JP2000028779A - Method and device for inspection of reactor control rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method capable of surely detecting small through holes and the like formed in reactor control rods by a simple and easy method in a short time. SOLUTION: This inspection method is for reactor control rods 3 formed in tube shape and the bottom of inside tube 3M formed in the inside wall 3a is closed. In this case, the reactor control rod 3 is dipped in water in the state of the bottom faces being downward. Ultrasonic wave is emitted toward an inside wall 3a of the reactor control rod 3. The reflection wave of the ultrasonic reflected on the inside wall 3a is received and the value indicating the reflection wave is compared to a set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a reactor control rod (fuel control rod) used in a nuclear power plant. The present invention relates to a device capable of easily and reliably detecting a defect.

[0002] As for this kind of fuel control rod wear measurement inspection, an appearance inspection, an ECT inspection, a strain gauge inspection and the like have been conventionally performed.

[0003]

However, since the appearance inspection is performed by the inspector's naked eye through a monitor using an underwater camera, the outer surface is easy to see, but the back side, the center, etc. are difficult to see, and the inspection time is short. For a long time. Further, there is a problem that the presence or absence of a minute through hole or the like cannot be determined.

The ECT inspection and the strain gauge inspection are
Although it is possible to obtain thinning information of the cladding tube (fuel control rod), it is not possible to reliably detect through holes and the like in these cases.

The present invention has been made in view of the above circumstances, and provides an inspection method and an inspection apparatus capable of reliably detecting a minute through-hole or the like formed in a fuel control rod by a simple method in a short time. It is intended to provide.

[0006]

A method of inspecting a reactor control rod according to the present invention inspects a reactor control rod which is formed in a tubular shape and has a closed bottom inside a tube formed inside an inner wall portion. In the method, the reactor control rod is immersed in water with the bottom part directed downward, and ultrasonic waves are transmitted toward the inner wall part of the reactor control rod, and the ultrasonic waves are A reflected wave after being reflected on the inner wall portion is received, and a value indicating the reflected wave is compared with a set value.

[0007] As a result of the comparison, when a decrease in the reflectivity of the ultrasonic wave is detected, it is found that water has entered the inside of the pipe of the reactor control rod. Can be detected. This is because if water enters the inside of the tube, the ultrasonic reflectivity of the inner wall portion directly facing the inside of the tube decreases. As the set value, a value of a reflected ultrasonic wave obtained in a state where the reactor control rod is not immersed in water is used.

According to the method for inspecting a control rod of a nuclear reactor of the present invention, the control rod is formed in a tubular shape having an inner wall and an outer wall, and a thick portion is formed between the inner wall and the outer wall. A method for inspecting a reactor control rod in which a bottom inside a tube formed inside the inner wall portion is sealed between the thick portion and the reactor,
The bottom part of the reactor control rod is immersed in water, and ultrasonic waves are transmitted toward the thick part of the reactor control rod, and the ultrasonic waves are reflected on at least the inner wall part and the thick part is formed. Receiving the reflected wave after passing through at the receiving position, in one of the state where water has not entered the inside of the pipe and the state where water has entered the inside of the pipe, the thick portion The timing at which the reflected wave that has passed should be received at the receiving position, and the amplitude that the reflected wave should have at the receiving position are calculated, and the reflected wave corresponding to the calculated timing and the amplitude is calculated. It is determined whether the signal is received at the receiving position.

A reactor control rod inspection apparatus according to the present invention is a reactor control rod for inspecting a reactor control rod formed in a tubular shape and having a closed bottom inside a tube formed inside an inner wall portion. An inspection device, an apparatus main body, a hole provided in the apparatus main body, through which the reactor control rod can be inserted, an ultrasonic transmitter and an ultrasonic receiver provided in the apparatus main body, The received signal received by the receiving unit, and comparing a signal set in advance, and comprises a comparison detection unit that detects a defect of the reactor control rod based on the comparison result, the ultrasonic receiving unit, The ultrasonic wave transmitted from the ultrasonic transmission unit toward the reactor control rod inserted into the hole is provided at a position where the ultrasonic wave reflected by the inner wall portion can receive a reflected wave.

The reactor control rod inspection apparatus according to the present invention further includes a centering mechanism for holding the reactor control rod in a state where the reactor control rod is aligned with the hole.

In the nuclear reactor control rod inspection apparatus according to the present invention, a plurality of the holes, the plurality of ultrasonic transmission sections and the plurality of ultrasonic reception sections are provided, and the apparatus main body includes a first plate section and the first plate section. And a second plate portion provided at a different height from the plate portion, a part of the plurality of holes and the ultrasonic transmitting portion and the ultrasonic receiving portion, the first plate portion And the other of the plurality of holes and the ultrasonic transmission unit and the ultrasonic reception unit are provided in the second plate unit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel control rod inspection apparatus according to the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 3 show a first embodiment. 1A and 1B show a fuel control rod inspection device according to the present embodiment, wherein FIG. 1A is a plan view and FIG. 1B is a side view. FIG. 2 shows the measurement principle according to the present embodiment. 3A and 3B show an example of a reception echo. FIG. 3A shows an example in which water does not exist in the fuel control rod, and FIG. 3B shows an example in which water exists.

In FIG. 1, reference numeral 30 denotes a fuel control rod inspection device. This fuel control rod inspection device 30
It is used in a state where it is set on the spent fuel rack 1 shown in FIG.

The object to be inspected by the fuel control rod inspection device 30 is a fuel control rod (reactor control rod) 3. The fuel control rod 3 is a metal tube. In FIG. 2, reference numeral 3a denotes a tube inner wall portion, 3b denotes a tube outer wall portion, 3S denotes a thick portion of the tube, and 3M denotes an inside (hollow portion) of the tube. Each end (upper and lower) of the fuel control rod 3 in the axial direction is in a state where the inside 3M is sealed between the thick part 3S (hereinafter, the inside 3M is sealed). Part 3M).

As shown in FIG. 1B, the spent fuel rack 1 is formed in a box shape having a substantially square shape in a plan view and having an opening formed in an upper portion.

The fuel control rod inspection device 30 of the present embodiment is
It employs a transmission type UT method, which is a type of ultrasonic inspection method.

The fuel control rod inspection device 30 of the present embodiment
U to detect the presence of water inside the pipe when there is a through hole
Since the T method is adopted, the through hole can be reliably detected without erroneous detection.

As shown in FIGS. 1A and 1B, the fuel control rod inspection device 30 includes a device main body 2. The device main body 2 is formed in a flat plate shape that is substantially square in plan view. The apparatus main body 2 is formed larger than the opening of the spent fuel rack 1 so that the apparatus main body 2 can be installed on the upper portion of the side wall of the spent fuel rack 1.

On the lower surface of the apparatus main body 2, positioning plates 21 are provided at positions along each side forming the planar shape of the apparatus main body 2, respectively. Positioning plate 2
1 is provided to protrude downward from the lower surface of the apparatus main body 2,
When the fuel control rod inspection device 30 (device main body 2) is placed on the spent fuel rack 1, each positioning plate portion 21 is accommodated in the side wall portion of the spent fuel rack 1, so that the spent fuel rack 1 can be positioned.

The positioning plate portion 21 is likely to be displaced in the horizontal direction by the fuel control rod inspection device 30 (device main body 2) placed at the official position on the spent fuel rack 1. When this happens, the misalignment is suppressed by interfering with (contacting with) the side wall of the spent fuel rack 1.

The apparatus main body 2 has a plurality of holes 12 penetrating in the thickness direction of the apparatus main body 2. These holes 12 are formed larger than the outer diameter of the fuel control rod 3 so that the fuel control rod 3 can be inserted therethrough.

As shown in FIG. 1 (a), when the apparatus main body 2 is viewed in a plan view, a line segment L, which is a center line on the left and right sides of the apparatus main body 2, is shown.
And four regions 2 formed by being divided by the line segment M
In a, 2b, 2c, and 2d, the arrangement of the holes 12 is symmetrical left and right and up and down, respectively. That is, the device body 2
Have four holes 12 formed symmetrically on the line segment L and the line segment M, respectively. Further, each of the four regions 2a, 2b, 2c, and 2d has the hole In addition to the portion 12, four holes 12 are formed at symmetrical positions.

In the upper part of the apparatus main body 2, around the holes 12, UT (ultrasonic) sensors 4 are provided, respectively.
Is provided. Each of these UT sensors 4 is constituted by a pair of an ultrasonic transmission / reception unit 4a and an ultrasonic transmission / reception unit 4b. The ultrasonic transmission / reception unit 4a and the ultrasonic transmission / reception unit 4b are provided at predetermined positions at symmetrical positions with the hole 12 interposed therebetween. In this case, the transmitting / receiving units 4a, 4b
Have a function of transmitting ultrasonic waves and a function of receiving ultrasonic waves, respectively. That is, when an ultrasonic wave is transmitted from the transmission / reception unit 4a, the transmission / reception unit 4b receives the ultrasonic wave. Conversely, when an ultrasonic wave is transmitted from the transmission / reception unit 4b, the transmission / reception unit 4a
Is to receive this.

These UT sensors 4 are installed at positions where an ultrasonic inspection is performed on each fuel control rod 3 inserted into each hole 12 and an optimum inspection result is obtained (FIG. 2).
reference). That is, the UT sensor 4 is provided at a position where an output signal (echo) from the fuel control rod 3 set by the alignment mechanism described below can be obtained.

Each hole 12 is provided with a centering mechanism 5 for holding the fuel control rod 3 in a stable state at the center position in each hole 12.

Further, guide pin receiving portions 6 are provided at four corners of the apparatus main body 2, respectively. The guide pin receiving portion 6 positions a control rod handling tool (not shown) for handling the fuel control rod 3 on the apparatus main body 2. Using the control rod handling tool, the fuel control rod 3 is inserted into the hole 12 and inspected by the UT sensor 4.

According to the present embodiment, the fuel control rod 3 is inserted into the spent fuel rack 1 in which water is stored. At this time, the thick portion 3S is formed on the inner and outer wall portions 3a and 3b of the fuel control rod 3.
Is formed, water is filled into the closed portion 3M through the through hole. The fuel control rod inspection device 30 of the present embodiment inputs ultrasonic waves to the fuel control rod 3,
Thick part (metal part) 3S while ultrasonic wave is reflected on inner wall part 3a
Is propagated. In the present embodiment, compared to the case where ultrasonic waves input to the normal fuel control rod 3 having no through hole propagate through the thick portion (metal portion) 3S, the sealing is performed when water exists in the sealing portion 3M. The presence or absence of water, that is, the presence or absence of a through-hole is determined based on the intensity of the received echo, focusing on the decrease in the ultrasonic reflectivity at the inner wall portion 3a facing the portion 3M (FIG. 3A). , (B)).

As shown in FIG. 2, when an ultrasonic wave is output from the ultrasonic transmission / reception section 4a, the ultrasonic transmission / reception section 4b transmits the reflected wave after the output ultrasonic wave passes through the thick portion 3S. Receive. The arrangement relationship of the ultrasonic transmission / reception units 4a and 4b is as follows.
In this way, the position is set to a position where the ultrasonic signal that has passed through the thick portion 3S can be received, and the ultrasonic transmitting / receiving section 4a (or 4
The output (wavelength, amplitude, etc.) of the ultrasonic wave transmitted from b) is also
The ultrasonic wave is set to a value such that the ultrasonic wave passes while being appropriately reflected within the thick portion 3S. That is, the ultrasonic transceiver 4a
Is output from the outer wall 3b of the fuel control rod 3 and then reflected a plurality of times in the thicker portion 3S between the inner wall 3a and the outer wall 3b to be reflected from the symmetrical position of the incident portion. (The reflected wave received by the ultrasonic transmission / reception unit 4b) is set to have an appropriate value.

In the present embodiment, the alignment mechanism 5 of the apparatus main body 2
The fuel control rod 3 positioned by the above is inspected by the UT sensor 4 previously fixed at a predetermined position of the apparatus main body 2, so that the received echo (reflected wave) at the time of flaw detection is detected.
, And the respective echo heights when water is present / absent in the sealed portion 3M are stabilized. In other words, according to the present embodiment, the variation (error) of the value of the received echo due to various conditions at the time of measurement and the like is small.

Therefore, by setting a gate at the position theoretically determined (position determined by two factors of the propagation time timing and the echo height) shown in FIG. That is, the fuel control rod 3
Can be detected. That is, in FIG. 3B, the echo (reflected wave)
By simply checking whether or not there is a through hole, the presence or absence of the through hole can be easily and reliably detected without overlooking the existence of the through hole or erroneous detection.

Furthermore, no matter where the through hole is located on the fuel control rod 3 within the level of the water stored in the spent fuel rack 1, the through hole extends from the through hole in the axial direction in the closed portion 3 M. Water penetrates over the entire length of the spent fuel rack 1 and accumulates to the same height as the water stored in the spent fuel rack 1. Therefore, even if the height position of the through hole is different from the height position of the UT sensor 4, the through hole can be reliably detected. That is, the inspection according to the present embodiment does not need to be performed over the entire length of the fuel control rod 3 and can be performed at one point, so that the inspection time can be shortened.

Further, according to the present embodiment, the UT sensor 4 is optimally arranged, and the fuel control rod 3 is stably held at a predetermined position by the alignment mechanism 5. As shown in FIGS. 3 (a) and 3 (b), a gate is applied to a fixed position (the hatched portion in FIG. 3 (b)), an echo having a certain amplitude or more and generated at a fixed timing (FIG. The presence / absence of water can be reliably determined only by examining the presence / absence of (equivalent to the echo shown in a)), and the reliability of the inspection can be improved.

Next, a second embodiment will be described with reference to FIGS.

Depending on the shape and type of the fuel control rod 3,
When it is difficult to lay out all the UT sensors 4 as shown in FIG. 1A, the UT sensors 4 have a hierarchical structure as shown in FIGS. In the present embodiment, the number of UT sensors 4 per layer is reduced to secure a mounting space. The sensor mounting plate 7 is mounted above the apparatus main body 2 via the support 8, and the reduced UT sensor 4 is arranged on the sensor mounting plate 7. As described above, according to the present embodiment, it is not necessary to carry out the inspection over the entire length of the fuel control rod 3 because the UT sensors 4 can be hierarchically arranged to eliminate the restrictions on the layout. This is because one point measurement is sufficient.

Next, a third embodiment will be described with reference to FIG.

The circles shown in FIG. 6 indicate the holes 12 of the apparatus main body 2 shown in FIG. As described with reference to FIG. 1A, when the apparatus main body 2 is viewed in plan,
The arrangement of the holes 12 (the arrangement of the fuel control rods 3 inserted into the holes 12) is symmetrical about the line L and the line M in FIG.

Therefore, the UT sensors 4 are not disposed in all the holes 12 as shown in FIG. 1A, but are disposed only around the holes 12 shown by hatching in FIG. By rotating the control rod handling tool by 90 degrees, it is also possible to inspect all the fuel control rods 3 inserted into all the holes 12. According to the present embodiment, the inspection is performed while rotating the fuel control rod 3 using the minimum necessary UT sensor 4, which leads to simplification of the flaw detection system and is advantageous in terms of maintenance.

Next, a fourth embodiment (application example) will be described with reference to FIG.

The inspection apparatus according to the present embodiment is arranged on a plurality of cards 10 of an existing control rod handling tool or multifunctional mast 9.
The UT sensor 4 is attached hierarchically. This inspection apparatus is provided with the UT according to the present invention when the fuel control rod 3 is stored in the control rod handling tool or the multi-function mast 9 during the handling of the fuel control rod 3 during the periodic inspection of the plant.
An inspection is performed.

The present embodiment is an inspection apparatus of a type to be mounted in a control rod handling tool or a multi-function mast. It is only necessary to attach the alignment mechanism 5 or the like), and there is no need to specially manufacture an inspection device and provide an inspection process. Therefore, it leads to cost reduction and shortening of the process, and the soundness of the fuel control rod 3 can be confirmed during the conventional work process.

The inspection using the apparatus of the present embodiment does not need to be performed over the entire length of the fuel control rod 3 and can be performed at one point, so that the UT sensors 4 can be arranged hierarchically.
This makes it suitable for introducing a control rod handling tool or a multi-function mast onto a card where the mounting space for the sensor is limited.

[0043]

According to the method for inspecting a nuclear reactor control rod of the present invention, a method for inspecting a nuclear reactor control rod which is formed in a tubular shape and whose bottom inside a tube formed inside an inner wall portion is sealed. Wherein the reactor control rod is immersed in water with the bottom part directed downward, and ultrasonic waves are transmitted toward the inner wall part of the reactor control rod, and the ultrasonic waves are emitted from the inner wall part. Receiving the reflected wave after reflected by the part, comparing the value indicating the reflected wave with a set value, and as a result of the comparison, a decrease in the reflectivity of the ultrasonic wave is detected, whereby the reactor control rod It can be seen that water has penetrated into the inside of the tube, and it can be detected that a through hole (defect) has occurred in the reactor control rod.
As the set value, a value of a reflected ultrasonic wave obtained in a state where the reactor control rod is not immersed in water is used.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a reactor control rod inspection apparatus according to the present invention, (a) is a plan view thereof, and (b) is a plan view thereof.
Is a sectional view thereof.

FIG. 2 is a plan view showing the measurement principle of the first embodiment.

FIG. 3 shows a detection result of the first embodiment,
(A) shows the case where there is no defect in the reactor control rod, and (b) shows the case where there is a defect.

FIG. 4 is a side view showing a second embodiment.

FIG. 5 is a plan view showing a second embodiment,
(A) shows the first plate portion, and (b) shows the second plate portion.

FIG. 6 is a side view schematically showing a third embodiment.

FIG. 7 is a side view showing a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spent fuel rack 2 ... Device main body 2a ... Area 2b ... Area 2c ... Area 2d ... Area 3 ... Fuel control rod 3a ... Inner wall part 3b ... Outer wall part 3M ... Inner and sealing part 3S ... Thick part 4 ... UT sensor Reference numeral 4a: Ultrasonic transmission / reception unit 4b: Ultrasonic transmission / reception unit 5: Alignment mechanism 6: Guide pin receiving unit 7: Sensor mounting plate 8: Support post 9: Multifunctional mast 10: Card 12: Hole 21: Positioning plate 30 … Fuel control rod inspection device L… Line segment M… Line segment

Claims (5)

[Claims] 1. A method for inspecting a reactor control rod, which is formed in a tubular shape and has a closed bottom inside a tube formed inside an inner wall portion, comprising: Immersed in water in a state of facing, transmitting ultrasonic waves toward the inner wall portion of the reactor control rod, receiving a reflected wave after the ultrasonic waves are reflected on the inner wall portion, A method of inspecting a reactor control rod that compares a value indicating a wave with a set value. 2. A tubular member having an inner wall portion and an outer wall portion, a thick portion formed between the inner wall portion and the outer wall portion, and formed inside the inner wall portion. A method for inspecting a reactor control rod in which a bottom inside a pipe to be sealed is sealed between the thick portion and the reactor, wherein the bottom of the reactor control rod is immersed in water; An ultrasonic wave is transmitted toward the thick portion, and the ultrasonic wave is reflected at least on the inner wall portion and a reflected wave after passing through the thick portion is received at a receiving position. The timing at which the reflected wave that has passed through the thick portion is to be received at the reception position in one of the state where water has not penetrated and the state where water has penetrated into the pipe, and Calculate the amplitude that the reflected wave should have at the receiving position, and calculate the calculated timing and Inspection method of determining a nuclear reactor control rods whether the received reflected wave by the receiving position corresponding to the amplitude. 3. A reactor control rod inspection apparatus for inspecting a reactor control rod, which is formed in a tubular shape and in which a bottom inside a tube formed inside an inner wall portion is sealed, the reactor control rod includes: A hole provided in the apparatus main body and through which the reactor control rod can be inserted, an ultrasonic transmitter and an ultrasonic receiver provided in the apparatus main body, and a reception signal received by the ultrasonic receiver, A comparison detection unit that compares a signal set in advance and detects a defect of the reactor control rod based on the comparison result, wherein the ultrasonic reception unit includes the atom inserted into the hole. A reactor control rod inspection device provided at a position capable of receiving a reflected wave after the ultrasonic wave transmitted from the ultrasonic transmission unit toward the reactor control rod is reflected on the inner wall portion. 4. The reactor control rod inspection apparatus according to claim 3, further comprising: a centering mechanism for holding the reactor control rod in a state where the reactor control rod is aligned with the hole. Reactor control rod inspection equipment. 5. The reactor control rod inspection device according to claim 3, wherein the hole, the ultrasonic transmission unit, and the ultrasonic reception unit are provided in plurality, respectively. A first plate portion and a second plate portion provided at a height different from the first plate portion, wherein one of the plurality of holes and the ultrasonic transmitting portion and the ultrasonic receiving portion is provided. The unit is provided in the first plate unit, and the other of the plurality of holes and the ultrasonic transmission unit and the ultrasonic reception unit is a reactor control unit provided in the second plate unit. Bar inspection device.