JPH0483153A - Corrosion detecting system and water quality control system - Google Patents

Abstract

PURPOSE:To highly sensitively detect and prevent the generation of a local corrosion by measuring respective potential differences between a plurality of collating electrodes inserted to a corrosion monitoring part or between them and the monitoring part. CONSTITUTION:A plurality of collating electrodes 1-1-3 are inserted to a pipeline from its flange part and set to, for example, a general pipeline part, a pipeline part receiving a stress, and a welded part 14 of the pipeline, respectively. Lead wires 13-1-3 taken from the nearest pipeline parts of these electrodes as their monitor parts and lead wires 13-4-6 connected to the respective electrodes are connected to a contact switching device 5. The wiring is conducted in such a manner that potential differences between the mutual electrodes and between the electrodes and the pipeline parts close thereto can be measured by ON-OFF of a switch. This measurement instruction is emitted from a computer conversion system, and the potential difference can be measured by a potentiometer through the wiring. When no corrosion is generated, the electric potentials are coincident to each other, and the generation of a corrosion and its position are detected by the measured potential difference.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to improving the soundness of structural materials exposed to a corrosive environment, and in particular, to detecting the occurrence of corrosion such as pitting corrosion and stress corrosion cracking. Relating to detection systems and water quality control systems.

[Conventional technology]

In the conventional corrosion detection system, JP-A-57-22
As described in Publication No. 535, pitting corrosion is detected by comparing the change in resistance of a corrosive element placed in a corrosive fluid and activated and the increase in radioactive substances downstream. It was a corrosion monitoring system to measure. In addition, as described in Japanese Patent Application Laid-Open No. 60-228912, corrosion monitoring enables the detection of minute corrosion by monitoring corrosion from the frequency distribution of ultrasonic waves incident on piping, containers, etc. and their reflected waves. That's the method. Also, JP-A-52-15
As described in Publication No. 0090, by connecting a pinpoint contact type waveguide to an AE position monitoring device with a zone selection function via a preamplifier and an AE sensor, it is possible to accurately monitor the occurrence and progress of cracks in the specimen. This is a crack behavior detection device that enables high detection. Also, as described in Japanese Patent Application Laid-open No. 61-95212,
By actually measuring cross-sectional area changes, fluctuating stress, and temperature at high-stress points in operating structures and monitoring them online, we can accurately grasp the progress of fatigue cracks and remaining life of structures, etc. It is a system that monitors the occurrence, propagation, and remaining life of fatigue cracks in structures. Furthermore, as described in Japanese Patent Application Laid-Open No. 179662/1983, by connecting a sensor attached to equipment to a signal processing device and a display/recording device, cracks caused by hydrogen corrosion in equipment under high temperature can be automatically detected. It is also a continuous monitoring system.

As a nuclear reactor water control system, JP-A-62-126
As described in Publication No. 398, by providing a device that measures the hydrogen peroxide concentration in the reactor core and a device that controls the hydrogen injection rate from the measured value, it is possible to optimally control the water quality in the reactor core. This is the reactor water quality control system. Corrosion environment monitoring systems currently being implemented at BWRs overseas.

Epli NP 3521. May, 1984 (EP
RI NP-3521 May, 1984).

Epli NP 3517. May, 1984 (EP
PI NP-3517 May, 1984).

Corrosion 183 Paper Number 122 (Corr
osion '83 PAPER NUMBER12
2) and corrosion 183 paper number 129
(Corrosion '83 PAPERNU
As described in MBER129), the corrosion environment is monitored by measuring the corrosion potential of stainless steel in the primary coolant using a reference electrode. Measures are being taken to prevent stress corrosion cracking by regulating the oxygen concentration in the primary cooling water. This is 5US304 steel 123
If it is 0 mV or less, SCC (stress corrosion cracking) will not occur. Regarding this, it was published in 1977-308.
As described in Publication No. 6, the corrosion potential, dissolved oxygen concentration, and hydrogen concentration of stainless steel in the primary cooling water were measured, and the corrosion potential was -250 to 600 mV, the dissolved oxygen concentration was 10 to 50 pPb, and the dissolved hydrogen concentration was The system is characterized by controlling the amount of dissolved hydrogen to be 150 ppb or less. These use reference electrodes as environmental monitors. In other words, by injecting H2 to lower the dissolved oxygen concentration, stress corrosion cracking will no longer occur 5US304
The potential of the reference electrode is 1230 mV, and the reference electrode has not been applied to the direct detection of stress corrosion cracking, and there is no example in which the reference electrode has been applied to the detection of stress corrosion cracking.

[Problem to be solved by the invention]

Conventional corrosion detection systems only detect local corrosion when it has occurred to a certain extent, and are unable to detect the very early stages of local corrosion. Regarding the control of hydrogen injection to prevent stress corrosion cracking, for example, in the case of potential measurement, the water quality environment inside the crack that occurs due to stress corrosion cracking is different from the water quality environment in the bulk. Even if the amount of hydrogen is controlled by the potential of a test piece that does not show stress corrosion cracking, it is impossible to control water quality appropriately.

Also, it is said that stress corrosion cracking will not occur if the potential is 1230mV or less, but the potential being measured is for a test piece that does not cause stress corrosion cracking as mentioned above.
There is no information on direct stress corrosion cracking. In addition, the water quality (dissolved oxygen concentration, dissolved hydrogen concentration, hydrogen peroxide concentration) and temperature differ in each location of a plant, so even if water quality is controlled based on values measured at a single location, the plant It is not possible to maintain sufficient soundness. Also SCC
It is only under certain water quality conditions that the potential at which no . In fact, it has been reported that when the conductivity changes, the potential changes.

Therefore, in order to determine whether stress corrosion cracking has occurred, in addition to a single SUS test piece, the temperature of the reactor water at that time,
Water quality such as conductivity and electrical conductivity also need to be measured. In other words, it was necessary to determine the potential at which SCC no longer occurs under various water quality conditions, compile it into a database, and determine whether SCC has occurred based on this.

The purpose of the present invention is to provide a corrosion detection system and a water quality control system that can sensitively detect and prevent the occurrence of localized corrosion such as stress corrosion cracking and pitting corrosion using the same method and equipment even when the temperature, water quality, etc. change. Our goal is to provide the following.

[Means to solve the problem]

In order to achieve the above object, the corrosion detection system according to the present invention inserts a plurality of reference electrodes into the corrosion monitoring part of the water system piping of a plant, and detects the potential difference between each reference electrode or the difference between each reference electrode and each reference electrode. The configuration is such that the potential difference between the reference electrode and the corresponding corrosion monitoring section is measured, and the occurrence and location of corrosion can be detected from the potential difference.

The location where corrosion occurs is detected when one of the respective potentials changes to the base side or when the respective potential difference exceeds a reference value.

Alternatively, the location where corrosion occurs may be detected by comparing the potential difference between at least two reference electrodes.

Furthermore, the reference electrode may be installed at a joint between dissimilar metals.

In the corrosive environment monitoring system, claims 1-
The corrosion detection system according to any one of Item 4 is installed at at least one location to evaluate the health or danger of the plant.

In the corrosion environment monitoring system equipped with the corrosion detection system according to any one of claims 1 to 4, each measured potential or potential difference.

It may be configured to display on a display system consisting of a CRT, a recorder, a recorder, and a plotter, and detect the occurrence of corrosion and its location based on the display.

Furthermore, in the corrosive environment monitoring system equipped with the corrosion detection system according to any one of claims 1 to 4, at least one alarm consisting of sound, voice, light, and CRT display is issued to indicate the occurrence of corrosion and the location thereof. A configuration may also be used.

In the corrosion environment monitoring system equipped with the corrosion detection system according to any one of claims 1 to 4, the rate of increase in the potential difference between each reference electrode, the increase rate of the potential difference between each reference electrode and the corrosion monitoring section, It may be configured to predict when stress corrosion cracking will occur based on the rate of increase in potential difference or the temporal change in each rate of increase.

Further, a corrosion environment monitoring system including the corrosion detection system according to any one of claims 1 to 4 may be configured to monitor temporal changes in each potential or potential difference to be measured.

Furthermore, the water quality control system includes the corrosive environment monitoring system according to any one of claims 5 to 9, and includes oxygen, nitrogen, hydrogen, NOx, Fe ions, Ni ions, H
The configuration includes a gas and chemical injection device for injecting at least one of NO and H2O (7).

In the water quality control system equipped with the corrosive environment monitoring system according to any one of claims 5 to 9, oxygen, nitrogen, hydrogen, NOx, Fe ions, Ni ions, which return the measured potential difference to approximately the reference value. , HNO, and H2
A configuration may also be adopted in which at least one of O2 is injected into the water system from at least one location.

Further, in a plant, any one of claims 1 to 12
The structure shall include at least one of the corrosion detection system, corrosion environment monitoring system, or water quality control system described in 1.

Furthermore, in a plant, at least one of the corrosion detection system, corrosion environment monitoring system, or water quality control system according to any one of claims 1 to 12 is applied to welded parts, heat affected zones, elbows, and bent pipes of metal materials. It may be provided in at least one location.

In a nuclear power plant, at least one of the corrosion detection system, corrosion environment monitoring system, or water quality control system according to any one of claims 1 to 12 is installed in a recirculation system bypass, a reactor water spray system piping, or a reactor purification system. The bent pipe section of the BWR plant primary system piping, which consists of system piping and recirculation system riser pipes.

It shall be arranged in at least one of the elbow, welding part, and welding heat affected zone.

In addition, in a nuclear power plant, at least one of the corrosion detection system, corrosion environment monitoring system, and water quality control system according to any one of claims 1 to 12 is installed at a welded part of a reactor pressure vessel and a primary system piping, and a boric acid water injection piping,
The structure may be such that it is installed at at least one of the bent pipe section, weld section, and weld heat affected zone of a reactor water structure consisting of a core support plate, an upper grid plate, and a core spray pipe.

[Effect]

According to the corrosion detection system of the present invention, when a specified metal is placed in a solution that is likely to cause pitting corrosion, the potential distribution near the metal is uniform if pitting corrosion does not occur. The potential measured will be the same no matter where it is placed. However, when pitting corrosion or stress corrosion cracking occurs in a certain area, that area becomes an anode and exhibits a potential distribution different from that of an area where general corrosion has occurred, and the potential measured by the reference electrode differs from the IR component. The potential will be lower. Therefore, if multiple reference electrodes are installed on a given metal material and a difference occurs in the potential between each reference electrode or between each reference electrode and the metal material, stress corrosion cracking or pitting corrosion may occur. This means that local corrosion has occurred. If the local corrosion is severe, (corrosion current) increases, IR loss increases, and the potential drop increases. Therefore, the degree of local corrosion can be determined by the magnitude of the potential drop. R (solution resistance)
When is small, that is, a solution with high conductivity has a smaller potential difference than a solution with low conductivity, even if (2) is the same.

Next, a material with dissimilar metal bonding of metal materials A and B (A-
When B) is immersed in a highly conductive solution, a hybrid potential system is established, so the potential difference between the material measured with the reference electrode close to side A and the potential difference between the material measured with the reference electrode close to side B is the same. be. However, the potential difference between the reference electrode and the material measured by bringing the reference electrode close to the contact area of A and B is measured by bringing it close to the A or B side because a large IR can be obtained even if R is small due to the large I at the contact area. The value differs from the value given. Therefore, in a solution with high conductivity, local corrosion can be detected by installing reference electrodes at the contact point and at a portion away from the contact point. When a material is immersed in a solution with low conductivity, the solution resistance is high and IR loss occurs, so the potential of the material measured with the reference electrode close to side A and the potential of the material measured with the reference electrode close to side B. If there is a difference between the potential of the material and the potential of the material, it can be seen that corrosion between dissimilar metals has occurred. Moreover, the greater the difference, the more severe the corrosion.

IR for detection of stress corrosion cracking, pitting corrosion, and dissimilar metal corrosion
The drop in internal potential of the reference electrode due to loss is utilized, and two methods are used to detect this drop in internal potential. That is, there are two cases: measuring the potential difference between a plurality of reference electrodes, and measuring the difference in potential between a material and a material measured using a plurality of reference electrodes. What is measured here is basically the same thing.

For example, the respective potentials of reference electrode A installed in a place where pitting corrosion occurs, reference electrode B installed in a healthy place, and the material are EA, Ea, and Ec (the internal potential is The location where it is present and the location where it is absent are the same). The potential difference between multiple reference electrodes is EA-Es, and the potential difference measured with each reference electrode as a reference is Ec-EA in areas where pitting corrosion has occurred, and EC-EB in healthy areas.
becomes.

Since each potential difference is measured, the measured potential difference is (Ec Ea) (Ec-EA): EA-
Ea, and the values measured by both methods are the same.

〔Example〕

Each embodiment of the present invention will be described with reference to the drawings.

[Example 1] In this example, nine reference electrodes 1 are installed in the pipes of the PLR system of a BWR plant shown in Fig. 2, and the potential difference between the reference electrodes, the reference electrodes installed at each location, and their installation are determined. This is an example of a corrosion detection system that attempts to detect stress corrosion cracking in piping systems by measuring the potential difference between lead wires from structural materials in the vicinity of the location. The details of the reference electrode insertion part are
It is shown in the figure.

As shown in FIG. 1, a plurality of reference electrodes are inserted through the flanges of the piping and set, for example, in normal piping parts 1-1, stressed piping parts 1-2, and welded parts 1-3 of the piping.

Also, lead wires (13-1, 13-2, 13-3) are taken from the piping portions very close to the set reference electrodes.

These lead wires and the lead wire connected to the reference electrode (
13-4, 13-5, 13-6) are connected to the contact switching device 5. Here, by turning the switch ON-OFF, for example, the potential difference between reference electrodes 1-1 and 1-2, the potential difference between reference electrodes 1-1 and 1-3, the potential difference between reference electrodes 1-2 and 1-
3, the potential difference between reference electrodes 1 to 1 and 13-1,
Potential difference between reference electrodes 1-2 and 13-2, and reference electrode 1
Wiring is done so that the potential difference between .about.3 and 13-3 can be measured.

This measurement command is issued from the computer calculation system 7 and can be measured using the potentiometer 6 via wiring. The potential difference measured here is sent via the computer calculation system 7 to an analysis result display system installed in a central control room (not shown), and is sent to a CRT, printer,
Displayed on plotter and recorder. Figure 3 shows the CRT
The potential difference between reference electrodes 1-1 and 1-2 and 1
This is an example showing a temporal change in the potential difference between ~1 and 1~3. Since March, the potential difference between reference electrodes 1-1 and 1-3 has increased rapidly. There was no change in the potential difference between reference electrodes 1-1 and 1-2. Normally, if the structural material is sound, the potential difference between all reference electrodes is theoretically O when the same reference electrode is used. However, if stress corrosion cracking occurs.

This location becomes the anode part (shore side), and the healthy part around it becomes the cathode part, so a current distribution occurs near the reference electrode and IR drops, and the reference electrode installed near the part where stress corrosion cracking occurred. An IR potential difference that exceeds a reference value occurs between the electrode and a reference electrode installed in the vicinity of another healthy structural material part, even though the reference electrode is the same. Because the potential difference between reference electrodes 1-1 and 1-2 did not change, and the potential difference between reference electrodes 1-1 and 1-3 changed,
It can be seen that stress corrosion cracking occurred near the welds where reference electrodes 1 to 3 were installed. When this potential difference exceeds a critical value indicating stress corrosion cracking, the occurrence of SCC is displayed on the CRT. Further, if the potential difference exceeds a dangerous value, a sound or audio alarm is issued and the stress corrosion cracking location detected by the above method is displayed on the same or other CRT. Figure 4 shows not the potential difference between the reference electrodes, but the potential difference between the reference electrode and the structural material (1 to 1 and 1
3-1.1 to 2, 13-2.1 to 3, and 13-3) are displayed on the CRT. As in the case of FIG. 3, the potential difference between the reference electrodes 1 to 3 and the structural material 13-3 decreases rapidly, indicating that stress corrosion cracking has occurred in the weld. The reference electrode used here may be an internal type or an external type, but it is desirable that it be stable for a long period of time.

This is because when the integrity of the reference electrode is no longer maintained and the potential changes, it is difficult to distinguish this from a case where this is caused by stress corrosion cracking. Even in the same location, when the plant is shut down or started up.

Although the temperature and water quality are different from those during steady operation, the presence or absence of stress corrosion cracking can be detected using the same equipment. The criteria for judgment are the same as those shown in FIGS. 3 and 4.

[Example 2] This example is an example in which an attempt was made to detect stress corrosion cracking in a reactor internal structure, as shown in FIG.

The dowel structure is the same as in Example 1, but the reference electrode is arranged in the reactor core through the in-furnace instrumentation tube as shown in FIG. Since all the structural members are electrically conductive, grounded, and have the same internal potential, there should be at least one lead wire from the structural members. FIG. 7 shows lead wires 13 connected to ECP sensors 1 to 4 to 9 and reactor internals 17.
-5 potential is displayed on the CRT. From the change in potential, it is detected that stress corrosion cracking or pitting corrosion has occurred in the vicinity where reference electrodes 1 to 4, 1 to 7 and 1 to 9 are installed. The same applies to the first embodiment, but although this system can detect abnormal phenomena in the reactor internals, it is difficult to determine the type of abnormal phenomena.

As shown in [Example 1] and [Example 2].

In order to detect localized corrosion such as stress corrosion cracking and pitting corrosion,
Insert multiple reference electrodes at the location of interest.

It can be detected by comparing the potential difference between these reference electrodes and the potential difference between each reference electrode and the reactor internal structure. In this case, there is no problem even if the metal types are different as long as there is continuity. However, this system can only be applied under the condition that the water quality and temperature remain the same. Therefore, for example, in the case of a corrosive environment monitoring system that monitors the health of the entire nuclear power plant, as shown in FIG. Potential measurement systems 19 consisting of switching devices and potentiometers must be installed at several locations of interest. Comparison of potential differences must be performed within each potential measurement system, but if the water quality is almost the same, for example, for those installed in a PLR system and a CUW system,
Comparisons may be made between each potential measurement system.

This system can also be applied to condensers.

[Embodiment 3] This embodiment is an example of a corrosion environment monitoring system to which a corrosion detection system is applied as a method for detecting corrosion between dissimilar metals.

As shown in FIG. 9, reference electrodes 1 to 10 to 12 are
5US304 pipe 20 vicinity, welding part vicinity and Z
It is installed near the r pipe 21.

Further, a conductivity gauge 23 for measuring the conductivity of the solution is installed inside the pipe. If the conductivity of the solution is low, the potential differences between reference electrodes 1 to 10 and lead wires 13-6 and 1 to 12 and 13-6 connected to the piping will not be the same, as described in the operation section. , it can be seen that the one with the lower potential is the anode part. Therefore, by monitoring the potential difference, it can be determined whether corrosion between dissimilar metals is occurring. If the conductivity of the solution is high, no potential difference will occur between the 5US304 piping 20 and the lead wire 13-6 and between the Zr piping 21 and the lead wire 13-6, but if corrosion between dissimilar metals occurs, Since a current flows locally, the potential difference between the reference electrodes 1 to 11 and the lead wire 13-6 is between 1 to 12 and 13-6 or between 1 to 10 and 13-6 due to the IR drop.
It is different from the potential difference between. Therefore, by constantly monitoring each of the three potential differences, the presence or absence of local corrosion can be detected, and the degree of local corrosion can be determined from the magnitude of these potential differences.

Figure 10 shows an example in which this system is applied to detect the presence or absence of local corrosion and its degree in high-temperature water containing 200 ppb of dissolved oxygen at 280°C in a pipe in which 5US304 pipe and Zr pipe are joined. be. Reference electrode 1
The potential difference between ~10 and lead wire 13-6 is 1~12 and 1
Since it is higher than the potential difference between 3 and 6, it can be seen that the side where 1 to 12 are installed, that is, the Zr piping side becomes an anode part, and local corrosion is progressing. The degree of local corrosion can be determined by the magnitude of the potential difference between O and Δ shown in the figure. A corrosion test between dissimilar metals is conducted under the same conditions in advance, and a dangerous value is set. If the potential difference between O and Δ exceeds the dangerous value, a warning is issued by voice or sound and on the CRT screen.

The same system was installed in a pipe where 5US316L pipe and Inconel pipe were joined, and the dissolved oxygen concentration was 200pp at 280℃.
When applied to a system in which high-temperature water containing B was flowing, there was no difference in the measured potential difference, and as a result of observing the cross section after the test, no corrosion occurred between dissimilar metals, confirming that the system is effective. It was done.

In the case of joining the above-mentioned 5US304 piping and Zr piping,
A similar cross-sectional examination revealed that the Zr piping was particularly severely corroded. Even with this, we were able to confirm that this system is effective.

[Embodiment 4] As shown in FIG. 11, this embodiment is a water quality control system that combines the potential measurement system shown in FIG. 8 and a gas and chemical injection device.

Gases and chemicals injected include oxygen, hydrogen, hydrogen peroxide,
Fe'' and Ni2+, etc. In this system, the state of the plant is controlled by the operations described below.

For example, when stress corrosion cracking is detected by the potential measurement system 19, the gas and chemical injection device 24 paired therewith is immediately activated to inject one or more of the gases and chemicals listed above.

FIG. 12 displays the results of injecting hydrogen gas into the PLR system. Hydrogen has been injected immediately since April due to a potential difference. Since the potential difference gradually decreases after reaching a certain maximum value, the amount of hydrogen injection is reduced accordingly, and the hydrogen concentration at that point also changes as the amount of hydrogen injection changes.

At this time, in the PLR system, the dissolved oxygen concentration in the piping system decreases when hydrogen is injected, and that in the water supply system also decreases, so the oxygen amount corresponding to the decrease is added to the gas and gas connected to the water supply system piping. It is injected into the water supply system in the form of 02 or H2O2 from a chemical injection device. The oxygen concentration and hydrogen concentration limited here are values measured using a high temperature water quality sensor.

These controls are automatically performed by a computer processing system.

[Embodiment 5] In this embodiment, plant water quality is controlled using the system shown in FIG. 11 using a method different from that in Embodiment 4. 02 injection, H2 injection, H2O2 injection, etc. can be performed at each location so that the difference in potential measured at each location is minimized. If the method described in Embodiment 4 is applied only at one location, the operation may not be effective at other locations.

Therefore, the health of the plant can be maintained by controlling the water quality at each location so that the difference in potential installed at each location of the plant returns to zero.

[Example 6] FIG. 13 shows an example in which the present invention is applied to predicting the timing of stress corrosion cracking. The conditions and system configuration are the same as in the first embodiment. The potential difference between reference electrodes 1-1 and 1-3 has started to rise since January. By expressing the variation in potential up to March in the form of an equation using the nonlinear least squares method, and using that equation to calculate the potential at which SCC occurrence occurs, it can be determined that SCC occurrence or crack growth will begin around April. can be predicted.

[Example 7] Fig. 14 and Fig. 15 show 1.2, 5, 6°, 8.9.
11 shows the structure of the internal reference electrode used in the device shown in FIG. The sensor body has Zr on the silver/silver chloride electrodes 27.28.
It is made of O229 coated material and is housed in a Pt-Rh case 30. As a cable, P t-Rh
/AQ20. /Pt-Rh MI cable 25 is used. A glass 26 is sealed between the MI cable 25 and the sensor body.

FIG. 16 shows these ECP sensors (reference electrodes) mounted on piping.

Note that piping refers to bent pipes, elbows, welded parts,
Welded heat affected zone or welded part of primary system piping of reactor pressure vessel and boric acid water injection piping, core support plate, upper grid plate,
This includes the curved pipe section, welded section, and weld heat-affected zone of the reactor water structure consisting of the core spray piping. The method shown on the right side of FIG. 16 is a method in which the MI cable 25 is passed through the flange of the pipe and welded there. The means shown on the left is a method in which the male connectors 31-1 are screwed into the flange portion of the piping and the cable is mounted using a locking method (Swagelock method). These methods can also be used for γ-ray irradiation. In a non-irradiated environment or in an environment where γ-rays are weak, it is also possible to seal with Teflon as a gasket.

FIG. 17 shows a means for installing an ECP sensor in the reactor of a nuclear power plant.
can be inserted into the reactor using the neutron flux monitor guide tube 33. The ECP sensor 1 is connected to a reactor pressure vessel 35 such as a downcomer, above core, and in core.
It can be installed at any location within the city. Note that the control rod drive mechanism housing 34 is illustrated in the figure. For the extraction part from the neutron flux monitor guide tube 33, the means shown in FIG. 14 may be used.

〔Effect of the invention〕

According to the corrosion detection system of the present invention, the occurrence of localized corrosion such as stress corrosion cracking and pitting corrosion in metal materials exposed to a corrosive environment is a simple system, and the same equipment and evaluation method can be used even when water quality or temperature changes. Since it can be detected in various plants, it is possible to diagnose the health of structural materials in environments where they come into contact with various aqueous solutions. Furthermore, by combining a gas injection device such as 02 or H2 with an ion injection device such as H2O, iron ions, and Ni, it is possible to optimally control water quality, which can be used to improve the health of the plant.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing Embodiment 1 of the present invention, Fig. 2 is a diagram in which Embodiment 1 is applied to BWR plant PLR piping, and Figs. 3 and 4 are diagrams in which Embodiment 1 is applied to prevent stress corrosion. Graph showing the display when detected, FIG. 5 is a configuration diagram showing Example 2,
FIG. 6 is an enlarged view showing the reference electrode arrangement in FIG. 5, FIG. 7 is a graph showing the display of stress corrosion cracking detected by applying Example 2, and FIG. 8 is a configuration diagram showing Example 3. Figure 9 is the 8th
FIG. 10 is a graph showing the display when the occurrence of corrosion between dissimilar metals is detected by applying Example 3, FIG. 11 is a configuration diagram showing Example 4, and FIG. 12 is an enlarged view showing the reference electrode shown in the figure. A graph showing the display of stress corrosion cracking detected by applying Example 4, FIG. 13 is a diagram explaining Example 6, FIG. 14 is a diagram showing the structure of the reference electrode of Example 7, and FIG. A in Figure 14
16 is a sectional view taken along line -A, FIG. 16 is a diagram showing the installation state of FIG. 15, and FIG. 17 is a diagram showing the reference electrode installed in the nuclear reactor. 1-1.1-2.1-3...Verification electrode. 5... Contact switching device, 13-1 to 13-6... Lead wire, 14... Welding part. 1st 1-1-1-3: row ft1 cast 5:9 Australia I〃~F/ 13-1-13-6: Goono W 14:4/I/,/mu: 7ZZ grip 174i/- Mekl-, 7'Aftcv
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Claims (1)

[Scope of Claims] 1. A plurality of reference electrodes are inserted into a corrosion monitoring section of water system piping of a plant, and the potential difference between each reference electrode or the corrosion monitoring section corresponding to each reference electrode and each reference electrode is determined. A corrosion detection system characterized by measuring a potential difference between the two and detecting occurrence of corrosion and its location based on the potential difference. 2. The corrosion detection system according to claim 1, wherein the location where the corrosion occurs is detected when one of the respective potentials fluctuates toward the base side or when the respective potential difference exceeds a reference value. 3. The corrosion detection system according to claim 1 or 2, wherein the location where the corrosion occurs is detected by comparing potential differences between at least two reference electrodes. 4. The corrosion detection system according to claim 1 or 2, wherein the reference electrode is installed at a joint between dissimilar metals. 5. A corrosive environment monitoring system, characterized in that the corrosion detection system according to any one of claims 1 to 4 is installed at at least one location to evaluate the health or danger of a plant. 6. The corrosion detection system according to any one of claims 1 to 4 is provided, and each of the measured potentials or potential differences is displayed on a display system consisting of a CRT, a recorder, a recorder, and a plotter; A corrosive environment monitoring system characterized by detecting the occurrence of corrosion and its location based on the following information. 7. The corrosion detection system according to any one of claims 1 to 4 is provided, and at least one alarm consisting of sound, voice, light, and CRT display is issued to indicate the occurrence of corrosion and its location. Corrosion environment monitoring system. 8. The corrosion detection system according to any one of claims 1 to 4, comprising a rate of increase in the potential difference between each reference electrode, a rate of increase in the potential difference between each reference electrode and the corrosion monitoring unit, or each. A corrosion environment monitoring system that predicts when stress corrosion cracking will occur based on temporal changes in the rate of increase in corrosion. 9. A corrosion environment monitoring system comprising the corrosion detection system according to any one of claims 1 to 4, and monitoring temporal changes in each potential or potential difference to be measured. 10. A gas and chemical injection device that is equipped with the corrosive environment monitoring system according to any one of claims 5 to 9 and that injects at least one of oxygen, nitrogen, hydrogen, NOx, Fe ions, Ni ions, HNO_2, and H_2O_2. A water quality control system characterized by comprising: 11. A system comprising the corrosive environment monitoring system according to any one of claims 5 to 9, in which oxygen, nitrogen, hydrogen, NOx, Fe ions, Ni ions, HNO_2 and H_2O_2 are used to return the measured potential difference to approximately the reference value. A water quality control system, characterized in that at least one is injected into the water system from at least one location. 12. A plant comprising at least one of the corrosion detection system, corrosion environment monitoring system, or water quality control system according to any one of claims 1 to 12. 13. At least one of the corrosion detection system, corrosion environment monitoring system, or water quality control system according to any one of claims 1 to 12 is applied to at least one of a welded part, a heat affected zone, an elbow, and a bent pipe part of a metal material. A plant characterized by being installed at certain locations. 14. At least one of the corrosion detection system, corrosion environment monitoring system, or water quality control system according to any one of claims 1 to 12 is installed in a recirculation system bypass, a reactor water spray system piping, a reactor purification system piping, and a recirculation system. A nuclear power plant, characterized in that the BWR plant primary system piping, which is composed of a circulation system riser pipe, is disposed at at least one of a bent pipe section, an elbow, a welding section, and a welding heat affected zone. 15. At least one of the corrosion detection system, corrosive environment monitoring system, and water quality control system according to any one of claims 1 to 12, a welded part of a reactor pressure vessel and a primary system pipe, and a boric acid water injection pipe, Core support plate, upper lattice plate,
A nuclear power plant, characterized in that the reactor water structure is installed in at least one of a curved pipe section, a welding section, and a welding heat affected zone of a reactor water structure consisting of a reactor core spray piping.