JP6426529B2 - Film thickness measuring method and film thickness measuring apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring the thickness of an oxide film which is exposed to a corrosive environment and formed on a metal material, and in particular, to an internal structure, pressure vessel and piping in contact with cooling water of a nuclear power plant Method and apparatus for measuring the thickness of an oxide film.

  In plant equipment such as nuclear power, managing the soundness of materials against stress corrosion cracking is an issue.

  High corrosion resistant stainless steel or Ni base alloy is used for the cooling water contact surface of the reactor internals, pressure vessels and piping of the reactor. In these devices, technology development has been advanced to prevent and predict the occurrence of cracks and the growth of cracks in response to material damage caused by stress corrosion cracking.

  One of the proposed factors for the occurrence of stress corrosion cracking is the destruction of the oxide film formed in a corrosive environment. The fracture of the oxide film is caused by the strain due to the difference between the crystal lattice spacing and the thermal expansion coefficient which occurs with the substrate, and the internal stress of the substrate and the externally applied stress. It is thought that local corrosion occurs due to the exposure of the new surface at the site where the oxide film is broken, and that it is the origin of the crack due to stress concentration.

  Here, as the oxide film becomes thicker, the strain between the substrates becomes larger and it becomes easy to be broken. However, the chemical composition of the substrate and the form and characteristics of the oxide film to be formed depending on the corrosive environment, and the adhesion to the substrate are different, and the thickness of the film which is easily broken is different. Furthermore, if the coating is relatively thin, it will be repaired even if breakage occurs.

  Therefore, in order to predict the occurrence of stress corrosion cracking mainly due to the destruction of the oxide film, the thickness of the oxide film is measured with high accuracy, and the time to reach the thickness of the oxide film where stress corrosion cracking may occur It is necessary to estimate, and high precision measurement enables prediction.

  As a method of measuring the film thickness, there are an electromagnetic induction method, for example, an eddy current method disclosed in Patent Document 1 and an optical method disclosed in Patent Document 2.

Unexamined-Japanese-Patent No. 7-218474 Japanese Patent Application Publication No. 2008-527173

  In general, the thickness of the oxide film at which stress corrosion cracking occurs is thin, and the thickness of the oxide film at which stress corrosion cracking occurs in a high temperature water environment simulating reactor cooling water is 1 μm or less. Moreover, in order to predict the occurrence of stress corrosion cracking, a measurement accuracy of about 0.2 μm or less is required.

  Here, the oxide film has a two-layer structure consisting of a uniform inner layer and a granular outer layer, and the measured value is difficult to stabilize. Furthermore, in the case of application in a nuclear reactor, it is necessary to take into account the influence of radiation noise at the detector, as it is measured in a radiation environment.

  In the methods described in Patent Documents 1 and 2 as described above, it is difficult to measure the film thickness with a measurement accuracy of about 0.2 μm or less when the thickness of the oxide film is 1 μm or less.

  The present invention provides a film thickness measuring method and apparatus which can be used in a radiation environment such as in a light water reactor and can measure the thickness of an oxide film having a thickness of 1 μm or less with a measurement accuracy of about 0.2 μm or less. Has its purpose.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present invention includes a plurality of means for solving the above problems, and an example thereof is a method of measuring the thickness of a film formed on the surface of the object to be measured, the surface being the object to be measured Bringing one or more pairs of current terminals and one pair of potential difference measurement terminals into contact, applying a predetermined load to the current terminals and pressing them against the object to be measured, and applying a constant current to the current terminals in this pressed state; The potential difference change is measured by changing the current value at a plurality of points on the surface to be measured by the potential difference measurement terminal, and the data of the plurality of measured potential difference changes are processed to obtain a measurement frequency at which a predetermined potential difference decrease is observed. The film thickness of the surface to be measured is determined from the applied current value.

  According to the present invention, in a state where the measuring device is not susceptible to radiation, the average thickness of a thin film of 1 μm or less is measured with an accuracy of about 0.2 μm even for a film having a granular outer layer on the surface Can.

It is a schematic diagram of the film thickness measuring apparatus used for the film thickness measuring method of this invention. It is a cross section of the oxide film formed by the corrosion test of an Example. Among the results of the potentiometric measurement of the embodiment, it is an example of a reduction-type potential difference change. Among the results of the potentiometric measurement of the embodiment, it is an example of a reduction-type potential difference change. It is an example of an increase type potential difference change among the potential difference measurement results of an example. It is an example of the figure which shows the electrical potential change by the electrical potential measurement by 3 A of applied currents of an Example. It is an example of the figure which shows the electrical potential change by the electrical potential measurement by the applied electric current 13A of an Example. It is a figure which shows the influence of an applied current on the frequency of occurrence of the potential difference decreasing type. It is a figure which shows the relationship between the applied current used as predetermined | prescribed electric potential difference reduction type | mold occurrence frequency, and average oxide film thickness.

  The film thickness measuring method and the measuring apparatus of the present invention use the phenomenon that the variation of the potential difference change caused by the variation of the surface state found by the present inventors is reduced by changing the applied current. The dependence of the frequency of the observed measurement on the applied current, that is, the correlation between the value of the applied current and the thickness of the film when the rate at which the potential difference decreases becomes a predetermined value among the data of time changes of the plurality of measured potential differences. Is used to determine the film thickness.

  Hereinafter, a film thickness measuring method and a film thickness measuring device according to an embodiment of the present invention will be described using FIGS. 1 to 9. First, an outline of a film thickness measuring apparatus will be described with reference to FIG. FIG. 1 is a view showing an outline of a film thickness apparatus of the present embodiment.

  In FIG. 1, the film thickness measuring device 20 includes a measuring device body 4, a DC power supply 13, a potentiometric precision measuring instrument 14, a signal line 31, a current supply line 32, and a data processing / recording device 17.

  The measuring device body 4 has a current terminal 5, a potential difference measuring terminal 6, an actuator 8 and a fixing mechanism 12. A direct current power supply 13 for applying a constant direct current connected via a current supply line 32 to the outside of the measuring apparatus main body 4, a potentiometric precision measuring instrument 14 connected via a signal line 31, A data processing and recording device 17 is provided.

  The measuring device main body 4 has one or more pairs of current terminals 5 and a pair of potential difference measuring terminals 6 placed on the surface 15 to be measured, and is specified to a pair of needle-like current terminals 5 arranged outside the sensor block 7 A constant current is applied between the current terminals 5 while loading a load, and a so-called four-terminal method structure is employed in which the potential difference change generated at the time of constant current application is measured at a pair of potential difference measuring terminals 6 disposed inside. It is done.

A constant current is supplied from the DC power supply 13 to the current terminal 5 via the current supply line 32. The potential difference measurement terminal 6 is connected to an external potential difference precision measuring instrument 14 by a signal line 31. The current supply line 32 and the signal line 31 have a sufficient length so that a constant current can be applied between a pair of current terminals 5 from a remote place and the potential difference can be measured. Therefore, by taking a sufficiently long current supply line 32 and signal line 31 can be measured remotely from the location of measuring an oxide film. As a result, it is possible to bring only the measuring apparatus main body 4 into a severe environment such as a radiation environment or water, and to place the DC power supply 13 and the potentiometric precision measurement instrument 14 at a remote place not affected by these severe environments. Measurement becomes possible.

  Furthermore, the measuring device main body 4 provided with the current terminal 5 and the potential difference measuring terminal 6 is provided with an actuator 8. The actuator 8 uses a motor, a hydraulic pressure, a piezoelectric element, or a shape memory alloy, and applies a constant load to the current terminal 5 and the potential difference measurement terminal 6 during the measurement of the potential difference. The load during measurement is set by the amount of movement of the sensor block 7 by the actuator 8.

  Furthermore, the load being measured by the compression spring 10A connected to the current terminal 5 and the compression spring 10B connected to the potential difference measurement terminal 6 can be brought into contact with the measurement target surface 15 sufficiently to allow the potential difference measurement. Be kept constant. The compression spring 10A and the compression spring 10B are disposed in the cylindrical terminal guide 9 so that the current terminal 5 and the potential difference measurement terminal 6 vertically contact the measurement target surface 15 along the terminal guide 9. ing. With regard to the load applied to the current terminal 5 and the potential difference measuring terminal 6, the pressing force of the current terminal 5 requires an appropriate load for creep deformation of the film, while the pressing force of the potential difference measuring terminal 6 is the contact resistance. The load is preferably set to be different because it is a load necessary to enable a stable potential difference measurement without change during measurement. Therefore, it is desirable that the spring constants of the compression spring 10A and the compression spring 10B have different values.

  Further, the measuring device main body 4 is provided with a cover 40 around the periphery and sends air from the outside with a blower 41 etc., and discharges water in the vicinity of the measuring device main body 4, especially around the current terminal 5 and the potentiometric measurement terminal 6. Is desirable. By this, even if it is a measurement object under the environment with which water was always always covered, such as the inside of a light water reactor, measurement of film thickness is attained.

  The shape of the tip of the current terminal 5 and the potentiometric measurement terminal 6 and the pressing force against the surface 15 to be measured are conditions under which the applied current dependency of the measurement frequency at which the potential difference decreases can be seen for the oxide film to be measured. Are previously considered and designed. This enables highly accurate measurement that captures the potential difference decrease.

  For example, the current terminal 5 has a pointed tip with a predetermined radius of curvature designed to penetrate the film to be measured by Joule heating due to load and energization. The potentiometric measurement terminal 6 can stably contact the coarse outer layer film 3 having irregularities formed on the surface as shown in FIG. 2 described later, so that the potential difference can be measured, and a load can be appropriately applied. It has a pointed tip with a radius of curvature like that.

  The mechanism is not particularly limited as long as a constant load is applied to the current terminal 5 and the potential difference measurement terminal 6 during measurement.

  Furthermore, it is desirable to have a mechanism that can also turn on and off the load. Therefore, as in the present embodiment, the load 8 is in charge of turning on and off the load by depression by the actuator 8, and the compression springs 10A and 10B having different spring constants are used for the current terminal 5 and the potential difference measuring terminal 6, respectively. It is desirable that the With these structures, it is possible to perform measurement with a high accuracy and constant load during measurement.

  In addition, the measuring device main body 4 provided with the current terminal 5 and the potential difference measuring terminal 6 is fixed with the support leg 11 so that the load set by the current terminal 5 and the potential difference measuring terminal 6 is pressed against the measurement target surface 15 It is fixed to the surface 15 to be measured by the mechanism 12. The configuration of the fixing mechanism 12 is not particularly limited as long as it is a mechanism for fixing the measurement target surface 15 to the device, but a motor, a structure that applies a pressing force to the measurement target by air pressure and oil pressure, or the measuring device main body 4 itself The vacuum pad attached to the above, and the structure etc. which exhibit the adsorption power by a magnet further are considered.

  Here, by applying a load to the current terminal 5 and applying a current, the oxide film creep-deforms due to the generated Joule heat and stress, and the thickness of the oxide film having a low electrical conductivity locally decreases. This causes a decrease in the potential difference after application of the current. However, the situation is different depending on the place where the tip of the current terminal 5 is in contact with a non-flat, film having the granular outer layer film 3. In the case of a thin oxide film having a thickness of 1 μm or less, the expected creep deformation does not occur due to the variation of the surface state, or the film is locally thin.

  However, there is a condition that the variation of the potential difference change caused by the variation of the surface state becomes smaller by changing the applied current. This phenomenon is used to determine the film thickness from the applied current dependence of the frequency of measurements where a potential drop is seen. Therefore, a data processing / recording device 17 is provided which records the applied current and the data of the potential difference measurement and performs arithmetic processing.

  The data processing / recording unit 17 stores data of a plurality of potential difference changes measured by changing the current value with respect to the surface 15 to be measured, which is measured by the potentiometric precision measuring instrument 14. In addition, when a predetermined measurement frequency at which a potential difference decrease is set in advance for each measurement target is reached (when the ratio of the number of data in which a potential difference decrease is observed in a plurality of measurements becomes a predetermined value) The applied current value is calculated from the plurality of potential difference change data, the applied current value at the predetermined measurement frequency is calculated, and the film thickness of the surface 15 to be measured is calculated from the applied current value. Therefore, the data processing / recording device 17 is a predetermined measurement frequency at which the potential difference decrease determined for each measurement object is measured, and the measurement frequency, which are measured using a reference test piece having a known film thickness in advance. The relationship between the applied current value and the film thickness (master curve) is stored.

  It should be noted that a plurality of measurement device bodies 4 are arranged on the target surface 15 to be measured, and the DC power supply 13 outside the measurement device body 4 and the potentiometric precision measuring instrument 14 are shared, and each measurement device body 4 is a measurement target surface It is desirable from the viewpoint of measurement efficiency to fix by the fixing mechanism 12 corresponding to 15 and simultaneously measure the change in potential difference.

  Next, the measuring method of the film thickness which concerns on this embodiment is demonstrated.

  According to the film thickness measuring method of the present invention, one or more pairs of current terminals 5 and a pair of potential difference measuring terminals 6 are disposed on the film to be measured, and a constant current is applied while applying a predetermined load to the current terminals 5. The potential difference change is measured at the potential difference measurement terminal 6 when applied, and the film thickness is determined from the applied current dependency of the measurement frequency at which the potential difference decrease is observed.

  Specifically, first, the apparatus main body 4 as shown in FIG. 1 is fixed to the surface to be measured using the fixing mechanism 12. Next, the current terminal 5 and the potential difference measurement terminal 6 are pressed against the surface 15 to be measured with a predetermined load using the actuator 8. As a result, the current terminal 5 is pressed against the measurement target surface 15 by the actuator 8 and the compression spring 10A, and the potential difference measurement terminal 6 is pressed against the measurement target surface 15 by the actuator 8 and the compression spring 10B.

  Next, with the current terminal 5 and the potential difference measuring terminal 6 pressed against the surface 15 to be measured, a constant current is applied between the one or more pairs of current terminals 5 by the DC power supply 13. Measure the time change of The measurement of the time change of the potential difference is carried out at the same time a plurality of times at different positions by changing the value of the current applied between the one or more pairs of current terminals 5.

  In the measurement method of the present embodiment, it is necessary to increase the number of times of measurement in order to obtain the frequency of measurement showing a potential difference decrease. Therefore, the DC power supply 13 and the potentiometric precision measuring instrument 14 outside the measuring instrument body 4 are shared, and the measuring instrument body 4 as shown in FIG. It is desirable to measure. Thereby, potentiometric measurement can be performed efficiently, and the time to estimate the oxide film thickness can be shortened.

  Next, the data processing / recording device 17 processes the data of the plurality of measured potential difference changes, and a predetermined measurement frequency (potential difference decrease type occurrence probability) in which the potential difference decrease is preset for each measurement object is obtained. The applied current value is determined, and the film thickness of the surface 15 to be measured is determined from the relationship between the applied current value and the film thickness when the measurement frequency at which the predetermined potential difference decrease is observed is obtained.

  Note that, using a reference test piece having a known film thickness in advance, the predetermined measurement frequency at which a potential difference decrease is observed, and the correlation (master curve) between the applied current value and the film thickness at that measurement frequency It is desirable to measure in advance.

  By using the film thickness measuring device and the film thickness measuring method having the above-mentioned features, it can be used in a radiation environment such as in a light water reactor, and the thickness of an oxide film having a thickness of 1 μm or less is about 0.2 μm It becomes possible to measure with the following measurement accuracy. The oxide film thickness thus measured is utilized, for example, for measuring the life of stress corrosion cracking caused by using the oxide film thickness as an index, and can contribute to the long-term soundness measurement of a structure such as a nuclear power plant.

  Hereinafter, examples of the present invention will be described below using specific examination results.

  What served as the base material of the test piece of a present Example is what processed the austenitic stainless steel SUS316L rolling material of 10 mm of board thickness. Table 1 shows the chemical composition of the substrate.

  A plurality of plate-shaped test pieces of 40 × 140 × 19 (mm) were collected from the base material having the composition shown in Table 1.

  Next, planar polishing or machining was performed on the measurement surface of the collected test piece. Planar polishing was employed as a surface machining process to simulate a machined surface with a practical roughness, such that the terminals were relatively uniform in measurement.

  After planar polishing or machining, the test piece was immersed in a pressure vessel connected to a high-temperature high-purity water circulation loop at 288 ° C. at 8 MPa to form an oxide film on the surface of the test piece. The high-temperature high-purity water is adjusted with oxygen gas and nitrogen gas so that the dissolved oxygen concentration is 8 ppm in the water quality adjustment tank, and the ion exchange resin is circulated to maintain the electric conductivity at 0.1 μS / cm or less (normal temperature) did. The immersion time was 100 hours or 500 hours to change the thickness of the oxide film to be formed. After immersion for a predetermined time, the test piece was taken out of water, dried and subjected to measurement.

The oxide film of the test piece immersed in high-temperature high-purity water consists of magnetite and hematite which are angled higher than Fe ₃ O ₄ . FIG. 2 shows an example of observation of the cross section of the oxide film.

  As shown in FIG. 2, the oxide film is formed on the surface side of the metal substrate 1 and has a two-layer structure of a dense inner layer film 2 and a coarse outer layer film 3. The average thickness of the sum of the two layers is about 0.5 μm. The average thickness of the oxide film including the inner layer film 2 and the outer layer film 3 formed under various conditions is measured by cross-sectional observation, and the surface finish of the material to be measured and the corrosion test conditions are shown in Table 2.

For the potential difference measurement, a four-terminal type film thickness measuring apparatus 20 whose configuration is schematically shown in FIG. 1 was used. A direct current was passed between a pair of needle-like current terminals 5 disposed outside the sensor block 7, and the potential difference was measured by the potential difference precision measuring instrument 14 via the pair of inner potential difference measurement terminals 6. The load at the time of measurement was set by the amount of movement of the sensor block 7 by the actuator 8, and was kept constant during measurement by the compression spring 10A connected to the current terminal 5 and the compression spring 10B connected to the potential difference measurement terminal 6. It was in the state.

  The tip of current terminal 5 and potential difference measurement terminal 6 is processed with a radius of curvature of 0.5 mm, and in the preliminary examination conducted while changing the load load, the load difference is stable at 14.4 [N] and the potential difference changes It used after confirming that it could measure.

  In addition, the load load is fixed at 14.4 [N], and constant DC current applied between current terminals 5 by DC power supply 13 is 1, 3, 5, 7, 9, 11, 13 or 15A and a plurality of currents It applied as a value and measured the time-dependent change of potential difference. In order to avoid the measurement of inrush current immediately after applying DC current, the potential difference changes with time after delaying approximately 0.01 seconds after DC current is applied, and the potential difference is measured every 1 second, up to 21 It measured to times. In the measurement, as much as possible, the portion near the center of the measurement surface was randomly targeted to the portion not measured before.

  Using three types of test pieces having the above oxide film formed on the surface, the time change of the potential difference between terminals by the direct current potential difference method was measured at an arbitrary site. An example of a measurement result is shown in FIG. 3 to FIG.

  As shown in FIG. 3 to FIG. 5, as a result of measurement, it was found that the characteristics of the time change of the potential difference are not necessarily constant for each measurement. As the tendency of a large potential change, it was observed that the potential difference rises and falls during the measurement. However, the change behavior is not monotonous, and there is one that descends once and then rises (FIG. 3), one that rises and then descends (FIG. 4), and one that changes intermittently along the way (FIG. 5) And complicated.

  Therefore, after application of direct current, one with a large decrease in potential difference in the initial stage (between about 10 and 15 seconds) of potential difference measurement is a potential difference decrease type (Figures 3 and 4), and one with a large increase in potential difference is a potential difference increase type It was divided roughly as (Figure 5).

  Next, FIG. 6 and FIG. 7 show examples of the results of the time change of the potential difference when the applied DC current is changed and measured a plurality of times, with the potential difference as the basis of the minimum potential.

  As described above, the measurement results show different behavior for each measurement under the same applied DC current, but viewed as a whole, as shown in the example of the case where the applied DC current shown in FIG. It could be roughly divided into potential difference type. Furthermore, as shown in the example of the case where the applied DC current shown in FIG. 7 is 13 A, it was found that the potential difference decreasing type increased and the potential difference increasing type decreased.

  Considering that it is used as a test, it is desirable to adopt a potential difference decreasing type that can be determined from the potential difference decrease at the beginning of measurement as a measurement index. Therefore, the relationship between the frequency of the potential difference decreasing type and the applied direct current was arranged for the test surface of each processing surface and the immersion time. The results are shown in FIG. In FIG. 8, the measurement was performed 10 to 12 times with each applied DC current, and the frequency was calculated from the number of times in which the potential difference decrease potential change was shown.

  As shown in FIG. 8, for any of the test pieces, the frequency of the potential difference decreasing type tends to increase as the applied DC current increases. Moreover, in the test piece with the largest coating thickness (milling surface, 500 hours immersion), the tendency started from the point where the applied DC current is low. Therefore, the relationship between the frequency of appearance of this potential difference decreasing type and the thickness of each film was investigated, and the relationship between the applied direct current reaching the appearance frequency of the potential difference decreasing type arbitrarily set was investigated.

  FIG. 9 shows the relationship between the applied DC current value and the film thickness when the occurrence frequency of the potential difference decreasing type is set to 0.7, 0.8, and 0.9, respectively.

  As shown in FIG. 9, there is a relatively good correlation between the film thickness and the applied DC current value reaching each appearance frequency, and in the present embodiment, when the appearance frequency is set to 0.7, the applied DC current value It was found that the correlation between the film thickness and the film thickness is the best, and it is possible to distinguish the difference between the film thickness of 0.2 μm or less.

  From the above examination, in the time change of the potential difference a plurality of times, the applied DC current value when the potential difference decreasing type becomes a predetermined frequency is determined, and the film thickness is determined from the applied DC current value. It was found that the thin oxide film thickness of 0 μm or less can be quantitatively measured nondestructively even if the accuracy is about 0.2 μm.

  The present invention is not limited to the above embodiment, and various modifications and applications are possible. The embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

1: Metal base material,
2: Inner layer film,
3: Outer layer film,
4: Measuring device body,
5: Current terminal,
6: Potentiometric measurement terminal,
7: Sensor block,
8: Actuator,
9: Terminal guide,
10A, 10B: Compression spring,
11: Support legs,
12: Fixing mechanism,
13: DC power supply,
14: Potentiometric precision measuring instrument,
15: measurement target table surface,
17: Data processing / recording device,
20: Film thickness measuring device,
31: Signal line,
32: Current supply line,
40: Cover,
41: Blower.

Claims (10)

A method of measuring the thickness of a film formed on the surface of a measurement target,
Bringing one or more pairs of current terminals and a pair of potential difference measurement terminals into contact with the surface to be measured;
Apply a predetermined load to the current terminal and press it against the measuring object,
In this pressed state, a constant current is applied to the current terminal, and a change in potential difference is measured by changing the current value at a plurality of points on the surface to be measured by the potential difference measurement terminal,
A method of measuring a film thickness, comprising processing data of a plurality of measured potential difference changes and determining a thickness of a film on the surface to be measured from an applied current value at which measurement frequency at which a predetermined potential difference decrease is observed is obtained. . In the film thickness measurement method according to claim 1,
A film thickness measuring method comprising: simultaneously contacting the surface of the object to be measured with a main body consisting of one or more pairs of current terminals and a pair of potential difference measuring terminals simultaneously at a plurality of locations. An apparatus for measuring the thickness of a film formed on a surface to be measured, the apparatus comprising:
One or more pairs of current terminals for applying current to the surface to be measured;
A DC power supply for applying a constant current between the terminals of the one or more current terminals;
A current supply line for supplying current from a DC power supply to the one or more current terminals;
A pair of potentiometric measurement terminals for measuring a current value flowing between the one or more current terminals;
A measuring instrument for measuring the voltage between the pair of potential difference measuring terminals;
A signal line electrically connecting the pair of potential difference measurement terminals and the measuring instrument;
A first load member for pressing the one or more current terminals against the surface of the object to be measured when measuring a time change of a current value;
A second load member for pressing the pair of potentiometric measurement terminals against the surface to be measured when measuring the time change of the current value;
A third load member for performing a load ON / OFF operation on the one or more current terminals and the pair of potential difference measurement terminals;
The data of a plurality of potential difference changes measured by changing the current value of the surface to be measured measured by the measuring device are stored, and the target to be measured is determined from the applied current value at the predetermined measurement frequency at which the potential difference decreases. A film thickness measuring device comprising: a data processing / recording device for calculating a film thickness on a surface. In the film thickness measuring device according to claim 3,
The data processing / recording apparatus stores a predetermined measurement frequency in which the potential difference decrease obtained for each measurement object is measured and the relationship between the applied current value and the film thickness at the measurement frequency, which are measured in advance. Coating thickness measuring device characterized by the above. In the film thickness measuring device according to claim 3,
A film thickness measuring device characterized in that the current terminal has a pointed end with a predetermined radius of curvature designed to penetrate a film to be measured by Joule heat generation by load and current conduction. In the film thickness measuring device according to claim 3,
The film thickness measuring device according to claim 1, wherein the first load member is a compression spring, and the second load member is a compression spring having a spring constant different from that of the first load member. In the film thickness measuring device according to claim 3,
A film thickness measuring device characterized in that any one of an electric motor, a hydraulic pressure, a piezoelectric element, and a shape memory alloy is used for the third load member. In the film thickness measuring device according to claim 3,
The apparatus further comprises a fixing mechanism for fixing the third load member to the measurement target,
The film thickness measuring device, wherein the fixing mechanism fixes the third load member to the object to be measured by any of a motor, a pressing force by air pressure and oil pressure, a vacuum pad, and an attracting force by a magnet. In the film thickness measuring device according to claim 3,
The object to be measured is a member disposed in a nuclear reactor,
It said signal line and said current supply line between the instruments and the DC power source disposed can be sufficiently reduced position and measured the effects of radiation by the nuclear reactor of the nuclear reactor A film thickness measuring device having a length for connecting In the film thickness measuring device according to claim 3,
A cover covering the current terminal and the potential difference measurement terminal;
A film thickness measuring device, further comprising: a blower for blowing air into the cover.

Images