JP2023094904A - Corrosion potential sensor and method of manufacturing corrosion potential sensor - Google Patents

Abstract

To provide a corrosion potential sensor capable of measuring ECP of structural members more accurately than before regardless of the distance between the corrosion potential sensor and the structural member, and a manufacturing method of a corrosion potential sensor.SOLUTION: A corrosion potential sensor 1 includes: a hollow metal housing 2; a reference electrode 5 that is provided in the longitudinal direction of the metal housing 2 and protrudes from one end of the metal housing 2; an insulator 3 formed at one end of the metal housing 2 and covering at least part of the reference electrode 5; a first metal oxide film 6a that covers the junction between the metal housing 2 and the insulator 3; and a second metal oxide coating 6b covering at least part of the periphery of one end of the metal housing 2 on which the first metal oxide coating 6a is formed.SELECTED DRAWING: Figure 5

Description

The present invention relates to corrosion potential sensors and methods of manufacturing corrosion potential sensors.

As an example of a corrosion potential sensor that can more accurately measure the corrosion potential of structural members, there is a technique described in Patent Document 1. The corrosion potential sensor of Patent Document 1 includes a reference electrode, an insulator, an electrode to be measured, and a sensor body. A reference electrode made of zirconium metal is fixed in an insulator made of zirconium oxide. A stainless steel sensor barrel surrounds one end of the insulator and is attached to the insulator. An electrode to be measured is attached to the surface of the insulator so as to cover the side surface of the insulator and the periphery of the tip surface of the insulator. The electrode to be measured is made of the same material as the structural member of the nuclear power plant, which is the object of corrosion potential measurement. A zirconium electrode wire is connected through the insulator to the reference electrode. A core wire of a mineral-insulated cable inserted into the sensor body is connected to the zirconium electrode wire, and a metal outer tube of the mineral-insulated cable is connected to the sensor body.

JP 2013-079830 A

In a nuclear power plant, equipment and piping, which are structural members, are constructed from structural materials such as stainless steel and nickel-based alloys. These structural materials exhibit susceptibility to stress corrosion cracking (SCC) under certain conditions. Therefore, in order to maintain the soundness of nuclear power plants, SCC countermeasures are applied to the structural members of nuclear power plants.

Moreover, in recent years, SCC countermeasures have been applied to the structural members of nuclear power plants from the viewpoint of improving economic efficiency such as improving the facility utilization rate of nuclear power plants and extending the life of the nuclear power plants.

Techniques aimed at improving the corrosion resistance of materials, improving stress, or mitigating corrosive environments are applied as SCC countermeasures. In boiling water reactors (BWR), hydrogen injection is widely applied in Japan and overseas as one of the SCC countermeasures based on improving the corrosive environment of reactor cooling water (reactor water) to which structural members are exposed. .

Reactor water contains oxygen and hydrogen peroxide, which cause corrosion and are generated by radiolysis of water in the reactor pressure vessel (reactor). ing. In hydrogen injection, hydrogen is added to the reactor water by adding hydrogen to the feed water, and this hydrogen reacts with oxygen and hydrogen peroxide to return the oxygen and hydrogen peroxide to the water. As a result of lowering the oxygen and hydrogen peroxide concentrations in the reactor water, the corrosion potential (ECP: Electrochemical Corrosion Potential) of the structural member is lowered, and the occurrence of SCC is suppressed.

Furthermore, as a technology to promote the reduction of ECP during hydrogen injection, for example, a platinum group noble metal element is injected into the reactor water, and the catalytic action of the platinum group noble metal element on the electrochemical reaction of hydrogen causes the structural members to be damaged during hydrogen injection. There is a technique that greatly reduces the ECP.

In applying these techniques, it is necessary to know the ECP of the structural members that come into contact with the reactor water of the nuclear power plant with high accuracy. ECP is shown as potential relative to the reference electrode used. The standard hydrogen electrode potential is widely used as a reference, with 0 V being the reference at each temperature vs. SHE (versus Standard Hydrogen Electrode) is attached after V, which is a unit of potential difference.

ECP measurement is performed by installing a corrosion potential sensor in the reactor or in a pipe connected to the reactor and measuring the potential difference between the corrosion potential sensor and structural members. Corrosion potential sensors generate a constant potential (reference potential) that serves as a reference for ECP measurements under operating conditions. For this reason, corrosion potential sensors are also called reference electrodes. By measuring the potential difference between the potential of the structural member under the conditions of reactor water temperature, oxygen concentration, hydrogen peroxide concentration, and reactor water flow rate and the reference potential of the corrosion potential sensor, using an electrometer, The ECP of the structural member can be known.

When attempting to measure the ECP of a BWR plant in situ, it is necessary to install a corrosion potential sensor directly on pipes or equipment and immerse it in reactor water. For example, when installing a corrosion potential sensor in a recirculation system pipe, insert the corrosion potential sensor into a cylindrical measuring seat (flange) provided in the recirculation system pipe and contact with the reactor water flowing in the recirculation system piping. The measuring seat is made of the same 304 stainless steel or 316NG steel (316L steel of nuclear grade) as the recirculation system piping.

However, when the corrosion potential sensor is attached to the measuring seat in a state where the detection part of the corrosion potential sensor reaches inside the inner surface of the recirculation system pipe, the flow of the reactor water in the recirculation system pipe does not reach the corrosion potential sensor. It hits and is disturbed at the tip of the corrosion potential sensor. Furthermore, since the corrosion potential sensor is perpendicular to the flow of high-velocity reactor water in the recirculation system piping, the flow vibration may damage the corrosion potential sensor.

Therefore, it is required to align the tip of the corrosion potential sensor with the inner surface of the recirculation pipe and attach the corrosion potential sensor to the measuring seat. When the corrosion potential sensor is attached to the measuring seat in this way, the space between the corrosion potential sensor and the inner surface of the measuring seat is also filled with the reactor water flowing through the recirculation system piping.

When the tip of the corrosion potential sensor inserted into the measuring seat provided in the recirculation system pipe and attached to the measuring seat is aligned with the inner surface of the recirculation system pipe, the corrosion potential sensor When the width of the gap formed between the tip and the inner surface of the measuring seat is large, the corrosion potential sensor measures the ECP of the metal housing surface of the corrosion potential sensor instead of the ECP of the inner surface of the recirculation pipe.

The reason is that the ECP measurement is performed by measuring the potential difference between the corrosion potential sensor and the surface of the piping/structural material, but the piping/structural material and the signal line of the corrosion potential sensor and the housing of the corrosion potential sensor are All of them are installed in an electrically conducting state in the reactor water.

Therefore, since the BWR reactor water is pure water and has a high liquid resistance, if the distance between the tip of the corrosion potential sensor and the pipe surface becomes longer than the distance between the tip of the corrosion potential sensor and the corrosion potential sensor housing, The corrosion potential sensor housing is the closest ground plane to the tip of the corrosion potential sensor. Therefore, the corrosion potential sensor measures the potential of the corrosion potential sensor housing. Corrosion potential sensors are therefore unable to accurately measure the ECP of the structural member.

For this reason, in order for the corrosion potential sensor to accurately measure the ECP of a structural member, the distance between the side surface of the detection portion at the tip of the corrosion potential sensor and the inner surface of the measuring seat should be It must be sufficiently smaller than the distance from the metal housing of the potential sensor.

Therefore, as in the above-mentioned Patent Document 1, in a corrosion potential sensor comprising an insulator, a reference electrode arranged in the insulator, and a metal housing attached to the insulator surrounding one end of the insulator, A corrosion potential sensor has been developed in which a cage-shaped or cylindrical electrode to be measured is arranged on the side of the detection part of the corrosion potential sensor. The electrode to be measured is made of the same material as the ECP measurement object such as the recirculation pipe. Thereby, the potential difference between the detection part of the corrosion potential sensor and the electrode to be measured can be measured, so that the ECP of the ECP measurement object can be measured more accurately.

However, boiling water nuclear power plants use various metal materials such as carbon steel, stainless steel, and nickel-based alloys depending on their structural members. It is necessary to change the electrode material, which is very difficult.

In addition, the ECP of the electrode to be measured, which is made of the same material as the structural member, is measured in the furnace, but the ECP of the actual structural member is not measured. Care must be taken to handle it as an ECP.

SUMMARY OF THE INVENTION An object of the present invention is to provide a corrosion potential sensor and a method of manufacturing a corrosion potential sensor that can measure the ECP of a structural member more accurately than before, regardless of the distance between the corrosion potential sensor and the structural member. is.

The present invention includes a plurality of means for solving the above problems. To give an example, a metal housing having a hollow structure and a metal housing provided in the longitudinal direction of the metal housing. a reference electrode protruding from one end; an insulator formed at one end of the metal housing and covering at least a portion of the reference electrode; and a first metal oxide covering a junction between the metal housing and the insulator. and a second metal oxide coating that covers at least part of the outer circumference of one end of the metal casing on which the first metal oxide coating is formed.

According to the present invention, the ECP of a structural member can be measured more accurately than before, regardless of the distance between the corrosion potential sensor and the structural member. Problems, configurations and effects other than those described above will be clarified by the following description of the embodiments.

FIG. 4 is an explanatory diagram showing an example of a state in which a corrosion potential sensor is installed on a pipe; FIG. 3 is an explanatory view showing a detecting portion at the tip of a reference technology corrosion potential sensor and its installation state in a pipe; FIG. 3 is an explanatory view showing the detection part of the corrosion potential sensor of the example and its installation state in a pipe; FIG. 4 is a characteristic diagram showing the relationship between the distance L between the pipe and the corrosion potential sensor and the potential detected by the corrosion potential sensor; It is a cross-sectional schematic diagram of the corrosion potential sensor of the Example of this invention. It is a cross-sectional schematic diagram of the corrosion potential sensor in the modification of the Example of this invention. FIG. 5 is a schematic cross-sectional view of a corrosion potential sensor in another modified example of the embodiment of the present invention;

An embodiment of a corrosion potential sensor and a method of manufacturing a corrosion potential sensor according to the present invention will be described with reference to FIGS. 1 to 7. FIG. In the drawings used in this specification, the same or corresponding components are denoted by the same or similar reference numerals, and repeated descriptions of these components may be omitted.

First, the circumstances leading to the present invention will be described.

The present inventors have developed a corrosion potential sensor that can suppress the influence of the ECP on the surface of the metal housing of the corrosion potential sensor and accurately measure the ECP on the surface of the structural member when the corrosion potential sensor is installed on a structural member of a nuclear power plant. We considered the configuration.

First, an example of installation locations of corrosion potential sensors in a boiling water reactor (BWR) will be described with reference to FIGS. 1 to 3. FIG. FIG. 1 is an explanatory diagram showing an example of a state of installation of a corrosion potential sensor in a pipe, FIG. 2 is an explanatory diagram showing a detecting portion at the tip of a corrosion potential sensor of reference technology and its installation state in a pipe, and FIG. 3 is an embodiment. 1 is an explanatory view showing a detection part of a corrosion potential sensor and its installation state in a pipe.

As shown in FIG. 1, the corrosion potential sensor 101 is inserted into a measurement seat 13 welded to a hole formed in the recirculation system pipe 12 or the bottom drain pipe 12 of the BWR. A detection portion at the tip of the corrosion potential sensor 101 is a sensor that contacts the reactor water flowing in the pipe 12 and measures the ECP of the pipe 12 .

The measuring seat 13 installed in the recirculation system pipe 12 is called a flange type and has a diameter of about φ80 to 300 mm. Also, the measuring seat 13 installed in the bottom drain pipe 12 is called a manifold type and has a diameter of about φ25 to 30 mm.

Since the dimensions of the corrosion potential sensor 101 are approximately 150 mm×approximately φ10 mm, when the corrosion potential sensor 101 is installed on the measurement seat 13, the distance between the measurement seat 13 or the pipe 12 and the detection part of the corrosion potential sensor 101 is The distance is several tens to several hundred mm for the flange type and several mm for the manifold type.

In the corrosion potential sensor 101 shown in FIGS. 1 and 2, an insulator 103 made of cylindrical zirconia (zirconium oxide: ZrO ₂ ) located in the detection portion of the sensor is joined to a metal housing 102 by a brazing portion 104. be. A region filled with platinum black powder 108 inside the insulator 103 is used as a reference electrode 105 for ECP measurement. A reference electrode 105 consisting of a core wire made of platinum is inserted into an insulator 103 filled with platinum black powder 108, and the reference electrode 105 is led out through a metal wire 107 in a mineral insulated cable.

The corrosion potential sensor 101 is inserted into a measuring seat 13 welded to a pipe 12 (for example, a recirculation pipe) or a hole formed in the pipe 12, as shown in FIG.

At this time, the detection part at the tip of the corrosion potential sensor 101 is arranged on the inner surface of the pipe 12 . The ECP of the pipe 12 is measured by connecting the metal wire 107 connected to the reference electrode 105 and arranged in the metal housing 102 and the wiring 15 connected to the pipe 12 to, for example, the electrometer 14 and measuring the electrometer. This is done by measuring the potential difference at 14 between the reference electrode 105 and the tubing 12 .

Here, as shown in FIG. 2, the corrosion potential sensor 101 detects the ECP of the pipe 12 when the distance L between the detecting portion of the corrosion potential sensor 101 and the pipe 12 is small. On the other hand, when the distance L between the detection part of the corrosion potential sensor 101 and the pipe 12 is large and exceeds the distance M between the detection part of the corrosion potential sensor 101 and the metal housing 102, the corrosion potential sensor 101 detects the ECP of the metal housing 102. detect.

Therefore, the inventors of the present invention determined the distance L between the detection portion of the corrosion potential sensor 101 and the pipe 12, the distance M between the detection portion of the corrosion potential sensor 101 and the metal housing 102, and the corrosion potential sensor 101. After studying the relationship between the ECP and the corrosion potential sensor 1, as shown in FIG.

As a result, the ECP of the metal housing 2 is blocked by the metal oxide film 6, and the detection of the ECP of the metal housing 2 by the corrosion potential sensor 1 can be suppressed. The corrosion potential sensor 1 can detect the ECP of the pipe 12 even when the distance L is greater than the distance M between the detection portion of the corrosion potential sensor 1 and the metal housing 2 .

In the corrosion potential sensor 101 shown in FIG. 2, the ECP of the metal member closest to the detection part of the corrosion potential sensor 101, for example, the pipe 12 or the metal housing 102 of the corrosion potential sensor 101 can be detected in a BWR. , due to the extremely limited range of electric potential in the environment of reactor water with low conductivity.

The relationship between the distance L between the detection portion of the corrosion potential sensor 101 and the pipe 12, the distance M between the detection portion of the corrosion potential sensor 101 and the metal housing 102, and the potential E detected by the corrosion potential sensor 101 is as follows. It is represented by the following formula (1).

In equation (1), ECP _p indicates the ECP of the pipe 12, ECP _m indicates the ECP of the metal housing 2 of the corrosion potential sensor 1, and _ρw indicates the resistivity of the reactor water.

On the other hand, as shown in FIG. 3, when the surface of the metal housing 2 of the corrosion potential sensor 1 is covered with the metal oxide film 6, the potential E detected by the corrosion potential sensor 1 is expressed by the following formula: (2).

In equation (2), ρ _c indicates the resistivity of the metal oxide film 6 and N indicates the film thickness of the metal oxide film 6 .

FIG. 4 is a characteristic diagram showing the relationship between the distance L between the pipe and the corrosion potential sensor and the potential detected by the corrosion potential sensor. The characteristics shown in FIG. 4 are the distance L between the pipe 12 and the corrosion potential sensor 1 and the potential detected by the corrosion potential sensor 1 when the distance M between the detection part of the corrosion potential sensor 1 and the metal housing 2 is 30 mm. is calculated based on the formulas (1) and (2).

In FIG. 4, the horizontal axis represents the distance L between the pipe 12 and the detection part of the corrosion potential sensor 1, the vertical axis represents the potential detected by the corrosion potential sensor 1, the lower end of the vertical axis represents the ECP of the pipe 12, and the upper end of the vertical axis represents the ECP of the pipe 12. It corresponds to the ECP of the metal housing 2 of the corrosion potential sensor 1 . That is, the closer the potential detected by the corrosion potential sensor 1 is to the lower end of the vertical axis, the more accurately the corrosion potential sensor 1 can measure the ECP of the pipe 12 . and the ECP of the metal casing 2 are mixed.

First, the reference technology corrosion potential sensor shown in FIG. If the distance L between the pipe 12 and the corrosion potential sensor 101 is within several millimeters, the ECP mixture derived from the metal housing 102 constituting the corrosion potential sensor 101 is small, and the corrosion potential sensor 101 detects the ECP of the pipe 12 with accuracy. Good measurement.

On the other hand, when the distance L between the pipe 12 and the corrosion potential sensor 101 exceeds 20 mm, the influence of the ECP of the metal housing 102 constituting the corrosion potential sensor 101 becomes large, and the detected potential of the corrosion potential sensor 101 12 ECP and the ECP of the metal housing 102 are mixed.

Therefore, in order to accurately measure the ECP of the pipe 12 using the corrosion potential sensor 101 of the reference technology as shown in FIG. Therefore, there is a possibility that the ECP of the pipe 12 cannot be measured accurately with the flange type measurement seat where the distance between the pipe 12 and the detection part of the corrosion potential sensor 101 is several tens to several hundred mm. , the corrosion potential measurement conditions using the corrosion potential sensor are limited.

On the other hand, in the corrosion potential sensor 1 with the metal oxide film 6 applied to the surface of the metal housing 2 as shown in FIG. ECP contamination derived from the metal housing 2 constituting the corrosion potential sensor 1 is small, and the corrosion potential sensor 1 can measure the ECP of the pipe 12 with high accuracy.

Therefore, by using the corrosion potential sensor 1 shown in FIG. 3, even if the distance between the pipe 12 and the detection part of the corrosion potential sensor 1 is several tens to several hundred mm, the ECP of the pipe can be accurately measured. measurement becomes possible.

The structure of the corrosion potential sensor according to the embodiment of the present invention reflecting the results of the above studies will be described with reference to FIGS. 5 to 7. FIG. 5 to 7 are schematic cross-sectional views of the corrosion potential sensor of this embodiment.

The corrosion potential sensor 1 of this embodiment shown in FIG. A reference electrode 5, a metal wire (lead wire) 7, a metal/metal oxide powder 8, a sealing plug 9, a mineral insulated cable 10, and a metal housing, which are provided in the longitudinal direction and protrude from one end of the metal housing 2. A first metal oxide film 6a that covers the joint between the body 2 and the insulator 3, and a second metal oxide film 6a that covers at least part of the outer circumference of one end of the metal housing 2 on which the first metal oxide film 6a is formed. It has a metal oxide coating 6b.

The insulator 3 and the metal housing 2 are joined by a brazing portion 4 .

One end of the reference electrode 5 is connected to the metal wire 7 at the junction 11 inside the insulator 3 or the metal housing 2 . The other end of the reference electrode 5 serves as a sensing portion, and is placed inside the insulator 3 filled with the metal/metal oxide powder 8 . is covered with an insulator 3. The metal/metal oxide powder 8 in the insulator 3 is sealed from the metal housing 2 side of the corrosion potential sensor 1 by a sealing plug 9 having a hollow structure.

In the corrosion potential sensor 1 of the present embodiment, as shown in FIG. 5, the outer surface of the portion where the insulator 3 and the metal housing 2 are joined by the brazing portion 4 is covered with the first metal oxide film 6a. A portion of the outer surface of the metal housing 2 is covered with a second metal oxide film 6b.

Furthermore, the second metal oxide coating 6b covers at least part of the first metal oxide coating 6a. FIG. 5 shows a configuration in which one surface of the first metal oxide film 6a on the second metal oxide film 6b side is covered with the second metal oxide film 6b.

As described above with reference to FIGS. 2 and 3, since the distance M between the detection portion (the end of the reference electrode 5) of the corrosion potential sensor 1 and the metal housing 2 is about 30 mm, the pipe 12 and the corrosion potential sensor It is necessary to form a first metal oxide film 6a and a second metal oxide film 6b on the brazed part 4 and part of the outer surface of the metal housing 2 according to the distance L from 1 .

For example, when the distance L between the pipe 12 and the corrosion potential sensor 1 is 100 mm, the first metal oxide coating 6a and the second metal It is desirable to cover with an oxide film 6b. Since the insulating first metal oxide film 6a and the second metal oxide film 6b cut off the potential of the brazing part 4 and the metal housing 2, the ECP mixture derived from the brazing part 4 and the metal housing 2 is prevented. is suppressed, allowing the corrosion potential sensor 1 to accurately measure the ECP of the pipe.

The corrosion potential sensor of this embodiment is not limited to the structure shown in FIG. 5, and an example of other forms will be described below with reference to FIGS. 6 and 7. FIG.

A corrosion potential sensor 1A shown in FIG. 6 has a form in which a second metal oxide film 6b1 entirely covers the outer periphery of a metal housing 2, and a flange-type measuring seat having a diameter exceeding 100 mm is mounted on a corrosion potential sensor 1A. It is a suitable form when installing. In the corrosion potential sensor 1A shown in FIG. 6, as shown in FIG. 6, it is desirable that the brazed portion 4 is also covered with the insulating first metal oxide film 6a.

A corrosion potential sensor 1B shown in FIG. 7 includes an insulator 3b, a metal housing 2, a reference electrode 5b, a metal wire (lead wire) 7, and a first metal oxide covering a joint portion between the metal housing 2 and the insulator 3b. It has a coating 6a2 and a second metal oxide coating 6b2 that covers at least part of the outer circumference of one end of the metal housing 2 on the side where the first metal oxide coating 6a is formed.

In the corrosion potential sensor 1B shown in FIG. 7, the reference electrode 5b is exposed on the opposite side of the metal housing 2 of the insulator 3b, and has a structure in which the reference electrode 5b is in direct contact with the reactor water.

Even in a configuration in which the reference electrode 5b is in direct contact with the reactor water like the corrosion potential sensor 1B shown in FIG. It can be in the form of Moreover, it is possible to adopt a form in which the junction between the reference electrode 5b and the insulator 3b is covered with the insulating first metal oxide film 6a2.

The metal housing 2 in the corrosion potential sensors 1, 1A, and 1B shown in FIGS. ), and 316L stainless steel (SUS316L).

The insulators 3 and 3b are made of zirconia, yttrium oxide ( _Y2O3 , yttria), aluminum oxide ( _{Al2O3 ,} alumina ₎ , partially stabilized zirconia (PSZ), yttria stabilized zirconia (YSZ), or the like. , at least one or more.

The reference electrodes 5, 5b can be made of one or more of iron, silver/silver chloride electrodes, platinum electrodes, zirconium electrodes, and the like.

The first metal oxide coatings 6a, 6a2 and the second metal oxide coatings 6b, 6b1, 6b2 are made of zirconia, yttria, alumina, partially stabilized zirconia, and yttria stabilized zirconia, like the insulators 3, 3b. etc., it can be composed of at least one or more.

Next, among the methods of manufacturing the corrosion potential sensors 1, 1A, and 1B according to the present embodiment, a method of forming the first metal oxide coatings 6a and 6a2, and a method of forming the second metal oxide coating on the outer surface of the metal housing 2. A method for forming the coatings 6b, 6b1, 6b2 will be described.

Physical vapor deposition ( PVD: Physical Vapor Deposition) method, chemical vapor deposition (CVD: Chemical Vapor Deposition) method, thermal spraying method, sol-gel method, metal organic decomposition (MOD: Metal Organic Decomposition) method, coating method, and the like. can be used.

Also, the first metal oxide films 6a, 6a2 and the second metal oxide films 6b, 6b1, 6b2 are preferably formed simultaneously by the above-described forming method.

Next, the effects of this embodiment will be described.

The corrosion potential sensors 1, 1A, and 1B of the present embodiment described above are provided with a metal housing 2 having a hollow structure and a reference electrode protruding from one end of the metal housing 2, which is provided in the longitudinal direction of the metal housing 2. 5 and 5b, insulators 3 and 3b formed at one end of the metal housing 2 and covering at least a part of the reference electrodes 5 and 5b, and a second electrode covering the junction between the metal housing 2 and the insulators 3 and 3b. 1 metal oxide coatings 6a, 6a2 and second metal oxide coatings 6b, 6b1, 6b2 covering at least part of the outer periphery of one end of the metal casing 2 on which the first metal oxide coatings 6a, 6a2 are formed and have.

By covering at least the sides of the outer circumference of the metal casing 2 near the reference electrodes 5 and 5b with the second metal oxide coatings 6b, 6b1, and 6b2, the reference electrode 5 on the surface of the metal casing 2 is , 5b are insulated to prevent the corrosion potential sensors 1, 1A, and 1B from measuring the ECP of the surface of the metal housing 2 that constitutes itself. Therefore, the distance between the side surfaces of the reference electrodes 5 and 5b, which are the detection portions of the corrosion potential sensors 1, 1A, and 1B, and the inner surface of the measuring seat is the same as the detection portions of the corrosion potential sensors 1, 1A, and 1B and the metal housing 2. The corrosion potential sensors 1, 1A, and 1B can accurately measure the ECP of the structural member even if the distance is greater than the distance from . , the restriction on the distance between the corrosion potential sensor and the ECP measurement object can be relaxed.

Such corrosion potential sensors 1, 1A, and 1B are installed in other pipes of the BWR plant (for example, reactor cleanup system pipes, drain pipes and feed water pipes connected to the bottom of the reactor, etc.) can be used to measure the ECP of Furthermore, it can be used to measure the ECP of pipes and the like in pressurized water nuclear and thermal power plants, especially structures made of carbon steel, iron-based alloys or nickel-based alloys, the surfaces of which are in contact with the cooling water of the reactor. Measurement of the corrosion potential of components, specifically for stress corrosion cracking (SCC) of stainless steels and nickel-based alloys or Flow Accelerated Corrosion (FAC) of carbon steels and nickel-based alloys as an indicator of water quality conditions It can be said that the corrosion potential sensor is suitable for use in measuring the corrosion potential.

In addition, since the second metal oxide coatings 6b, 6b1, 6b2 cover at least a part of the first metal oxide coatings 6a, 6a2, the exposed portions of the metal housing 2 can be reduced, resulting in more accurate ECP. measurement can be realized.

Furthermore, since the second metal oxide film 6b1 covers the entire outer periphery of the metal housing 2, there is a possibility that the reference electrodes 5 and 5b may measure the ECP of the metal housing 2. Even if the distance from the inner surface of the measuring seat becomes very large, the ECP of the structural member of the plant can be measured with high accuracy.

In addition, by simultaneously forming the first metal oxide films 6a, 6a2 and the second metal oxide films 6b, 6b1, 6b2, the time required for film formation can be shortened, and the manufacturing efficiency of the corrosion potential sensors 1, 1A, 1B can be reduced. can be improved.

<Others>
The present invention is not limited to the above embodiments, and various modifications and applications are possible. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations.

Reference numerals 101, 1, 1A, 1B Corrosion potential sensors 102, 2 Metal housings 103, 3, 3b Insulators 104, 4 Brazed portions 105, 5, 5b Reference electrode 6 Metal oxide films 6a, 6a2 First metal oxide coatings 6b, 6b1, 6b2 Second metal oxide coatings 107, 7 Metal wires 108, 8 Metal/metal oxide powder 9 Sealing plug 10 Mineral insulated cable 11 Reference electrode and Joint portion with metal wire 12 Piping 13 Measuring seat 14 Electrometer 15 Wiring

Claims (11)

a metal housing with a hollow structure;
a reference electrode provided in the longitudinal direction of the metal housing and protruding from one end of the metal housing;
an insulator formed at one end of the metal housing and covering at least a portion of the reference electrode;
a first metal oxide film that covers a joint between the metal housing and the insulator;
and a second metal oxide film that covers at least a part of the outer circumference of one end of the metal housing on which the first metal oxide film is formed. The corrosion potential sensor of claim 1, wherein
The corrosion potential sensor, wherein the second metal oxide coating covers at least part of the first metal oxide coating. The corrosion potential sensor of claim 1, wherein
The corrosion potential sensor, wherein the second metal oxide film covers the entire outer periphery of the metal housing. The corrosion potential sensor of claim 1, wherein
The corrosion potential sensor, wherein the insulator covers the end of the reference electrode. The corrosion potential sensor of claim 1, wherein
The corrosion potential sensor, wherein the reference electrode is exposed on a side of the insulator opposite the metal housing. The corrosion potential sensor of claim 1, wherein
A corrosion potential sensor, wherein the first metal oxide coating and the second metal oxide coating contain at least one of zirconium oxide, yttrium oxide, and partially stabilized zirconia. The corrosion potential sensor of claim 1, wherein
A corrosion potential sensor, wherein the reference electrode is made of any one of silver/silver chloride, iron, zirconium and platinum. The corrosion potential sensor of claim 1, wherein
A corrosion potential sensor, wherein the insulator contains at least one of zirconium oxide, yttrium oxide, and aluminum oxide. a metal housing having a hollow structure; a reference electrode provided in the longitudinal direction of the metal housing and protruding from one end of the metal housing; A method of manufacturing a corrosion potential sensor comprising: an insulator covering a portion thereof;
forming a first metal oxide film covering a joint between the metal housing and the insulator;
and forming a second metal oxide film covering at least a part of the outer periphery of one end of the metal housing on which the first metal oxide film is formed. Production method. In the method for manufacturing a corrosion potential sensor according to claim 9,
The first metal oxide coating and the second metal oxide coating are formed by a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, a thermal spray method, a sol-gel method, a metalorganic decomposition (MOD) method. , and a coating method. In the method for manufacturing a corrosion potential sensor according to claim 9,
A method of manufacturing a corrosion potential sensor, wherein the first metal oxide coating and the second metal oxide coating are formed simultaneously.

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