JPS5954903A - Method and apparatus for measuring thickness of coated pipe without destruction - Google Patents

Abstract

PURPOSE:To obtain the thickness of a zirconium liner coated pipe throughout the entire surface highly reliably and simply in a short time, by applying different frequencies to the measuring coils in two eddy current type thickness measuring systems, and utilizing the generated eddy currents. CONSTITUTION:For example, the thickness of a coated fuel pipe filled with nuclear fuel and the thickness of a pure zirconium liner, which is lined on the inner surface of the main body of a zirconium alloy coated pipe are measured without destruction.in a first eddy current type thickness measuring system 10 utilizing eddy currents, a high frequency is applied, and the thickness of the liner layer is measured. The output signal (a) is inputted to an operation system 11. In a second eddy current type thickness measuring system 12, a low frequency is applied and the thickness of the coated fuel pipe is measured by utilizing the eddy currents. The result signal (b) is inputted to the operation system 11. In this system, comparison and operation are performed based on the calibrating curves of the thicknesses of the coated fuel pipe and its liner layer, which are sotred in advance. The computed results are outputted to a recording system 13 and analog or digital displays are performed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to cladding tubes and! The present invention relates to a method and device for non-destructively measuring the thickness of a zirconium lychee fuel cladding tube as a nuclear fuel element used in a nuclear reactor core. [Technical background of the invention and its problems] A fuel cladding tube containing a nuclear reactor is provided. The main function of this □ fuel cladding tube is to prevent nuclear valley fissures generated by nuclear fission of nuclear fuel from escaping into the cooling medium. Zirconium alloys such as zircaloy-2 and zircaloy-4, which have a relatively high pi″t7 strength and are extremely stable, are widely used. Zirconium alloys have good ductility and are suitable for cooling media. Although it has excellent properties such as being non-reactive, fuel cladding made of 2-ruconium alloy can cause damage to the reactor due to interaction with the nuclear fuel if the reactor power increases rapidly. The causes of this failure were mechanical interaction between the fuel cladding tube and the nuclear fuel due to the thermal expansion coefficient, and corrosion, angularity, and product size in the fission products. Stress corrosion and corrosion cracking are thought to be caused by the superimposed effect of corrosion and are advised.

The first step is to prevent stress corrosion cracking of fuel and cladding tubes.
A zirconium liner fuel cladding tube 1 as shown in the figure has been developed. This fuel cladding tube 1 has a pure zirconium coating (liner layer) 3 applied to the inner circumference of a cladding tube body 2 made of a zirconium alloy. In the cladding tube body 2, -
) This zirconium liner j is lined with pure zirconium which is softer than the ruconium alloy (Vickers hardness: Zirka 4E2 is about 170 DPT (pure zirconium is about 701) PH) and provides the zirconium liner layer 3. @3 reduces the stress acting on the fuel cladding tube 1 and prevents corrosive fission products from coming into direct contact with the cladding tube body 2, thereby suppressing damage to the fuel cladding tube 1 due to stress corrosion cracking. There is.

However, in order to guarantee the damage prevention function of the fuel cladding tube 1, it is required that the entire circumference and length of the fuel cladding tube 1 be lined with pure zirconium of a predetermined thickness. . However, the currently adopted method of measuring the wall thickness between the zirconium alloy cladding tube body and the zirconium and nium liner layers of the fuel core and cladding tube cuts both ends of the fuel cladding tube and optically measures the cut surface. This is a destructive measurement method that measures wall thickness using

However, the destructive measurement method in which the fuel cladding tube is cut and the cut surface is optically measured is cumbersome and takes a long time to measure, and it is only possible to measure near the tube end. It is not possible to measure the wall thickness over the entire length of the fuel cladding tube.
There were many problems in quality control of fuel cladding. □・
′:′ [Object of the invention] ・・This invention takes the above-mentioned points into consideration, and provides a method for easily measuring the outer wall thickness of the cladding tube and the wall thickness of the liner layer over the entire length of the cladding tube in a non-destructive manner. The present invention aims to provide a method and device for non-destructively measuring the wall thickness of a cladding tube.
□ [Summary of the invention] □ In order to achieve this object, the invention provides a method for measuring the wall thickness of a cladding tube in which a liner layer is applied to the cladding tube body, using an eddy current that applies a high coil frequency. The inspection coil of the type wall thickness measurement system is brought close to or in contact with the liner layer of the cladding tube, and the thickness of the liner layer is measured from the phase difference of alternating current caused by the difference in electrical resistivity between the cladding tube body and the liner layer. At the same time, the wall thickness of the cladding tube is measured in the same manner by applying a frequency lower than the above-mentioned high frequency to the inspection coil, and by applying a different coil frequency to the eddy current type wall thickness measurement system. This invention provides a method (first invention) for non-destructively measuring the wall thickness of a cladding tube.
'1, ■.

・In order to achieve the above-mentioned object, the present invention provides an apparatus for measuring the wall thickness of a cladding tube in which a liner layer is applied to a cladding tube body. The first eddy current wall thickness measurement system measures the thickness of the cladding tube, the second eddy current wall thickness measurement system measures the thickness of the cladding tube, and the eddy current measurement signals from both measurement systems are manually measured. a calculation system for calculating the wall thickness of the cladding tube and the liner layer thickness; The present invention provides an apparatus (second invention') for non-destructively measuring the wall thickness of a cladding tube, which is set to apply a coil frequency higher than that of the test coil.
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[Embodiment of the Invention] □ An embodiment of the invention will be described with reference to the accompanying drawings. □ Figure 2 is a block diagram showing the first principle of measurement of an apparatus for non-destructively measuring the wall thickness of a cladding tube according to the present invention. Wall thickness of cladding tube 1 and 1. Curconium alloy cladding tube body 2
A pure zirconium liner layer 30 lined on the inner peripheral surface of the
An example suitable for non-destructively measuring layer thickness is shown below.
・In FIG. 2, the reference numeral 10 indicates the first eddy current type wall thickness measurement system that uses eddy current, and the thicker side of this byssus is measured according to the measurement principle described later. The thickness of the pure zirconium liner layer 3 is measured by the eddy current method, and the output signal a is input to the calculation system 11.・ .

On the other hand, the calculation system 11 also receives a measurement signal from the second eddy current thickness measurement system 12 based on the eddy current method.

The second eddy current wall thickness measurement system 12 measures the thickness of the fuel cladding tube 1 (
Similar to the first eddy current type wall thickness measurement system 10, the wall thickness is measured using eddy current. Both measuring systems 10 and 12
Measurement/signals a and b outputted from are input to the calculation system 11, where the pre-built-in fuel cladding tube 1 and its liner layer 3. The wall thickness of the fuel cladding tube 1 and the thickness of the liner layer 3 are calculated by comparison with the calibration curve. This calculation result is output to the recording system 13,
At this point, Ana was almost four inches away. is displayed digitally on the left.

Next, the book explains the tenth measurement principle of the first eddy current wall thickness measurement system with reference to FIG. In this explanation, for the sake of simplicity, the measurement of the wall thickness of a flat conductive material 15 instead of the liner layer 3 of the fuel cladding tube 1 will be explained as an example.

The first eddy current wall thickness measurement system 10 has a probe-type test coil 16 that is brought close to or in contact with the conductive material 15 , and the test coil 16 is connected to a high-frequency oscillator 17 . Zoroz type probe □ Coil 16 is made of conductive material 17
Wrap the inspection coil around a virtual rod extending perpendicularly from the surface to be measured □
It is the type that is equipped. ' □However, the high frequency oscillator I7 has a high frequency band, for example 200 or 300
A high frequency wave of about 3 MHz is oscillated from the song z, and this □ high frequency wave is applied to the test coil 16. When the test coil 16 is brought close to the conductive material 15 with a high frequency applied thereto, an eddy current 18 is generated in the conductive material 15 due to electromagnetic induction. The magnitude of the eddy current 18 changes due to factors such as changes in resistivity of the conductive material 15, changes in magnetic permeability, changes in the shape of the conductive material 15, and changes in the distance between the test coil 16 and the conductive material 15. Therefore, consider these in advance. On the other hand, the eddy current 18 generated in the conductive material 15 affects the test coil 16 by electromagnetic induction, changing the impedance of the test coil 16. Therefore, by capturing changes in the inogi dance of the test coil 16, various information can be obtained regarding the conductivity and material.

By the way, when the zirconium alloy of Kulkaroy-2 is used for the cladding body 2 of the fuel cladding 1, the electrical resistivities of the cladding body 2 and the pure zirconium liner layer 3 are approximately 70 Ωam and approximately 50 μΩcm, respectively. Approximately 40 between options
There is a difference in resistivity between the two. This difference in resistivity appears as a phase difference in the alternating current obtained from the test coil 16, and the phase and phase differences vary depending on the thickness of the liner layer 3 lined with pure zirconium. . The range of change is between the phase due only to the zirconium alloy and the phase due only to pure zirconium, and changes within this range depending on the thickness of the pure zirconium film.

Therefore, the phase change signal of the first eddy current wall thickness measurement system 10 is calibrated in advance by using a sample of a fuel cladding tube whose thickness of the liner layer 3 of pure zirconium is known.
1. If a repair is made, the liner layer thickness of pure zirconium can be measured from the change in phase for a sample (fuel cladding) whose liner layer thickness is unknown. ,
.

At that time, external factors that change the impedance of the test coil 16, such as the test coil 16 and the sample (fuel cladding)
In order to eliminate the adverse effects caused by changes in the distance between the two and changes in the shape of the sample, 1. It is best to use a probe-type test coil that can contact the sample over as small an area (point) as possible.

When this probe-type test coil was actually fabricated, the test coil was brought into point contact with a pure zirconium liner layer from the inside, and a high frequency of I MHz was applied to the test coil to perform a test, the graph shown in Figure 4 was obtained. Obtained. FIG. 4 shows the thickness of the liner layer 3 of the fuel cladding tube 1 whose liner layer thickness has been measured in advance by conventional optical measurement, which is a destructive measurement, and the thickness measured by the first eddy current wall thickness measurement system 10. This figure shows that there is a linear relationship between the output power measured by the eddy current method and the thickness of the liner layer 3 lined on the inner circumferential surface of the fuel cladding tube 1. This indicates that measurement can be performed using the flow-type wall thickness measurement system 10. Therefore, the probe-type inspection coil 16 of the first eddy current type wall thickness measurement system 19 is inserted into the inner surface of the fuel cladding tube 1 in an axial or spiral direction.
, over the entire length or entire surface of the fuel cladding tube 1. The thickness of the liner layer 3 can be measured.

Next, the second eddy current type wall thickness measurement system 12 will be explained.

The second eddy current wall thickness measurement system 12 non-destructively measures the thickness (wall thickness) of the fuel cladding tube 1 using the eddy current method, and its measurement principle is shown in FIG. Since it is the same as that, the explanation will be omitted. However, the wall thickness of the fuel cladding tube 1 is approximately 1 mm in the case of a standard tube, which is approximately 10 times the thickness of the liner layer 3, so the coil frequency applied to the probe type inspection coil is approximately 1 KHz to 200 or 300 KHz. A low frequency band is desirable.

Therefore, instead of the high frequency oscillator 17 shown in FIG.
A low frequency oscillator that oscillates a frequency of about 200 to 300 KHz is used, and the low frequency from this low frequency oscillator is applied to the test coil.
・ □ Several 1 OKH on the inspection coil of the second eddy current wall thickness measurement system 12
When a test similar to the one described above was conducted by actually applying the low frequency of z, the graph shown in FIG. 5 was obtained. Fifth
The figure shows a constant difference between the actual wall thickness of the fuel cladding tube 1 (thickness obtained by optical measurement) and the output from the second eddy current wall thickness measurement system 12 (output by the eddy current method). It can be seen that the thickness of the fuel cladding tube 1 can be determined by the second eddy current wall thickness measurement system 12, which has a correlation (linear relationship).

Therefore, by scanning the probe-type inspection coil of the second eddy current wall thickness measurement system 12 along the inner or outer surface of the fuel cladding tube 1 in the axial or helical direction, one fuel can be measured.
The wall thickness of the cladding tube 1 can be measured non-destructively over the entire length or the entire surface.

In the description of one embodiment of the present invention, the case where a probe-type test coil is used in the first and second eddy current type wall thickness measurement systems has been described, but it is also possible to use an interpolation-type test coil or a penetrating-type test coil. May be used. Among them, the die test coil is a type in which a coil is wound around an imaginary rod arranged in the direction of the coating q6Q, and the winding diameter of the coil is m? The through-type inspection coil is a type in which the coil is loosely wound around the outside of the cladding tube, and the winding diameter of the coil is larger than the outside diameter of the cladding tube. □In the case of a penetrating type inspection, the pipe thickness or liner layer thickness of the fuel cladding tube can be measured at the same time when the fuel cladding tube is suspended horizontally in the 0 circumference μ direction. Therefore, by combining various types of test coils, it is possible to effectively measure the wall thickness of the fuel cladding tube and the liner layer thickness over the entire length and surface in a non-destructive manner.

In addition, in this invention, an example of measuring the wall thickness of a fuel cladding tube that accommodates nuclear fuel has been described, but this is not necessarily limited to fuel cladding tubes, and cladding tubes such as double-layered tubes made of conductive material. If the wall thickness + m++ is constant, then can be obtained.

〔Effect of the invention〕

As described above, in the present invention, eddy currents generated by applying different frequencies to the inspection coil of an eddy current type wall thickness measurement system are used to measure the wall thickness of the cladding tube (pipe thickness) and the liner layer. Since thickness can be measured non-destructively, inspection work is significantly simplified compared to optical wall thickness measurement using conventional destructive inspection methods, and inspection time can be significantly shortened. It is possible to measure the wall thickness over the entire surface with high reliability, and it is particularly suitable for measuring the wall thickness of fuel cladding tubes containing nuclear fuel. Since the tube thickness and liner layer thickness can be measured non-destructively over the entire length or entire surface of the cladding tube, the cladding tube can be managed with high reliability.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a fuel cladding tube containing nuclear fuel;
The figure shows the coating according to this invention! Fig. 3 is a block diagram showing the measurement principle of an apparatus for non-destructively measuring the wall thickness of . , a graph showing the correlation between the eddy current output from the first eddy current thickness measurement system and the thickness of the liner layer determined by optical measurement, and Figure 5 is from the second eddy current thickness measurement system. It is a graph showing the correlation between the output by the eddy current method and the wall thickness of the cladding tube (tube thickness) determined by optical measurement. DESCRIPTION OF SYMBOLS 1... Fuel cladding tube, 2... Cladding tube main body, 3... Liner layer, 10... First eddy current wall thickness measurement system, 11...
・Calculation system, 12...Second eddy current type wall thickness measurement system, 13.
... Recording system, 15... Conductive material, 16... Zorope type inspection coil, 17... High frequency oscillator, 18...
Eddy current. Applicant's agent: Shizuo Hatano Figure 2 Sonohisa 4 Ougi. 5th ward, light palm, 1 seat fee, 1~! Pipe Thickness Procedure Amendment (Voluntary) January 3, 1980 □ Commissioner of the Japan Patent Office Kazuo Wakasugi □ 1, Indication of the Case 1983 Patent Application No. 165096 2, Name of the Invention Non-destructive measurement method and device 3. Relationship with the amendment person case Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. (1 person) 4. Agent (zip code 105) Shinbashi, Minato-ku, Tokyo 5-chome 14-2-6, the number of inventions will increase due to the amendment. 7. Subject of the amendment Clarification (1) of "Detailed Description of the Invention" in the book 8. Contents of the amendment (1) "Conductive material 17J described in page 10, lines 10 to 11 of the specification" Corrected to "Conductive material 15." (2) In the same book, page 14, line 11, change “a certain amount of time” to “
Corrected to ``within the allowable range of wall thickness in between.

Claims (1)

[Claims] 1. A liner layer is applied to the cladding tube body: In the method of measuring the wall thickness of the cladding tube, an inspection of an eddy current wall thickness measurement system in which a high coil frequency is applied. When the coil is brought close to or in contact with the liner layer of the cladding tube, the phase difference of the alternating current caused by the difference in electrical resistance and rate between the cladding tube body and the liner layer causes a change in the layer: In addition to measuring the thickness, the above...
Measure the wall thickness of the cladding tube □ in the same manner by applying a frequency lower than Takaoka's wave number to the test coil, and □ applying a different frequency □ wave number to the eddy current thickness measurement system. A method for non-destructively measuring the wall thickness of a cladding tube, characterized by: measuring the wall thickness of a cladding tube and its liner layer. : ・′ 2. The cladding tube is a fuel cladding tube that accommodates nuclear fuel.
The cladding tube main body is made of a zirconium alloy, and the cladding tube body according to claim 1 is made of ruconium, and the lie 1 layer applied to the inner circumference of the cladding tube body is made of ruconium. A method for measuring thickness non-destructively. 3. For the wall thickness measurement of fuel cladding tube and inspection coil,
Apply a coil frequency in a low frequency band □ of about 10 KH'z to about 100 KHz, and apply a coil frequency of several hundred KH'z to 3' MI to the test coil for measuring the layer thickness of the fuel cladding liner.
(The □coil frequency in the high frequency band of about z is
□ A method for non-destructively measuring the wall thickness of a cladding tube according to claim 2. ″ □4. A patent claim in which the inspection liner uses a Zorope type inspection coil for measuring the local thickness, and a □ insert 1 or □ through □ type coil is used for measuring the average wall thickness in the circumferential direction of the cladding tube. A method for non-destructively measuring the wall thickness of a cladding tube described in Items 1 and 3 of □. , input the eddy current measurement signals from the first eddy current two-thickness measurement system for measuring the thickness of the □ litchi □ layer of the test tube, the measurement system, and the - side strip system, and □ input the eddy current measurement signals from the □ side strip system. Meat gate 1 and its lie Q, - Thickness measurement system requires a small amount of ml inspection, voice coil has a second eddy current. □6. The cladding tube is a fuel cladding tube that contains and contains nuclear fuel, and the main body of this cladding tube is made of a zircoium alloy. 1. A device for non-destructively measuring the wall thickness of a cladding tube according to claim 5, wherein an inner layer of pure zirconium is applied to the inner circumferential surface of the cladding tube. 7. First vortex The military style wall thickness measurement system has a probe type inspection coil that approaches or comes into contact with the liner layer of the cladding tube, and the second eddy current type wall thickness measurement system has a probe coil that approaches or contacts the liner layer of the cladding tube. A probe-type test coil that is in contact with the surface or in contact with the surface is provided.
A device that non-destructively measures the wall thickness of a pipe covered by 5fiK. hi"'e,, 輯' The first or second eddy current wall thickness measurement system includes: ■! An insert, mold, or A device for non-destructively measuring the wall thickness of a cladding tube according to claim 5, wherein the penetrating inspection coil is provided with a wide opening as necessary.