JP2012098217A - Surface treatment device for control rod of nuclear reactor, and program for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automated surface treatment technology for a control rod of a nuclear reactor having a structure hard for a uniform polish processing.SOLUTION: A surface treatment device 10 for a control rod of a nuclear reactor includes a tool 30 mounted with a rotating polishing-member 35, detection means 20 for detecting a contact force of the polishing-member 35 that comes into contact with a surface of the control rod of the nuclear reactor, and a pedestal 11 for making the tool 30 scan the surface so that the contact force may be within a prescribed range.

Description

  The present invention relates to a surface treatment technique for improving a residual stress generated in a manufacturing process of a control rod for a nuclear reactor.

The nuclear reactor control rod is a cross-shaped elongated U-shaped blade having a neutron absorber disposed therein, and adjusts the power distribution of the nuclear reactor and controls the core reactivity.
In this blade, a tensile residual stress is generated in a manufacturing process in which a stainless steel sheet is bent and further welded. There is a concern that this tensile residual stress may cause stress corrosion cracking in the blade in the reactor water environment, and there is a demand for improving this tensile residual stress.
As a method for improving such tensile residual stress, there is known a method of causing plastic deformation on the surface by rotating and pressing a tool coated with an abrasive, and improving tensile residual stress to compressive stress (for example, Patent Documents 1, 2).

JP-A-8-174422 JP 2007-178157 A

By the way, it is known that there is a significant correlation between the surface roughness after polishing and the residual stress. On the other hand, in view of the fact that the above-described work for improving the tensile residual stress is all performed manually, it can be said that it is difficult to improve the tensile residual stress uniformly throughout. In particular, it can be said that uniform polishing to the U-shaped R portion of the blade of the control rod is difficult.
Therefore, conventionally, the improvement quality of the tensile residual stress in the control rod has a problem that must depend on the skill level of the operator's skill.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an automated surface treatment technique for a control rod for a nuclear reactor having a structure in which uniform polishing is difficult to perform.

  In a nuclear reactor control rod surface treatment apparatus, a tool equipped with a rotating abrasive, a detection means for detecting an abutting force of the abrasive abutting on the surface of the reactor control rod, and the abutting force within a predetermined range And a gantry that scans the tool on the surface.

  ADVANTAGE OF THE INVENTION According to this invention, the automated surface treatment technique is provided with respect to the control rod for nuclear reactors which has a structure where uniform polishing construction is difficult.

The block diagram which shows embodiment of the surface treatment apparatus of the control rod for reactors which concerns on this invention. Explanatory drawing of the principle which detects contact force in embodiment. (A)-(C) is operation | movement explanatory drawing of the surface treatment apparatus of the control rod for reactors which concerns on embodiment. (D)-(F) is operation | movement explanatory drawing of the surface treatment apparatus of the control rod for reactors which concerns on embodiment. The flowchart which shows control of the surface treatment apparatus of the control rod for reactors concerning embodiment. (A) is a side view showing another embodiment of the mounted abrasive, (B) is a cross-sectional view showing a BB cross section of FIG. 6 (A), (C) is an abrasive having an eccentric function A side view and (D) are sectional views showing a DD section of Drawing 6 (C). (A) is a perspective view of a control rod for a nuclear reactor, (B) is a sectional view of a blade, and (C) is an explanatory view of a locus of an abrasive with respect to the blade surface.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
First, referring to FIG. 7, a description will be given of a control rod for a reactor to which the present invention is applied. As shown in FIG. 7A, the reactor control rod 40 (hereinafter also simply referred to as “control rod 40”) has a blade 42 formed from a tie rod 41 serving as an axial center so as to have a cross-shaped cross section. Has been. As shown in the cross-sectional view of FIG. 7B, the blade 42 is welded to the tie rod 41 at the end of a sheath 43 made of U-shaped stainless steel plate, and a plurality of neutron absorbers are contained therein. 44 is arranged.

  The control rod 40 is held by a clamping device (not shown) that clamps both ends in the longitudinal direction when the surface treatment is performed. The clamping device can be rotated at an arbitrary angle around the tie rod 41 to switch the surface of the blade 42 facing the surface treatment device 10.

As shown in FIG. 1, the reactor control rod surface treatment apparatus 10 (hereinafter simply referred to as “apparatus 10”) includes a tool 30 equipped with a rotating abrasive 35 and a reactor control rod 40 (FIG. 7). The detecting means 20 for detecting the abutting force of the abrasive 35 that abuts on the surface of the above and the gantry 11 for scanning the tool 30 on the surface so that the abutting force falls within a predetermined range.
And the connection part 12 has connected the detection means 20 and the tool 30 so that attachment or detachment is possible.

The detection means 20 includes a support member 22 that supports the tool 30, a restriction member 21 that restricts the displacement of the support member 22 relative to the gantry 11, and an elastic member 24 that elastically couples the support member 22 and the gantry 11. And a detector 23 that detects the biasing force ΔW or the deformation amount ΔY of the elastic member 24 as a contact force.
Here, the detector 23 is specifically a load cell that detects the biasing force ΔW of the elastic member 24 or a displacement sensor that detects the deformation amount ΔY of the elastic member 24.
The elastic member 24 is provided with a damper function (not shown) so as not to be excited by the rotational vibration of the abrasive 35.

Here, the principle of detecting the contact force of the abrasive 35 in the apparatus 10 will be described with reference to FIG.
When the state in which the abrasive 35 is not in contact with the control rod 40 (the solid line portion in FIG. 1 and the one-dot chain line portion in FIG. 2) is taken as the origin, the elasticity generated by the abrasive 35 in contact with the control rod 40 The urging force ΔW or the deformation amount ΔY of the member 24 represents the following equation as the elastic coefficient k of the elastic member 24.
ΔW = k · ΔY (1)

  Here, the urging force ΔW acting downward in FIG. 2 corresponds to the contact force from the abrasive 35 to the control rod 40. Therefore, the contact force of the abrasive 35 can be derived by detecting the biasing force ΔW of the elastic member 24, or the deformation amount ΔY can be detected and derived from the above equation (1). And when it is going to adjust the contact force of the abrasive 35, it can carry out by adjusting the space | interval of the surface of the control rod 40, and the mount frame 11. FIG.

As shown in FIG. 1, the tool 30 has a motor 32 fixed to a housing 31 that supports an abrasive 35 around the Z axis. Then, the rotational power of the motor 32 is transmitted to the pulley 34 via the transmission belt 33, and the abrasive 35 provided coaxially with the pulley 34 is rotated.
Here, the motor 32 is controlled to rotate at a constant speed so that the number of rotations thereof becomes a set value even if the contact force applied to the abrasive 35 varies.

The abrasive 35 has a thick circular disk shape, and a shaft body (not shown) integrally formed with the pulley 34 is passed through and fixed to the center hole thereof. The abrasive 35 is obtained by adhering abrasive grains to a synthetic fiber having an elastic nonwoven fabric structure. For example, a Scotch Bright (registered trademark) CNS product manufactured by 3M can be suitably used.
When the outer peripheral surface of the rotating abrasive 35 is moved while being pressed against the surface of the control rod 40, the tensile residual stress is improved to the compressive stress.

  It is preferable to use the abrasive 35 properly because the polishing conditions vary depending on the object to be polished (for example, the flat portion and the R portion of the control rod). Further, since the rotational speed of the abrasive 35 is a factor that greatly affects the quality of the polished surface, fluctuation within a certain range is allowed, but when fluctuation exceeding a certain allowable value occurs, the polishing work is automatically performed. It is desirable to interrupt.

The surface scanning means 13 can set the gantry 11 at an arbitrary angle at an arbitrary position in the space near the control rod, and can move the gantry 11 at a constant linear velocity between the two set points. Further, the surface scanning means 13 moves while adjusting the distance between the surface of the control rod 40 and the gantry 11 in accordance with a command from the control means 14 to be described later in the process of linearly moving between the two points set as described above. It can be done.
Specifically, the surface scanning unit 13 can be realized by a multi-indirect manipulator or the like, but is not limited thereto.

With reference to FIG. 7C, the locus of the abrasive that scans the surface of the blade 42 will be described.
In this manner, the gantry 11 (FIG. 1) is scanned so that the abrasive 35 reciprocates on the surface of the control rod 40 in the direction from the axial center to the blade tip (appropriately shown in FIGS. 3A and 3B). )reference). The abrasive 35 slides in the axial direction and reciprocates in the direction from the axial center toward the blade tip. Thus, the slide width in the axial direction of the abrasive 35 is determined so that the polishing regions c1, c2, c3 formed by the reciprocation of the gantry 11 have an overlap with the polishing region by the previous reciprocation.

The tensile residual stress existing on the surface of the control rod 40 tends to be linearly continued along the axial direction. For this purpose, the direction of the axis of rotation of the abrasive 35 is aligned with the linear direction, and polishing is performed by reciprocating the gantry 11 in the linear vertical direction.
Note that the amount of overlap is determined by automatically recognizing the polishing regions c1, c2, and c3 based on the difference in the intensity of reflected light on the surface of the polishing surface by an image sensing mechanism (not shown) attached to the tip of the tool 30. Done. And polishing construction can be carried out efficiently by minimizing the overlap margin.

  The control means 14 instructs the motor 32 to determine the rotational speed of the abrasive 35, operates the surface scanning means 13 of the gantry 11 according to the set moving speed, contact force, polishing direction and number of polishings of the abrasive 35, Based on a signal (biasing force ΔW or deformation amount ΔY) from the detection means 20, the trajectory of the gantry 11 is corrected, and an instruction to attach / detach the detection means 20 and the tool 30 in the connecting portion 12 is given.

  Further, the control means 14 has storage means for storing the position information of the scanned gantry 11, and calculation means for calculating the wear amount of the abrasive 35 by comparing the past position information and the current position information, Based on the calculation result, the rotational speed of the abrasive 35 is changed to control the peripheral speed. Further, it has a function of instructing the surface scanning means 13 to replace the tool 30 when the wear amount exceeds a specified value.

  That is, when the abrasive 35 is worn out, the position of the gantry 11 comes close to the surface of the control rod 40 by a reduced radius compared to the state before the wear. This reduced radius can be derived from the position information of the gantry 11 before wear and the position information of the gantry 11 after wear. Alternatively, the reduced radius of the abrasive 35 can be directly detected by a distance sensor (not shown) provided on the tool 30.

Further, when the abrasive 35 is worn, the peripheral speed of the abrasive 35 decreases under a condition where the rotational speed is constant. From the viewpoint of maintaining the uniformity of the polished surface, the peripheral speed may be constant. desired. Therefore, it is possible to perform control to increase the rotational speed of the motor 32 in accordance with the reduced radius of the abrasive 35.
Further, when the radius of decrease exceeds the specified value, it can be determined that the life of the abrasive 35 has expired, and the replacement timing can be determined.

As shown in FIGS. 3A to 3C and FIGS. 4E and 4F, when polishing the flat portion and the R portion of the control rod 40, separate abrasives 35 (35A and 35B) are used. Use.
This is because the contact area of the abrasive 35 is different between the flat part and the R part, so even polishing with the same contact force does not result in uniform polishing. Therefore, when the polishing region changes from the flat portion to the R portion, the abrasive material type is automatically changed, and the polishing radius can be changed with the uniform contact force by changing the rotation radius of the abrasive material 35.

As shown in FIG. 4D, a tool 30A equipped with a polishing material 35A for a flat portion of a control rod and a tool 30B equipped with a polishing material 35B for the R portion are placed on the mounting table 36. . In addition, a tool 30 for replacing the abrasive 35 whose life has expired is also placed.
Detection of the boundary portion between the flat portion and the curved portion can be performed by recognizing the shape of the object to be polished by prior sensing using a laser position detection sensor or the like. As described above, by automatically identifying the boundary portion, it is possible to automatically replace the abrasive and sort the type.

The control operation of the apparatus 10 will be described with reference to the flowchart of FIG.
First, the control means 14 loads the scanning program of the surface scanning means 13 (S11), and further loads the set value of the contact force of the selected abrasive 35 (S12). Then, this scanning program is executed (S13), and polishing of the polishing region (flat portion of the control rod) targeted by the selected abrasive 35 is started (S14: No).

  When the signal (the biasing force ΔW or the deformation amount ΔY) relating to the contact force output by the detection means 20 is within the allowable range (S15: No), the gantry 11 is in contact with the surface of the control rod 40 according to the scanning program. Scanning is performed while maintaining the interval (S13, S14: No). And when it remove | deviates from the allowable range (S15: Yes), the space | interval of the mount 11 and the surface of the control rod 40 is adjusted so that it may be in an allowable range (S16), and the positional information after adjustment is memorize | stored (S16). S17).

  Since the adjustment amount of the interval between the gantry 11 and the surface of the control rod 40 is related to the amount of abrasion of the abrasive 35, the rotation speed is reset so that the peripheral speed of the abrasive 35 becomes constant. (S18). In this way, when the selected polishing material 35 continues to polish the target polishing region (S19: No), when the adjustment amount of the interval becomes larger than the allowable range, If the lifetime has expired, the tool 30 is replaced (S20).

  When the polishing of the polishing region (flat portion of the control rod) targeted by the selected abrasive 35 is completed (S14: Yes), the tool 30 is then replaced with a tool 30 for polishing the R portion of the control rod. (S21: No, S22), and the flow from S12 to S21 is repeated. Then, when the polishing of the entire area of the control rod is completed, the program is terminated (S21: Yes).

Another embodiment of the abrasive to be mounted will be described with reference to FIG.
In the tool 30 (FIG. 1), a plurality of abrasives 35 can be stacked and attached to the rotating shaft 37. Thereby, the scanning distance of the gantry 11 can be shortened and the surface treatment of the control rod can be made efficient.

However, when the abrasive 35 is formed of a laminate, as shown in FIGS. 6A and 6B, a step may occur on the peripheral surface of the laminate due to variations in the diameter of each abrasive 35.
If the presence of such a step is left as it is, polishing unevenness is caused on the surface of the control rod, leading to a reduction in polishing quality.

  Therefore, as shown in FIGS. 6C and 6D, each of the abrasives 35 is decentered by the decentering means 38 so that a portion without such a step is formed. As described above, it is clear that the polishing unevenness on the surface of the control rod is considerably eliminated by eliminating the step in at least a part of the laminate of the abrasive 35.

  In order to recognize the presence of such a step, it is conceivable to provide sensors that individually detect the reaction force applied to each abrasive 35 from the contact surface. Then, the eccentric means 38 is adjusted so that the load values output from the individual sensors are uniform.

The present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented within the scope of the common technical idea.
For example, in the surface treatment apparatus, each unit can be realized as a function program by a computer, and the function programs can be combined to operate as a surface treatment program.

  DESCRIPTION OF SYMBOLS 10 ... Surface treatment apparatus, 11 ... Mount, 12 ... Connection part, 13 ... Surface scanning means, 14 ... Control means, 20 ... Detection means, 21 ... Restriction member, 22 ... Support member, 23 ... Detector, 24 ... Elastic member , 30, 30A, 30B ... tool, 31 ... housing, 32 ... motor, 33 ... transmission belt, 34 ... pulley, 35, 35A, 35B ... abrasive, 36 ... mounting table, 37 ... rotating shaft, 38 ... eccentric means 40 ... Reactor control rod, 41 ... Tie rod, 42 ... Blade, 43 ... Sheath, 44 ... Neutron absorber, c1, c2, c3 ... Polishing region, [Delta] Y ... Deformation amount, [Delta] W ... Energizing force.

Claims (8)

A tool with rotating abrasive, and
Detection means for detecting the contact force of the abrasive that contacts the surface of the nuclear reactor control rod;
A surface treatment apparatus for a control rod for a nuclear reactor, comprising: a gantry that scans the surface of the tool so that the contact force is within a predetermined range. The surface treatment apparatus for a nuclear reactor control rod according to claim 1,
The detection means includes
A support member for supporting the tool;
A regulating member for regulating the displacement of the support member relative to the gantry in one direction;
An elastic member for elastically coupling the support member and the gantry;
And a detector for detecting an urging force or a deformation amount of the elastic member as the abutting force. In the surface treatment apparatus for a nuclear reactor control rod according to claim 1 or 2,
A connecting part for detachably connecting the detecting means and the tool;
A surface treatment apparatus for a reactor control rod, comprising: a tool equipped with a polishing material for a flat portion of the reactor control rod; and a mounting table for the tool equipped with a polishing material for the R portion. . In the surface treatment apparatus for a control rod for a nuclear reactor according to any one of claims 1 to 3,
Storage means for storing positional information of the scanned gantry;
A calculation means for calculating the amount of wear of the abrasive by comparing the past position information and the current position information,
A surface treatment apparatus for a control rod for a nuclear reactor, wherein the rotational speed of the abrasive is changed based on the calculation result to control the peripheral speed. The surface treatment apparatus for a control rod for a nuclear reactor according to any one of claims 1 to 4,
Storage means for storing positional information of the scanned gantry;
A calculation means for calculating the amount of wear of the abrasive by comparing the past position information and the current position information,
A surface treatment apparatus for a control rod for a nuclear reactor, wherein the tool is replaced when the amount of wear exceeds a specified value. In the surface treatment apparatus for a control rod for a nuclear reactor according to any one of claims 1 to 5,
The tool is
Laminate and install multiple abrasives,
An apparatus for treating a surface of a control rod for a nuclear reactor, comprising: eccentric means for decentering each of the abrasives so that a portion having no step is formed on a peripheral surface of the laminate. The surface treatment apparatus for a control rod for a nuclear reactor according to any one of claims 1 to 6,
The gantry is scanned so that the abrasive reciprocates in the direction from the axial part toward the blade tip part on the surface of the control rod for the reactor,
A surface treatment apparatus for a control rod for a nuclear reactor, characterized in that the polishing region by the reciprocation has an overlap with the polishing region by the previous reciprocation. On the computer,
A function to control the number of rotations of abrasives attached to the tool,
A function of detecting the contact force of the abrasive that contacts the surface of the nuclear reactor control rod;
A surface treatment program for a nuclear reactor control rod, wherein a function of causing the tool to scan the surface so that the contact force falls within a predetermined range is executed.

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