JPS6249955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically centering a control rod drive mechanism (hereinafter referred to as CRD) housing used for on-site installation of a control rod drive mechanism (hereinafter referred to as CRD) housing in a nuclear reactor pressure vessel.

Figure 1 shows the installed state of the CRD housing, with 1 indicating the reactor pressure vessel, 2 the CRD housing, and 3 the core support. To install the CRD housing 2 in the reactor pressure vessel 1, insert the CRD housing 2 from the outside of the bottom of the reactor pressure vessel 1, and weld it to the stub 4 provided at the bottom of the reactor pressure vessel 1 at the welding part 5. do.

The CRD housing 2 contains a control rod drive device and is designed to move up and down in order to move the control rods, so its installation precision is required to be extremely high.

Therefore, when installing the CRD housing,
Installation centering is performed, and the conventional installation centering method is to use an alignment scope 6 placed on the core support 3 and the upper and lower ends of the CRD housing 2 inserted from the bottom of the reactor pressure vessel 1. This is done using the attached alignment targets 7 and 8.

Fig. 2a shows the main part of Fig. 1, and Fig. 2b and c show parts A and B of Fig. 1, respectively.
Figure d shows the alignment scope 6, core support 3, CRD housing upper end 21, and CRD housing lower end 22 hole centers shown in Figure a.

The centering accuracy of CRD housing 2 is, for example,
When the distance between the core support 3 and the CRD housing upper end 21 and the length of the CRD housing 2 are approximately 4 m, the center of the CRD housing upper end 21 is set at φ0.76 with respect to the center of the hole of the core support 3. At the same time, the upper end of the CRD housing 2
1, the center of the lower end 22 of the CRD housing must be within φ5.08.

In order to obtain such centering accuracy, (1) First, align the hole in the core support 3 and the center of the target 31 installed on the core support 3 (the center is indicated on the target 31 as shown in Figure 2d). Place the target 31 on the core support 3 so that the crosshairs (crosshairs formed) coincide with each other.

(2) Place the alignment scope 6 on the core support 3 and use the attached water level meter to
The alignment scope 6 is centered horizontally.

(3) Using the alignment scope 6, measure the center of the alignment scope 6 (the alignment scope 6 has a crosshair that indicates the center as shown in Figure 2 d) and the core support 3.
The center of the target 31 set in the hole is aligned with the center of the target 31.

(4) Next, adjust the focus of the alignment scope 6 and measure the misalignment of the center of the target 7 installed at the upper end 21 of the CRD housing with respect to the center of the core support 3. This measurement is performed by rotating the alignment scope 6 in 90° increments.
The measurement was carried out twice, and the average value of the four measurements was used as data. As a result of this measurement, if the core of the CRD housing upper end 21 is not within the tolerance,
Move the CRD housing lower end 22 so that it is within tolerance.

(5) Center the CRD housing lower end 22 in the same way.

In this way, the centering of the CRD housing is completed, and then the centered CRD housing 2 is welded to the stub 4 at the welding part 5 shown in FIG. During welding, the CRD housing 2 is deformed, so the installation of the CRD housing 2 is performed while performing the above-mentioned operations (4) and (5) and the welding operation alternately.
And, such centering and installation work takes about
Conducted on 200 CRD housings.

However, in such conventional methods, (1) the centering of the alignment scope is performed by a human based on the water level, which takes time and the accuracy varies depending on individual differences;

(2) Since centering is performed visually using an alignment scope, measurement accuracy varies due to individual differences. Also, the measurement time becomes longer.

(3) If the center of the CRD housing is not within the tolerance, the person measuring the deviation with the alignment scope informs the operator at the bottom of the CRD housing and adjusts the CRD housing according to the amount of deviation. However, the distance between the person measuring the alignment scope and the worker at the bottom of the CRD housing is approximately 8 meters or more, and they cannot communicate directly, so it is easy to make communication errors or operational errors.

(4) It is necessary to install targets at the core support and the upper and lower ends of the CRD housing, but it is necessary to prepare targets of several different sizes depending on the machining tolerances of these parts, and the alignment work is not easy.

(5) Four measurements are required to obtain data on one misalignment, which increases the number of measurements.

There were other drawbacks.

The purpose of the present invention is to eliminate such drawbacks and enable automatic centering of the CRD housing.The present invention aims to eliminate such drawbacks and to enable automatic centering of the CRD housing. When welding the control rod drive mechanism housing to the stub, the upper part of the control rod drive mechanism housing is supported by a gimbal support, and the lower part is supported by a sliding bearing, which is supported by a spherical bearing. A laser oscillator is fixed on the support rod of the device and has an automatic vertical centering mechanism that includes a fixed prism and a vertical correction prism that is always held vertically on the core support of the reactor pressure vessel, and is used to drive the control rod. A light receiver is installed at the upper end and lower end of the mechanism housing, which is composed of a plurality of photocell arrays, and which detects the irradiation position of the laser beam from the laser oscillator on the photocell array and outputs it to a control device. The present invention is characterized in that the positional deviation of the control rod drive mechanism housing with respect to the beam is calculated, and the centering device is driven based on the calculation result of the positional deviation to perform automatic centering.

That is, the present invention uses a laser oscillator with an automatic vertical centering mechanism, and utilizes the linear propagation characteristics of laser light and the fact that the energy distribution of the laser spot is a Gaussian distribution to create a photocell for use as a photoreceptor. In combination with this, the centering of the CRD housing is performed using a laser, and the obtained displacement amount is fed back.
This makes it possible to automatically correct the core of the CRD housing.

Examples will be described below.

FIG. 3a shows a state in which a CRD housing is installed using an automatic centering device used in an embodiment of the automatic centering method for a CRD housing of the present invention, and FIG. 3b shows the same state. The core support 3 and the light receivers 11 and 12 of the CRD housing upper end 21 and lower end 22 of FIG. 3a are shown in correspondence with FIG. 3a. In this figure, 9 is a laser oscillator with an automatic vertical centering mechanism installed on the core support 3, and 10 is the upper end 2 of the CRD housing.
1 is a beam splitter installed at 1; 11 is a photoreceiver installed to face the laser beam reflected by the beam splitter 10 and is composed of a plurality of photocell arrays; 12 is a beam splitter 1;
It is a light receiver composed of a plurality of photocell arrays provided at the lower end 22 of the CRD housing facing the laser beam that has passed through the CRD housing.
CRD housing 2 is attached to the lower end 22 of the CRD housing.
An automatic centering device 13 that supports the automatic centering device 13, a control device that controls these devices, and the like are provided. In addition, if the laser oscillator 9 is inserted into the core support 3 hole,
The center of the laser beam and the center of the hole are configured to coincide, and the receivers 11 and 12 are also
The center of the diameter of the upper end 21 and lower end 22 of the CRD housing is configured to match the center of the light receiver with one touch.

FIG. 4 shows an outline of the operating mechanism of this automatic centering device. A laser beam emitted from a laser oscillator 9 is incident on a light receiver 11 or 12, and the energy of the laser beam is converted into an electric current. Ru. Control circuits (microcomputers) 14 and 15 are connected to the light receiver 11 and the light receiver 12, respectively.
or 15, the position of the laser beam within the photocell array of the photoreceiver 11 or 12 is detected. The outputs of the laser oscillator 9 and control circuits 14 and 15 are input to a control device (arithmetic circuit) 16, where arithmetic processing is performed. The output of this control device 16 gives instructions to, for example, three circuits. First, if the CRD housing 2 is misaligned, it will automatically be brought within tolerance according to the amount of misalignment.
This is an instruction circuit to the automatic centering device 13 for moving the CRD housing 2, and is connected via an amplifier 17. The second is an instruction circuit to the display 18 for displaying the core position of the CRD housing 2, and the third is an instruction circuit to the recorder 19 for instructing to record the core measurement results.

Figure 5 shows a specific example of a laser oscillator with an automatic vertical centering mechanism, where a shows the situation when the laser beam is directed in the vertical direction, and b shows the situation when the laser beam is directed in a direction different from the vertical direction. It shows. As shown in FIG. 5a, when the laser beam emitted from the laser oscillator 9 is directed in the vertical direction, the laser beam emitted from the laser oscillator 9 passes through the lens 91 and then points in the vertical direction. Correction prism 92, fixed prism 9
3, the direction is changed to be parallel to the original laser beam, and the lens 94 turns the laser beam into a parallel beam. Therefore, even if the laser beam from the laser oscillator 9 is different from the vertical direction as shown in FIG. However, the laser beam passing through the lens 94 is always vertical, allowing automatic vertical centering.

FIG. 6 is a diagram explaining the structure of a photoreceiver and the principle of position detection using a laser beam using this photoreceiver. The photoreceivers 11 and 12 have a size of A×B as shown in FIG. Consists of an array of 100 photocells arranged two-dimensionally, and a laser beam
200 is irradiated onto four photocells, . . . as shown in FIG. When 200 laser beam spots are incident on an array of 100 photocells, a current is generated depending on the amount of energy in the laser. Since the light intensity distribution of the laser beam is a Gaussian distribution, the position of the laser beam can be determined by calculating the apex of the Gaussian distribution. Here, the coordinate axes inside each photocell 100 are set at the upper end 21 of the CRD housing.
In the receiver 11, x (top), y (top), bottom end 22
The coordinates of each photocell 100 array are X (top) and Y (top) for the photoreceptor 11 at the top end 21, and X for the photoreceiver 12 at the bottom end 22. (bottom), Y (bottom), and in FIG. 6a, the position of each photocell 100 is indicated by m and n as shown in FIG. 6a, centering on the center of the photocell 100 array. The position can be expressed by the following equation.

Here, x and y can be determined by the following equation by measuring the laser beam detected by the photocell 100 array shown in FIG. 6b.

Therefore, as shown in FIG. 6c, the core support 3
When the distance to the upper end 21 of the CRD housing, the length of the CRD housing 2, and the distance from the lower end 22 of the CRD housing to the spherical bearing 26 of the automatic centering device 13 are l ₁ , l ₂ , and l ₃ , respectively. , 6th
The amount of movement X, Y and X〓, Y〓 necessary for centering the CRD housing as shown in Figure d can be determined by the following equations.

FIGS. 7a and 7b are a plan sectional view and a longitudinal sectional view, respectively, of a main part of a specific example of an automatic centering device. In these figures, 23 is a support rod of the CRD housing 2, 24 is a gimbal support that supports the upper part of the support rod 23, 25 is a sliding bearing provided at the lower part of the support rod 23, and 26 is a support rod that supports the inclination of the CRD housing 2. 27 and 28 are the X fine movement motor and Y fine movement motor, respectively, and 29 and 30 are the X fine movement motor and the Y fine movement motor, respectively. .

Then, X, Y, X obtained by equation (3)
〓、Y〓, X fine movement motor 2
7, Y fine movement motor 28, X fine movement motor 2
9, Y = The fine movement motor 30 is driven and the CRD
Centering of the housing 2 is performed. The order of this measurement is shown in a flowchart as shown in FIG.

FIG. 9 shows the main part of another embodiment, in which a light receiver 110 and a light receiver 120 are provided with holes 111 and 121 having dimensional tolerances, respectively. In the case where the light receivers 110 and 120 are provided with holes having dimensional tolerances in this way, if the core is inserted into the hole, the completion of centering can be immediately known. Therefore, the work of centering the CRD housing can be performed more easily.

As shown by the dashed line in FIG. 4, an automatic welding means 20 including an amplifier and an automatic welding machine is connected to the control device 16 to prevent misalignment during welding between the CRD housing 2 and the stub 4. The welding start position is determined according to the amount of misalignment, and an automatic misalignment correction welding algorithm is installed to correct the amount of misalignment. If the configuration is configured to automate the welding work, installation and welding of the CRD housing can be done easily. It is also possible to automate everything.

As is clear from the above explanation, this example
Since the CRD housing automatic centering method automatically centers the CRD housing, it is possible to perform accurate centering easily and easily.

As described above, the method for automatically centering a CRD housing of the present invention enables automation of centering of a CRD housing, and has great industrial effects.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram illustrating a conventional CRD housing installation method, Fig. 2 a is a sectional view illustrating the main parts of Fig. 1, and Figs. 2 b and c are the same as in Fig. 2 a. Detailed sectional view of parts A and B, second
FIG. 3d is an explanatory diagram of the same essential parts, FIG. The figure is also a block diagram of the embodiment, No. 5
Figures a and b are explanatory diagrams for explaining the structure and operating principle of an automatic vertical centering mechanism using a laser oscillator, which is also used in the example;
b, c, and d are explanatory diagrams for explaining the structure of a light receiver used in the example and the principle of position detection using a laser beam using this light receiver;
FIG. 7a is a plan sectional view of the automatic centering device used in the embodiment, FIG. 7b is a longitudinal sectional view, and FIG. 8 is a diagram of the automatic centering method used in the embodiment. The flowchart, FIG. 9, is an explanatory diagram of the main part of another embodiment. 1...Reactor pressure vessel, 2...CRD housing,
3... Core support, 4... Stub, 9... Laser oscillator, 11, 12... Light receiver, 13... Automatic centering device, 23... Support rod, 24... Gimbal support, 2
5... Sliding bearing, 26... Spherical bearing, 27... X fine movement motor, 28... Y fine movement motor, 29...
...Lens, 92...Vertical correction prism, 93...Fixed prism.

Claims (1)

[Claims] 1. When welding the control rod drive mechanism housing inserted from outside the bottom of the reactor pressure vessel to the stub provided at the bottom, the control rod drive mechanism housing is supported at its upper part with a gimbal support and whose lower part is supported by a spherical surface. A prism supported by a sliding bearing, fixed on a support rod of a centering device that can be driven three-dimensionally, and fixed to the core support of the reactor pressure vessel, and a vertical correction that is always maintained vertically. A laser oscillator having an automatic vertical centering mechanism including a prism is installed, and the control rod drive mechanism housing is configured with a plurality of photocell arrays at the upper and lower ends of the control rod drive mechanism housing, and the laser beam from the laser oscillator is irradiated onto the photocell array. Install a light receiver that detects the position and outputs it to the control device.
A control rod drive mechanism characterized in that the control device calculates a positional deviation of the control rod drive mechanism housing with respect to the laser beam, and drives the centering device based on the calculation result of the positional deviation to perform automatic centering. How to automatically center the housing.