portion 26B formed on one side surface of the tie rod 2, and joined to the tie rod 2 by a welded portion 27A (see FIG. 17), and the tab 12B is formed on the other side surface of the tie rod 2. It is placed on the stepped portion 26A and joined to the tie rod 2 by the welded portion 27B (see FIG. 18).

  In the present embodiment, each effect produced in the first embodiment can be obtained. Unlike the control rod 1 of the first embodiment, the control rod 1D of the present embodiment has a protruding portion 19 formed on the side surface of the tie rod 2 facing the hafnium members 7A and 7B. It is difficult to see directly from the portion 15A, and it is difficult to see the back wave of the welded portion 27B directly from the opening 15. For this reason, the appearance of the back wave of the welded portion 27A can be inspected by inserting the fiberscope into the sheath 4 from the opening 15A. Further, the appearance inspection of the back wave of the welded portion 27 </ b> B can be performed by inserting a fiberscope into the sheath 4 from the opening 15. Also in the conventional control rod shown in FIG. 14, a fiberscope is inserted into the sheath 4 through the opening 15B and the appearance inspection of the back of the welded portion 17 is performed. In the appearance inspection of the back wave of the welded portion 17 in this conventional control rod, the fiberscope is bent so that the fiberscope axis extends in the axial direction of the tie rod 2 in the sheath 4, and the inside of the sheath is passed through the opening 15B. Therefore, it takes a long time for the appearance inspection of the back surface of the welded portion 17. In contrast, in the control rod 1D of the present embodiment, when the appearance inspection of the back surface of the welded portion 27A is performed, the fiberscope is directed from the opening portion 15A to the inner surface of the sheath 4 facing the opening portion 15A. Insert it. For this reason, the appearance inspection of the welded portion 27A in the control rod 1D can be performed easily and in a shorter time than the conventional control rod. The appearance inspection of the back wave of the welded portion 27B in the control rod 1D is the same as that of the welded portion 27A.

  The compressive residual stress can be applied to the back surfaces of the welded portions 27A and 27B in the present embodiment as follows. That is, by using the injection nozzle 30 whose tip is bent toward the welded portion 27A (or the welded portion 27B), the welded portion 27A (or the welded portion 27A (or the opening portion 15) is inserted into the opening 15A (or the opened portion 15). Compressive residual stress can be applied to the back surface of the welded portion 27A (or welded portion 27B) by shot peening in which fine metal particles 32 are injected and collided with the back surface of the welded portion 27B).

  The control rod of Example 4 which is another Example of this invention is demonstrated using FIGS. 19-23. The control rod 1E of the present embodiment is a control rod used in a boiling water reactor.

  The control rod 1E of the present embodiment has a configuration using a tie rod 2 that does not have the protrusion 19 instead of the tie rod 2 that has the protrusion 19 formed in the control rod 1. The other structure of the control rod 1E is the same as that of the control rod 1.

  Tabs 35A and 35B are formed at both ends of the sheath 4 having a U-shaped cross section. The positions of the tabs 35A and 35B in the axial direction of the tie rod 2 are shifted from each other in the axial direction, similarly to the tabs 12A and 12B of the control rod 1. In the control rod 1E, the side surface 33 of the tie rod 2 facing the hafnium members 7A and 7B disposed in the sheath 4 is a flat surface. The tie rod 2 is formed with a tab 34A protruding from the side surface 33 toward the tab 35A and a tab 34B protruding toward the tab 35B. The tab 34A and the tab 35A are joined at the welded portion 14A, and the tab 34B and the tab 35B are joined at the welded portion 14B. The welded portion 14A and the welded portion 14B are also displaced from each other in the axial direction of the tie rod 2 (see FIGS. 19 and 20).

  The back surface of the welded portion 14A faces the opening 15A, and the back surface of the welded portion 14B faces the opening 15.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  A control rod according to embodiment 6, which is another embodiment of the present invention, will be described with reference to FIGS. 24 and 25. FIG. The control rod 1F of the present embodiment is a control rod used in a boiling water reactor and has substantially the same configuration as the control rod 1 of the first embodiment.

  In the control rod 1F, a tab 12B formed at one side end of the sheath 4 having a U-shaped cross section is joined to the tie rod 2 by a welded portion 14B (see FIG. 25). The respective back surfaces of the tab 12B and the welded portion 14B face the opening 15 formed between the other side end portion of the sheath 4 in which the tab 12A is formed and the tie rod 2. Although not shown in FIG. 25, a tab 12A formed at the side end of the sheath 4 is joined to the tie rod 2 by a welded portion 14A. The back surfaces of the tab 12A and the welded portion 14A face the other opening 15A formed between the side end of the sheath 4 where the tab 12A is formed and the tie rod 2. The control rod 1F is provided with compressive residual stress by water jet peening on the back surfaces of the tab 12B and the welded portion 14B and the back surfaces of the tab 12A and the welded portion 14A.

  In the control rod 1F assembled by welding, the back surfaces of the tab 12B and the welded portion 14B face the opening 15, and the back surfaces of the tab 12A and the welded portion 14A face the other opening 15A. In the same manner as in Example 1, it is possible to easily inspect the back surfaces of the welded portions 14A and 14B.

  Unlike the control rod 1D of the fourth embodiment, the control rod 1F is not formed on the side surface of the tie rod 2 facing the hafnium members 7A and 7B. Further, the control rod 1F does not have the tabs 13A and 13B formed on the tie rod 2 like the control rod 1 of the first embodiment.

  In the control rod 1F, when there are no defects on the back surfaces of the welded portions 14A and 14B, water jet peening is performed on the back surfaces of the tab 12B and the welded portion 14B and the back surfaces of the tab 12A and the welded portion 14A. Thus, compressive residual stress is applied.

  A method for manufacturing the control rod 1F including a step of applying compressive residual stress to these back surfaces using water jet peening will be described below. The manufacturing method of the control rod 1F is the same as the method of manufacturing the control rod 1 in Example 1 except for the step of applying the residual compressive stress. Here, the step of applying compressive residual stress by water jet peening will be mainly described.

  Water jet peening on the back surface of the welded portion between the tab and the tie rod in the control rod 1F is performed using a water jet peening apparatus 41, which is a compressive residual stress applying apparatus shown in FIG. The water jet peening apparatus 41 includes an injection nozzle 47, a high-pressure pump 49, and an injection nozzle scanning device. The injection nozzle scanning device includes a traveling device 42, an arm 44, a moving device 45, and a lifting device 46.

  The traveling device 42 is attached to a pair of guide members 43 provided on the upper surface of the support base 50 installed in the water tank 53 so as to travel. The arm 44 is attached to the traveling device 42 and extends in the horizontal direction in a direction orthogonal to the guide member 43. A moving device 45 is attached to the arm 44 so as to be movable along the arm 44. An elevating device 46 is attached to the moving device 45 so as to be movable up and down. An injection nozzle 47 having an injection port formed at the tip is attached to the lower end portion of the lifting device 46 so as to be rotatable in the vertical direction, and is connected to a high-pressure pump 49 by a high-pressure hose 48.

  The support rod 51 arranged in parallel in the water tank 53 in which the water 54 is stored in the state that the control rod 1F to which water jet peening is applied is assembled in the same manner as in the first embodiment and the tie rod is arranged in the horizontal direction. And 52 are removably fixed to the support bases 51 and 52, respectively. The lengths of the support bases 51 and 52 to which the control rod 1F is attached are longer than the axial length of the control rod 1F. A gap 64 is formed between the support base 51 and the support base 52. One blade of the control rod 1F facing downward is inserted into the gap 64, and two blades orthogonal to the blade are placed on the upper surfaces of the support bases 51 and 52, respectively. Yes. In this state, the welded portion 14B of one blade is in contact with the upper surface of the support base 52, and the welded portion 14A of another blade existing on the opposite side of this blade by 180 ° is in contact with the upper surface of the support base 51. doing. The control rod 1 </ b> F and the support bases 51 and 52 are immersed in the water 54 in the water tank 53, and the upper surface of the support base 50 is located above the water surface in the water tank 53.

  The support base 50 is arranged in parallel with the support bases 51 and 52, and the lengths of the support base 50 and the pair of guide members 43 are also longer than the axial length of the control rod 1F. For this reason, by moving the traveling device 42 along the guide member 43, the injection nozzle 47 is movable over the entire axial length of the control rod 1F.

  When the traveling device 42 is moved along the guide member 43, the injection nozzle 47 moves in the axial direction of the control rod 1F. When the moving device 45 is moved along the arm 44, the spray nozzle 47 moves in the width direction of the blade of the control rod 1F. The lifting device 46 moves the spray nozzle 47 in the vertical direction. The spray nozzle 47 is aligned with the water jet peening start point of the control rod 1F by the traveling device 42, the moving device 45, and the lifting device 46. That is, by moving the traveling device 42 along the guide member 43 and moving the moving device 45 along the arm 44, the injection nozzle 47 is positioned closest to the handle of the control rod 1F in one blade. It is located directly above the welded portion 14B. In this state, the lifting device 46 is lowered to insert the injection nozzle 47 into the opening 15, and when the tip of the injection nozzle 47 is lowered to a predetermined position, the lowering of the lifting device 46 is stopped. Thereafter, the injection nozzle 47 is rotated in the vertical direction to make the injection port of the injection nozzle 47 face the back surface of the welded portion 14B (see FIG. 25).

  The high-pressure pump 49 is driven, and high-pressure water boosted by the high-pressure pump 49 is supplied to the injection nozzle 47 through the high-pressure hose 48. This high-pressure water is jetted as a jet 62 from the jet port of the jet nozzle 47 toward the back surface of the welded portion 14B. Shock waves generated by the collapse of a large number of cavitation bubbles contained in the injected jet 62 are generated on the back surface of the welded portion 14B, the side surface 63 of the tie rod 2 facing the inner region of the sheath 4, and the back surface of the tab 12B. Colliding and compressive residual stress is applied to the back surface of the welded portion 14B, the side surface 63 of the tie rod 2 and the back surface of the tab 12B. The jet nozzle 47 is moved in the axial direction of the control rod 1F within the single opening 15 facing the welded portion 14B by the traveling device 42 while jetting the jet 62. Thus, water jet peening in the axial direction of the control rod 1F is applied to the back surface of one welded portion 14B.

  After the construction of the water jet peening on the back surface of one welded portion 14B is completed, the high pressure pump 49 is stopped and the lifting device 46 is moved upward. When the injection port of the injection nozzle 47 reaches above the opening 15, the lifting of the lifting device 46 is stopped. Thereafter, the traveling device 42 is moved in the axial direction of the control rod 1F, and the injection nozzle 47 is moved to a position directly above another welded portion 14B located next to the welded portion 14B on which water jet peening has been applied. And the raising / lowering apparatus 46 is lowered | hung and the injection port of the injection nozzle 47 is inserted in the other opening part 15 located right above the another welding part 14B. In this state, as described above, a jet 62 of high-pressure water is jetted from the jet nozzle 47 and is compressed to the back surface of another welded portion 14B by a shock wave generated by the collapse of cavitation bubbles contained in the jet 62. Residual stress is applied.

  As described above, in one blade placed on the support bases 51 and 52, water jet peening is performed on the back surfaces of the plurality of welds 14B at one side end of the U-shaped sheath 4. It is constructed in order. After the completion of the water jet peening on the back surface of all the welds 14B at the side end of this blade, the position of the injection port of the injection nozzle 47 is changed to the blade inserted in the gap 64 by the elevating device 46. With the tie rod 2 as the center, the blade is raised above the upper end of the other blade positioned 180 ° opposite, and the moving device 45 causes the spray nozzle 47 to pass directly above the blade and move to the tip side of the arm 44. The injection nozzle 47 is located directly above the blade 2 on which water jet peening is applied and the blade (blade placed on the upper surface of the support base 51) located 180 ° opposite to the tie rod 2. In this state, the injection nozzle 47 is rotated 180 ° in the horizontal plane. By this rotation, the injection port of the injection nozzle 47 faces the side surface of the blade in the vertical state.

  The elevating device 46 is lowered, and its injection port is inserted into an opening 15A formed between tabs 12A adjacent in the axial direction directly above the welded portion 14A contacting the upper surface of the support base 51. It is lowered until it is done. With the injection port of the injection nozzle 47 inserted into the opening 15A, the jet 62 of high-pressure water is injected from this injection port, and water jet peening is applied to the back surface of the welded portion 14A. Water jet peening is applied to the back surfaces of all the weld portions 14A existing in the axial direction of the control rod 1F in the same manner as the water jet peening operation for the back surface of the weld portion 14B described above. After completion of the water jet peening for all the welded portions 14A of the blades in contact with the upper surface of the support base 51, the control rod 1F is lifted, and the control rod 1F is rotated 90 ° above the support bases 51 and 52. Then, another blade (for example, a blade on which water jet peening is applied in contact with the support base 52) is inserted into the gap 64. Water jet peening is applied to each welded portion 14 </ b> A in contact with the support base 51 and each welded portion 14 </ b> B in contact with the support base 52 in the blades in contact with the support bases 51 and 52, respectively. The control rod 1F is rotated by 90 ° to perform water jet peening on the back surfaces of the welds 14A and 14B in all blades.

  In the control rod 1F, the opening 15 is formed facing the back surface of the welded portion 14B, and the opening 15A is formed facing the back surface of the welded portion 14A. Therefore, on the back surfaces of the welded portions 14A and 14B, respectively. On the other hand, it is possible to easily apply compressive residual stress by water jet peening.

  In the present embodiment, each effect produced in Citation 1 can be obtained.

  A control rod according to embodiment 7, which is another embodiment of the present invention, will be described with reference to FIG. The control rod 1G of the present embodiment is a control rod used in a boiling water reactor and has substantially the same configuration as the control rod 1F of the sixth embodiment. In the control rod 1G, compressive residual stress is applied to the back surface of the welded portion 14A between the tab 12A and the tie rod 2 and the back surface of the welded portion 14B between the tab 12B and the tie rod 2 by laser peening.

  Since the opening 15A opposes the back surface of the welded portion 14A and the opening 15 opposes the back surface of the welded portion 14B, the control rod 1G assembled by welding is welded after assembly as in the first embodiment. Inspection of the back surfaces of the portions 14A and 14B can be easily performed.

  When there are no defects on the back surfaces of the welded portions 14A and 14B, laser peening is performed on the back surfaces of the tab 12B and the welded portion 14B and the back surfaces of the tab 12A and the welded portion 14A in the control rod 1G. Applied and compressive residual stress is applied. For the laser peening operation, a laser peening apparatus, which is a compressive residual stress applying apparatus, is used. The laser peening apparatus has a configuration in which the injection nozzle 47 is replaced with a laser irradiation head 55 and the high-pressure hose 48 is replaced with an optical fiber 56 in the water jet peening apparatus 41 shown in FIG. Other configurations of the laser peening apparatus are the same as those of the water jet peening apparatus 41.

  Similar to the construction of the water jet peening in the sixth embodiment, the support bases 50, 51 and 52 are arranged in the water tank 53 in which the water 54 is stored. The support bases 51 and 51 are immersed in the water 54, and the control rod 1G for performing laser peening is also immersed in the water 54. As with the control rod 1F, the control rod 1G for laser peening has one blade placed on the upper surface of the support base 51 and the other blade placed on the upper surface of the support base 52. And 52 are removably secured. Each of the traveling device 42, the moving device 45, and the lifting device 46 is moved, and the tip of the laser irradiation head 55 is inserted into, for example, the opening 15 formed facing the back surface of the welded portion 14B.

  A laser having a pulse time width of several nanoseconds to several tens of nanoseconds generated by a laser transmitter (not shown) connected to the optical fiber 56 is transmitted to the laser irradiation head 55 through the optical fiber 56. This laser is irradiated in water from the laser irradiation head 55 toward the back surface of the welded portion 14B. High-pressure plasma is generated by this laser irradiation, and an impact force is generated accordingly. By this impact force, compressive residual stress is applied to the back surface of the welded portion 14B. Residual compressive stress is applied to the back surface of each welded portion 14B existing in the axial direction of the control rod 1G while repeatedly moving the traveling device 42 in the axial direction of the control rod 1G and raising and lowering the lifting device 46. In the same manner as in Example 6, laser peening is performed on the back surfaces of all the welds 14A and 14B existing in the control rod 1G, and compressive residual stress is applied.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  A control rod according to embodiment 8, which is another embodiment of the present invention, will be described with reference to FIGS. 27 and 28. FIG. The control rod 1H of the present embodiment is a control rod used in a boiling water reactor and has substantially the same configuration as the control rod 1 of the first embodiment. In the control rod 1H, compressive residual stress is applied to the back surface of the welded portion 14A between the tab 12A and the tie rod 2 and the back surface of the welded portion 14B between the tab 12B and the tie rod 2 by rod peening.

  Since the opening 15A faces the back surface of the welded portion 14A and the opening 15 faces the back surface of the welded portion 14B, in the control rod 1H assembled by welding as in the first embodiment, the welded portion 14A and Inspection of each back surface of 14B can be performed easily.

  When there is no defect on the back surfaces of the welded portions 14A and 14B, rod peening is performed on the back surfaces of the tab 12B and the welded portion 14B and the back surfaces of the tab 12A and the welded portion 14A in the control rod 1H. Applied and compressive residual stress is applied. For the construction of the rod peening, a rod peening device 41A which is a compressive residual stress applying device is used.

  The rod peening device 41A includes a vibrator 57 and a vibrator scanning device to which a plurality of thin rods 58 are attached. The vibrator scanning device includes traveling devices 42A and 42B, an arm 44, a moving device 45, and a lifting device 46. The vibrator 57 to which the plurality of thin rods 58 of the rod peening apparatus 41A is attached is the vibrator described in FIG. 4 of Japanese Patent Application Laid-Open No. 6-155172, and includes a plurality of thin wire wires. The thin rod 58 is replaced.

  The traveling device 42 </ b> A is attached to a pair of guide members 43 </ b> A provided on the upper surface of the support base 52 installed on the floor so as to travel. The traveling device 42 </ b> B is attached to a pair of guide members 43 </ b> B provided on the upper surface of the support base 51 installed on the floor so as to be able to travel. A gap 64 into which one blade of the control rod 1H is inserted is formed between the support bases 51 and 52. The arm 44A is attached to the traveling devices 42A and 42B and extends in the horizontal direction in a direction orthogonal to the guide members 43A and 43B. A moving device 45 is attached to the arm 44 </ b> A so as to be movable along the arm 44. An elevating device 46 is attached to the moving device 45 so as to be movable up and down. The vibrator 57 is attached to the lower end portion of the lifting device 46 so as to be rotatable in the vertical direction.

  A control rod 1H for performing rod peening is fixed to the upper surfaces of the support bases 51 and 52, respectively. That is, one blade of the control rod 1H is inserted into the gap 64, and two blades orthogonal to the blade are placed on the upper surfaces of the support bases 51 and 52 and fixed to these support bases. . Each of the traveling devices 42A and 42B, the moving device 45, and the lifting device 46 is moved, and each rod 58 attached to the vibrator 57 is inserted into, for example, the opening 15 formed facing the back surface of the welded portion 14B. To do. When the tip of each rod 58 comes into contact with the back surface of the welded portion 14B, the descent of the lifting device 46 is stopped.

  The vibrator 57 is connected to an air hose (not shown) connected to a compressor (not shown). When performing the rod peening, the working air is supplied from the compressor to the vibrator 57 through the air hose. The vibrator 57 is actuated by the actuating air, and the rods 58 are vibrated. Each vibrating rod 58 strikes the back surface of the welded portion 14B at the tip. The hit portion on the back surface of the welded portion 14B is crushed, and tensile plastic strain is generated in this portion. By constraining the deformation due to the plastic strain to the surroundings, a compressive residual stress can be applied to the striking portion on the back surface of the welded portion 14B by rod peening. While repeatedly moving the traveling devices 42A and 42B in the axial direction of the control rod 1H and ascending and descending the lifting device 46, each rod 58 makes a back against the back surface of each welded portion 14B existing in the axial direction of the control rod 1H. A residual compressive stress is applied by applying a blow. In the same manner as in Example 6, rod peening is applied to the back surfaces of all the welds 14A and 14B existing in the control rod 1H, and compressive residual stress is applied.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  A control rod according to Embodiment 9 which is another embodiment of the present invention will be described with reference to FIGS. 29 and 30. FIG. The control rod 1I of the present embodiment is a control rod used in a boiling water reactor and has substantially the same configuration as the control rod 1 of the first embodiment. In the control rod 1I, compressive residual stress is applied to the back surface of the welded portion 14A between the tab 12A and the tie rod 2 and the back surface of the welded portion 14B between the tab 12B and the tie rod 2 by crushing.

  Since the opening 15A faces the back surface of the welded portion 14A and the opening 15 faces the back surface of the welded portion 14B, in the control rod 1I assembled by welding as in the first embodiment, the welded portion 14A and Inspection of each back surface of 14B can be performed easily.

  When there are no defects on the back surfaces of the welded portions 14A and 14B, the control rod 1I is crushed against the back surfaces of the tab 12B and the welded portion 14B and the back surfaces of the tab 12A and the welded portion 14A. Is applied and compressive residual stress is applied. For the crushing work, a crushing device 41B, which is a compressive residual stress applying device, is used.

  The crushing processing device 41B has a configuration in which the vibrator 57 and the rod 58 are replaced with a crushing processing head 59 in the rod peening device 41A used in the eighth embodiment. The other structure of the crushing processing apparatus 41B is the same as that of the rod peening apparatus 41A. The crushing processing head 59 has a steel ball 60 rotatably attached to its lower end.

  A control rod 1I for performing rod peening is fixed to the upper surfaces of the support bases 51 and 52, respectively. That is, one blade of the control rod 1I is inserted into the gap 64, and two blades orthogonal to the blade are placed on the upper surfaces of the support bases 51 and 52 and fixed to these support bases. . Each of the traveling devices 42A, 42B, the moving device 45, and the lifting device 46 is moved, and the steel ball 60 attached to the crushing head 59 is formed, for example, facing the back surface of the welded portion 14B. 15 is inserted. The lifting device 46 is lowered to press the steel ball 60 against the back surface of the welded portion 14 </ b> B, and a compressive load is applied to the steel ball 60. The welded portion 14B is crushed by the compression load applied to the steel ball 60. As a result, plastic deformation occurs on the back surface of the welded portion 14B, and compressive residual stress is applied to the back surface. The traveling devices 42A and 42B are moved in the axial direction of the control rod 1I, and the crushing processing head 59 is moved in the axial direction within one opening 15. The steel ball 60 is moved in the axial direction of the control rod 1I while being pressed against the back surface of the welded portion 14B. Compressive residual stress is applied over the entire length in the axial direction of the control rod 1 </ b> I on the back surface of the welded portion 14 </ b> B facing one opening 15.

  While repeating the movement of the traveling devices 42A and 42B in the axial direction of the control rod 1I and the raising and lowering of the lifting device 46, the steel balls 60 are applied to the back surface of each welded portion 14B existing in the axial direction of the control rod 1I. A residual compressive stress is applied by applying a blow. In the same manner as in Example 6, a crushing process is applied to the respective back surfaces of all the welds 14A and 14B existing in the control rod 1I, and compressive residual stress is applied.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  Instead of the crushing processing head 59 with the steel ball 60 attached to the lower end, as shown in FIG. 31, the crushing processing head 59A with the roller 61 attached to the lower end is used to exist in the control rod 1I. A crushing process may be applied to the back surfaces of all the welds 14A and 14B. The crushing processing head 59A is attached to the lifting device 46 of the crushing processing device 41B, and by lowering the lifting device 46, the roller 61 is pressed against the back surface of the welded portion 14B (or the welded portion 14A) and crushed. Similar to the processing head 59, compressive residual stress is applied to the back surface of the welded portion 14B (or welded portion 14A).

In each of the above-described Examples 1 to 9, a sheath 4 having a U-shaped cross section is filled with B ₄ C, which is a neutron absorbing member, instead of a hafnium member, which is a neutron absorbing member. You may apply to the control rod which has arrange | positioned the neutron absorber rod of this.

  1, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I ... control rod, 2 ... tie rod, 3 ... bundle, 4 ... sheath, 5 ... handle, 6 ... lower support member, 7A, 7B ... hafnium member, 12A, 12B, 13A, 13B, 34A, 34B, 35A, 35B ... tabs, 14A, 14B, 27A, 27B ... welds, 15A, 15B, 25, 25A ... openings, 20 ... abrasive wheels, 22 ... abrasive grains, DESCRIPTION OF SYMBOLS 23 ... Binder, 30 ... Injection nozzle, 32 ... Fine grain, 41 ... Water jet peening apparatus, 41A ... Rod peening apparatus, 41B ... Crush processing apparatus, 44 ... Arm, 45 ..., 46 ... Lifting apparatus, 46 ... Injection nozzle , 50, 51, 52 ... support base, 55 ... laser irradiation head, 57 ... vibrator, 58 ... rod, 59, 59A ... crushing processing head.

Claims (14)

A tie rod, a handle attached to one end portion of the tie rod, a lower support member attached to the other end portion of the tie rod, and a U-shaped cross section, both side ends are welded to the tie rod. A plurality of sheaths whose upper end is joined to the handle and the lower end is joined to the lower support member by welding and extending from the tie rods in all directions, and a neutron absorbing member disposed in each sheath With
A plurality of first projecting portions projecting toward the tie rod are formed at a first side end portion that is one of the side end portions of the sheath. A plurality of second projecting portions projecting toward the tie rod are formed on the second side end portion, which is the other side end portion,
The plurality of first protrusions are arranged so as to be shifted from the plurality of second protrusions in the axial direction of the tie rod,
The back surface of the first welded portion of the first protrusion and the tie rod is formed between the second protrusions adjacent in the axial direction of the tie rod between the tie rod and the second side end. 2 facing the opening,
A back surface of the second protrusion and the second welded portion of the tie rod is formed between the first protrusions adjacent in the axial direction of the tie rod between the tie rod and the first side end. A control rod for a nuclear reactor, characterized by facing one opening. The tie rod forms a third protruding portion that faces the first protruding portion of the sheath and extends toward the first side end portion of the sheath, and further faces the second protruding portion of the sheath. Forming a fourth protrusion extending toward the second side end of the sheath,
The said 1st welding part is a welding part of a said 1st protrusion part and a said 3rd protrusion part, and the said 2nd welding part is a welding part of a said 2nd protrusion part and a said 4th protrusion part. Control rod for nuclear reactors.   In the portion of the first opening facing the back surface of the second welded portion, the width in the direction orthogonal to the axis of the tie rod is orthogonal to the axis of the tie rod of the first opening. The width in the direction perpendicular to the axis of the tie rod is larger in the second opening than the second opening in the portion facing the back surface of the first welded portion. The control rod for a nuclear reactor according to claim 1 or 2, wherein the control rod is wider than a width in a direction perpendicular to the axis of the tie rod.   The control rod for a nuclear reactor according to claim 1 or 2, wherein a side surface of the tie rod facing the neutron absorbing member in the sheath is a flat surface.   The compressive residual stress is given to the back surface of the said 2nd welding part which opposes the said 1st opening part, and the back surface of the said 1st welding part which opposes the said 2nd opening part, respectively. A control rod for a nuclear reactor according to any one of the preceding claims. A handle is attached to the upper end of the tie rod, a lower support member is attached to the lower end of the tie rod, and the sheath extends in all directions from the tie rod in a state where a neutron absorber is disposed in a sheath having a U-shaped cross section. Arranged so that both end portions of the sheath are joined to the tie rod by welding,
Each joining of the both ends of the sheath to the tie rod is performed by a plurality of first protrusions protruding toward the tie rod at a first side end which is one of the side ends. A plurality of second projecting portions projecting toward the tie rod are formed at the second side end portion, which is the other side end portion of the both side end portions, and The first projecting portion of the tie rod is disposed between the tie rod and the second side end portion using the sheath that is displaced with respect to the plurality of second projecting portions in the axial direction of the tie rod. A second opening facing the back surface of the first welded portion of the first tie rod and the first tie rod is formed between the second projecting portions adjacent in the axial direction of the tie rod and the first side end. In the axial direction of the tie rod The plurality of first protrusions and the first protrusions are formed between the first protrusions adjacent to each other so as to form a first opening facing the second protrusion and the back surface of the second welded portion of the tie rod. A method for manufacturing a control rod for a nuclear reactor, which is performed by welding a plurality of second protrusions to the tie rod. The first projecting portion and the tie rod are welded to the third projecting portion formed on the tie rod, facing the first projecting portion of the sheath and extending toward the first side end portion of the sheath, and the first projecting portion. Welding one protrusion and
The second protrusion and the tie rod are welded to the fourth protrusion and the fourth protrusion formed on the tie rod, facing the second protrusion of the sheath and extending toward the second end of the sheath. The method for manufacturing a nuclear reactor control rod according to claim 6, wherein the two projecting portions are welded.   The atom according to claim 6 or 7, wherein compressive residual stress is applied to the back surface of the first weld through the second opening, and compressive residual stress is applied to the back of the second weld through the first opening. A method for manufacturing a control rod for a furnace.   The method for manufacturing a control rod for a nuclear reactor according to claim 8, wherein the compressive residual stress is applied to the back surfaces of the first welded portion and the second welded portion by polishing.   The method for manufacturing a control rod for a nuclear reactor according to claim 8, wherein the compressive residual stress is applied to the respective back surfaces of the first welded portion and the second welded portion by shot peening.   The method for manufacturing a control rod for a nuclear reactor according to claim 8, wherein the compressive residual stress is applied to the back surfaces of the first welded portion and the second welded portion by water jet peening.   The method for manufacturing a control rod for a nuclear reactor according to claim 8, wherein the compressive residual stress is applied to the back surfaces of the first welded portion and the second welded portion by laser peening.   The method of manufacturing a control rod for a nuclear reactor according to claim 8, wherein the compressive residual stress is applied to the back surfaces of the first welded portion and the second welded portion by rod peening.   The method for manufacturing a control rod for a nuclear reactor according to claim 8, wherein the compressive residual stress is applied to the back surfaces of the first welded portion and the second welded portion by crushing.

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