JP2020063906A - Control rod for nuclear reactor and manufacturing method thereof - Google Patents

Abstract

To provide a control rod for a nuclear reactor capable of eliminating a gap part and a welding part to prevent SCC and IASCC, and a method for manufacturing the control rod for a nuclear reactor.SOLUTION: A control rod for a nuclear reactor is composed of one member having: a blade region having a neutron absorber filling hole; a tie rod region supporting the blade region; and a handle region provided on one of lengthwise ends of the blade region and the tie rod region, in which the member has a melt-solidified structure. The control rod for a nuclear reactor having the above characteristics is manufactured by a metal lamination manufacturing method.SELECTED DRAWING: Figure 5

Description

  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 the reactor internal equipment used when the operation of the boiling water reactor is stopped and the core power is adjusted. The structure of a general control rod is as follows. That is, the control rod has a cross-shaped cross section, and its appearance is such that the blade extends from the cross-shaped axis. Generally, the axial center portion is called a tie rod, and the blade portion is called a blade. The control rod is inserted between the four fuel assemblies loaded in the core. At reactor startup, the control rods are withdrawn from the core. During the rated power operation, the control rods other than the control rods used for adjusting the reactor core power are pulled out from the core. In an emergency, water pressure is used to insert all control rods (reactor scrum).

  The control rod for a boiling water nuclear reactor further has a U-shaped sheath provided so as to surround each blade. In the space surrounded by the tie rod and the blade and the sheath, a neutron absorbing material (boron carbide powder, hafnium round bar or plate) is suspended and held by a handle. The handle and sheath are typically secured to the tie rods by welding. A part of the sheath is provided with a hole for cooling the contained neutron absorbing material. In some control rods using a plate-type neutron absorbing material, spot welding is performed between the sheath and the neutron absorbing plate.

  Generally, the material of the control rod is mainly SUS316L which is austenitic stainless steel. This material is known to have stress corrosion cracking (hereinafter referred to as "SCC") susceptibility in a specific environment. Furthermore, in a nuclear reactor, it is referred to as "IASCC", which is irradiation-induced stress corrosion cracking (hereinafter referred to as "IASCC"), which is accelerated by SCC susceptibility by receiving a large amount of neutron irradiation. ) Is known to be expressed.

  It is said that SCC (IASCC) occurs when three conditions of material factor, mechanical factor, and environmental factor are met at the same time. Furthermore, in IACC, the neutron irradiation dose is added as a generation factor in addition to the above three factors. As a material factor, it is considered that SCC is caused by impurity carbon forming chromium (Cr) carbide during welding, and measures have been taken to reduce the impurity carbon. Since it is known that mechanical factors occur under tensile stress, measures such as compression of surface stress by the peening method and polishing have been taken. Regarding the environmental factors, the dissolved oxygen concentration and chloride ions are the causes, so that the hydrogen injection method and the noble metal injection method have been performed. As a measure to reduce the neutron irradiation dose, a measure has 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 thereof have not been determined yet, and countermeasures are required.

  In a conventional control rod having a structure in which a sheath and a tie rod are joined by welding, a corrosion product accumulates between the sheath and the tie rod and between the sheath and the neutron absorber, which creates an environment in which crevice corrosion easily occurs. Further, in the structure in which the sheath and the neutron absorbing plate are spot-welded, residual stress is generated in the spot-welded portion, so that minute cracks are likely to occur. Therefore, it has been reported that minute cracks generated by intergranular corrosion and welding residual stress are affected by irradiation or the like, and progressed by IASCC, resulting in damage. This case has been published in the report of the Ministry of Economy, Trade and Industry's Nuclear Safety and Safety Agency report “Investigation Report on Cracks of Hafnium-type Control Rods of Boiling Water Nuclear Power Plant” dated May 31, 2006.

  As described above, in order to prevent the gap between the members forming the control rod and the SCC and IASCC starting from the weld, 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 to prevent IASCC, Patent Document 1 has a cross-shaped cross section, and is provided with a plurality of segments which are joined by welding and arranged side by side in an axial direction, The first segment, which is the uppermost segment, forms a plurality of neutron absorbing material filling holes that are machined from a single metal plate and that extend in the handle portion and axial direction and that are filled with neutron absorbing material. A second segment, which is a segment located at the lowermost part, is formed by combining a pair of blade elements each having a plurality of neutron absorbing material filling portions in a cross shape, and extends in the lower support portion and the axial direction to fill the neutron absorbing material. A pair of blade elements each having a plurality of neutron absorbing material-filled portions forming a plurality of neutron absorbing material-filled holes, which are combined in a cross shape. At least one third segment, which is the other segment disposed between the segment and the second segment, extends in the axial direction and forms four neutron absorber-filled holes filled with neutron absorber. The neutron absorber filling portion is configured by combining in a cross shape, the coupling of the segments, the control rod is characterized in that was performed by welding the neutron absorber filling portion of the adjacent segments. There is. According to Patent Document 1, since welding for connecting the handle portion and the neutron absorber filling portion is not required, it is possible to prevent irradiation-induced stress corrosion cracking of the control rod.

JP, 2010-71791, A

  The control rod shown in Patent Document 1 is a segment obtained by axially dividing a stainless steel plate material that constitutes a blade, and each segment is provided with a vertical hole, and the vertical hole is filled with a neutron absorbing material, and finally each segment The control rod is completed by welding and joining. Each segment is further provided with a bridge for connecting to the opposing blades, and the bridges are joined by welding. In Patent Document 1, since the control rod is divided in the length direction, it is not necessary to machine a long hole, and high machining accuracy can be exhibited. However, since each segment is connected by welding, it is not possible to sufficiently eliminate the possibility of SCC and IASCC starting from the weld.

  In view of the above circumstances, the present invention is to provide a control rod for a nuclear reactor, which can eliminate gaps and welds and prevent SCC and IASCC.

  The present invention, in order to achieve the above object, a blade region having a neutron absorbing material filling hole, a tie rod region supporting the blade region, and provided on one of the lengthwise ends of the blade region and the tie rod region. And a handle region, and the control rod for a nuclear reactor is characterized in that 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-mentioned characteristics, in which a blade region and a tie rod region are sequentially manufactured from a handle region serving as an upper end of the control rod by metal additive manufacturing. A method of manufacturing a characteristic control rod for a nuclear reactor is provided.

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

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

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

3 is a schematic cross-sectional view showing an example of a 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 blade area | region of FIG. It is a cross-sectional schematic diagram which shows the other example of the reactor control rod and fuel assembly which concern on this invention. It is a schematic diagram which expands one blade area | region of FIG. FIG. 2 is a sectional view taken along the line AA ′ of FIG. 1. 3 is an electron microscopic observation photograph of the prototype manufactured in Example 1. FIG. 5 is a diagram showing an XRD pattern of a precipitate of a prototype manufactured in Example 1. FIG. 5 is a cross-sectional view of a control rod for a nuclear reactor according to a second embodiment. It is a flow chart which shows an example of the manufacturing method of the control rod for reactors concerning the present 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 reactor control rods (hereinafter, also simply referred to as “control rods”) are roughly divided into members that form tie rods, blades, and handles. Conventionally, these members have been individually prepared and joined by welding or the like, so that it is not possible to eliminate the gaps and welds existing between the members, and the SCCs and welds are used as starting points. And IASCC could occur. In the present invention, the members forming the tie rod, the blade, and the handle are integrated by a metal additive manufacturing method (also simply referred to as “additive additive manufacturing method” or “three-dimensional metal additive additive manufacturing method”) using metal powder as a raw material. A control rod (also referred to as “integrally molded product” or “seamless control rod”) is manufactured. With such a configuration, it is possible to reliably eliminate the gap and the weld in the corrosive environment or the region where the heavy neutrons are superposed. 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 methods are roughly classified into a powder fusion layering method in which a powder (powder bed) formed in advance in layers is locally melted and solidified by irradiation with energy such as a laser or an electron beam, and a powder melting lamination method in which a powder is sprayed. There is a melt deposition method of melting and solidifying by irradiation of energy, and in any case, a three-dimensional layered structure can be formed by melting and solidifying powder.

  The metal layer formed by melting and solidifying has a melt-solidified structure (quenched solidified structure). Further, on the surface of the modeled object, traces (patterns) can be seen along the scanning direction of the laser or electron beam. These can be confirmed by observing the surface of the metal layer with a microscope (optical microscope or the like). Therefore, the control rod for a reactor of the present invention manufactured by the metal additive manufacturing method is characterized in that it has a melt-solidified structure and has a pattern on the surface. Hereinafter, a control rod for a reactor according to the present invention will be described in detail based on examples.

  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 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 supporting the four blade regions 4a to 4d. As described above, conventionally, the blade and the tie rod are separate members and are joined by welding or the like, but in the control rod 1a according to the present invention, these are composed of 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 ends of the blade regions 4a to 4d and the tie rod region 5 of the control rod 1a in the longitudinal direction. The handle region is a region used for transportation of the control rod 1a and the like. The handle area is described in FIG. 5 described later.

  The control rod 1a shown in FIG. 1 has a cross-shaped cross section formed by four blade regions 4a to 4d and a tie rod region 5, and four channel boxes each containing a fuel assembly (not shown). It is inserted between 20. The blade regions 4a to 4d are provided with a cylindrical neutron absorbing material filling hole 3 filled with a neutron absorbing material. Note that the neutron absorber filling holes 3 are provided only in one blade (blade region 4a) in FIG. 1, but in practice, the same number is provided in four blades. The number of the 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 end portion of the blade region of FIG. In FIG. 1, the tip portion 6a of the blade region 4a has a rectangular (square) shape. The shape of the tip portion may be an arc shape when viewed from the top surface, in addition to the rectangular shape shown in FIG. The arc shape is more preferable than the square shape because stress concentration can be relaxed.

  As shown in FIG. 1, adjacent blade regions are configured to form a right angle. 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 on which corrosion products are easily deposited, and therefore it is preferable that the corner portion is rounded to have an arc shape. . As a method of forming the corners in an arc shape, it is conceivable to form a near net shape structure by using a metal additive manufacturing method and form the corners in an arc shape. After shaping, by using a grinder process or the like, it becomes possible to accurately form the corner portion into an arc shape.

  FIG. 3 is a schematic cross-sectional view showing another example of the reactor control rod and the 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, the cross section of the channel box has a hexagonal shape in order to increase the packing density of the fuel rods 22, and the cross section of the control rod 1b fits between the three hexagonal channel boxes 21. Has 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 assembled.

  FIG. 4 is a schematic view enlarging one blade region of FIG. Similar to the control rod 1a shown in FIG. 1, the control rod 1b is composed of three blade regions 4 having neutron absorbing material filling holes 3 and a central tie rod region 5 supporting 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 according to the output of the core and the like. In FIG. 4, the shape of the tip portion 6 of the blade region 4 is a square shape when viewed from the upper surface, but as described above, the arc shape as shown in FIG. 2 is more preferable from the viewpoint of stress relaxation. It is suitable.

  In FIG. 3, adjacent blade regions 4 are configured to form 120 degrees. Similar to the case of FIG. 1, it is preferable that the corners have an arc shape because corrosion products easily accumulate. The manufacturing method is as described above.

  FIG. 5 is a sectional view taken along the line AA ′ of FIG. As shown in FIG. 5, one of the ends (upper end) in the length direction of the blade region 4 and the tie rod region 5 has a handle 7 used as a support portion or the like for carrying the control rod 1a. Is provided. The upper end portion of the control rod 1a including the handle 7 is referred to as a handle area 8. Below the handle region 8, a blade region 4 having a neutron absorber filling hole 3 and a tie rod region 5 are provided. The cross section taken along the line BB 'of FIG. 2 also has the configuration shown in FIG.

  The control rod 1a is divided into two regions according to the dose of neutrons when it is inserted in the core. That is, in the inserted state, it is close to the core part (close to the handle region 8), is exposed to high neutron irradiation (a region requiring high neutron absorption capacity) 9, and is far from the core part, and the neutron irradiation dose is almost the same. It is divided into a non-existing region (a region where neutron absorption capability is unnecessary) 10. The area 9 is referred to as "high irradiation area 9" and the area 10 is referred to as "low irradiation area".

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

As the neutron absorbing material filled in the neutron absorbing material filling hole 3, generally used powder or pellet of boron carbide (B ₄ C) or a bar material of hafnium (Hf) is suitable. When boron carbide is used as the neutron absorber, helium (He) gas may be 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 void so that the helium gas generated from the neutron absorbing material can escape to the outside. For example, it is preferable to fill the porous powder or the rod-shaped member or the elastic body (spring).

  As shown in FIG. 5, an end portion (lower end) 12 of the neutron absorbing material filling hole 3 opposite to the handle region 8 is an end for sealing the neutron absorbing material and the holder 11 in the neutron absorbing material filling hole 3. It is plugged. Since the end plug joint is provided in the low irradiation region 10, even if a gap or a weld is formed in the end plug joint, it does not become a starting point for the generation of IASCC. From the upper end of the control rod 1a corresponding to the high irradiation area 9 to the end plug joint, it is manufactured as an integrated structure by using the metal additive manufacturing method. As a result, in the control rod 1a, it is possible to eliminate a gap and a welded portion, which may be a starting point of the IASCC generation, from a region where the neutron irradiation amount is high and the IASCC generation is feared, and the control rod having excellent IASCC resistance. Can be provided.

  The end of the neutron absorber filling hole 3 is end plugged and sealed, and then joined to a drive system region 14 having a control rod drive device 13 for driving the control rod 1a. This joint 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 neutron irradiation amount 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 control rod for a nuclear reactor according to the present invention. As shown in FIG. 9, the manufacturing method of the control rod 1a according to the present invention includes S1: modeling of the handle region 8, S2: modeling of the blade region 4 and tie rod region 5, and S3: unmelted powder (raw metal powder). Removal, S4: filling the neutron absorbing material filling hole with the neutron absorbing material and the holding tool, S5: sealing the neutron absorbing material filling hole, and S6: joining the control rod driving device.

  In order to manufacture 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. To remove the powder, it is preferable to use a method such as shot peening or acid cleaning in order to increase the removal rate of the unmelted powder. After completion up to this point, as described above, the neutron absorbing material filling hole 3 is filled with the neutron absorbing material and the holder 11 in this order, sealed by end plug joining, and the separately manufactured drive system region 14 is joined. .

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

  In the above composition, Fe, Cr, and Ni, which are the main constituent elements of the mother phase, have relatively low reactivity, but Zr, Ta, and Ti, which are the additional elements, contain other metal elements and impurity elements (oxygen (O ) Etc.) and the compound formed by the binding tends to precipitate.

  Using the alloy having the above composition, a control rod 1a was prototyped by a metal additive manufacturing method. The composition of the produced alloy of the prototype is shown in Table 1 below.

  FIG. 6 is an electron microscope observation photograph (SEM (Scanning Electron Microscope) observation photograph) of the prototype manufactured in Example 1. From the observation result, it can be seen that the average crystal grain size of the matrix phase is reduced to 10 μm or less (about 5 μm). It is considered that this is because the crystal grains are made finer by the precipitates dispersed in the mother phase. Having such fine crystal grains is a characteristic attributed to the fact that they are produced by the metal additive manufacturing method.

From the analysis result of the prototype by EDS (Energy Dispersive x-ray Spectrometry), it was confirmed that the precipitate containing the additional element was finely dispersed. Only the precipitate was taken out using the extraction residue method, and the precipitation phase was identified using an X-ray diffraction (XRD) apparatus. FIG. 7 is a diagram showing an XRD pattern of the deposit of the prototype, and Table 2 shows the composition of the deposit. As shown in FIG. 7 and Table 2, it is understood that the precipitate is 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 matrix of the prototype, and the average grain size and number density of the precipitates.

As shown in Table 3, it can be seen that the precipitates having an average particle size of 15 nm are deposited 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 configured by separate members, are one member is novel. Japanese Patent Publication No. 2002-533736, which is a 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, and referring to the drawings, a blade, a tie rod, and a handle. Although it seems that it is composed of one member, no specific manufacturing method is disclosed. In addition, it is described that the transverse-hole-shaped absorption channel (described in FIG. 2a and 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), It has a structure in which the gap and welds cannot be excluded. Further, FIG. 2d discloses a control rod having a vertical absorption channel as in the present invention, but it is extremely difficult to accurately provide such a vertical hole in a member.

  In the control rod disclosed in Japanese Patent Laid-Open No. 2013-88157, which is another known document, the blade is manufactured as an integral structure by HIP processing. In this method, a plurality of long rectangular tubes containing a neutron absorber are arranged, sandwiched by thin plates called cover plates, and diffusion bonded by HIP processing to produce a blade having vertical holes. The blades are joined to the opposing blades at a bridge portion, and the bridge portion is joined by welding. Therefore, the bridge portion has a configuration in which the gap portion and the welded portion cannot be eliminated.

  Japanese Patent Laid-Open No. 2015-203636, which is another known document, discloses a core component manufactured by a metal laminating method, which is a control rod for a fast breeder reactor and is a target of the present invention. , A boiling water nuclear reactor control rod 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 welded portions in the high irradiation region 9 where IASCC is feared to occur. FIG. 8 is a sectional view of a reactor control rod according to the second embodiment. FIG. 8 is a sectional view of a portion of the control rod corresponding to the sectional view along the line AA ′ in FIG. 1. The control rod 1c according to the second embodiment is different from the control rod 1a according to the first embodiment in that an opening 15 is provided in the tie rod region 5. By providing the opening 15 in the tie rod region 5 as described above, the rigidity of the control rod can be reduced.

  When the blade region, the tie rod region and the handle region are manufactured as one body, a structure having high rigidity is obtained. Due to its function, the control rod needs to be rapidly inserted into the core during an earthquake. The channel box surrounding the control rod is made of zirconium alloy. The tensile strength and the 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 due to the shaking of the earthquake. The control rods are inserted into the core along the warp of the channel box while the control rods themselves generate warp. Therefore, if the rigidity of the control rod is high, the warp of the control rod will be smaller than the warp of the channel box, and it may collide with the channel box, resulting in damage or damage, and in the worst case, insertion failure. Increase.

  Therefore, in order to match the rigidity of the control rod with the channel box, the control rod 1c according to the present embodiment shown in FIG. 8 has an opening 15 in the tie rod region 5. With the method of joining the blade and the tie rod after preparing them as separate members as in the prior art, it is difficult to form an opening at a portion to be a joining portion of each member. In the metal additive manufacturing method, powders are laminated, so that the structure shown in FIG. 8 can be easily manufactured. By providing the opening 15 in the tie rod region 5 as described above, it is possible to eliminate the gap structure and the welded portion, exhibit high SCC resistance and IASCC resistance, and provide a control rod having a structurally appropriate rigidity. Become.

  In FIG. 8, the opening 15 has a quadrangular shape when the vertical cross section of the control rod 1 is viewed, but if it has an arc shape, it is possible to prevent corrosion products from accumulating at the corners. Therefore, it is more preferable. Other structures and manufacturing methods are the same as in the first embodiment.

  As described above, according to the present invention, a control rod for a reactor capable of eliminating a plow portion and a welded portion and preventing SCC Ohio IASCC, and a method of manufacturing a control rod for a reactor having such a feature. It has been demonstrated that can be provided.

  It should be noted that the present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, 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 / replace other configurations with respect to a part of the configurations of the respective embodiments.

  1a, 1b, 1c ... Control rod, 20, 21 ... Channel box, 22 ... Fuel rod, 3 ... Neutron absorbing material filling hole, 4, 4a-4d ... Blade area, 5 ... Tie rod area, 6, 6a, 6b ... Blade Tip, 7 ... Handle, 8 ... Handle area, 9 ... High irradiation area, 10 ... Low irradiation area, 11 ... Holder, 12 ... End plug joint, 13 ... Control rod drive device, 14 ... Drive system area, 15 ... Aperture.

Claims (14)

A blade region having a neutron absorber filling hole,
A tie rod region supporting the blade region,
The blade region and the tie rod region are each formed of a single member having a handle region provided at one of the ends in the lengthwise direction, and the member has a melt-solidified structure. Control rod for nuclear reactor.   2. The reactor control rod according to claim 1, wherein the tie rod region has an opening.   The reactor control rod according to claim 1, wherein the four blade regions and the tie rod regions form a cross-shaped cross section.   The control rod for a nuclear reactor according to claim 1, wherein the three blade regions and the tie rod region form a Y-shaped cross section. The control rod for a nuclear reactor is divided into two regions in the length direction, and of the two regions, the region nearer to the handle region and having a higher neutron irradiation amount is the upper region, and the remaining region is When I made it the lower area,
2. The neutron absorbing material filling hole in the upper region is filled with neutron absorbing material, and the neutron absorbing material filling hole in the lower region is not filled with neutron absorbing material. Control rod for nuclear reactor.   The neutron absorbing material filling hole in the lower region is characterized by being filled with a holder for holding the neutron absorbing material filled in the neutron absorbing material filling hole in the upper region. The control rod for a nuclear reactor according to claim 5.   The control rod for a nuclear reactor 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 the end of the blade region and the tie rod region opposite to the end where the handle region is provided,
The control rod for a nuclear reactor according to claim 1, wherein a control rod driving device for controlling the drive of the nuclear reactor control rod is connected to the end plug.   The neutron absorbing material filling hole is made longer than a region irradiated with neutrons, and the end plug and the control rod drive device are provided outside the region irradiated with the neutrons. Item 8. A control rod for a nuclear reactor according to item 8. The chemical composition of the member is, in mass%, 16 to 26% Cr, 8 to 22% Ni, 0.02 to 0.4% O, and 0.08 to 0.005% C. , 0.1 to 0.002% N, and
Further comprising at least one of 0.2-2.8% Zr, 0.4-5.0% Ta and 0.2-2.6% Ti,
The control rod for a nuclear reactor according to any one of claims 1 to 9, wherein the balance comprises Fe and unavoidable impurities.   The control rod for a nuclear reactor according to claim 1, wherein the average crystal grain size of the member is 10 μm or less. The member has a deposit, and among the deposits, those having an average particle size of 15 nm are deposited at a number density of 4.3 × 10 ²¹ m ⁻³ or more. The described control rod for a nuclear reactor.   The control rod for a nuclear reactor according to claim 12, wherein the precipitate is an oxide containing Zr, Ta or Ti. A blade region having a neutron absorber filling hole,
A tie rod region supporting the blade region,
A method for manufacturing a nuclear reactor control rod, comprising a single member having a handle region provided at one of the lengthwise ends of the blade region and the tie rod region, and
A method for manufacturing a control rod for a reactor, characterized in that the blade region and the tie rod region are sequentially manufactured from the handle region which is an upper end of the control rod for a nuclear reactor by metal additive manufacturing.

Images