WO2018131379A1 - Control rod for nuclear reactor and manufacturing method for same - Google Patents

Abstract

Provided are a control rod for a nuclear reactor and a method of manufacturing a control rod for a nuclear reactor with which gaps and welded portions are eliminated, and which are capable of preventing SCC and IASCC. This control rod for a nuclear reactor is characterized in being configured from one member including a blade region having a neutron absorbing material filling hole, a tie rod region which supports the blade region, and a handle region provided at one end in the length direction of the blade region and the tie rod region, and in that the member has a melt-solidified structure. The control rod for a nuclear reactor having the abovementioned characteristics is fabricated by means of a metal layered molding method.

Description

Reactor control rod and manufacturing method thereof

The present invention relates to a control rod for a nuclear reactor and a manufacturing method thereof.

A control rod for a boiling water reactor is one of in-reactor equipment that is used when the boiling water reactor is shut down or when the core power is adjusted. The structure of a general control rod is as follows. In other words, the control rod has a cross-shaped cross section, and the appearance of the control rod is such that the wings extend from the cross-shaped axis. In general, the axial portion is called a tie rod, and the wing portion is called a blade. The control rod is inserted between the four fuel assemblies loaded in the core. When the reactor starts up, the control rod is pulled out of the core. During the rated power operation, control rods other than the control rods used for adjusting the reactor core output are in a state of being pulled out of the core. In an emergency, all control rods are inserted using water pressure (reactor scram).

The control rod for the boiling water reactor further has a U-shaped sheath provided so as to surround each blade. A neutron absorber (boron carbide powder, hafnium round bar or plate) is suspended from the handle and held in the space surrounded by the tie rod and blade and the sheath. The handle and sheath are generally secured to the tie rod by welding. A part of the sheath is provided with a hole for cooling the encapsulated neutron absorber. Some control rods using plate-type neutron absorbers are spot-welded between the sheath and the neutron absorber plate.

Generally, SUS316L, which is mainly austenitic stainless steel, is used as a material for the control rod. This material is known to have stress corrosion cracking (hereinafter referred to as “SCC”) sensitivity in a specific environment. Furthermore, in the nuclear reactor, it is referred to as “IASCC”, which is induced by Irradiation Assisted Stress Corrosion Cracking (hereinafter referred to as “IRSCC”), which promotes SCC sensitivity by receiving a large amount of neutron irradiation. ) Is known to develop.

SCC (IASCC) is said to occur when three conditions of material factors, mechanical factors, and environmental factors are met at the same time. Furthermore, in IACC, in addition to the above three factors, the amount of neutron irradiation is added as a generation factor. As a material factor, it is considered that the impurity carbon generates chromium (Cr) carbide at the time of welding, which is a cause of SCC, and measures to reduce the impurity carbon have been taken. Since mechanical factors are known to occur under tensile stress, measures have been taken by compressing surface stress by peening and polishing. As for environmental factors, the hydrogen injection method and the noble metal injection method have been performed because of the dissolved oxygen concentration and chloride ions. As a measure to reduce the amount of neutron irradiation, measures have been taken by changing the arrangement of control rods. However, at present, the SCC phenomenon in the reactor internal structure is reduced as compared with the initial plant, but the generation mechanism and complete suppression have not been established yet, and countermeasures are required.

In a control rod having a structure in which a conventional sheath and tie rod are joined by welding, corrosion products accumulate between the sheath and the tie rod and between the sheath and the neutron absorber, and an environment in which crevice corrosion easily occurs. Further, in the structure in which the sheath and the neutron absorbing plate are spot-welded, a residual stress is generated in the spot welded portion, so that minute cracks are likely to occur. For this reason, there have been reported cases in which minute cracks generated by intergranular corrosion and welding residual stress are affected by irradiation and the like, and the damage is caused by progressing by IASCC. This case has been published in the report of the Ministry of Economy, Trade and Industry's Nuclear Safety and Security Agency dated May 31, 2006, “Survey Report on Cracks of Hafnium Type Control Rods in Boiling Water Nuclear Power Plants”.

As described above, in order to prevent SCC and IASCC starting from the gap between the members constituting the control rod and the welded portion, it is necessary to reduce the gap between the members and the stress generated in the member as much as possible. As a technique for reducing the welded portion and preventing IASCC, Patent Document 1 includes a plurality of segments that are cross-shaped in cross section and are joined together by welding and arranged in the axial direction. The first segment, which is the uppermost segment, is processed from a single metal plate to form a handle portion and a plurality of neutron absorber filling holes extending in the axial direction and filled with a neutron absorber. A pair of blade elements each having a plurality of neutron absorber filling portions are combined in a cross shape, and the second segment, which is the lowest segment, extends in the lower support portion and the axial direction and is filled with neutron absorbers A pair of blade elements each having a plurality of neutron absorber filling portions forming a plurality of neutron absorber filling holes formed in a cross shape, The at least one third segment, which is another segment disposed between the segment and the second segment, extends in the axial direction and forms a plurality of neutron absorber filling holes filled with the neutron absorber. A control rod comprising a neutron absorbing material filling portion combined in a cross shape, and joining the segments to each other by welding the neutron absorbing material filling portions of adjacent segments is disclosed. Yes. According to Patent Document 1, since welding for joining the handle portion and the neutron absorbing material filling portion is not required, it is said that irradiation-induced stress corrosion cracking of the control rod can be prevented.

JP 2010-71791 A

The control rod shown in Patent Document 1 is a segment in which a stainless steel plate material constituting a blade is divided in the axial direction, each segment is provided with a vertical hole, and the vertical hole is filled with a neutron absorbing material. The control rod is completed by welding the joints. Each segment is further provided with a bridge for connecting to the blades facing each other, and the bridge is joined by welding. In Patent Document 1, since the control rod is divided in the length direction, long hole processing is not required, and high processing accuracy can be exhibited. However, since the segments are joined by welding, the possibility of occurrence of SCC and IASCC starting from the welded portion cannot be sufficiently excluded.

In view of the above circumstances, it is an object of the present invention to provide a control rod for a nuclear reactor that eliminates a gap and a weld and can prevent SCC and IASCC.

In order to achieve the above object, the present invention is provided at one of a blade region having a neutron absorber filling hole, a tie rod region that supports the blade region, and an end portion in the longitudinal direction of each of the blade region and the tie rod region. The control rod for a nuclear reactor is characterized in that the control rod is constituted by one member having a handle region, and the member has a melt-solidified structure.

Further, the present invention is a method of manufacturing a control rod for a reactor having the above-described features, and is manufactured by metal additive manufacturing in the order of a blade region and a tie rod region from a handle region serving as an upper end of the control rod. A method for manufacturing a control rod for a nuclear reactor is provided.

More specific configurations of the present invention are described in the claims.

According to the present invention, it is possible to provide a reactor control rod capable of preventing SCC and IASCC by eliminating gaps and welds and a method for manufacturing such a reactor control rod.

Issues, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a schematic cross-sectional view illustrating an example of a nuclear reactor control rod and a fuel assembly according to Embodiment 1. FIG. It is a cross-sectional schematic diagram which shows the other example of the front-end | tip shape of the braid | blade area | region of FIG. It is a cross-sectional schematic diagram which shows the other example of the control rod for nuclear reactors and fuel assembly which concerns on this invention. FIG. 4 is a schematic diagram enlarging one blade region of FIG. 3. FIG. 2 is a cross-sectional view taken along line AA ′ in FIG. 1. 2 is an electron microscope observation photograph of a prototype manufactured in Example 1. FIG. 4 is a diagram showing an XRD pattern of a deposit of a prototype manufactured in Example 1. FIG. 6 is a cross-sectional view of a nuclear reactor control rod according to Embodiment 2. FIG. It is a flowchart which shows an example of the manufacturing method of the control rod for reactors which concerns on this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

[Basic idea of the present invention]
As described above, the nuclear reactor control rod (hereinafter also simply referred to as “control rod”) is roughly divided into members constituting a tie rod, a blade, and a handle. Conventionally, since these members were individually prepared and joined by welding or the like, the gaps and welds existing between the members could not be excluded, and the SCC was started from the gaps and welds. And IASCC may occur. In the present invention, the members constituting the tie rod, the blade and the handle are integrated by a metal additive manufacturing method using metal powder as a raw material (also simply referred to as “additive additive manufacturing method” or “three-dimensional metal additive manufacturing method”). A control rod (also referred to as “integral molded product” or “seamless control rod”) is produced. According to such a structure, a clearance part and a welding part can be excluded reliably in the area | region where a corrosive environment and a heavy neutron overlap. Therefore, SCC and IASCC starting from the gap and the weld can be reliably prevented.

The metal additive manufacturing method is known as a method for directly obtaining a member having a three-dimensional shape. The method is roughly divided into a powder melt laminating method that obtains a shape by locally melting and solidifying a powder (powder bed) formed in advance in layers by irradiation with energy such as a laser or an electron beam, and while spraying the powder. There is a melt deposition method in which melting and solidification are performed by irradiation of energy, and in any case, a three-dimensional layered object can be formed by melting and solidifying powder.

The metal layer formed by melting and solidifying has a molten and solidified structure (rapidly solidified structure). In addition, on the surface of the modeled object, traces (patterns) can be seen along the scanning direction of a laser or an electron beam. These can be confirmed by observing the surface of the metal layer with a microscope (such as an optical microscope). Therefore, the reactor control rod of the present invention manufactured by the metal additive manufacturing method has, as appearance characteristics, having a melt-solidified structure and a pattern on the surface. Hereinafter, based on an Example, the control rod for nuclear reactors which concerns on this invention is explained in full detail.

Hereinafter, the configuration of the control rod according to the present invention will be described in detail. FIG. 1 is a schematic cross-sectional view showing an example of a nuclear reactor control rod and a fuel assembly according to the present invention. As shown in FIG. 1, the control rod 1a according to the present invention has four blade regions 4a to 4d and a tie rod region 5 that supports the four blade regions 4a to 4d. As described above, the blade and the tie rod are conventionally separate members and joined by welding or the like, but the control rod 1a according to the present invention is constituted by one member. In the control rod 1a of the present invention, a region corresponding to a conventional blade member is referred to as a “blade region”, and a region corresponding to a conventional tie rod member is referred to as a “tie rod region”. Although not shown in FIG. 1, a handle region is provided at one of the lengthwise ends of the blade regions 4a to 4d and the tie rod region 5 of the control rod 1a. The handle area is an area used for transportation of the control rod 1a. The handle area is described in FIG.

The control rod 1a shown in FIG. 1 has a cross-shaped cross section composed of four blade regions 4a to 4d and a tie rod region 5, and includes four channel boxes in which fuel assemblies (not shown) are accommodated. 20 is inserted. The blade regions 4a to 4d are provided with a cylindrical neutron absorber filling hole 3 filled with a neutron absorber. The neutron absorber filling holes 3 are provided only in one blade (blade region 4a) in FIG. 1, but in actuality, the same number is provided in four blades. The number of neutron absorber filling holes 3 is appropriately changed depending on the output of the core and the like.

FIG. 2 is a schematic view showing another aspect of the tip of the blade region in FIG. In FIG. 1, the tip 6a of the blade region 4a has a square (square) shape. In addition to the square shape shown in FIG. 1, the shape of the tip portion may be an arc shape when viewed from above. The arc shape is more preferable because the stress concentration can be relaxed than the square shape.

As shown in FIG. 1, the adjacent blade regions are configured to form a right angle. Since the corner portion (X portion in FIG. 1) formed by the blade regions 4a to 4d and the tie rod region 5 is a portion where corrosion products are easily deposited, it is preferable to round the corner of this portion into an arc shape. . As a method of making the corner portion into an arc shape, it is conceivable to form a near net shape structure using a metal additive manufacturing method and to make the corner portion into an arc shape. By using grinder processing or the like after modeling, the corner portion can be accurately formed into an arc shape.

FIG. 3 is a schematic cross-sectional view showing another example of a nuclear reactor control rod and a fuel assembly according to the present invention. FIG. 3 shows a structure in which the core structure is denser than the structure shown in FIG. In the embodiment shown in FIG. 3, in order to increase the packing density of the fuel rods 22, the shape of the cross section of the channel box is hexagonal, and the cross section of the control rod 1 b is set so as to fit between the three hexagonal channel boxes 21. The shape is a Y-shape. The shape control rod 1b having a Y-shaped cross section is inserted between three channel boxes 21 surrounding a fuel assembly in which a plurality of fuel rods 22 are grouped.

FIG. 4 is a schematic diagram enlarging one blade region of FIG. Similar to the control rod 1 a shown in FIG. 1, the control rod 1 b is composed of three blade regions 4 having neutron absorber filling holes 3 and a tie rod region 5 in the central portion that supports them. The number of neutron absorber filling holes 3 in each blade region 4 is the same. The number of the neutron absorber filling holes 3 is changed in accordance with the output of the core or the like. In FIG. 4, the shape of the tip portion 6 of the blade region 4 is a square shape when viewed from above, but as described above, the arc shape as shown in FIG. Is preferred.

In FIG. 3, each adjacent blade region 4 is configured to form 120 degrees. As in the case of FIG. 1, the corners are preferably arcuate because corrosion products are likely to accumulate. The manufacturing method is as described above.

FIG. 5 is a cross-sectional view taken along the line AA ′ of FIG. As shown in FIG. 5, a handle 7 used as a support portion or the like for carrying the control rod 1a is provided at one end (upper end) of each of the blade region 4 and the tie rod region 5 in the longitudinal direction. Is provided. An upper end portion of the control rod 1 a including the handle 7 is a handle area 8. A blade region 4 having a neutron absorber filling hole 3 and a tie rod region 5 are provided below the handle region 8. 2 also has the structure shown in FIG.

The control rod 1a is divided into two regions depending on the amount of neutron irradiation in the state inserted in the core. That is, in the inserted state, it is close to the core (near the handle region 8), is away from the core 9 (region where high neutron absorption capability is required) 9 to receive high neutron irradiation, and almost no neutron dose There are no regions (regions that do not require neutron absorption capability) 10. The region 9 is referred to as “high irradiation region 9”, and the region 10 is referred to as “low irradiation region”.

The neutron absorber filling hole 3 penetrates from the upper end to the lower end of the blade region 4. Of the neutron absorber filling hole 3, the high irradiation region 9 needs to be filled with a neutron absorber, but the low irradiation region 10 does not need to be filled with a neutron absorber. Therefore, the neutron absorber filling hole 3 in the high irradiation region 9 is filled with a conventional neutron absorber, and the neutron absorber filling hole 3 in the low irradiation region 10 is not filled with the neutron absorber, but the high irradiation region. It is preferable to provide a holder 11 for supporting the neutron absorber filled in the neutron absorber filling hole 3 of 9 from below. The holder 11 that is not a neutron absorber can also be referred to as a “dummy material”.

As the neutron absorber filled in the neutron absorber filling hole 3, generally used boron carbide (B ₄ C) powder or pellets and hafnium (Hf) rod are suitable. When boron carbide is used for the neutron absorber, helium (He) gas is generated by the (n, α) reaction, and the internal pressure of the neutron absorber filling hole 3 may increase. Therefore, as the holder 11 provided in the low irradiation region 10, it is preferable to use a structure having a gap so that helium gas generated from the neutron absorbing material can escape to the outside. For example, it is preferable to fill with a porous powder or a rod-shaped member or an elastic body (spring).

As shown in FIG. 5, the end (lower end) 12 opposite to the handle region 8 of the neutron absorber filling hole 3 is an end for sealing the neutron absorber and the holder 11 to the neutron absorber filling hole 3. It is plugged. Since the end plug joint portion is provided in the low irradiation region 10, even if a gap portion and a welded portion are generated in the end plug joint portion, it does not become a starting point of occurrence of IASCC. The upper end of the control rod 1a corresponding to the high irradiation region 9 to the end plug joint is manufactured as an integral structure using a metal additive manufacturing method. As a result, in the control rod 1a, it is possible to eliminate gaps and welds that may be the starting point of IASCC generation from areas where the neutron irradiation amount is high and IASCC may be generated, and the control rod has excellent IASCC resistance. Can be provided.

The end of the neutron absorber filling hole 3 is end-plug joined and sealed, and then joined to a drive system region 14 having a control rod driving device 13 for driving the control rod 1a. This joining is welded by laser welding, TIG welding, or the like. Similar to the end plug joint described above, the drive system region 14 is a region where the amount of neutron irradiation is extremely low, and the occurrence of SCC and IASCC is not a concern even if the weld remains.

FIG. 9 is a flowchart showing an example of a method for manufacturing a reactor control rod according to the present invention. As shown in FIG. 9, the manufacturing method of the control rod 1a according to the present invention is as follows: S1: Modeling of the handle region 8, S2: Modeling of the blade region 4 and the tie rod region 5, S3: Unmelted powder (raw metal powder) Removal, S4: Neutron absorber filling hole and neutron absorber filling hole are filled, S5: Neutron absorber filling hole is sealed, and S6: Control rod drive unit is joined in this order.

In order to produce the control rod 1a having the structure shown in FIG. 5 by the metal additive manufacturing method, when the metal powder is laminated on the stage, the handle region 8 is the lower end and the end plug joint 12 is the upper end. Go. That is, the layers are stacked from the upper end to the lower end in FIG. After the lamination is completed, the unmelted powder raw material remaining in the neutron absorber filling hole 3 is removed. For removing the powder, it is preferable to use a technique such as shot peening or acid cleaning in order to increase the removal rate of the unmelted powder. After completing so far, as described above, the neutron absorber filling hole 3 is filled with the neutron absorber and the holder 11 in this order, sealed by end plug joining, and a separately manufactured drive system region 14 is joined. .

The material constituting the control rod 1 is not particularly limited, but it is possible to provide a control rod having higher IASCC resistance by using the following alloy having high neutron irradiation resistance. . A preferred alloy composition is 16% to 26% Cr, 8% to 22% Ni, 0.02% to 0.4% O, 0.08% to 0.005% C, and 0% by mass. 0.1-0.002% N, and at least of 0.2-2.8% Zr, 0.4-5.0% Ta and 0.2-2.6% Ti One kind is further contained, and the balance consists of Fe and inevitable impurities.

In the above composition, Fe, Cr, and Ni, which are the main constituent elements of the matrix, have relatively low reactivity, but the additive elements Zr, Ta, and Ti are other metal elements and impurity elements (oxygen (O ) And the like, and the compound formed by bonding is likely to precipitate.

A control rod 1a was prototyped by metal additive manufacturing using an alloy having the above composition. The composition of the fabricated prototype alloy is shown in Table 1 below.

FIG. 6 is an electron microscopic observation photograph (SEM (Scanning Electron Microscope) observation photograph) of the prototype manufactured in Example 1. From the observation results, it can be seen that the average crystal grain size of the matrix is refined to 10 μm or less (about 5 μm). This is presumably because the crystal grain size is refined by the precipitates dispersed in the matrix. Having such fine crystal grains is a feature resulting from the production by the metal additive manufacturing method.

From the analysis result of the prototype EDS (Energy Dispersive x-ray Spectrometry), it was confirmed that the precipitate containing the additive element was finely dispersed. Using the extraction residue method, only the precipitate was taken out and the precipitated phase was identified using an X-ray diffraction (XRD) apparatus. FIG. 7 is a diagram showing an XRD pattern of the precipitate of the prototype, and Table 2 shows the composition of the precipitate. As shown in FIG. 7 and Table 2, the precipitate is found to be an oxide of Zr (ZrO or ZrO ₂ ) which is an additive element of the alloy.

Table 3 shows the average crystal grain size and maximum crystal grain size of the mother phase of the prototype, and the average grain size and number density of the precipitates.

As shown in Table 3, it can be seen that precipitates having an average particle diameter of 15 nm are precipitated at a number density of 4.3 × 10 ²³ m ⁻³ or more.

As described above, the control rod according to the present invention in which the blade, the tie rod, and the handle, which are conventionally constituted by separate members, are one member, is novel. Japanese Laid-Open Patent Publication No. 2002-533736, which is a well-known document, discloses a control rod for a boiling water reactor in which a center and an absorption blade are arranged in a cross shape. Referring to the drawings, a blade, a tie rod, and a handle are disclosed. However, no specific manufacturing method is disclosed. In addition, it is described that a horizontal hole-shaped absorption channel (described in FIG. 2a or the like) corresponding to the neutron absorber filling hole of the control rod according to the present invention is sealed by welding or the like (paragraph 0020), The gap portion and the welded portion cannot be excluded. Further, FIG. 2d discloses a control rod having a vertical hole-like absorption channel as in the present invention, but it is extremely difficult to accurately provide such a vertical hole in the member.

A control rod disclosed in JP 2013-88157 A, which is another known document, has a blade manufactured as an integral structure by HIP processing. In this method, a plurality of long rectangular tubes containing neutron absorbers are arranged, sandwiched between thin plates called cover plates, and diffusion-bonded by HIP processing to produce a blade having a vertical hole. The blades are joined to each other by a blade and a bridge, and the bridge is joined by welding. Therefore, it has the structure which cannot exclude the clearance gap part and the welding part in the bridge | crosslinking part.

Another known document, Japanese Patent Laid-Open No. 2015-203636, discloses a core component manufactured by a metal lamination method, but is a control rod for a fast breeder reactor and is a subject of the present invention. The configuration is different from that of a control rod for a boiling water reactor having a tie rod and a handle.

The control rod 1a according to the first embodiment described above has a structure having high IASCC resistance by eliminating gaps and welds in the high irradiation region 9 where the occurrence of IASCC is a concern. FIG. 8 is a cross-sectional view of a nuclear reactor control rod according to the second embodiment. FIG. 8 is a cross-sectional view of a portion of the control rod corresponding to the cross-sectional view taken along the line AA ′ in FIG. A difference of the control rod 1c according to the second embodiment from the control rod 1a of the first embodiment is that an opening 15 is provided in the tie rod region 5. By providing the opening 15 in the tie rod region 5 in this way, the rigidity of the control rod can be reduced.

¡If the blade area, tie rod area, and handle area are manufactured as a single body, a highly rigid structure is obtained. Due to its function, the control rod needs to be quickly inserted into the core during an earthquake. The channel box surrounding the control rod is made of a zirconium alloy. The tensile strength and elongation of the zirconium alloy are 410 MPa and 20% or more, respectively, and the channel box made of the flexible zirconium alloy is warped by the shaking of the earthquake. The control rod is inserted into the core along the warp of the channel box while the control rod itself is also warped. Therefore, if the control rod has high rigidity, the warpage of the control rod will be smaller than the warpage of the channel box, causing collision with the channel box, causing damage and breakage, and in the worst case, causing poor insertion. Rise.

Therefore, in order to match the rigidity of the control rod to the channel box, the control rod 1c according to this embodiment shown in FIG. 8 has an opening 15 in the tie rod region 5. In the conventional method in which the blade and the tie rod are prepared as separate members and then joined together, it is difficult to make an opening in a portion to be a joining portion of each member. In the metal additive manufacturing method, since the powder is laminated, the structure shown in FIG. 8 can be easily manufactured. By providing the opening 15 in the tie rod region 5 in this way, it is possible to eliminate the gap structure and the welded portion, exhibit high SCC resistance and IASCC, and provide a control rod having structurally appropriate rigidity. Become.

In FIG. 8, the opening 15 has a quadrangular shape when the longitudinal cross section of the control rod 1 is viewed. However, when the circular arc shape is used, it is possible to prevent the accumulation of corrosion products at the corners. Since it can do, it is more preferable. Other structures and manufacturing methods are the same as those in the first embodiment.

As described above, according to the present invention, the control rod for a nuclear reactor that can eliminate the gap and the welded portion and prevent the SCC Oo IASCC and the method for manufacturing the nuclear reactor control rod having such characteristics are provided. It was demonstrated that can be provided.

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

1a, 1b, 1c ... control rod, 20, 21 ... channel box, 22 ... fuel rod, 3 ... neutron absorber filling hole, 4, 4a-4d ... blade region, 5 ... tie rod region, 6, 6a, 6b ... blade Tip, 7 ... handle, 8 ... handle region, 9 ... high irradiation region, 10 ... low irradiation region, 11 ... holder, 12 ... end plug joint, 13 ... control rod drive device, 14 ... drive system region, 15 ... Aperture.

Claims (14)

A blade region having neutron absorber filling holes;
A tie rod region that supports the blade region;
The blade region and the tie rod region are each composed of a single member having a handle region provided at one end in the longitudinal direction, and the member has a melt-solidified structure. Reactor control rod. The reactor control rod according to claim 1, wherein the tie rod region has an opening. The nuclear reactor control rod according to claim 1, wherein the four blade regions and the tie rod region form a cross-shaped cross section. The nuclear reactor control rod according to claim 1, wherein the three blade regions and the tie rod region form a Y-shaped cross section. The reactor control rod is divided into two regions in the length direction, and the region of the two regions that is close to the handle region and has a higher neutron irradiation amount is the upper region, and the remaining region is When using the lower area,
The neutron absorber filling hole in the upper region is filled with a neutron absorber, and the neutron absorber filling hole in the lower region is not filled with a neutron absorber. Reactor control rod. The neutron absorber filling hole in the lower region is filled with a holder for holding the neutron absorber filled in the neutron absorber filling hole in the upper region. The control rod for a nuclear reactor according to claim 5. The nuclear reactor control rod according to claim 6, wherein the holder is a porous powder, a rod-shaped member, or an elastic body. An end plug is provided at an end of the blade area and the tie rod area opposite to the end where the handle area is provided,
The reactor control rod according to claim 1, wherein a control rod drive device that controls the drive of the reactor control rod is connected to the end plug. The neutron absorber filling hole is made longer than a region irradiated with neutrons, and the end plug and the control rod driving device are provided outside the region irradiated with neutrons. Item 9. A control rod for a nuclear reactor according to Item 8. The component has a chemical composition of 16 to 26% Cr, 8 to 22% Ni, 0.02 to 0.4% O, and 0.08 to 0.005% C in mass%. 0.1 to 0.002% N, and
And further comprising at least one of 0.2 to 2.8% Zr, 0.4 to 5.0% Ta and 0.2 to 2.6% Ti,
The control rod for a nuclear reactor according to any one of claims 1 to 9, wherein the balance is made of Fe and inevitable impurities. The control rod for a nuclear reactor according to any one of claims 1 to 9, wherein an average crystal grain size of the member is 10 µm or less. 12. The member according to claim 11, wherein the member has a precipitate, and the precipitate having an average particle diameter of 15 nm is precipitated at a number density of 4.3 × 10 ²¹ m ⁻³ or more. The reactor control rod as described. 13. The nuclear reactor control rod according to claim 12, wherein the precipitate is an oxide containing Zr, Ta, or Ti. A blade region having neutron absorber filling holes;
A tie rod region that supports the blade region;
A method of manufacturing a control rod for a nuclear reactor composed of a single member having a handle region provided at one of longitudinal ends of each of the blade region and the tie rod region,
A method for manufacturing a nuclear reactor control rod, wherein the blade region and the tie rod region are formed in the order of the blade region and the tie rod region in the order of the upper end of the nuclear reactor control rod.

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