JP2006219710A - Device for forming surface-treated layer, method for forming surface-treated layer and control rod for atomic furnace at which the surface-treated layer is formed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a surface-treated layer with two step structures having different film thicknesses with a transit part having a prescribed shape interposed. <P>SOLUTION: First anode rods 32 with a curved shape plurally arranged around a sheathed tube 21 at almost equal intervals each other, and in which the distance with the sheathed tube 21 is made short toward the depth direction of a solution 31 are fed with electric current from either power source 38. Second anode rods 37 arranged at the inside of an insulating shielding member 36 at the inside of the first anode rods 32, and plurally arranged around the sheathed tube 21 piercing the central part at almost equal intervals are fed with electric current from the other power source 39, the opening area of a through-hole 38 provided at the central part of an insulating diaphragm 35 at the edge part of the shielding member 36 is made into a tapered shape where it reduces from the side of each first anode rod 32 to the side of each second anode rod 37, and the electric current sneaking from each anode rod 32 to the inside of the shielding member 36 is gradually reduced, so as to form a transit part of the surface-treated layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus and method for forming a surface treatment layer such as plating, and is used, for example, to form a surface treatment layer on the surface of a control rod for a nuclear reactor.

  FIG. 1 shows a fuel assembly and a control rod for a nuclear reactor, and the configuration thereof will be briefly described. FIG. 1 shows an example of a fuel assembly used in a pressurized water reactor and a control rod inserted into the fuel assembly.

  The fuel assembly 1 has two types of nozzles, and connects the upper nozzle portion 5 and the lower nozzle portion 6 disposed at the upper end portion and the lower end portion, and the upper nozzle portion 5 and the lower nozzle portion 6. , A plurality of hollow control rod guide tubes 3 parallel to each other, a support lattice 4 having a square lattice structure provided in the length direction of the control rod guide tube 3, and one each inserted into a lattice opening of the support lattice 4 The plurality of fuel rods 2 are provided.

  On the other hand, the control rod 10 seals the upper end and lower end of a hollow stainless steel tube to form an elongated rod-like body, and the lower end side has a shell shape. Inside the control rod 10, a neutron absorber made of a silver-indium-cadmium alloy rod and a holding spring are accommodated. The plurality of control rods 10 are used as control rod clusters 7 with their upper ends held by the spider assembly 12. The spider assembly 12 includes a hub portion 8 that is detachably connected to a drive shaft (not shown), a plurality of vane portions 9 that extend radially from the hub portion 8, and a finger portion 11 that receives and fixes the control rod 10. The hub portion 8 is configured to move up and down with the operation of the drive shaft. A plurality of control rods 10 move up and down in the control rod guide tube 3 as the control rod clusters 7 connected by the hub portion 8 move up and down.

  The control rod 10 for a nuclear reactor controls the output of the nuclear reactor by adjusting the insertion length of the control rod 10 with respect to the fuel assembly 1 constituting the nuclear reactor core. Usually, when the nuclear reactor is operating, the rated output operation is performed, so that the control rod 10 is often pulled up above the fuel assembly 1 with the tip portion remaining. In order to suppress the output of the nuclear reactor, a part of the control rod 10 is slightly inserted into the fuel assembly, and when the nuclear reactor is stopped, the entire control rod 10 is inserted into the fuel assembly 1. To do. Furthermore, at the time of emergency stop of the nuclear reactor, the entire control rod 10 is quickly inserted into the fuel assembly 1 within a predetermined time by using free fall of the control rod 10. Thus, the control rod 10 is extremely important for the control of the nuclear reactor and also for safety, and is required to operate correctly even in an emergency.

FIG. 2 shows the positional relationship of the control rod 10 in each state (when operating and when stopped) with respect to the related members of the fuel assembly 1 and the control rod 10.
As shown in FIG. 2, an upper core plate 15 is disposed above the upper nozzle portion 5 of the fuel assembly 1, and a control rod cluster guide having a continuous guide tube 17 and a guide support plate 18 above the upper core plate 15. A tube 16 is provided. Further above these, the spider assembly 12 and the like connected to the drive shaft are arranged. During normal operation, when the control rod cluster 7, that is, the control rod 10 is pulled up from the fuel assembly 1, only the lower end portion of the control rod 10 is inserted into the control rod guide tube 3. The portion is positioned in the control rod cluster guide tube 16 above (see the control rod 10a in FIG. 2).

  Further, the control rod 10 at the time of emergency stop needs to be inserted quickly at a predetermined insertion length, and finally decelerated to a speed that does not receive an impact, so that the control rod guide tube 3 is inserted. A dash pot 3a for increasing the resistance of the control rod 10 by the coolant and decelerating the insertion speed of the control rod 10 by reducing the inner diameter of a part of the control rod guide tube 3 is provided at the lower end of the control rod. Thus, the tip of the control rod 10 is inserted into the dash pot 3a, and finally stops at this position (see the control rod 10b in FIG. 2).

  In the region of the control rod cluster guide tube 16, the coolant that has flowed upward in the fuel assembly 1 changes the flow direction in various lateral directions toward a plurality of reactor outlet nozzles (not shown) to cool the control rod cluster guide tube 16. It is a part where the strength or direction of the flow of material is irregular, and due to irregularity of the flow of coolant, the control rod 10 vibrates randomly, and the surrounding members, for example, the continuous guide tube 17 etc. There is a risk that the cladding tube will wear due to contact. In the worst case, the wear on the surface of the control rod 10 may cause the control rod 10 to break. The breakage of the control rod 10 may hinder the insertion operation of the control rod 10 during an emergency stop. Don't be on top.

  Therefore, in order to prevent the surface of the control rod 10 from being worn, a surface treatment layer such as chrome plating is formed on the outer surface of the steel pipe constituting the control rod 10. It is covered. The surface treatment layer of the control rod 10 desirably has a film thickness that suppresses wear on the surface of the control rod 10 to obtain a predetermined life and does not affect the insertion property of the control rod 10. Further, in consideration of the structure of the dash pot 3a, the surface treatment of the front end portion of the control rod 10 inserted into the dash pot 3a is made so that the dash pot 3a can be inserted without stopping by contacting the reduced portion of the inner diameter of the dash pot 3a. The film thickness of the layer cannot be made too thick compared to the film thickness of the surface treatment layer other than the tip. Therefore, on the surface of the control rod 10, a surface treatment layer having a two-stage structure with different film thicknesses other than the tip portion and the tip portion of the control rod 10 is formed (see Patent Document 1). As described above, the structure of the control rod 10 is closely related to the structure of the fuel assembly 1 and the like, including the surface treatment layer formed on the outer surface of the control rod 10.

JP-A-11-153585

  As described above, the thickness of the surface treatment layer of the control rod is formed to a predetermined thickness corresponding to the portion of the control rod in consideration of wear resistance and insertability, but the thickness changes. Examination of the part (hereinafter referred to as the transition part), in particular, examination of the influence on the insertability was insufficient. For example, if the transition part has a staircase shape, localized resistance may occur, and the insertion time may be extended through the entire insertion process of the control rod. It is considered that it is desirable to have a predetermined shape, for example, a tapered shape, which may adversely affect not only the wear resistance but also the wear resistance.

  In order to obtain a surface treatment layer having a desired film quality or shape by forming a surface treatment layer having a two-stage structure with different film thickness with a transition portion having a desired shape interposed therebetween, It is complicated, takes time and costs, and has the following problems, making it difficult to obtain a desired surface treatment layer.

  For example, the formation of a surface treatment layer having a two-stage structure with different film thicknesses is generally performed in two steps by plating. In this case, by forming the surface treatment layer twice, the surface treatment layer has a two-stage structure with different film thicknesses, so that the upper surface treatment layer is stacked on the lower surface treatment layer. The film thickness of the surface treatment layer cannot be obtained stably, and there are problems such as adhesion of the upper surface treatment layer. Also, with this method, it is extremely difficult to make the transition portion into a desired shape.

  In addition, by using the anode side electrode arranged at a different distance from the object to be plated, such as a control rod, there is also a method for simultaneously constructing a surface treatment layer having a two-stage structure with different film thickness without overlapping the surface treatment layer. However, since the target is long (about 4 m), in this case, it is difficult to control to stabilize the range of the formed transition portion, and the accuracy of the film thickness of the entire surface treatment layer may be deteriorated. there were.

  Furthermore, after the surface treatment layer with a thin film thickness has reached the desired film thickness, the part is covered with a shielding jig and the current is shielded so that no new surface treatment layer is formed on that part. There is also a method of continuously constructing a surface treatment layer having a two-stage structure with different film thicknesses. In this case, the surface treatment layer of the control rod, such as a rough surface of the thin film treatment layer already formed, is used. There was a possibility that the wear resistance and insertability could not be satisfied.

  In order to obtain a good surface treatment layer, the thickness of the surface treatment layer is important not only for the transition part but also for the shape of the terminal part of the surface treatment layer. For example, in general, the sacrificial electrode is disposed near the end of the control rod, and the surface treatment layer is deposited on the sacrificial electrode, thereby preventing the surface treatment layer from being deposited on the end of the control rod. Although a method of providing an appropriate boundary between the formed portion and the non-formed portion of the treatment layer is also used, the surface treatment layer is deposited on the sacrificial electrode each time the surface treatment layer is formed, and the size of the sacrificial electrode varies. Therefore, if the deposited surface treatment layer is not removed every time construction is performed, the formation state of the surface treatment layer at the end of the control rod, specifically, the film thickness and the position of the boundary are stably obtained. I couldn't. This phenomenon occurs even during one construction, and the state of the sacrificial electrode changes during one construction, which changes the state of formation of the surface treatment layer at the end of the control rod. It was not possible to obtain the construction results.

  Thus, if the position of the end portion of the surface treatment layer is not stable, for example, in the case of a tubular object to be plated such as a control rod, the position of the end portion of the surface treatment layer changes in the circumferential direction and appears to wave Occurred, and the manufacturing yield was deteriorated. Moreover, when the layer thickness of the terminal portion is increased, the insertion property is also affected. When such a undulation phenomenon occurs, it is conceivable to handle the end portion of the surface treatment layer by polishing, but the surface treatment layer with high wear resistance and the steel pipe having a lower hardness than the surface treatment layer are considered. It is not easy to polish the boundary portion, and since the thin tube is easily deformed, it is difficult to reduce the deterioration of the manufacturing yield.

  In general, when a surface treatment layer is formed on an object to be plated, the outer surface of the object to be plated is held by an electrode, and an electric current is passed through the object to be plated through the electrode. However, if the object to be plated is long like a control rod or is a material or shape having a large energization resistance, in this method, the current required for the plating process is spread over the entire surface of the object to be plated, It was not possible to supply stably and the surface treatment layer could not be made uniform. In addition, when the energization position for the object to be plated is outside the plating liquid surface, the object to be plated itself becomes high temperature due to the specific resistance of the object to be plated and the heat generated by energization, which causes problems such as material deterioration and deformation. It was causing.

As described above, the formation of a surface treatment layer having a two-stage structure with different film thicknesses has various problems in the conventional method, and the formation of a surface treatment layer on a long object such as a control rod is not possible. , Making the above problems more difficult to solve. And the following surface treatment layer forming apparatus and forming method which overcome the above-described problems have been desired.
(1) A surface treatment layer having a two-stage structure with different thicknesses is continuously formed with a transition portion having a desired shape interposed therebetween so as to improve the insertability of the control rod without impairing the wear resistance. .
(2) Stabilize the film thickness of each surface treatment layer, and have high adhesion to the object to be plated and a smooth surface state.
(3) The film thickness at the end portion of the surface treatment layer is decreased continuously or stepwise with a small width, and the end portion is positioned at a stable position in the circumferential direction.
(4) Even for a material to be plated of a material having a large energization resistance or a long material, the current distribution on the surface of the material to be plated is made constant so that the film thickness of the surface treatment layer to be formed is uniform. To be.
(5) A desired surface treatment layer can be formed in a single step without requiring post-treatment such as polishing.

  The present invention has been made in view of the above problems, and a surface treatment layer forming apparatus, a formation method, and a surface treatment layer for forming a surface treatment layer having a two-stage structure with different thicknesses sandwiching a transition portion having a predetermined shape are formed. An object of the present invention is to provide a controlled rod for a nuclear reactor.

An apparatus for forming a surface treatment layer according to a first invention for solving the above-described problems is as follows.
A solution containing the material constituting the surface treatment layer, the target member forming the surface treatment layer being immersed except for its upper end, and
A plurality of first anode rods having a curved shape in which the distance between the target member and the target member is shortened in the depth direction of the solution, and a plurality of the anode members are arranged at substantially equal intervals around the target member.
An insulating shielding member that is disposed inside the plurality of first anode rods and through which the target member penetrates a central portion;
A plurality of second anode rods arranged inside the shielding member and arranged at substantially equal intervals around the target member;
An insulating partition plate provided at the lower end of the shielding member;
It is provided at the center of the partition plate, and is formed into a tapered shape or a staircase shape so that the target member penetrates and the opening area decreases from the first anode rod side to the second anode rod side. Through holes,
And a plurality of power supplies connected to the first anode rod and the second anode rod, each independently supplying a current.

An apparatus for forming a surface treatment layer according to a second invention for solving the above-described problems is as follows.
In the surface treatment layer forming apparatus according to the first invention,
An insulating upper holding member and a lower holding member for holding the upper end portion and the lower end portion of the target member are provided, and an end portion of the upper holding member and the lower holding member on the side holding the target member is provided as the target. A taper shape or a staircase shape is formed such that the opening area decreases toward the end of the member.

An apparatus for forming a surface treatment layer according to a third invention for solving the above-described problems
In the surface treatment layer forming apparatus according to the first and second inventions,
When the target member has a hollow shape,
A conductive member having a length equivalent to that of the target member and having a size capable of being inserted into a hollow portion of the target member, and a plurality of conductive members provided on the surface of the conductive member, and configured from a material having good conductivity. A negative electrode member having an elastic member formed,
The cathode member is inserted into a hollow portion of the target member, and the elastic member is brought into contact with an inner wall surface of the target member.

An apparatus for forming a surface treatment layer according to a fourth invention for solving the above-described problems is
In the surface treatment layer forming apparatus according to the third invention,
As the elastic member, a strip-shaped leaf spring, a cylindrical leaf spring, or a ring-shaped wire is used.

An apparatus for forming a surface treatment layer according to a fifth invention for solving the above-described problems
In the surface treatment layer forming apparatus according to the third and fourth inventions,
Covering the outside of the cathode member with a conductive cylindrical mesh member, inserting the cathode member together with the mesh member into a hollow portion of the target member, and passing the elastic member through the mesh member, It is characterized by being brought into contact with the inner wall surface of the target member.

An apparatus for forming a surface treatment layer according to a sixth invention for solving the above-described problems is as follows.
In the surface treatment layer forming apparatus according to the first and second inventions,
When the target member has a hollow shape,
The conductive member has a length equivalent to that of the target member, is a size that can be inserted into a hollow portion of the target member, and has a cylindrical conductive member with good conductivity provided with a slit in the longitudinal direction. A negative electrode member having an inflatable expansion member disposed in the conductive member along the longitudinal direction;
The cathode member is inserted into a hollow portion of the target member, the expansion member is expanded, and the conductive member is brought into contact with an inner wall surface of the target member.

An apparatus for forming a surface treatment layer according to a seventh aspect of the present invention for solving the above problem is as follows.
In the apparatus for forming a surface treatment layer according to the first to sixth inventions,
One power source is controlled to supply a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined thickness is formed,
The other power supply supplies a constant second predetermined current smaller than the first predetermined current to the second anode rod until a surface treatment layer having a second predetermined thickness smaller than the first predetermined thickness is formed. Then, after the surface treatment layer having the second predetermined thickness is formed, a third predetermined current lower than the current for forming the surface treatment layer is applied until the supply of current to the first anode rod is stopped. Controlled to supply to the second anode rod.

An apparatus for forming a surface treatment layer according to an eighth invention for solving the above-described problems is as follows.
In the apparatus for forming a surface treatment layer according to the first to sixth inventions,
One power source is controlled to supply a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined thickness is formed,
On the other hand, the other power source has a predetermined time obtained by subtracting a time for forming a surface treatment layer having a second predetermined film thickness smaller than the first film thickness from a time for forming a surface treatment layer having a first film thickness. A third predetermined current lower than a current for forming the surface treatment layer is supplied to the second anode rod, and the first treatment film is formed until the surface treatment layer having the first predetermined film thickness and the second predetermined film thickness is formed. Control is performed to supply a constant second predetermined current smaller than the predetermined current to the second anode rod.

A control rod for a nuclear reactor in which a surface treatment layer according to a ninth invention for solving the above problem is formed,
The target member on which the surface treatment layer is formed is a cladding tube of a control rod for a nuclear reactor,
Using the surface treatment layer forming apparatus according to any of the first to eighth inventions, a surface treatment layer having a two-stage structure with different thicknesses is formed on the cladding tube, and between the surface treatment layers with different thicknesses. The film thickness is continuously changed within a predetermined range.

A method for forming a surface treatment layer according to a tenth aspect of the present invention for solving the above problem is as follows.
In the solution containing the material constituting the surface treatment layer, the target member for forming the surface treatment layer is dipped except for its upper end,
A plurality of the anode members are arranged at substantially equal intervals around the target member, and a current from one power source is supplied to the curved first anode rod whose distance from the target member becomes shorter in the depth direction of the solution. Supply
The second power source is disposed on the inner side of the insulating shielding member on the inner side of the plurality of first anode rods, and a plurality of second anode rods are arranged at substantially equal intervals around the target member penetrating the central portion. Supply current from
The target member penetrates through the center of the insulating partition plate provided at the lower end of the shielding member, and the opening area decreases from the first anode rod side to the second anode rod side. By forming such a tapered or stepped through hole, the current flowing from the first anode rod into the shielding member is gradually reduced.

A method for forming a surface treatment layer according to an eleventh invention for solving the above-described problems is as follows.
In the method for forming a surface treatment layer according to the tenth aspect,
The insulating upper holding member that holds the upper end portion and the lower end portion of the target member, and the end portion of the lower holding member that holds the target member toward the end side of the target member has an opening area thereof It is formed in a taper shape or a step shape that decreases, and the current from the first anode rod or the second anode rod is gradually reduced.

A method for forming a surface treatment layer according to a twelfth aspect of the present invention for solving the above problem is as follows.
In the method for forming a surface treatment layer according to the tenth and eleventh inventions,
When the target member has a hollow shape,
A conductive member having a length equivalent to that of the target member and having a size capable of being inserted into a hollow portion of the target member, and a plurality of conductive members provided on the surface of the conductive member, and configured from a material having good conductivity. A cathode member having an elastic member is inserted into a hollow portion of the target member, and the elastic member is brought into contact with an inner wall surface of the target member.

A method for forming a surface treatment layer according to a thirteenth invention for solving the above-described problems is as follows.
In the method for forming a surface treatment layer according to the twelfth invention,
The elastic member is a strip-shaped plate spring, a cylindrical plate spring, or a ring-shaped wire.

A method for forming a surface treatment layer according to a fourteenth aspect of the present invention for solving the above problem is as follows.
In the method for forming a surface treatment layer according to the twelfth and thirteenth inventions,
Covering the outside of the cathode member with a conductive cylindrical mesh member, inserting the cathode member together with the mesh member into a hollow portion of the target member, and passing the elastic member through the mesh member to the target It is made to contact the inner wall surface of a member, It is characterized by the above-mentioned.

A method for forming a surface treatment layer according to a fifteenth aspect of the present invention for solving the above problems is as follows.
In the method for forming a surface treatment layer according to the tenth and eleventh inventions,
When the target member has a hollow shape,
The conductive member has a length equivalent to that of the target member, is a size that can be inserted into a hollow portion of the target member, and has a cylindrical conductive member with good conductivity provided with a slit in the longitudinal direction. Along the longitudinal direction, a negative electrode member having an inflatable expansion member disposed inside the conductive member is inserted into a hollow portion of the target member,
The inflating member is inflated, and the conductive member is brought into contact with an inner wall surface of the target member.

A method for forming a surface treatment layer according to a sixteenth aspect of the present invention for solving the above problem is as follows.
In the method for forming a surface treatment layer according to the tenth to fifteenth inventions,
One of the power supplies supplies a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined film thickness is formed,
The other power source supplies a constant second predetermined current smaller than the first predetermined current to the second anode rod until a surface treatment layer having a second predetermined film thickness that is thinner than the first predetermined film thickness is formed. Then, after the surface treatment layer having the second predetermined thickness is formed, a third predetermined current lower than the current for forming the surface treatment layer is applied until the supply of current to the first anode rod is stopped. It supplies to a 2nd anode rod, It is characterized by the above-mentioned.

A method for forming a surface treatment layer according to a seventeenth aspect of the present invention for solving the above problem is as follows.
In the method for forming a surface treatment layer according to the tenth to fifteenth inventions,
One of the power supplies supplies a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined film thickness is formed,
The other power source is a predetermined time obtained by subtracting a time for forming a surface treatment layer having a second predetermined film thickness thinner than the first film thickness from a time for forming a surface treatment layer having a first film thickness. A third predetermined current lower than a current for forming the surface treatment layer is supplied to the second anode rod, and the first treatment film is formed until the surface treatment layer having the first predetermined film thickness and the second predetermined film thickness is formed. A second predetermined current smaller than a predetermined current is supplied to the second anode rod.

A control rod for a nuclear reactor in which a surface treatment layer according to an eighteenth aspect of the present invention for solving the above problems is formed,
The target member on which the surface treatment layer is formed is a cladding tube of a control rod for a nuclear reactor,
Using the method for forming a surface treatment layer according to the tenth to seventeenth inventions,
A surface treatment layer having a two-stage structure with different film thicknesses is formed on the cladding tube, and the surface treatment layers with different film thicknesses are formed so as to continuously change within a predetermined range. And

  According to the first and tenth inventions, a surface treatment layer having a two-stage structure having different film thicknesses can be simultaneously formed on a target member, and a transition portion between surface treatment layers having different film thicknesses can be continuously formed. It is possible to obtain a desired shape in which the film thickness changes. Since the two-stage surface treatment layer has no overlapping portion, it has excellent adhesion and can improve wear resistance. In addition, the film thickness of the surface treatment layer at each site can be stably and uniformly formed, and the position and shape of the transition portion of the surface treatment layer can be stably controlled to a desired position and shape. For example, even for a long target member such as a control rod for a nuclear reactor, the film thickness of the surface treatment layer can be stably and uniformly formed, and the position and shape of the transition portion of the surface treatment layer can be set to a desired value. The position and shape can be controlled stably. Furthermore, since the surface treatment layer having a two-stage structure is formed at the same time, it is possible to simplify the construction process and reduce the construction cost.

  According to the second and eleventh inventions, since the target member is held by the insulating lower holding member and upper holding member having a tapered shape or the like, the deposition of the surface treatment layer on the non-formed portion can be reliably prevented. The terminal portion of the surface treatment layer can be stably formed at a desired position and a desired shape. In addition, the lower holding member and upper holding member made of an insulating material do not deposit a surface treatment layer during construction, eliminating the need for operations such as removing the surface treatment layer, thus reducing costs during construction. It becomes.

  According to the third to sixth and twelfth to fifteenth inventions, since the cathode member is inserted into the target member and used, a plurality of contact members can be applied to the inner wall surface with the same contact pressure over the entire length of the target member. A good contact state can be obtained, and the uniform thickness of the surface treatment layer can be formed over the entire length of the target member, with the energization on the surface of the target member being constant. Further, when the above-described cathode member is used, scratches and energization marks due to the cathode member do not remain, so that post-treatment such as removal of scratches is not necessary, and cost can be reduced.

  According to the seventh, eighth, sixteenth, and seventeenth inventions, the surface treatment layers having different thicknesses are continuously formed while maintaining the surface condition of the thin surface treatment layers in good condition. can do.

  According to the ninth and eighteenth aspects, since the range and shape of the transition portion are appropriate, the insertion property of the control rod itself can be improved, and the quality control for the insertion property can be improved. . Also, the wear resistance can be improved by making the wear resistance range as long as possible.

  The formation of the surface treatment layer according to the present invention will be described in detail with reference to FIGS.

  FIG. 3 shows the detailed structure of the control rod on which the surface treatment layer according to the present invention is formed. FIG. 3A shows the structure of the entire control rod, and FIG. 3B is an enlarged view of a region C in FIG.

  The control rod 10 is a hollow stainless steel tube sheathed tube 21 whose upper end and lower end are welded to an upper end plug 22 and a lower end plug 25 so that the inside is sealed. The upper end plug 22 is formed with a narrow diameter portion 23 to be inserted into the finger portion 11 of the spider assembly 12 shown in FIG. 1 and a fixing screw portion 24. When the control rod cluster 7 is configured, A fastening cap nut or the like is screwed onto the screw portion 24. The lower end plug 25 has a shell shape at the lower end side, and the upper end side thereof is hermetically connected and fixed to the lower end portion of the cladding tube 21 by a circumferential weld 26. A neutron absorber 27 is accommodated inside the cladding tube 21 above the lower end plug 25, and further, a compression coil spring 28 for holding the neutron absorber 27 is interposed above the neutron absorber 27. The neutron absorber 27 is formed of a silver-indium-cadmium (eg, Ag: 80%, In: 15%, Cd: 5%) alloy rod.

  In the range A, a chromium plating layer 29 having a thickness of about 30 μm is applied to the outer surface of the cladding tube 21 as a wear-resistant surface treatment layer. Further, a chromium plating 29 having a film thickness of about 10 μm is applied in a range of about 300 mm from the lower end of the cladding tube 21 and in a range B excluding the heat-affected portion (about 5 mm) of the circumferential weld 26. The film thickness of the chromium plating layer 29 in the range B is determined in consideration of reliably obtaining a gap with the dashpot 3a, that is, insertability and wear resistance. As described above, the cladding tube 21 is formed with the chromium plating layers 29 having two different film thicknesses, and these are formed continuously and simultaneously as described later. As shown in FIG. 3B, a tapered transition portion D in which the film thickness of the chrome plating layer 29 continuously changes is formed over a range of about 15 mm at the boundary between the ranges A and B. Has been.

  The control rod 10 having the above-described configuration is assembled like the control rod cluster 7 shown in FIG. 1 and inserted into the control rod guide tube 3 of the fuel assembly 1 forming the nuclear reactor core or pulled out, and It will be used for power control of the furnace. During the rated power operation of the nuclear reactor, the control rod 10 is in a state of being pulled up above the core. However, due to the flow of the coolant, the control rod 10 is moved to the upper part of the control rod guide tube 3 or the adjacent member of the control rod cluster guide tube 16. Even if the control rod 10 comes into contact, the wear damage of the cladding tube 21 is suppressed by the chrome plating following the range A to the range B. Further, even when the control rod 10 is rapidly inserted below the control rod guide tube 3 due to free fall or the like when the reactor core is urgently stopped, the cladding tube 21 in the range B and the dashpot portion 3a of the control rod guide tube 3 Since a predetermined gap is secured between them, the drop impact of the control rod 10 can be absorbed without impairing the insertability.

  Furthermore, since the transition portion D at the boundary between the ranges A and B has a tapered shape in which the film thickness continuously changes within a suitable length range, the chrome plating layers having two different film thicknesses are simply used. Compared with the formed one, the insertion property of the control rod 10 itself can be improved. If the transition part D is not set to an appropriate length (or not managed in production), the transition part D is too short (for example, the width of the transition part D is substantially 0). In this case, the fluid drag increases locally through the insertion process, and the insertion time may become longer, or the portion may be physically caught by the dashpot 3a, and the insertion property may be adversely affected. In addition, when the transition portion D is too long, if the transition portion D is too long in the range A direction, the thinned range of the chrome plating applied for wear resistance is widened, and the wear resistance is lowered. If it is too long in the direction, the insertability may be adversely affected.

  Next, a method of forming the surface treatment layer 29 having the above configuration on the cladding tube 21 will be described with reference to FIGS. 4A and 4B are schematic views of the apparatus for forming a surface treatment layer according to the present invention. FIG. 4A is a top view and FIG. 4B is a perspective view. 5 is a view for explaining the cross section of the surface treatment layer forming apparatus shown in FIG. 4A and the connection state of the power source. FIGS. 6 and 7 are cathode members inserted into the cladding tube 21. FIG. FIG. Further, FIG. 8 is a graph for explaining a method of controlling the current supplied to the surface treatment layer forming apparatus.

  As shown in FIGS. 4 and 5, the surface treatment layer forming apparatus according to the present invention includes a plurality of long tubes arranged around a cladding tube 21 (target member) immersed in a chrome plating solution 31. The first anode rod 32 is provided. When viewed from the top (see FIG. 4A), the first anode rods 32 are arranged at equal intervals or in a predetermined range on concentric circles around the cladding tube 21 to be plated. It arrange | positions so that it may become substantially equal intervals in the inside. Here, as an example, a configuration in which six first anode bars 32 are arranged is shown. Furthermore, the first anode rod 32 itself is formed in a curved shape, and as it goes in the depth direction of the solution 31, in other words, as it moves away from the connection portion of the first electrode 32 connected to the power source 38, 1 The anode rod 32 and the cladding tube 21 are arranged so that the distance between them is shortened, and the position is fixed by a fixing member (not shown).

  This is because the cladding tube 21 and the first anode rod 32 are long, so that the resistivity of the cladding tube 21 made of SUS (stainless steel) or the first anode rod 32 made of iron or the like is taken into account. In order to supply a uniform current over the entire length of 21, the distance between the cladding tube 21 and the first anode rod 32 is appropriately changed in accordance with the current attenuation of the surface due to the energization loss. In particular, when chrome plating is deposited on the surface of the long cladding tube 21, the current value for deposition is large (for example, about 200A), so the effect of the presence or absence of the above configuration is remarkable. It is possible to deposit chromium plating with a uniform film thickness over the entire length of the cladding tube 21. This portion becomes the surface treatment layer in the range A described above. As the chromium plating solution 31, a mixed solution of chromic acid and sulfuric acid containing a material constituting the chromium plating is heated to about 50 ° C. and used.

  A cylindrical lower holding member 33 is disposed on the lower side of the surface treatment layer forming apparatus, and a cylindrical upper holding member 34 is disposed on the upper side of the surface treatment layer forming apparatus. The lower end and the upper end of the cladding tube 21 are held inside. In the lower holding member 33, the cladding tube 21 is inserted into the lower holding member 33 from above using the weight of the upper end plug 22, the small diameter portion 23, and the screw portion 24 (see FIG. 3A). After that, the gap between the lower holding member 33 and the cladding tube 21 is stable, so that the current from the first anode rod 32 to the end of the cladding tube 21 is uniform in the circumferential direction of the cladding tube 21. It can be shielded. Further, the lower holding member 33 itself is made of an insulating material such as vinyl chloride, so that the current to the inner side of the lower holding member 33 can be completely shielded, and the dimension of the non-plated portion of the cladding tube 21 is accurate. I manage well.

  Furthermore, a taper portion 33a whose opening area decreases as it approaches the end portion of the cladding tube 21 is formed at the upper end portion of the lower holding member 33, and chromium formed on the cladding tube 21 by this taper portion 33a. The shape of the end portion of the plating is accurately controlled. Specifically, as the end of the cladding tube 21 is approached, the current from the first anode rod 32 gradually decreases due to the inclination of the taper portion 33a, and the film thickness of the deposited chromium plating is continuously increased accordingly. It is formed to decrease. The amount of decrease in the chromium plating film thickness can be changed by changing the inclination angle of the taper portion 33a, and a predetermined chromium plating film thickness with a desired width (width in the length direction of the cladding tube 21). Therefore, the film thickness can be set to 0 (non-formed state).

  In addition, the upper holding member 34 does not simply hold the cladding tube 21 but contributes to the formation of the shape of the upper end portion of the chrome plating, like the lower holding member 33. It is. Specifically, the upper holding member 34 is also formed of an insulating material such as vinyl chloride having no electrical conductivity, and further, the lower end portion of the upper holding member 34 is moved closer to the end portion of the cladding tube 21. A tapered portion 34a is formed in which the opening area is reduced. Due to the inclination of the taper portion 34a, the current from the second anode rod 37, which will be described later, gradually decreases as the end of the cladding tube 21 is approached. It is formed so as to decrease, and the film thickness can be reduced to 0 (non-formed state) from a predetermined chromium plating film thickness with a desired width (width in the length direction of the cladding tube 21).

  Further, the tapered portion 34a of the upper holding member 34 is provided with a plurality of holes or gaps, and by using the gas generated at the time of chrome plating deposition, the generated gas is appropriately discharged from the tapered portion 34a, The terminal portion of the chrome plating is stably in a desired position and a desired shape. Instead of the tapered portions 33a and 34a, a stepped portion having a plurality of steps may be used.

  As described above, by using the lower holding member 33 and the upper holding member 34, it is possible to reliably prevent the chrome plating from being deposited on the non-formed portion, and to stabilize the chrome plating terminal portion at a desired position and a desired shape. Can be formed. For example, even when chrome plating is formed on the tubular cladding tube 21, the position of the end portion of the chrome plating does not undulate in the circumferential direction. In the case of the present invention, unlike the conventional sacrificial electrode, the chrome plating does not deposit on the insulating lower holding member 33 and the upper holding member 34, so that the work such as removing the chrome plating is not necessary. Time cost can be reduced.

  A cylindrical shielding member 36 having a ring-shaped partition plate 35 is disposed on the lower end side of the first anode rod 32 on the upper side of the surface treatment layer forming apparatus and inside the first anode rod 32. In this arrangement, the cladding tube 21 penetrates the central portion of the member 36. A plurality of second anode rods 37 are arranged inside the shielding member 36. Similarly to the first anode rod 32, the second anode rod 37 is viewed from above (see FIG. 4A), and the second anode rods 37 are equidistant from each other on a concentric circle around the cladding tube 21. Alternatively, they are arranged and fixed at substantially equal intervals within a predetermined range. The partition plate 35 and the shielding member 36 are made of an insulating material such as vinyl chloride, like the lower holding member 33 and the like. In addition, here, as an example, a configuration in which three second anode rods 37 are arranged is shown. Thus, the shielding member 36 is disposed inside the first anode rod 32, and the second anode rod 37 is disposed further inside the shielding member 36, and the shielding member 36 is the first anode rod 32. Current from the plurality of second anode rods 37 arranged in the shielding member 36 is supplied to the cladding tube 21 in the shielding member 36. ing.

  In the case of the second anode rod 37, since the target range of the cladding tube 21 to be chrome-plated is not wide, it is not necessary to have a curved shape like the first anode rod 32, and a linear shape is used. With the above configuration, it is possible to uniformly deposit a thin chrome plating on a desired portion of the cladding tube 21, that is, on the cladding tube 21 in the shielding member 36. It becomes a processing layer. Further, the shielding member 36 can form chromium plating layers having different thicknesses so that the current from the first anode rod 32 and the current from the second anode rod 37 do not interfere with each other.

  And the ring-shaped partition plate 35 is provided in the lower end side of the shielding member 36, and the structure of this partition plate 35 contributes to formation of the transition part D mentioned above. Specifically, the partition plate 35 is provided with a circular through hole 38 through which the cladding tube 21 penetrates at the center thereof, and the inner wall surface 38 a of the through hole 38 faces the inside of the shielding member 36. That is, it is formed in a tapered shape inclined so that the opening area of the through hole 38 decreases from the first anode rod 32 side to the second anode rod 37 side.

  This aims at the same operation as the tapered portion 33a of the lower holding member 33 described above, and the shape of the chrome plating formed on the cladding tube 21 by the tapered inner wall surface 38a, that is, the transition portion D. The shape is controlled. Specifically, in the vicinity of the inner wall surface 38a, the current from the first anode rod 32 is not shielded, but the inner wall surface 38a goes around from the first anode rod 32 due to the inclination of the inner wall surface 38a toward the inner side of the shielding member 36. The current is gradually decreased, and the film thickness of the formed chrome plating is continuously reduced as the current flowing around decreases. The amount of decrease in the chrome plating film thickness can be changed by changing the inclination angle of the inner wall surface 38a, and the desired width (length of the cladding tube 21) can be changed from the chrome plating film thickness in the range A to the range B. The film thickness can be continuously changed to the chromium plating film thickness.

  Further, the size of the through hole 38 (distance from the surface of the cladding tube 21 to the inner wall surface 38a of the through hole 38) and the distance from the partition plate 35 to the tip of the second anode rod 37 also control the shape of the transition portion D. Therefore, the distance from the surface of the cladding tube 21 to the inner wall surface 38a of the through hole 38 is determined in consideration of the current flowing from the first anode rod 32, and the tip of the second anode rod 37 is It is arranged so as to be in the vicinity of the boundary between the range B and the transition part D. A plurality of steps (stepped portions) may be provided on the inner wall surface 38a instead of the tapered inner wall surface 38a.

  In addition, in the apparatus for forming a surface treatment layer according to the present invention, not only the configuration of the anode rods 32 and 37 and the shielding members 33 and 36 described above, but also the configuration on the cathode side, the connection state of the power source, and the supply of current The method has also been devised in a unique way.

  Specifically, the cathode side is not a conventional configuration in which the end portion of the cladding tube 21 is connected to the power source side, but a cathode member 41 whose end portion is connected to the power source side as shown in FIG. A plurality of leaf springs 42a that the cathode member 41 has are inserted into the hollow cladding tube 21 and are configured to contact the inner wall surface of the cladding tube 21 with an equal contact pressure over the entire length. As shown in FIG. 6A, the cathode member 41 is provided with a copper square bar 42 (conductive member) having a length equivalent to that of the cladding tube 21, and a plurality of the cathode members 41 on the surface of the square bar 42. And a strip-shaped leaf spring 42a (elastic member) having an elastic force.

  In consideration of the fact that the cladding tube 21 is thin and has a large specific resistance of the cladding tube 21 itself made of SUS or the like, copper or the like having a good electrical conductivity is used. By using the plate spring 42a having a force, a large number of contacts are made to contact the inner wall surface of the cladding tube 21 with a uniform contact pressure, so that the current flowing into the surface of the cladding tube 21 is stably and evenly energized. It is a thing. The number of leaf springs 42a needs to be a number that allows a uniform current to flow on the surface of the cladding tube 21 in consideration of the size and length of the cladding tube 21 and the ease of energization. With the above configuration, it is possible to deposit chromium plating evenly on the surface of a long object to be plated such as the cladding tube 21 of the control rod.

  In the surface treatment layer forming apparatus according to the present invention, the surface treatment layer having a two-stage structure with different film thicknesses is formed. For this purpose, the contact density of the cathode member 41 in the range A is increased, It is desirable to make chrome plating easy to deposit and to lower the contact density of the cathode member 41 in the range B so that it is difficult to form the chrome plating. Therefore, the density of the leaf springs 42a provided on the square bars 42 of the cathode member 41 may be increased in the portion corresponding to the range A and decreased in the portion corresponding to the range B.

  Further, it is desirable to arrange the energization start position of the cathode member 41, that is, the position of the leaf spring 42 a closest to the power supply side to be below the water surface of the solution 31. As a result, heat generation due to energization of the cladding tube 21 can be prevented, and deterioration of the material or deformation of the cladding tube 21 can be suppressed.

  Moreover, as another structure of a cathode member, what is shown in FIG.6 (b) may be sufficient. The cathode member 40 shown in FIG. 6 (b) is provided inside a mesh member 43 (net-like member) in which a wire having good conductivity, for example, a wire obtained by silver-plating a thin copper wire is knitted into a cylindrical mesh. The cathode member 41 shown in FIG. 6A is inserted, and these are inserted into the cladding tube 21 and used. By using the cathode member 40, the mesh member 43 is inserted between the cathode member 41 and the cladding tube 21, and the cathode member 40 is placed on the inner wall surface of the cladding tube 21 in more places. Evenly and more stably, contact energization can be performed. In addition, the contact surface pressure can be reduced as the number of contact points increases, and contact scratches and energization marks on the inner wall surface of the cladding tube 21 can be prevented.

  Further, as another example of the structure of the cathode member, as shown in FIGS. 7A and 7B, if it is a protrusion-like elastic member that applies an even contact pressure to the inner wall surface of the cladding tube 21, But you can. Specifically, the cathode member 44 of FIG. 7A is provided with a plurality of cylindrical plate springs 44a on the surface of the square bar 42, and the inner wall surface of the cladding tube 21 is elastically deformed by the plate springs 44a. It is intended to touch evenly. Further, the cathode member 45 of FIG. 7B is provided with a plurality of thin wire wires 44a on the surface of the square bar 42, and is equal to the inner wall surface of the cladding tube 21 by elastic deformation of the ring wire 45a. It is something that comes in contact. The cathode members 44 and 45 shown in FIGS. 7 (a) and 7 (b) may be used alone and inserted into the cladding tube 21, or as shown in FIG. 6 (b). It may be inserted into the member 43 and inserted into the cladding tube 21 together with the mesh member 43.

  In addition, as another configuration example of the cathode member, as shown in FIG. 8, as long as an equal contact pressure is obtained on the inner wall surface of the cladding tube 21. Specifically, the cathode member 46 in FIG. 8 includes a cylindrical pipe 47 (conductive member) made of copper or the like having good conductivity and slits 47 a in the longitudinal direction, and the longitudinal direction of the pipe 47. And an inflatable balloon 48 (inflatable member) disposed therein. Here, the pipe 47 has a length equivalent to that of the cladding tube 21 and can be inserted into the hollow portion of the cladding tube 21. Further, when the balloon 48 is inflated, the pipe 47 becomes the inner wall surface of the cladding tube 21. It is a size that can be touched. The balloon 48 expands when the inside is pressurized with air or the like, and is made of a heat-resistant material. In use, the cathode member 46 is inserted into the hollow portion of the cladding tube 21 and air or the like is injected from the tube 48 a to inflate the balloon 48 so that the pipe 47 is in close contact with the inner wall surface of the cladding tube 21.

  In this way, by using the cathode member having the above configuration inserted into the cladding tube 21 and using the cathode member over the entire length of the cladding tube 21, a plurality of good contact states can be obtained with uniform contact pressure on the inner wall surface. Therefore, even if there is a temperature change due to energization or the like at the contact portion between the cladding tube 21 and the cathode member, the energization on the surface of the cladding tube 21 becomes constant, and it is even over the entire length of the cladding tube 21. A chromium plating film thickness can be deposited. In addition, when the cathode member having the above-described configuration is used, scratches and energization marks due to the cathode member do not remain, and post-processing such as removal of the scratches is not necessary, and cost can be reduced.

Furthermore, in the apparatus for forming a surface treatment layer according to the present invention, as shown in FIG. 5, a power source 38 and a power source 39 are independently connected to the first anode rod 32 and the second anode rod 37, respectively. The current supplied to the first anode rod 32 and the second anode rod 37 is controlled independently. Specifically, as shown in FIG. 9A, in the power source 38 that supplies current to the first anode rod 32, the chromium plating deposited in the range A has a desired film thickness (first predetermined film thickness). It is controlled so that the current I1 (first predetermined current) is supplied for a predetermined time t ₁ until it becomes, and the power source 39 that supplies the current to the second anode rod 37 has a chromium plating deposited in the range B. but between the predetermined time t ₂ until thin desired thickness than the range a (second predetermined thickness), the current I2 (second predetermined current) is controlled to be supplied. Then, the power supply 39, and after a predetermined time t ₂ has elapsed, the current is reduced to a current I3 (third predetermined current) is controlled to be supplied until the predetermined time t _1. This is because, if a chrome plating layer having a desired film thickness is formed in the range B and then the current is lowered, the potential difference is reversed and a corrosive environment is created, and the surface of the deposited chrome plating is etched. Since there is a possibility of affecting insertability due to wear resistance and slipperiness deterioration, by continuing to pass a current I3 lower than the current value at which the chrome plating is deposited, the chrome plating can be made without increasing the thickness of the chrome plating. This is for maintaining the surface well.

Further, as shown in FIG. 9B, the current control in the power source 39 may be reversed from that in FIG. 9A. Specifically, in the power supply 39 supplies current to the second anode rod 37, the predetermined time t ₁ until the predetermined time t ₃ when minus a predetermined time t _2, the lower current I3 from current value chromium plating is precipitated first is supplied to the second anode rod 37, and, after a predetermined time t ₃ has elapsed, until the predetermined time t _1, that is, until the chrome plating is deposited chromium plating and range B is deposited range a becomes a desired thickness A constant current I2 larger than the current I3 and smaller than the current I1 is supplied to the second anode rod 37. Here, in the power supply 38 which supplies an electric current to the 1st anode rod 32, the same electric current control as Fig.9 (a) is performed.

  In order to favorably deposit the chromium plating on the cladding tube 21, the current is made to flow backward before plating, that is, the current flows from the cathode side cladding tube 21 toward the anode rods 32 and 37. After activating the surface of the cladding tube 21 or activating the surface of the cladding tube 21 by acid cleaning with acidic chemicals such as hydrochloric acid and nitric acid, it is desirable to deposit chromium plating by the above method. .

  As described above, by using the apparatus for forming a surface treatment layer according to the present invention, a surface treatment layer having a two-stage structure having different film thicknesses as shown in FIG. 3 can be formed simultaneously. The transition part between the surface treatment layers having different film thicknesses can have a desired shape in which the film thickness continuously changes. The two-stage surface treatment layer formed in this way has no overlapped portion, so it has excellent adhesion and wear resistance, and the surface of the surface treatment layer including the transition portion is smooth. can do. Further, the film thickness of the surface treatment layer can be formed stably and uniformly, and the position and shape of the transition part and the terminal part of the surface treatment layer can be stably controlled to a desired position and shape. Furthermore, since the surface treatment layer having a two-stage structure is formed at the same time, it is possible to simplify the construction process and reduce the construction cost. If the surface treatment layer is applied to the nuclear reactor control rod, a product with excellent wear resistance and insertability can be provided at low cost.

  In the present invention, the formation of the surface treatment layer on the reactor control rod has been mainly described as an example. However, the method and apparatus for forming the surface treatment layer according to the present invention are not limited to the reactor control rod. As long as a surface treatment layer having a multistage structure with different film thicknesses is required, any surface treatment layer can be applied, and application to a long object to be plated is particularly suitable.

It is a figure which shows an example of the control rod (control rod cluster) inserted in a fuel assembly used for a pressurized water reactor and a fuel assembly. It is a figure which shows the positional relationship of the control rod at the time of an operation | movement and a stop with respect to the related member of a fuel assembly and a control rod. FIG. 3A shows the structure of the entire control rod, and FIG. 3B is an enlarged view of a region C in FIG. FIG. 4A is a schematic top view of a surface treatment layer forming apparatus according to the present invention, and FIG. 4B is a perspective view thereof. It is a figure explaining the cross section of the formation apparatus of the surface treatment layer shown to Fig.4 (a), and the connection state of a power supply. It is a figure which shows an example of the genital side electrode inserted in a cladding tube. It is a figure which shows the other example of the genital side electrode inserted in a cladding tube. It is a figure which shows the further another example of the genital side electrode inserted in a cladding tube. It is a graph explaining the control method of the electric current supplied to the formation apparatus of the surface treatment layer which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel assembly 3 Control rod guide tube 7 Control rod cluster 10 Control rod 21 Cladding tube 29 Surface treatment layer 32 First anode rod 33 Lower holding member 35 Partition plate 36 Shield member 37 Second anode rod 38 Power source (first anode rod) side)
39 Power supply (second anode rod side)
41 Cathode member

Claims (18)

A solution containing a material constituting the surface treatment layer, in which a target member forming the surface treatment layer is immersed;
A plurality of first anode rods having a curved shape in which the distance between the target member and the target member is shortened in the depth direction of the solution, and a plurality of the anode members are arranged at substantially equal intervals around the target member.
An insulating shielding member that is disposed inside the plurality of first anode rods and through which the target member penetrates a central portion;
A plurality of second anode rods arranged inside the shielding member and arranged at substantially equal intervals around the target member;
An insulating partition plate provided at the lower end of the shielding member;
It is provided at the center of the partition plate and is formed in a tapered shape or a staircase shape so that the target member penetrates and the opening area decreases from the first anode rod side to the second anode rod side. Through holes,
An apparatus for forming a surface treatment layer, comprising: a plurality of power supplies connected to the first anode rod and the second anode rod, each independently supplying a current. In the formation apparatus of the surface treatment layer of Claim 1,
An insulating upper holding member and a lower holding member for holding the upper end portion and the lower end portion of the target member are provided, and an end portion of the upper holding member and the lower holding member on the side holding the target member is provided as the target. An apparatus for forming a surface treatment layer, characterized by having a tapered shape or a stepped shape so that an opening area thereof decreases toward an end portion side of the member. In the surface treatment layer forming apparatus according to claim 1 or 2,
When the target member has a hollow shape,
A conductive member having a length equivalent to that of the target member and having a size capable of being inserted into a hollow portion of the target member, and a plurality of conductive members provided on the surface of the conductive member, and configured from a material having good conductivity. A cathode member having an elastic member formed,
An apparatus for forming a surface treatment layer, wherein the negative electrode member is inserted into a hollow portion of the target member, and the elastic member is brought into contact with an inner wall surface of the target member. In the formation apparatus of the surface treatment layer of Claim 3,
A strip-shaped plate spring, a cylindrical plate spring, or a ring-shaped wire is used as the elastic member. In the formation apparatus of the surface treatment layer of Claim 3 or Claim 4,
Covering the outside of the cathode member with a conductive cylindrical mesh member, inserting the cathode member together with the mesh member into a hollow portion of the target member, and passing the elastic member through the mesh member, An apparatus for forming a surface treatment layer, wherein the surface treatment layer is brought into contact with an inner wall surface of a target member. In the surface treatment layer forming apparatus according to claim 1 or 2,
When the target member has a hollow shape,
The conductive member has a length equivalent to that of the target member, is a size that can be inserted into a hollow portion of the target member, and has a cylindrical conductive member with good conductivity provided with a slit in the longitudinal direction. A negative electrode member having an inflatable expansion member disposed in the conductive member along the longitudinal direction;
An apparatus for forming a surface treatment layer, wherein the cathode member is inserted into a hollow portion of the target member, the expansion member is expanded, and the conductive member is brought into contact with an inner wall surface of the target member. In the surface treatment layer forming apparatus according to any one of claims 1 to 6,
One power source is controlled to supply a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined thickness is formed,
The other power supply supplies a constant second predetermined current smaller than the first predetermined current to the second anode rod until a surface treatment layer having a second predetermined thickness smaller than the first predetermined thickness is formed. Then, after the surface treatment layer having the second predetermined thickness is formed, a third predetermined current lower than the current for forming the surface treatment layer is applied until the supply of current to the first anode rod is stopped. A surface treatment layer forming apparatus controlled to be supplied to a second anode rod. In the surface treatment layer forming apparatus according to any one of claims 1 to 6,
One power source is controlled to supply a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined thickness is formed,
On the other hand, the other power source has a predetermined time obtained by subtracting a time for forming a surface treatment layer having a second predetermined film thickness smaller than the first film thickness from a time for forming a surface treatment layer having a first film thickness. A third predetermined current lower than a current for forming the surface treatment layer is supplied to the second anode rod, and the first treatment film is formed until the surface treatment layer having the first predetermined film thickness and the second predetermined film thickness is formed. An apparatus for forming a surface treatment layer, wherein the apparatus is controlled to supply a constant second predetermined current smaller than a predetermined current to the second anode rod. The target member on which the surface treatment layer is formed is a cladding tube of a control rod for a nuclear reactor,
Using the surface treatment layer forming apparatus according to any one of claims 1 to 8,
A surface treatment layer having a two-stage structure with different film thicknesses is formed on the cladding tube, and the surface treatment layers with different film thicknesses are formed so as to continuously change within a predetermined range. A control rod for a nuclear reactor in which a surface treatment layer is formed. Immerse the target member that forms the surface treatment layer in a solution containing the material constituting the surface treatment layer,
A plurality of the anode members are arranged at substantially equal intervals around the target member, and a current from one power source is supplied to the curved first anode rod whose distance from the target member becomes shorter in the depth direction of the solution. Supply
The second power source is disposed on the inner side of the insulating shielding member on the inner side of the plurality of first anode rods, and a plurality of second anode rods are arranged at substantially equal intervals around the target member penetrating the central portion. Supply current from
The target member penetrates through the center of the insulating partition plate provided at the lower end of the shielding member, and the opening area decreases from the first anode rod side to the second anode rod side. A method for forming a surface treatment layer, characterized by forming a tapered or stepped through-hole and gradually reducing the current flowing from the first anode rod into the shielding member. In the formation method of the surface treatment layer according to claim 10,
The insulating upper holding member that holds the upper end portion and the lower end portion of the target member, and the end portion of the lower holding member that holds the target member toward the end side of the target member has an opening area thereof A method of forming a surface treatment layer, wherein the surface treatment layer is formed in a taper shape or a step shape that decreases, and the current from the first anode rod and the second anode rod is gradually reduced. In the formation method of the surface treatment layer of Claim 10 or Claim 11,
When the target member has a hollow shape,
A conductive member having a length equivalent to that of the target member and having a size capable of being inserted into a hollow portion of the target member, and a plurality of conductive members provided on the surface of the conductive member, and configured from a material having good conductivity. A method for forming a surface treatment layer, comprising: inserting a negative electrode member having a formed elastic member into a hollow portion of the target member and bringing the elastic member into contact with an inner wall surface of the target member. In the formation method of the surface treatment layer according to claim 12,
The method of forming a surface treatment layer, wherein the elastic member is a strip-shaped plate spring, a cylindrical plate spring, or a ring-shaped wire. In the formation method of the surface treatment layer according to claim 12 or claim 13,
Covering the outside of the cathode member with a conductive cylindrical mesh member, inserting the cathode member together with the mesh member into a hollow portion of the target member, and passing the elastic member through the mesh member to the target A method for forming a surface treatment layer, which comprises contacting an inner wall surface of a member. In the formation method of the surface treatment layer of Claim 10 or Claim 11,
When the target member has a hollow shape,
The conductive member has a length equivalent to that of the target member, is a size that can be inserted into a hollow portion of the target member, and has a cylindrical conductive member with good conductivity provided with a slit in the longitudinal direction. Along the longitudinal direction, a negative electrode member having an inflatable expansion member disposed inside the conductive member is inserted into a hollow portion of the target member,
A method for forming a surface treatment layer, wherein the expansion member is expanded, and the conductive member is brought into contact with an inner wall surface of the target member. In the formation method of the surface treatment layer in any one of Claims 10 thru | or 15,
One of the power supplies supplies a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined film thickness is formed,
The other power source supplies a constant second predetermined current smaller than the first predetermined current to the second anode rod until a surface treatment layer having a second predetermined film thickness that is thinner than the first predetermined film thickness is formed. Then, after the surface treatment layer having the second predetermined thickness is formed, a third predetermined current lower than the current for forming the surface treatment layer is applied until the supply of current to the first anode rod is stopped. A method for forming a surface treatment layer, wherein the surface treatment layer is supplied to a second anode rod. In the formation method of the surface treatment layer in any one of Claims 10 thru | or 15,
One of the power supplies supplies a constant first predetermined current to the first anode rod until a surface treatment layer having a first predetermined film thickness is formed,
The other power source is a predetermined time obtained by subtracting a time for forming a surface treatment layer having a second predetermined film thickness thinner than the first film thickness from a time for forming a surface treatment layer having a first film thickness. A third predetermined current lower than a current for forming the surface treatment layer is supplied to the second anode rod, and the first treatment film is formed until the surface treatment layer having the first predetermined film thickness and the second predetermined film thickness is formed. A method for forming a surface treatment layer, wherein a second predetermined current smaller than a predetermined current is supplied to the second anode rod. The target member on which the surface treatment layer is formed is a cladding tube of a control rod for a nuclear reactor,
Using the method for forming a surface treatment layer according to any one of claims 10 to 17,
A surface treatment layer having a two-stage structure with different film thicknesses is formed on the cladding tube, and the surface treatment layers with different film thicknesses are formed so as to continuously change within a predetermined range. A control rod for a nuclear reactor in which a surface treatment layer is formed.

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