JPH0563758B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a detection device for detecting the degree of wear of control rods used in fuel assemblies of pressurized water reactors, mainly nuclear reactors.

(Prior Art) Generally, in a fuel assembly for a pressurized water reactor, 16 to 24 guide thimble tubes are arranged between a large number of squarely arranged fuel rods (for example, 17 x 17). Control rods R ₁ (length approximately 4 m), which have the same number of control rods as the thimble tubes and are bundled by spiders S as shown in Figure 8, are inserted into the thimble tube or pulled out from there to supply fuel. The degree of reactivity is controlled.

In order to prevent the control rod bundle R pulled upward from the assembly during operation of the reactor from swinging, the control rod bundle R is placed in the pressure vessel at seven locations at predetermined intervals in the height direction to prevent it from swinging (card portions). Normally, when the control rod bundle R is repeatedly raised and lowered as described above, the surface of the control rod _R1 wears out, especially the part that contacts the card part. During periodic inspections, it was only possible to visually observe bending and changes in color using an underwater television, but it was not possible to directly and quantitatively accurately detect the state of wear on all control rods.

For this reason, recently, multiple small differential transformer type sensors, each with a movable magnetic core and a sensor attached to the end of a plate-shaped contact spring, have been installed around the fuel rod to be inspected. The contact spring is always in contact with the control rod, and the lifting device raises and lowers the control rod to measure the overall amount of wear over the entire length of the control rod. A strain gauge type sensor with a strain sensor installed on top is installed, and the strain sensor is constantly in contact with the control rod, and the strain sensor is rotated around the fuel rod and raised and lowered to prevent wear on the circumferential surface of the control rod. A system for automatically and quantitatively detecting is proposed in Japanese Patent Laid-Open No. 151792/1983.

(Problem to be Solved by the Invention) By the way, although the above-mentioned known system can automatically and quantitatively detect the wear state of the control rod, it requires a plurality of differential transformer type sensors per control rod. Since a single strain gauge type sensor is used, the entire control bundle requires a considerable number of parts, making the configuration extremely complex, and the differential transformer type sensor in this system is located around the control rod. It is placed at a fixed location in the direction and does not move, and can only measure a fixed location over the entire length, and cannot measure any arbitrary position in the circumferential direction.
Strain gauge type sensors that measure the circumferential position of control rods are susceptible to noise and have problems in terms of stability and durability, and the strain sensors are constantly pressed against the control rods by spring force. As a result, the sensor will become wedged in the worn part of the control rod, and if the control rod is moved up or down in this state, there is a risk that the sensor may be twisted or damaged.

Therefore, the present invention quantitatively detects the state of wear on the circumferential surfaces of all control rods at the same time using a stable and durable measuring means, which has a simple configuration, and which does not cause damage to the measuring means. The aim is to submit an inspection device that can withstand long-term use.

(Means and effects for solving the problem) Based on the above object, the present invention provides an apparatus for inspecting the degree of wear of control rods, which includes an upper board for suspending a set of control rod bundles, and a storage area for storing fuel assemblies. It consists of a lower board that can be easily placed, and between both boards a holding frame is arranged which can be moved up and down, rotatably supporting a predetermined number of cylindrical shafts into which the control rods of the control rod bundle are respectively inserted. One differential transformer is provided in which one contact is rotatably provided along the side surface of each cylindrical shaft so that the tip protrudes into the shaft, and the tip of the core shaft contacts the bottom surface of each contact. and a slip ring that connects it to a power source, etc., and abutment rods are attached to the top of each contact at regular intervals along the axis of each cylinder to rotate the contact outward. The degree of wear of each control rod is detected by rotating each cylindrical shaft by a first stepping motor on the lower board and moving the holding frame up and down by a second stepping motor. It is a feature.

Then, during periodic inspections, if the control rod bundle is suspended from the upper board and the control rods are inserted through each cylinder shaft on the holding frame, the tips of the contacts on the side of the cylinder shaft will each be part of the surface of the control rod. When the first stepping motor is started, each cylindrical shaft rotates, and each contactor slides on the entire circumference of the rod surface, and the lateral movement of the contactor changes depending on the degree of wear. This is converted into a vertical displacement of the core axis of the dynamic lance and taken out as a voltage value.

When each cylinder shaft rotates once, the second stepping motor starts, raises the holding frame to a certain height, and then stops.The first stepping motor operates again to rotate the cylinder shaft, and the contactor The degree of wear is detected at different heights. Then, such operations are repeated.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, F is the horizontal frame of the inspection device,
The upper board 1 and lower board 2 having the required width are the control rods.
Posts 3 at the four corners with a height of about one-sixth of the length of R ₁
A control rod holder 4 (hereinafter simply referred to as a cradle) is connected to form a box frame shape, and on the upper substrate 1 is a frame-shaped control rod holder 4 for receiving a control rod bundle R to be inspected.
and a temporary calibration rod stand 5 that accepts a reference calibration rod R ₁ ′ (Fig. 2) that has the same structure as the control rod bundle but is shorter than this.
(hereinafter simply referred to as temporary storage tables) are arranged side by side, and the parts of the board 1 that correspond to the inside of these cradle 4 and temporary storage table 5 have insertion holes 4a and 5 for control rods or calibration rods, respectively.
A required number of holes are drilled, and hanging rings 6 are provided at the corners.

Positioning pins 7 are vertically installed at the four corners of the lower board 2, and when the lower board 2 is placed on the storage rack 20 in the storage pool, the positioning pins 7 at both ends are fixed as shown in FIG. The above-mentioned pedestal 4 and the later-described cylindrical shaft assembly are connected to the middle storage rack 20 by engaging with the opposite side walls of the three horizontally arranged storage racks 20.
A first stepping motor _m1 for rotating the cylinder axis is mounted on the lower substrate 2.
and a second stepping motor _m2 for raising and lowering the cylinder shaft.

A cylindrical shaft holding frame 10 having a U-shape from the front is disposed between the upper board 1 and the lower board 2, and this holding frame 10 is provided with a screw piece 9a at the center of the outside of the vertical wall, and has upper and lower sides on both sides as shown in FIG. is equipped with a slide piece 9b, and the screw piece 9a is screwed into a screw rod 8 installed vertically on the second stepping motor _m2 ,
The slide piece 9b engages with the rail 3a provided on the side surface of the front and rear pillars 3 on one side, and the stepping motor
It is supported so that it can be raised and lowered within a certain range by rotating forward and backward _m2 .

Moreover, the upper horizontal wall 10a and the lower horizontal wall 10 of the holding frame 10
The same number of cylindrical shafts ₁₁ as the control rods R1 into which the control rods _R1 are inserted are arranged in alignment with the insertion holes 4a of the pedestal 4, and their upper and lower ends are connected to the upper and lower horizontal walls 10a. , 10b, and gears 12 that mesh with each other are provided at a constant height position below each cylinder shaft 11, as shown in FIGS. As shown in FIG. 3, two gears 12 are rotatably disposed on the lower substrate 2, and are connected to the main shaft of the first stepping motor _m1 via a spline shaft 13 that allows the gears 12 to move up and down within a certain range. It is connected to the upper pinion 14.

Then, as shown in FIGS. 2 and 5, the window holes of the cylinder shafts are inserted along the sides of the thin central part of each cylinder shaft 11 (only one is shown for clarity in the figure). one contactor 15 which is spring-biased so that its tip protrudes inward through 11a and is rotatable in the inward and outward directions; and one contactor 15 in which the tip of the core shaft 16a is in contact with the lower surface of this contactor 15. A slip ring 17 connects the primary coil and secondary coil of the dynamic transformer 16 and one differential transformer 16 to a power source or a detection meter provided in the data processing device 21 (FIG. 7) on the poolside, respectively. They are installed vertically side by side.

Furthermore, abutting rods 18 are arranged along the cylinder axis 11 at regular intervals on the upper part of the contactor 15,
When the contactor 15 moves up a certain range together with the cylinder shaft 11, the contactor 15 abuts against this and rotates outward to release the contact with the control rod _R1 .

When using the above configuration, the first
As shown in the figure and FIG. 2, the positioning pins 7 at both ends of the lower board 2 are fitted into the two empty storage racks 20 arranged in parallel in the pool, and the machine frame F is placed on the racks 20. A reference calibration rod R ₁ ′ with a known amount of wear is prepared in advance on the temporary holding table 5, and prior to measurement of the control rod R ₁ , this reference calibration rod R ₁ ′ is operated by a crane above the pool. Move each calibration rod R1' to the pedestal 4 side using the handling tool T (Fig. 7), insert each calibration rod _R1 ' into each lower cylinder shaft 11 from the insertion hole 4a of the upper substrate 1, and insert each cylinder shaft on its surface. At the same time as the upper contactor 15 is brought into contact, each differential transformer 16 is energized, and the voltage characteristics exhibited by the transformer 16 with respect to the reference diameter of each calibration rod R ₁ ′ are checked, so-called zero point setting of each differential transformer 16 is performed. conduct.

At the end of the reference measurement in this way, the cylinder axis 1
1 and the reference calibration rod R ₁ ' from the pedestal 4, return it to the temporary holder 5, and replace it with the used control rod.
Handle R ₁ and insert it into the insertion hole 4a of the pedestal 4 using the tool T.
The head spider S is inserted into each cylindrical shaft 11 so that it comes into contact with the pedestal 4 through. At that time, each cylinder shaft 1
The tip of the contactor 15 on R1 will just touch the lower end of the uppermost card contact portion of each control rod _R1 .

When the control rod R ₁ is set in this way, the first stepping motor m ₁ is started at the same time as each differential transformer 16 is energized, and the rotation of the motor m ₁ is transferred from the gear 14 to each cylinder shaft 11. This will be transmitted to the upper gear 12, and each cylinder shaft 11 will rotate at the required speed, and the contactor 15 integrated with this will also rotate to rub the entire surface of the control rod _R1 . Therefore, the horizontal movement of the contactor 15 according to the wear degree of each surface part is converted into a vertical displacement of the core shaft 16a of the differential transformer 16 and detected as a voltage value, and the signal is processed as data. The data are sequentially sent to the device 21. Then, if the contactor 15 and the cylinder shaft 11 rotate once,
The first stepping motor _m1 stops and the second stepping motor _m2 starts at the same time, and the screw rod 8
Rotate within a specified range and stop. Due to this,
The holding frame 10 supporting the cylinder shaft assembly is lifted by a certain height (approximately 1 mm) via the screw piece 9a screwed into the screw rod 8.

Then, the first stepping motor _m1 is started again to rotate each cylinder shaft 11, and the contactor 15 integrated therewith detects a different surface from the previous one all around,
Then, the second stepping motor _m2 starts,
Lift the holding frame 10 to a certain height again and remove the contact 15.
After repeating several times the operation of detecting a new surface around the entire circumference, the contact 15 passes over the upper end of the card contact part of the uppermost stage of the control rod R ₁ and reaches the abutment rod 18.
As a result, the contactor 15 is rotated outward and released from contact with the control rod _R1 .

At that point, the second stepping motor _m2 now reverses and lowers the holding frame 10, which has been raised by a certain height (the wear range of the card contact part), to its original low position, but at the same time, the handling tool T ( 7) is started, and the control rod R ₁ is moved so that the lower end of the second stage card contact part of the control rod R ₁ contacts the contactor 15.
pull up. Then, in the second stage of the card contact section, the entire circumference detection by the contactor 15 is carried out step by step as described above, and the above operation is repeated for the number of stages of all the card contact sections. The degree of wear for all control rods _R1 can be detected simultaneously and accurately. Control rods that are severely worn are replaced with new ones, and those that are only slightly worn are reused.

Note that the first and second stepping motors
A series of operations of m ₁ , m ₂ and the handling tool are controlled by a control means built into the data processing device 21 .

(Effects of the invention) This invention can be used as an inspection device for the degree of wear of control rods.
With the above configuration, during periodic inspections, the state of wear in the circumferential direction and the axial direction of all the control rods in the control rod bundle can be checked simultaneously and automatically.
Not only is it possible to detect quantitatively with high precision, but also only one stable and durable differential transformer type measuring means is associated with one control rod, so compared to the above-mentioned known methods, It has a simple configuration with a small number of parts, is easy to handle, and has high measurement reliability.In addition, the slip ring ensures signal transmission to the differential transformer without any problems, so there is no risk of breaking the signal line, and the signal accuracy is high. The advantage is that the contactor is brought into contact with the control rod only when it is in the area where measurement is required, and the control rod is moved without contact by moving the contactor away from the control rod where measurement is not required. It has excellent durability without the risk of twisting or damaging the contacts, and is useful for safe operation of nuclear reactors.

[Brief explanation of the drawing]

The drawings show an embodiment of the invention, and FIG. 1 is a partially cutaway perspective view of the entire device. Figure 2 is its front view. FIG. 3 is a partially cutaway side view of FIG. 1 seen from the right side. FIG. 4 is a plan view showing the arrangement of the cylinder shaft and gears. FIG. 5 is an enlarged sectional view of the cylinder shaft. 6A and 6B are cross-sectional views taken along the lines X-X and Y-Y in FIG. 5. FIG. 7 is a front view showing the state of use. 8th
The figure is a front view of the control rod bundle. In the figure, 1... upper substrate, 2... lower substrate, 3...
...Strut, 4...Control rod cradle, 5...Calibration rod temporary holder, 7...Positioning pin, 10...Holding frame, 10
a, 10b...Side wall, 11...Cylinder shaft, 12...Gear, 13...Spline shaft, 15...Contact, 1
6...Differential transformer, 17...Slip spring,
m ₁ , m ₂ ...first and second slipping motors.

Claims (1)

[Claims] 1 Consists of an upper board that suspends a set of control rod bundles and a lower board that can be placed on a storage rack for fuel assemblies, and between the two boards there are predetermined slots into which the control rods of the control rod bundle are inserted. A holding frame that rotatably supports several cylindrical shafts is arranged to be movable up and down, and one contact can be rotated along the side of each cylindrical shaft so that its tip protrudes into the shaft. At the same time, one differential transformer with the tip of the core shaft in contact with the bottom surface of each contact, and a slip ring to connect this to a power source, etc. are installed, and the top of each contact is contacted at a fixed interval. An abutment rod for rotating the child outward is disposed along each cylinder axis, and each cylinder axis is rotated by a first stepping motor on the lower substrate, and the holding frame is rotated by a second stepping motor. 1. A wear degree inspection device for control rods, characterized in that the degree of wear of each control rod is detected by moving the control rods up and down using a ping motor.