JPS6138404A - Measuring method of thickness of liner layer and thickness of zircalloy of liner coated pipe - Google Patents

Abstract

PURPOSE:To improve measuring accuracy, by applying three frequencies to a coil in a pipe, so that the penetrating depth of one frequency is approximately equal to the total thickness of the pipe, that of one frequency is approximately equal to the thickness of a liner layer and that of one frequency is smaller than the thickness of the liner layer, and removing the fluctuation of lift-off and the change in sensitivity from the measured values of said three signals obtained by said application of the three frequencies. CONSTITUTION:A liner coated pipe (a) comprises a base material of zircalloy and a liner layer of pure zirconium. The pipe (a) is rotated by a rotary machine (b). A probe (d) is moved in the axial direction of the pipe by a driving device (c). A frequency is applied to a coil so that the penetrating depth is approximately equal to the total thickness of the pipe (a). A frequency is applied so that the depth is approximately equal to the thickness of the liner layer. A frequency is applied so that the depth is smaller than the thickness of the liner layer. The change in impedance of the coil is converted into voltage change by an eddy current flaw detector (e). The voltage is inputted to an operating device (f). The effects of the lift-off signal and the sensitivity change to the thickness signals are removed by the operating process based on various relationships of the measured values of the specified 3 frequencies. The thickness of the liner layer, the thickness of zircalloy and the total thickness obtained in this way are displayed on a display device (g).

Description

Detailed Description of the Invention The industrial field of application is to fill a 411 tube with berent-like molten metal and use it as a fuel rod for a nuclear power reactor. When lining the pipe and using it as a groove bottom, use Zircaloy to create a thick liner layer! I would like to find a way to non-destructively measure y and derive an accurate thickness value.

(Prior Art) Fuel rods for nuclear power reactors are groove-bottomed by filling a cladding tube with a large number of fuel pellets. Zircaloy tubes are often used as cladding tubes because of their corrosion resistance, non-rebelliousness, strength, and Kuden 30 rating.

Zircaloy is a zirconium alloy, Zircaloy 2 (
(hereinafter referred to as Zr-2) is an
, 1.5; Fe, 0.12; ni.

0.05; Cr-0.10k included.

Rapid increases and decreases in power are essential for highly efficient operation of nuclear power reactors. To do this rapid output fluctuation:
Fi, in a single Zircaloy-covered tube, there is a concern that stress N corrosion δJ may occur due to the expansion of the fuel pellet. In response to IK fi 9, cladding tubes with an ultra-thin liner layer of zirconium (hereinafter sometimes referred to as Zr) have been developed and are beginning to be used. This liner-covered tube 82 needs to have a liner layer of a predetermined thickness for reasons such as strength issues, and it is also necessary to guarantee the Zircaloy W which is the base material. The total wall thickness of the v1 cladding pipe is, for example, 860 μm, whereas the liner γ is 80 μm, which is about 1096 μm of the total wall thickness.

This liner branch is made from a double tube made by covering a flailed Zirfnik tube with a Zircaloy tube, and is made by repeatedly cold working and annealing it. Therefore, nine tubes are manufactured with a thickness of 900 mm liner layer.

The decision as to whether Zircaloy's 〃 is within the specified specification value is not only an important matter for management on the user side, but also an important matter for improving the gN development of manufacturing technology.

Destructive testing and non-destructive testing can be considered to determine the constant thickness of the composite material layer made of two types of liner M cladding, but the length of the liner cladding is 4 m, and destructive saving (I/J*r) is based on the actual measurement of the sample taken from both bridges of the pipe, so only that part can be guaranteed, and it is essential to measure the entire length of the pipe. In some cases non-destructive testing is required. For this non-destructive inspection, an ultrasonic method and a flow method can be considered. However, the ultrasonic method from outside the tube cannot be used because it is impossible to distinguish between the boundary red echo between the extremely thin liner layer and the Zircaloy portion and the bottom surface reflection echo.

Eddy current method from inside the pipe 11: If the difference in JgfIt ratio between the liner layer and the Zircaloy part is used, the liner layer's
The principle of the Uryu method is to flow an alternating current and bring the coil close to the metal surface = 9 metal surface Gl: simple current flows. An induced cape m field is induced by the eddy current, and this induced magnetic field ↓
The impedance of the coil changes at this point, and this impedance change provides information on the surface of the target jt1. The liner cladding pipe is made up of 11:2 circulation, and the impedance changes depending on the change in the thickness of the upper layer, and the impedance change ω changes even if the total wall thickness of the main pipe changes. Therefore, these t F1a 611 can be used at a constant rate.However, the distance between the coil and the surface of the target FA, that is, the variation in lift-off, greatly affects the impedance change II.Therefore, the impedance change due to the above-mentioned impedance is Therefore, at a single frequency.

It is impossible to measure the liner layer thickness and the total wall thickness simultaneously, and it is very difficult to remove the 70,000-meter shape. (Unexamined Japanese Patent Publication No. 59-67405.

″r@kaisho 59-67406, etc.).

(Problems to be Solved by the Invention) The present invention provides a solution to the above-mentioned difficulties of the prior art, and provides a method that makes it possible to simultaneously and accurately measure the liner layer thickness of a liner-clad tube and the Zircaloy thickness t'' from the inner surface of the tube. The purpose is to give

(Rounding means and action to solve the problem) The present invention has the following features:
When defining the layer W- of the liner cladding in a non-destructive manner,
The frequency applied to the coil of the Mfi method from the inner pipe liner side is 61! when the penetration depth is near the full wall thickness, near the liner station, and when the liner layer thickness is small. Simultaneous +1: Using the measurement frequency &, the obtained 6 signal measurement values are delayed according to a certain method, and the 7 to 7 fluctuations are
By removing the influence of the 7 signal on the thickness signal and the influence of the thickness signal on the sensitivity change, it is possible to derive the accurate thickness 4ti.

The single light beam 8A will be explained in detail below with reference to the attached drawings.

FIG. 1 schematically shows a cross-section of a composite liner-clad tube consisting of a base material of Zircaloy (Zr-2) and a liner layer of pure zirconium, and the actual dimensions are as described above.

The relative magnetic permeability μr of both zirconium and zircaloy is 1, but the specific resistance ρ of Zr is 40 [μΩ・α]Zr −
2 is 70 [μΩ・1]υ degrees, and by using the difference of 1/ρ) in the Keyaki Denpei σ between the two, it is possible to measure the thickness of the liner layer from the inside of the tube using the eddy current method. It is also possible to measure wall thickness. However, these direct 6tll constant errors are large.

When applying the eddy current method, the distance a between the coil and the metal surface
1, that is, 7 to 7e, is greatly influenced.

In this address aA, the following three interrelated properties are named for the signals due to L7 to 7 fluctuations, the signals due to liner layer thickness fluctuations, and the signals due to total thickness fluctuations, and the basic ( Based on these, we are trying to derive the accuracy of the thickness value.

1] Lift-off affects the sensitivity of both the signal due to liner thickness variation and the signal due to total wall thickness variation.

2 ninri 7 too 7 strange! The VNCJC signal is additively combined with the signal due to the liner layer thickness variation (No. 8) and the signal due to the total thickness variation.

6) Signals due to variations in the liner layer thickness, signals due to changes in the total thickness, and signals due to changes in the total thickness have different dependencies on frequency.Based on these properties, as a means of this investigation method, we first The following six frequencies are selected in relation to the penetration depth. Then, measurements of six types of frequencies are obtained at the same time.

5 types J! The application position within η of the measurement of one skill number is the same.

Regarding the penetration depth k, the eddy current induced in the coil by the frequency applied to the coil concentrates on the surface side of the metal due to the skin effect, and decreases exponentially as the depth from the surface increases.

Here, ω: angular frequency (2πf), f: frequency/'
= # r m] In the case of a liner-clad tube, the above formula holds similarly if the ratio of electrical conductivity of Zr to Zr-2 is corrected to the thickness of the Zr layer. In the present invention, for a liner-clad tube Highly accurate thickness: o't w < Select the following five frequencies to be applied to the coil of the eddy current method as pre-trapping, apply them under the same setting conditions, and measure six measured values as impedance changes at the same time. get.

1) Circumference number used for measuring the total wall thickness: f, 3. The penetration depth is the total wall thickness of the liner cladding (near the reference value or nominal value.

l) Frequency f, used for measuring the liner layer thickness.

It is assumed that the VR waveform has a penetration depth close to the liner layer thickness (7i!iIP value or nominal value). This li! The signal obtained with one wave number is zrW-variant! It is highly sensitive to 1lIII GC and is almost insensitive to Zr -2hiko fluctuations, that is, it is ignored.

1) IJ 7) Frequency f used for off δ111 constant
s6 A frequency where the penetration depth is smaller than the liner layer thickness (same as above). The obtained reliability 4j- is Zr -2 thickness, which is insensitive to Zr thickness fluctuations and is negligible.

Tsum vf, < f! There is a relationship: <f a.

As a result of the above, each obtained Idf becomes the function of the following impedance vector equation.

The signal HE” obtained by fl = Z (Zr −2
, ri 〇(Zr, υten i(1n(Z)...(1) Signal obtained at f will; Mt2) = J((zr,
ri+:d2) (4 fists...(2) Signal obtained by fs;;,, (3>=''L13)(
4...(3)゛Here, Zr-2 is Zircaloy thickness,
Zr is the liner layer thickness, and l is the lift-off.

If this result is shown as a change in each vector component on the normalized impedance plane, it will be as shown in the second example. Second
The vertical axis of the figure is ωL/ωLO, which is obtained by normalizing the coil inductance ωL at the time of measurement with mLo in air alone, and the horizontal axis is the difference between the coil resistance R at the time of measurement and the coil pure resistance RO in air alone. Normalized with (IILO* (R-Ro J
/ mLof.

Using the previous equation, each vector component at each frequency in Figure 2 is: F(Zr −'l・l): Due to Zircaloy thickness variation (
=, which indicates that the sensitivity increases when the sensitivity is changed to y.

Sensitivity changes depending on It is shown that.

M(zr, υ: G(Zr・j) at frequency Vkft.

Welcome <t)-(i=1~5): ! /y
) O y 9tf+hti L ru Shin E
Out.

The following relationships exist between these tL and others.

(A) Su7to71 and l i, (1) ((111 with the moon)
1 has a strong relationship as shown in Figure 6.

(B) Also, In (ZrrlH assumes that Zrg is constant, and there is a relationship between 7 to 7 and 72 [5'J in Figure 4), and a relationship with liner thickness as shown in Figure 5, assuming that 7 to 7 is constant. be.

(0 mouth; (zr -2+t) l, to (zr, z month also has a 7211Q staff as in (B).

The thickness of the lift-off flange is determined by measuring at 68 specific waves and applying certain processing based on the above-mentioned 11 relationships from the obtained signal values.
By removing the influence of the sensitivity change of the superimposed L and thickness signal on
Reiner, who is in debt, asks for a threatening handiwork I Recaroy IV. Nawachi.

1) σ1 constant value IK3) IL (
3n (1 house is missing, 6th drawing 7th off is found, 7th off) to 1″L[2) (/small IBυ(1)1
is found.

2) Once the value of 7offg is determined, the measurement fjP'1 and l
i, (2) (from January to equation (2) = ri ln(Zr
Find υ1.

s) IM(Zr, υ1 to m5 The thickness of the quinal layer is determined from the diagram.

4) IBυ (January and 1 (zr, t)l is calculated from 7 to 7 and liner layer thickness n2.1ltl constant bar IMI) I
LCIF(Zr-2,1)I adds 1 to the formula (1).

5) IF (Zr-2+January value=Kuzilkaroy thickness is determined.

(Example) Fig. 6 shows 81 points of equipment borrowed when carrying out the method of the present invention. The liner to be measured is the ffl tube (aJ is rotated by a rotary machine (bJ and 1 drive Cc) to the L cuprose (dJ is moved parallel to the t-axis 141 in the tube. Prologue (d) in 11: A Vi absolute value type coil is embedded, and the coil diameter is approximately 1 mm.

This fill is becoming an impedance industry [flaw detector (e)]
The voltage is changed to voltage and read into the calculation device (f) incorporating the processing program according to the method of the present invention, and the resulting liner NIIN, Zircaloy thickness, and total wall thickness are displayed on the display (ω The f+ side frequency is f
r 100 KHz, f@F3 MHz.

rs52M112 tel.

(Effects of the Invention) According to the method of the present invention, fuel rods for nuclear power reactors (liner layer thickness of D'y inner corrugated pipe, Zircaloy thickness, total wall thickness t-
The eddy current method, a non-destructive method, allows measurement with high precision at the same time.9 As a result, these thickness values are guaranteed over the entire length and circumference of the pipe, ensuring safety in use. Effects such as being able to contribute to the improvement of personal security and production technology can be obtained).

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the cross section of the liner cladding tube, Figure 2
The figure is a chart showing signal changes on the normalized impedance plane when measurements are carried out by the method of the present invention, and Figure 6 shows the relationship between the vertical axis r (t1) +t) + and Shinabata Nori7 to71. The diagram shown, Figure S4, is a diagram showing the relationship between the vertical axis IH (Zr+/month and the tank shaft beam 7 to off l when the liner layer thickness is constant).
A diagram showing the relationship between l'Th(zr,l)l of it '4'lll and liner layer thickness on the horizontal axis, and FIG. 6 is a diagram of an example of a device for carrying out the method of the present invention. . (,)...liner cladding tube, (b)...rotation (view, (
c)...Drive device, (d)...Prologue, (eJ...Grief depth f3 device, (f)...Arithmetic device, (ω...Display device.

Claims (1)

[Claims] When the cladding tube containing fuel is a liner cladding tube in which the inner circumferential surface of a Zircaloy base material tube is lined with pure zirconium, in order to measure the layer thickness non-destructively, the penetration depth is measured from the liner side using an eddy current coil. The three-signal measurement value obtained simultaneously by applying three measurement frequencies near the total wall thickness, near the liner layer thickness, and smaller than the liner layer thickness shows that the lift-off signal caused by lift-off fluctuation is superimposed on the thickness signal. and a method for measuring the liner layer thickness and Zircaloy thickness of liner-clad tubes, which is characterized by eliminating the influence of sensitivity changes in thickness signals and making it possible to measure thickness with high accuracy.