JPS61225603A - liner thickness measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for non-destructively measuring the liner thickness of a liner tube, and is particularly used in the core of a nuclear reactor to measure iodine, a fission product. The present invention relates to a liner thickness measuring device for a pipe in which a zirconium liner is applied to the inner surface of a zirconium metal pipe in order to prevent stress corrosion cracking in an environment containing zirconium metal.

[Prior art]

A fuel cladding tube containing nuclear fuel is provided in the core of a nuclear reactor. The main function of this fuel cladding is to prevent fission products generated by nuclear fission of nuclear fuel from escaping into the surrounding cooling medium, and its material includes:
Zirconium alloys such as Zircaloy-2 and Zircaloy-4, which are strong up to relatively high temperatures and extremely safe, are widely used. This zirconium alloy has excellent properties such as good ductility and non-reactivity with cooling media, but fuel cladding made of zirconium alloy has
If the power of a nuclear reactor was suddenly increased, there was a risk that damage would occur due to interaction with the nuclear fuel. The cause of this damage is thought to be due to a combination of mechanical interaction based on the difference in coefficient of thermal expansion between the fuel cladding and the nuclear fuel, and the corrosive effects of corrosive products contained in nuclear fission products. Stress corrosion cracking is thought to be the cause.

Zirconium liner tubes have been developed to prevent stress corrosion cracking of fuel cladding tubes. This zirconium liner tube has a pure zirconium coating on the inner periphery of a zirconium alloy cladding tube body. By providing a zirconium liner layer on the cladding tube body by lining it with pure zirconium, which is softer than zirconium alloy, this zirconium liner layer relieves the stress acting on the fuel cladding tube.
It also prevents corrosive fission products from coming into direct contact with the cladding tube body, thereby suppressing damage to the zirconium liner tube due to stress corrosion cracking.

However, in order to guarantee the damage prevention function of the zirconium liner tube, it is required that the zirconium liner tube be lined with pure zirconium at a predetermined coating thickness over the entire circumference and entire length of the zirconium liner tube.

To measure the liner thickness of zirconium liner tubes, a method has been proposed in which a measuring coil is inserted into the tube and the measurement is performed using an electromagnetic induction method that captures impedance changes based on the resistance difference between the liner section and the cladding tube body. (For example, JP-A No. 5
No. 9-67405).

[Problem that the invention seeks to solve]

When measuring the liner thickness of, for example, a zirconium liner pipe using such a method, the impedance of the measuring coil changes when the measurement environment, for example, the environmental temperature changes, and the pipe temperature at the time of measurement of each zirconium liner pipe to be measured differs. In each case, measurement errors may occur because the specific resistance of the tube itself changes.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and involves measuring the thickness using a standard tube having a predetermined liner thickness, and comparing the measured value with the liner of the same standard tube that has been measured in advance. Determine the deviation from the measured thickness value, and subtract the deviation from the measured liner thickness value of the pipe to be measured to correct the measured liner thickness value of the pipe to be measured to the liner thickness measurement value at a predetermined environmental temperature. Accordingly, it is an object of the present invention to provide a liner thickness measuring device that can accurately measure liner thickness without being affected by environmental temperature.

The liner thickness measuring device according to the present invention is a device for measuring the liner thickness of a pipe to be measured in which a liner is applied to the surface of a metal pipe by an electromagnetic induction method, and is capable of measuring a standard pipe having a predetermined liner thickness in advance. a deviation calculating means for calculating the deviation between the measured liner thickness value of the liner placed on the pipe and the measured liner thickness value of the standard pipe when measuring the liner thickness of the pipe to be measured; and calculation means for subtracting the deviation calculated by the deviation calculation means to correct the liner thickness measurement value of the pipe to be measured.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a side view schematically showing the entire apparatus of the present invention (hereinafter referred to as the apparatus of the present invention), in which numeral 1 indicates a zirconium liner tube to be measured. 1 is a support tool 3.3 for the tubes to be measured 1 that are set up in multiple rows on a surface plate 2, and a tube holding jig 5.5 that is moved up and down by air cylinders 4.4. It is fixed horizontally at... Further, on the holder 112, a sensitivity calibration ta6 is installed on the distal end side (left side in the figure) of the tube to be measured l, and an insertion guide tube 7 and a sensitivity calibration test piece (not shown) are installed inside it. . One end of a standard tube 31 having the same inner and outer diameters as the tube to be measured 1 is connected to the proximal end side (right side in the figure) of the tube to be measured 1 via a tube connecting support 32. 31 is a similar support 3°3 on the same axis.
... and pipe holding jigs 5, 5... are fixed horizontally.

Reference numeral 8 denotes a cylindrical insertion rod with a bullet-shaped coil holder 9 attached to its tip and a signal line housed inside, and a solo bread ball-shaped spacer with the same diameter as the coil holder 9 is inserted into the abdomen at regular pinch intervals. 10 is installation. This insertion rod 8 is attached to a surface plate 11 disposed close to the surface plate 2 so that its longitudinal direction is connected to the pipe to be measured 1.
Endless chain 1 stretched so that the 0-axis length direction
It is supported horizontally by an insertion rod support 13 erected at 2, and arranged so that its axis coincides with the tube to be measured 1. Note that the chain 12 rotates freely.

A pulse motor 16 mounted on a measuring instrument trolley 15 arranged on a rail 14 on a surface plate 11 is disposed at the rear end of the insertion rod 8 (on the left side in the figure), and the pulse motor 16 can be rotated in forward and reverse directions. As the chain 12 is interlocked with the insertion rod support 13, the insertion rod 8 is moved forward and backward. When the insertion rod support 13 reaches the end on the side of the sensitivity calibrator 6, the insertion rod 8 is released. Further, an impedance measuring device 17 is installed on the measuring device trolley 15, and the output of the impedance measuring device 17 is transmitted to the cable carrier 1.
The signal is supplied to the A/D converter 101 through a signal line provided at 8, where it is analog/digitally converted and input to the arithmetic and control unit 100.

The pulse motor drive circuit 19 supplies a pulse drive current to the pulse motor 16 via the cable inside the cable carrier, rotates the pulse motor 16 in forward and reverse directions by an amount corresponding to the number of pulses, and moves the coil holder 9 forward and backward. Arithmetic control device 10
0 issues phase information to the pulse motor drive circuit 19 that determines the number of output pulses and the direction of rotation.

As shown in FIG. 2, the coil holder 9 has four measurement coils 22 arranged at equal intervals in the circumferential direction, each coil 22... The thickness or the thickness of the liner layer inside the standard tube 31 can be measured simultaneously at four points in the circumferential direction.

Signals related to the liner thickness of the tube under test 1 or the standard tube 31 detected by the coils 22 and output from the impedance measuring device 17 are converted into analog/digital signals by the A/D converter 101 and subjected to calculation control. It is input to the device 100, where the liner thickness etc. are calculated, and the calculated values are stored in the memory 10.
2 is stored. The arithmetic and control unit 100 displays the calculated value on the display 21, and if the calculated value is abnormal, the alarm 2o issues an alarm.

The procedure for measuring the liner thickness using the apparatus of the present invention configured as described above will be described below.

First, the arithmetic and control unit 100 outputs a predetermined number of pulses to the pulse motor drive circuit 19 to drive the pulse motor 16 to insert the coil holder 9, which is in a fixed position above the surface plate 11, to the sensitivity calibration position fi6. At this position, each coil 22
The arithmetic control device 100 performs sensitivity calibration based on the signal detected by the impedance measuring device 17.

Sensitivity calibration is performed using a sensitivity calibration test piece (
(not shown), that is, based on the amount of lift-off.

The lift-off amount in one coil 22 is T^μm
When the impedance changes from 78 μm to 78 μm, the impedance measured before and after the change is shown in Figure 3. wL/wLo ) on the complex plane of π, OB,! : shall be indicated. The arithmetic and control device 100 calculates the amount of change in the two impedances, that is, the absolute value 1Δzzt 1 of i−■(−ΔZjt,),
The angle α1 formed with the real number component axis (horizontal axis) is determined. Then, in the same way, the absolute value α2 of the impedance change amount of each of the remaining three coils 22... α3. The α number is determined, and the amplification factors A1°A2, A3, A4 (-1/
Find lΔZl, l).

This allows the arithmetic and control device 100 to adjust the level of the signals detected by the coils 22, . . ., or in other words, calibrate the sensitivity of the coils.

On the other hand, the direction Zll is the impedance change direction due to lift-off, and the direction perpendicular to this is the impedance change only due to the liner thickness. Therefore, the impedance change direction vy due to lift-off and V perpendicular to this
By determining the x direction in the α section, finding the component in this direction from the measured value, and multiplying it by each A+ (i-1 to 4), the liner thickness can be measured without sensitivity difference between coils. . That is, the sensitivity calibrator 6 is used to perform the above-mentioned calibration using known test pieces with constant liner thickness and different lift-off amounts, and the sensitivity calibrator 6 is used to perform the above-mentioned calibration using known test pieces with constant liner thickness and different lift-off amounts.
is stored in the storage device 102. It goes without saying that the direction of impedance change vy due to lift-off is toward the point (0, 1) on the vertical axis.

A1 and α quantities for these four coils (i-1 to 4
) is calculated by the arithmetic and control device 100 and stored in the memory 102, and the arithmetic and control device 100 calculates the standard tube 31. When measuring the thickness of each liner of the pipe to be measured 1, AI + α1
is taken in from the memory 102 and the impedance measuring device 17
The signal inputted from the controller is changed and corrected by A I + α1.

When the sensitivity calibration as described above is completed, the arithmetic and control unit 10
0 is standard tube 31. In order to measure the liner thickness of the pipe to be measured 1, calculations and controls are performed as shown in FIG.

FIG. 4 shows a flowchart showing the calculation and control contents of the calculation and control device 100. First, in preparation for measurement, the arithmetic and control unit 100 outputs a predetermined number of pulses to the pulse motor drive power source 19, and further advances the insertion rod 8 to position the coil holder 9 within the standard tube 31.

As a result, the coils 22... detect the liner thickness of the standard tube 31, and the arithmetic and control unit 100 changes and corrects the input signal related to the detected value using A i Hα1, and outputs the corrected measured value Ms+( 1-1 to 4) are stored in the memory a102 as standard values. This measured value Msl
For this, measurements are taken at multiple locations in the axial direction of the standard tube 31, and the average value is determined. This increases the reliability of the measurements.

When such measurement preparation is completed, the arithmetic and control device 100 starts measurement. In this measurement, each time the pipe to be measured l is measured, for example, the liner thickness of the standard pipe 31 is measured before the measurement.

The arithmetic and control unit 100 outputs a predetermined number of pulses to the pulse motor drive power source 19 to advance the coil holder 9 from its home position into the standard tube 31, and input signals detected by the coils 22 to the AI. .

The measured value MsI'(i
-1 to 4) are stored in the storage device 102, and the following calculations are performed.

The arithmetic and control unit 100 subtracts the previously measured value Msl from this measured value Msl' to obtain the absolute value of the deviation 1ΔMs+, and if the absolute value of the deviation deviates from the preset deviation tolerance upper limit K, An alarm is issued by the alarm device 20 as a measurement abnormality, and the operator is notified.

The operator performs a new sensitivity calibration, which ensures accurate measurements no matter how the environmental temperature changes. Note that the above-mentioned upper limit of allowable deviation is set to a value at which the impedance of the coil 22 changes and measurement cannot be performed accurately. If the absolute value of the deviation is smaller than K, the next measurement is performed. That is, the arithmetic and control device 100 outputs a predetermined number of pulses to the pulse motor drive power source 19 to move the coil holder 9 back from inside the standard tube 31 into the tube to be measured 1, and the coil 22...
Similarly, the detected and input signal is changed and corrected based on the AI and α amount, and the measured values MI I (i-1 to 4) are obtained.

Then, the following +1+ formula obtained based on the reason explained later is set in the arithmetic and control device 100, and the arithmetic and control device 100 uses this +1) formula, the above measured value Mll, and the acquired value MSi + from the memory 102. The true liner thickness Mtl (i-1 to 4
) can be determined, and this Mt is displayed on the display 21.

MtI-MJI-CM3I'Msl)-(1)
In this way, the true liner thickness can be measured based on the environmental temperature when measuring the pipe 1 to be measured and its measured value M1i! ,
This is because there is the following relationship between them.

Figure 5 is a graph showing this relationship, with the horizontal axis representing the environmental temperature T and the vertical axis representing the measured liner thickness (Mll). This is a summary of the results of measurements taken when the tube was subjected to different environmental temperatures T, and the broken line is a summary of the results of measurements made when the environmental temperature T was varied within the same range for a zirconium liner tube with a liner thickness of 60 μm. . As can be understood from this figure, both the solid line and the broken line are straight lines, and their slopes are the same.

Therefore, the measured value MN, is +
As expressed by equation 11, the standard environmental temperature To (
Since it can be corrected to the true liner thickness MI, which is regarded as the liner thickness measured when This is because it can be measured as .

In the above embodiment, the coil holder moves forward without rotating in the circumferential direction relative to the zirconium liner tube.

Although measurements are taken by moving the coil holder backwards, the present invention is not limited to measuring in this way; it is also possible to adopt a configuration in which the coil holder is moved forward and backward while rotating relative to the zirconium liner tube. Of course.

Furthermore, although the liner thickness of a zirconium liner tube is measured in the above embodiment, the present invention is not limited to measuring the liner thickness of a zirconium liner tube, but can also be applied to a tube lined with a metal tube made of other materials. Of course, it is possible to measure the

〔effect〕

As detailed above, the present invention measures the thickness of a standard tube having a predetermined liner thickness, and the deviation between the measured value and the liner thickness measurement value of the standard tube measured in advance. is calculated, and the deviation is subtracted from the measured liner thickness of the pipe under test to correct the measured liner thickness of the pipe under test to the measured liner thickness at a predetermined environmental temperature, so there is no influence on the environmental temperature. This allows accurate measurement of liner thickness.
Furthermore, measurement abnormalities can be determined during measurement based on the above-mentioned deviations, which provides excellent effects such as always being able to perform accurate measurements.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is a schematic sectional view showing the arrangement of the measurement coil, and Fig. 3 is a coil sensitivity based on only the impedance component related to the liner thickness based on the impedance measurement value. Figure 4 is a flowchart showing the calculations and control contents of the arithmetic and control unit, and Figure 5 is a graph showing the relationship between environmental temperature and liner thickness measurements. be. 1... Zirconium liner tube 6... Sensitivity calibrator 3
1...Standard tube 100...Arithmetic and control device Hsu Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Kawa
Noboru':! , 3 Figure xi 3A & (T) Atsushi 5 Figure 6 Tomome

Claims (1)

[Claims] 1. In an apparatus for measuring the liner thickness of a pipe to be measured in which a liner is applied to the surface of the metal pipe by electromagnetic induction method, the liner thickness is measured in advance for a standard pipe with a predetermined liner thickness. deviation calculating means for calculating the deviation between the liner thickness measurement value of the standard pipe and the liner thickness measurement value of the standard pipe when measuring the liner thickness of the pipe to be measured; 1. A liner thickness measuring device comprising: arithmetic means for correcting a liner thickness measurement value of a pipe to be measured by subtracting the deviation calculated by the means. 2. The standard tube is arranged on the same axis as the tube to be measured, and the liner thickness of the standard tube can be measured each time the liner thickness of the tube to be measured is measured. A liner thickness measuring device according to claim 1.