JPH0387643A - Electrochemical electrode and electrochemical cell using this electrode - Google Patents

Abstract

PURPOSE:To provide the longer life and higher stability of the Ag/AgX (X: Cl, Br, I) electrode as represented by Ag/AgCl by coating a solid electrolyte, which is hardly soluble in an aq. sol., with a porous insulating layer. CONSTITUTION:Ag/AgX (X: Cl, Br, I) is sealed into ceramics or synthetic resin having fine pores so that the liquid junction with reactor water is executed not by the direct contact of the AgX with the soln. but by the contact thereof with the soln. impregnated into the fine pores of the ceramics or the synthetic resin. Namely, the electrode is formed by welding a molten silver halide 7 on the front end of a silver wire 1 and mechanically pressure-molding a ceramics layer 6 around this silver. The ceramics layer 2 is pressure-molded in the upper part of the silver wire 1 in order to prevent the direct contact of the silver wire 1 with the reactor water or cooling water. Alumina powder, magnesia powder, etc., are used for the ceramics layers 6, 2. The electrode is stably supported by means of a holder 3 of a lock fitting, the lock fitting 4 and a structural material 5. A lead wire is connected to the other end of the silver wire 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a silver-silver chloride electrode that is used today as a reference electrode necessary for electrical and electrochemical water quality diagnosis systems and monitoring techniques in nuclear power plants, thermal power plants, etc. This invention relates to an electrode structure that achieves long life, high durability, and high stability, and an electrochemical sensor using the same.

[Conventional technology]

Conventionally, regarding reference electrodes in high-temperature water, in recent years Reference Electrode for B.R. (1987) Copyright 1987 Electric, Power, Research, Institute, Inc.
PWRs, Copyright 1987 Elec
tricPower Re5search In5tit
ute Inc.). A g / A a discussed in this and actually put into use
All CQ reference electrodes have a structure in which silver silver chloride is placed in a solution containing CQ- ions. A g/A
a The CQ electrode is a basic and typical reference electrode for electrochemical measurement, and is an excellent reference electrode with a small temperature coefficient.

However, until now, silver silver halide Ag/AgX (X: CQ, Br) typified by this Ag/A g Cn.

There are no A g / A g

There have also been attempts to suppress the outflow of the electrolyte by providing a pressure-balanced structure, as described in Japanese Patent Application Laid-Open No. 63-67134.

JP-A-59-174748 discloses a device in which an electrolyte is introduced into a cell using a diaphragm for electrolysis.

This electrochemical cell uses a diaphragm to select the chemical species to be analyzed, and it is essential to use a diaphragm that has excellent permselectivity and is highly durable under high temperature, high pressure water environmental conditions and in radiation fields. Currently, no resin diaphragm has been found that satisfies these conditions. Furthermore, the electrochemical cell structure is complex, and the equipment inside the reactor is difficult in principle. Electrolyte is injected in advance to lower the impedance of the electrochemical cell and the impedance of the reference electrode, and the diaphragm is radial and cracks can occur. If even a small portion is broken due to such reasons, it becomes impossible to selectively separate and quantify dissolved oxygen in principle.

A method of separating and quantifying dissolved hydrogen has been considered, as described in Japanese Patent Application Laid-Open No. 58-215549, but it uses a selective hydrogen permeable membrane as described above, and has the same problems as described above.

As described in JP-A-56-77751, the pH of high-temperature water is measured by using zirconium oxide as a membrane for a hydrogen ion sensing element, but under conditions of a constant pH. It can also be used as a reference electrode, and is currently an important element that provides the basic structure of the high-temperature, high-pressure Kinoshita pH electrode. Furthermore, this patent publication is the first to show that oxygen ion conductive ceramics can function as a membrane for a hydrogen ion sensing element, and is therefore regarded as a fundamental invention. However, based on the ceramic membrane potential used in this patent publication, the ceramic membrane used as a reference electrode is used as a reference electrode, and a 3@polar system electrochemical cell comprising two counter electrodes and two working electrodes is constructed. This poses great difficulties due to its high impedance properties. Also, in this case, it is almost impossible to use both the reference electrode and the counter electrode. Furthermore, it is susceptible to temperature gradients and shocks peculiar to ceramic materials, and has durability problems, so there is no prospect that it will be able to withstand use between periodic plant inspections.

In the 57th Annual Conference of the Electrochemical Society (Kyoto, 1990) Abstracts No. 2C21, the principle of the separation and quantitative method of oxygen, hydrogen peroxide, and hydrogen is presented. There is no mention of what kind of low impedance reference electrode should be attached to the cell.

Conventional electrochemical measurement cells using a reference electrode include a three-electrode system having a working electrode (detection electrode) and a counter electrode, or a two-electrode system having a cell structure in which the reference electrode and the counter electrode are used together. Other measurement methods are not used today due to their lack of precision.

Electrochemical Methods, John Wiley & Sons, Inc.

1980 pages 553-573 (Electrochemical Method, J
ohn Wiley&5ons.

Inc., (1980), pp553-573), this potential control device for electrochemical measurements (
The input stage for the potential of the reference electrode of the potentiostat is a voltage follower stage, which is basically a feedback circuit to the control amblifier. For this reason,
Measurement stability is achieved by keeping the impedance to this input stage as low as possible.

Leads to precision. Otherwise, the oscillation phenomenon will be cursed.

However, to date, there has been no electrochemical cell with low impedance reference electrode characteristics that can be installed inside a nuclear reactor or in a plant piping system to perform general electrochemical measurements, not just dissolved oxygen. Based water quality monitoring especially in nuclear reactors.

The situation is such that it cannot be carried out in-5 in the cooling water system.

[Problem to be solved by the invention]

The technique related to the conventional reference electrode described above is that the CQ- ion concentration that determines the Ag/AgC1 electrode potential (AgCI2+e-*Ag+Cu-) is based on reactor water in the electrolyte.

Changes due to leakage into cooling water, 10% in less than a month
This is to cause a potential fluctuation close to 0 mV.

In addition, the solubility of AgCQ itself becomes higher in high-temperature water than at room temperature, resulting in a decrease in the elution of Ag(11).
There is a natural lifespan limit for A g CQ. The pressure-balanced reference electrode with a piston valve does not have any countermeasures against the inherent diffusion phenomenon or leakage of electrolyte from the wall surface in contact with the piston valve or the wall surface in contact with the zirconia plug, and the current problem is potential instability. (Outflow of electrolytic solution containing halogen ions) etc. are caused by this.

The above-mentioned conventional technology involves the preparation of a low-impedance reference electrode for in-5 in-itu electrochemical analysis in a nuclear reactor system, and the specific arrangement relationship, shape, and overall configuration of the reference electrode, working electrode, counter electrode, etc. No consideration has been given to chemical cells, and therefore, problems such as how to install them and durability, especially under harsh conditions such as inside a nuclear pressure vessel, remain completely untouched.

The present invention aims to solve the above two problems and provide a reference electrode that achieves a long life and high stability of the Ag/AgX (X:CLBr+I) electrode represented by Ag/AgCQ.

An object of the present invention is to provide an electrochemical cell that is based on a low impedance, highly durable, and compact reference electrode t pH electrode, and is capable of performing electrochemical measurements in high-temperature, high-pressure water. A neutron instrumentation tube is installed inside the pressure vessel to enable sensing of dissolved oxygen, dissolved hydrogen, dissolved hydrogen oxide, pH + ECP (corrosion potential), etc.

[Means to solve the problem]

In the present invention, a solid electrolyte that is poorly soluble in an aqueous solution is coated with a porous insulating layer, and the porous insulating layer can be penetrated by the aqueous solution, and ions generated when the electrolyte is dissolved in the aqueous solution. An electrochemical electrode characterized by having micropores that suppress leaching of.

Specifically, the present invention provides silver halide or silver sulfate at the tip of a silver wire, covers the silver halide or silver sulfate with a porous ceramic layer or a porous resin layer, and the porous body is the one described above. A reference electrode is characterized by comprising:

A dispersion layer in which the silver halide or silver sulfate is dispersed in the micropores of the porous ceramic layer or porous resin layer is provided between the silver halide or silver sulfate and the ceramic layer or porous resin layer. Located at the reference electrode.

Further, in the present invention, the silver wire is covered with a metal cylinder through a porous ceramic layer, and one end of the metal cylinder has a hole through which an aqueous solution of the test object permeates, and the ceramic layer can be penetrated by the aqueous solution, and The silver wire has micropores that suppress the leakage of ions generated when dissolved in an aqueous solution, and the other end of the metal cylinder is sealed with a ceramic sintered body, and the aqueous solution permeates the porous ceramic and The reference electrode is characterized in that a lead wire insulated by a ceramic layer is connected to a terminal on the opposite side of the silver wire through which the aqueous solution permeates and prevents leakage to the outside from the other end. In addition, there is a pH electrode having a structure similar to that described above, in which a metal wire carrying a solid substance exhibiting a potential corresponding to the hydrogen ion concentration of the solution is covered with a metal cylinder via a porous ceramic layer.

The present invention can be an electrochemical cell having a working electrode and a reference electrode, or a counter electrode.

AgX (X: CQ, Br, I) is sealed inside ceramics or synthetic resin with pores, and the liquid junction with reactor water is A, g X directly welds CCQBr-I-, etc. The liquid junction is created not by contacting with a solution containing or not containing a liquid, but by contacting a solution that has been impregnated into the pores of the ceramic or synthetic resin.

In order to achieve the above object, in the present invention, a reference electrode of an electrochemical cell and a metal oxide electrode that exhibits characteristics as a pH electrode that exhibits a potential corresponding to the hydrogen ion concentration are directly coated with fine porous ceramics or resin. However, the electrolyte ions generated due to the solubility of each electrode at each temperature are dispersed within the porous material, which has the feature of lowering impedance. The electrode thus obtained is integrated with a working electrode and a counter electrode based on a microelectrode to constitute a compact electrochemical cell in which electrochemical measurements can be performed.

Additionally, MI cables (Mineral cables) are installed inside the reactor.
This is made possible by using the MI cable's sheath material (Insulator Cable) and passing the lead wire leading to the electrode of the electrochemical cell through the MI cable.
(basically electrically short-circuited with the structural material) and the lead wire (core wire) of the electrode in the cable are bonded using ceramic metallizing technology, and high-temperature, high-pressure water penetrates into the insulating layer of the MI cable. It prevented

[Effect]

When AgX comes into contact with the solution that has impregnated the pores of the ceramic or synthetic resin, the AgX is dissolved as follows.

A, g
Corresponds to saturation solubility. When AgX is in direct contact with the solution, X- in the vicinity of AgX easily diffuses directly into the reactor water, and since the volume of the solution of AgX in direct contact is large, the elution of A and gX is a real problem. It has become a thing.

However, when A, g
The elutable solution volume of gX is the conventional A g/A,
g Extremely small compared to X. In addition, the X-
The mass transfer resistance between passing through the pores and exiting into the solution valve is large, and the elution of AgX into the 7-volume liquid bulk can be suppressed as much as possible. As a result, stable X- (near the saturation concentration) is always supplied into the pores near AgX, and the A g / A g It exhibits long life and highly stable potential.

The electrochemical cell mentioned above uses a low-impedance, long-life reference electrode protected by a fine porous layer, and the cell lead wire is basically protected by an MI cable, so the electrochemical cell can be used for a long period of time. Measurements can be performed stably. As a result, in-5 in-itu water quality analysis of high-temperature, high-pressure water can be performed stably during Plan I operation, and circuit oscillations and the like are not observed and malfunctions do not occur.

〔Example〕

Example 1 The electrode shown in FIG.
Ceramic layer 2, which is obtained by welding and mechanically press-forming ceramic layer 6 around it, is also press-formed in the same way. To prevent the silver wire from coming into direct contact with reactor water or cooling water, a ceramic coat 2 is applied to the top of the silver wire. Alumina powder, magnesia powder, etc. are used for the ceramic layer. This electrode is stably supported by a metal fitting holder with tightening of 3 and 4.5, a metal fitting with W6 fitting, and a structural material. A lead wire is connected to the other end of the silver wire.

In FIG. 2(A), the two electrodes shown in FIG. 1 were used, and the potential difference between the electrodes was measured with time as the horizontal axis. As shown in the figure, no potential difference appeared between the two electrodes even after about 5 months from the start of the measurement. If the silver-silver chloride electrode with the structure shown in Figure 1 shows a stable unipolar potential, if you prepare two of the same @ electrode and measure the potential between the electrodes, the potential difference will be zero in principle. . Since each electrode is unstable and it is impossible to imagine that the changes over time for both electrodes would be exactly the same for more than five months, Figure 2 (A) shows that the electrode according to the present invention is extremely stable. , indicating that it has excellent durability. This is because the silver-silver chloride electrode that has been used as a reference electrode has been used via a solution such as KCQ<potassium chloride, and KCIIk and other substances may leak into the reactor water or cooling water, causing A g /
It is greatly different from that which shows potential fluctuation in about - months due to the dissolution of A g C (l).Also, as shown in Fig. 2 (B), one electrode is shown in the first drawing, and the other is Bare A, g without ceramics 6 in Figure 1
/ A g C If you measure the potential difference between the electrodes, it will be approximately 1
A rapid potential difference appeared after a little over 0 days. This is Ag/Ag
Since the potential difference is around +500 mV with respect to Cl11, the unipolar potential at the center of the A g/A g+ system and the A g
/ A g Cf), close to the potential difference with the system, bare A
This is probably due to the appearance of bare silver (Ag) lines due to the elution of AgCQ from the g/AgCQ electrode. The fluctuation in potential is thought to be due to the fact that the equilibrium state near the silver wire is not fully satisfied because the bare electrode is exposed to the flow. From FIG. 2, it has become clear that the electrode having the configuration shown in FIG. 1 is extremely stable and has excellent durability. A shown in Figure 2 (A)
The potential stability of the g/AgCQ electrode is A in a high-temperature pure water environment.
It appears that the chloride ions CQ generated by the dissolution of gCQ are distributed in the ceramic pores in a saturated state, and the concentration remains constant over time. In addition, the improvement in durability is thought to be due to the fact that the diffusion of eluted AgCQ through the ceramic pores is much smaller than the normal bare Ag (1!) in contact with the solution.Porous The ceramic layer reduces the elution rate of Ag ions to 10-12 mol.
It is preferable to set the density to have micropores such that /aJ-8 or less.

Example 2 The silver-silver chloride electrode (Ag/AgBr) shown in FIG. 3 is an Ag/AgCQ electrode having a structure including an inner layer 7 of AgCQ and an outer layer of a ceramic layer in which pores are impregnated with AgCI2. Although the initial potential stability of this electrode is inferior to that shown in FIG. 1, the impedance of the electrode is low. The rest is the same as in Example 1.

Example 3 Figure 4 shows an Ag/AgCQ electrode, with an inner layer 7 containing AgCQ, an intermediate layer 9 containing a ceramic layer with pores impregnated with AgCQ,
This structure has a ceramic layer 6 as the outermost layer that is in direct contact with reactor water and cooling water, and also has the electrode structure shown in Example-1 and Example-2. It also has excellent durability and stability. Others are the same as above.

Embodiment 4 In FIG. 5, the inner layer 9 has a ceramic layer in which the pores are impregnated with AgCQ, and the outer layer 6 has a ceramic layer. The structure is such that the inner layer 9 connected to the silver wire has the effect of increasing the connection strength.

The rest is the same as above.

Embodiment 5 In FIG. 6, the inner M9 has a ceramic layer in which the pores are impregnated with AgCQ, the intermediate layer 7 has an AgC1 layer, and the outermost layer 6 has a ceramic layer.

The electrode of this construction can have a longer life compared to the electrode shown in FIG. Others are the same as above.

Embodiment 6 FIG. 7 shows an electrode composed of an inner layer 9 of a ceramic layer impregnated with AgCQ in its pores, an intermediate layer 7 of an AgCQ layer, and an outermost layer of a ceramic layer impregnated with Ag(l).

This electrode has a lower specific vane impedance than the electrode having the configuration shown in FIG. Others are the same as above.

Example 7 In Fig. 8, the inner layer 9 has a ceramic layer in which the pores are impregnated with AgCQ, the outermost layer is the ceramic layer 6, and the middle layer is the inner layer. It has ceramic layers 7 and 9, and has higher durability than the structure shown in FIG. Others are the same as above.

Example 8 Figure 9 shows an Ag/Ag wire made of a platinum wire with a silver coating layer or other good electrical conductor 1o as an electron current collector.
It is a CΩ electrode. 7 and 6 are respectively Ag as in Figure 1.
CQ, ceramics. The electrode with this configuration is the structural material 5
It is possible to increase the mechanical strength when fixing the electrode to the electrode, and to improve the adhesive force with the ceramic coating 2. This ceramic coating 2 and current collector 10
The adhesion and adhesion force can greatly affect the potential stability of the electrode. That is, when the current collector 0 comes into direct contact with cooling water or reactor water 8, there is a possibility that an oxidation-reduction reaction will proceed through the contact surface, and the potential as a reference electrode will no longer be A g CQ +e →It is output as a hybrid potential instead of the unipolar potential of the Ag+CI2 reaction. Others are the same as above.

Example 9 FIG. IO shows that the inner layer 12 contains a single Ag
It has a structure containing I (silver iodide) or AgBr (silver bromide). Silver silver iodide (Ag/AgI) electrodes and silver silver bromide (Ag/AgBr) electrodes are also A g / A g
It can be used as a reference electrode like the CQ system. Ag/
AgI gives an electrode potential of AgI+e-+Ag+I,
Ag/AgBr gives that of AgB r+e+Ag+B r .

Similar to AgCQ, by wrapping Ag I and AgBr with the ceramic layer 6, A, gI, AgB
The elution rate of r could be suppressed, and high durability and long life could be achieved. Others are the same as above.

Example 10 In Figure 11, JW12 contains silver halide (Ag CR).

The outermost layer is a porous resin 16 with fine pores surrounding the silver wire 1 (AgI, A, gBr), and a resin coating instead of a ceramic coating is used as a shielding material for the silver wire 1.
Alternatively, it is an electrode constructed using a tube. As with the previous electrodes, this electrode structure can suppress the elution rate of silver halide and extend its life. Others are the same as above.

Embodiment 11 FIG. 22 shows an electrode having a structure in which the inner layer 12 is silver halide, the intermediate layer 15 is a ceramic layer containing silver halide, and the outer layer M6 is a ceramic layer. This electrode also has excellent durability and stability as a silver halide electrode. Others are the same as above.

Example Work 2 Figure 13 shows silver halide 12 in the inner layer, porous resin containing silver halide in the middle layer 6, ceramic layer 6 in the outer layer, resin coating on the third layer as a shield for the silver wire, or , tube 13, which is an electrode having a structure having a second layer, that is, a ceramic coating layer on the outer layer. In order to further improve the shielding of the silver wire that is the current collector,
It is coated with resin and has a silver halide electrode structure with high durability and long life.

Embodiment 13 FIG. 14 shows an electrode with an electrode storage cell F to avoid direct exposure to the flux of reactor water and cooling water. By suppressing the flow around the electrode, the electrode having this electrode housing cell can further reduce elution and diffusion of silver halide into the cooling water system, thereby achieving high durability and long life. By using ceramic 8 or a porous resin plug, the flow around the electrode can be suppressed as much as possible.

Embodiment 14 Similar to FIG. 14, FIG. 15 shows a reference electrode having an electrode housing cell 17 to avoid being affected by the flux of reactor water and cooling water. The silver halide 12 is directly inserted into the electrode storage cell 17 without coating with ceramics or the like.
It is stored. By using ceramics 18 or porous resin plugs, storage cells 17 are formed as in Example 14.
suppresses the diffusion and flow of ionic species inside the reactor water. Silver halide is in a state close to saturation concentration in the electrode storage cell,
Since the outflow of silver halide into the reactor water through the plug 18 is suppressed, the electrode shown in FIG. 25 can exhibit a stable electrode potential as in the previous embodiments. Others are the same as above.

Example 15 FIG. 16 shows a cross section of an electrochemical cell in a neutron instrumentation tube in a nuclear reactor. 21 is a case that houses each electrode of the electrochemical cell, and is made of 5US316L steel. A hole is provided at the top of 21 to allow reactor water and liquid to enter and exit. By providing this hole, it is possible to measure while grasping information on reactor water while minimizing disturbance of electrochemical analysis, pH measurement, and corrosion potential measurement due to convection in the electrochemical cell due to the flow of reactor water. I can do it. 22 indicates a low impedance silver/silver ion reference electrode. 23 is diameter 20
This figure shows a U-shaped working electrode made of μm microplatinum wire. 2
4 shows a platinum/thallium oxide (T Q 203) type pH electrode whose electrode potential responds to the hydrogen ion concentration in the reactor water. 25 indicates a counter electrode made of a 50 μm platinum wire. 2
6 has tungsten metallized on the surface of aluminum oxide (Al2O2) sintered body, and 27 MI cable (Mine
This is a sealing member to prevent reactor water from entering the ceramic insulator of the MI cable and lowering the insulation resistance between the cable sheath and the core wire when connecting the core wire and the counter electrode of the MI cable. The working electrode section 26 of the working electrode section 23 also has exactly the same role. 2
8 indicates a welded portion.

As seen in this figure, reactor water directly enters the cell container at the top of this electrochemical cell structure, but the structure is such that reactor water cannot enter into the space shown at the bottom. In this space, the four MI cables are embedded in 29 metal tubes and routed out of the reactor through instrumentation tubes, connected to conventional potentiostats, function generators, and potentiometers, and connected to computers using conventional interface techniques. and various electrochemical measurements (e.g.
Pulse voltammetry, random pulse portammetry, etc.) can be performed, connect the lead wire to the structural material that is electrically shorted to 29.28, and measure the potential difference between it and 22 with an electrometer. By doing so, it is possible to measure the corrosion potential of stainless steel under the water quality environment inside the reactor.

Furthermore, by connecting an electrometer to 22 and 24, the potential of the 24 electrodes based on the reference electrode 22 can be determined. Therefore, by measuring the potential difference in 22.24, p, I of the reactor water
(This electrochemical cell can measure 22,
The four electrodes 23, 24, and 25 are placed close to each other. In the case of this figure, the inner diameter of the cell 21 filled with reactor water is 20 mm.

In order to install the four electrodes as close as possible within this cell, the electrodes are arranged in a circular pattern.

FIG. F is an enlarged detailed view of the 22 reference electrode sections shown in FIG. 16. This reference electrode consists of a silver/silver ion electrode. 30 is silver wire, 3rd wire is aluminum oxide (AQz
It is composed of a compression molded body of fine powder (300 mesh) of Os), and has 39 liquid junction holes (0.5 mm diameter
) and can store the silver ions eluted from the silver. The rate at which AQ 203 powder diffuses into the reactor water changes depending on the compression strength of the AQ 203 powder in 31. The elution rate of silver ions is 1O-f2
It was possible to suppress IIIoQ/d-8 or less.

36 is A g / A g ten electrode sheath, 32 is AQz
The seal is made of an Oa sintered body and has tungsten metallized on its surface, and is connected by gold solder 34. This prevents reactor water from entering the adapter case 38 and into the MI cable, thereby preventing the insulation resistance from decreasing. 33 is the AQZ○3 insulating layer. 34 indicates the same welding location as 28. 35 is 5US304
MI cable core wire with 10 silver lead wires.

This lead wire 35 is connected to the silver wire 30. 37 is MI
The cable sheath is the same as the core wire, 5US304! It is l material. 38 is an adapter for connecting the MI cable and the electrode section. The alumina M edge ff31 is pressure-molded to the extent that water can penetrate therethrough, but it has fine pores that suppress the elution of reacted silver ions.

FIG. 8 is an enlarged detailed view of the pH electrode of FIG. 16.24. 40 is TQ203, and 41 is platinum which serves as an electron current collector. This structure is Example 15
It is similar to In TQ20s, TQ ions are eluted into the alumina compact due to the intrusion of reactor water and are stored as TQ ions. It is preferable to use a similar elution rate for TQ ions.

Example 16 Figure I9 differs from Figure 16 in that it doubles as an Ag/Ag 10 type reference electrode, reducing the number of electrodes by one and making it more compact and easier to install in the instrumentation pipe. This is what I did. Therefore, 42 is a column contact/reference electrode that utilizes the low impedance characteristic shown in FIG.

The electrochemical cell shown in this figure is compact, but has a working Fi23 and a counter electrode (A g / A g + reference electrode).
It is used in such a way that no large electrolytic current is passed between them. This is because ohmic loss (IR loss) between the working electrode 23 and the counter electrode 42 is directly added to the input/output potential during electrochemical measurement of the working electrode, which may make it difficult to accurately monitor the potential and current. Or A g / A g + is Ag←→A
This is the potential of a half-cell reaction based on the g++e reaction, and is a type of reaction with high electrochemical reversibility (reaction resistance: large reaction rate → high reversibility), even when a small amount of current is applied from the outside. Although there is a current value at which the potential does not vary significantly, there is no case where the potential does not change at all when a current is applied externally, although there are differences in degree. It is desirable to use small microelectrodes or pulse measurements with short electrolysis time.

Example 17 Figure 20 shows the 50 μm platinum pair wA25 shown in Figure 16.
By directly electrically shorting the M
The structure is such that the I cable is passed through and a threaded portion is provided in the metal tube 29 to fix the electrochemical cell. The electrochemical cell shown in this figure is shown in FIG.

Unlike FIG. 19, the area of the counter electrode is extremely larger than that of the working electrode, and it is possible to suppress the IR loss between the working electrode and the counter electrode to a minimum.

5US316L steel does not exhibit noble metal electrode characteristics like platinum electrodes, so if a large current is passed for a long time with cell case 1 on the anode side, the SUS material will corrode and contaminate the electrochemical cell. This may lead to destruction of the joints, etc. Using a microelectrode, analysis experiments (based on reduction reactions) were continued for one year, and even if only iron from the SUS material of the cell case was selectively eluted, the electrolytic current at the microelectrode, which is the working electrode, was reduced to 0.1 μA. If set, iron elution will be 2■
/ year. Therefore, in reality, there is no problem of elution from the cell case.6 [Effects of the Invention] According to the present invention, it is possible to extend the life of the reference electrode that provides the reference potential of the monitoring system, and to achieve high stability. It can be maintenance free.

According to the present invention, electrochemical analysis can be performed in a nuclear reactor using a low-impedance reference electrode, and the reference electrode structure is protected by a fine porous layer. It is also possible to set the elution of reference electrode component ions from the water interface to less than 10"moα/ad-8 with flux, and it has an extremely long life (15 years with a 0.5g silver/silver ion reference electrode). (above), and can perform stable electrochemical analysis.Therefore, the technology that has been developed in the field of electrochemical measurement can be applied to the analysis of water quality in nuclear reactors. For the first time, the water quality inside the reactor was measured in -5Ltu.
A method for accurately grasping information inside the reactor can be realized. This technology makes it possible to consider reactor life extension plans based on specific water quality data.

In addition, water quality sensing technology will gain dramatically higher reliability due to the electrochemical cell structure, which has a lifespan longer than the regular inspection period of a nuclear reactor.

[Brief explanation of drawings]

The second construction drawing is a ceramic-silver silver chloride (
FIG. 2 is a characteristic diagram showing potential measurement results, FIGS. 3 to 15 are cross-sectional views of reference electrodes shown in Examples 2 to 14, and FIG. 16 is a cross-sectional view of a reference electrode shown in Examples 2 to 14. Cross-sectional view of an electrochemical cell integrated with electrode 2 working electrode, counter electrode, and pH electrode,
FIG. 17 is a cross-sectional view of a ceramic integrated silver/silver ion reference electrode. Figure 8 shows ceramic-integrated thallium oxide pH
Cross-sectional view of the electrode, Figure 19 shows the reference electrode/counter electrode, counter electrode,
A cross-sectional view of an electrochemical cell integrated with a pH electrode. FIG. 20 is a sectional view of an electrochemical cell integrated with a reference electrode 7, a working electrode, a counter electrode, and a pH electrode, which has a counter electrode in the electrochemical cell case. 1... Silver wire, 2... Ceramic coat, 3... Tightening is a metal fitting holder, 4... Tightening is a metal fitting, 5...
Structural material, 6... Ceramic layer, 7... Silver chloride, 9
... Silver chloride permeated ceramic layer, 21 ... Electrochemical cell case, 22 ... Reference electrode, 23 ... Working electrode, 24 ... pH electrode, 25 ... Counter electrode, 26 ... Ceramics Terminal, 27...MI cable, 28...Welded part, 29...MI cable conduit, 30...Silver, 3
Engineering...A Q 208 Compressed powder. 32...A Q 203 cap, 33...AQ2
03 Powder insulation layer, 34...Welded part, 35...5US
304 lead wire, 36... sheath of reference electrode section, 37
...MI cable sheath, 38...MI cable and reference electrode part connection adapter, 39...liquid junction hole, 4o
...T Q 203 (thallium oxide), 41...
・Platinum, 42...Reference Figure 1 Figure (A) ○ 0.6 1.6 22.53 Time (Month) 3.6 4.55 (B) Time (Month) Figure 5 Figure 5 Figure Figure Figure Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20

Claims (1)

[Scope of Claims] 1. A solid electrolyte that is poorly soluble in an aqueous solution is covered with a porous insulating layer, the porous insulating layer is permeable to the aqueous solution, and the electrolyte is not soluble in the aqueous solution. An electrochemical electrode characterized by having micropores that suppress leaching of ions generated by dissolution. 2. A silver halide material or silver sulfate is provided at the tip of the silver wire, the silver halide or silver sulfate is covered with a porous insulating layer made of a porous ceramic layer or a porous resin layer, and the porous insulating layer is A reference electrode characterized in that it has micropores through which the aqueous solution can permeate and which suppresses leaching of ions generated by dissolving the electrolyte in the aqueous solution. 3. In claim 2, the silver halide or silver sulfate is placed between the silver halide or silver sulfate and the ceramic layer or porous resin layer in the micropores of the porous ceramic layer or porous resin layer. Reference electrode with dispersed dispersion layer. 4. The reference electrode according to claim 2, wherein the silver halide or silver sulfate is formed by a dispersion layer dispersed within the micropores of the porous ceramic layer or the porous resin layer. 5. The reference electrode according to claim 4, wherein the inner layer of the dispersion layer is formed with silver halide or silver sulfate. 6. Covering the silver wire with a metal cylinder through a porous ceramic layer, the ceramic layer being permeable to the aqueous solution,
The metal tube has micropores that suppress the leaching of ions generated when the silver wire is dissolved in an aqueous solution, one end of the metal tube has a hole that allows the aqueous solution of the test object to penetrate, and the other end of the metal tube is made of ceramic. The aqueous solution is sealed with a sintered body to prevent the aqueous solution from penetrating the porous ceramic and leaking out from the other end, and the terminal on the opposite side of the silver wire through which the aqueous solution permeates is sealed with a ceramic layer. A reference electrode characterized in that an insulated lead wire is connected to the reference electrode. 7. A metal wire carrying a solid electrolyte exhibiting a potential corresponding to the hydrogen ion concentration of the aqueous solution is covered with a metal cylinder via a porous ceramic layer, and the ceramic layer is permeable to the aqueous solution, and The solid electrolyte has fine pores that suppress the leaching of ions generated when dissolved in an aqueous solution, and has a hole at one end of the metal cylinder that allows the aqueous solution of the specimen to penetrate,
The other end of the metal tube is sealed with a ceramic sintered body to prevent the aqueous solution from penetrating the porous ceramic and seeping out from the other end, and to prevent the aqueous solution from penetrating the silver wire. A pH electrode characterized in that a lead wire insulated by a ceramic layer is connected to a side terminal. 8. The pH electrode according to claim 7, wherein the solid substance is thallium oxide. 9. In an electrochemical cell having a working electrode and a reference electrode providing a reference potential,
The reference electrode has a porous insulating layer covering a solid electrolyte that is poorly soluble in an aqueous solution, and the porous insulating layer can be penetrated by the aqueous solution, and the porous insulating layer is formed by dissolving the electrolyte in the aqueous solution. An electrochemical cell characterized by having micropores that suppress the leaching of ions. 10. The electrochemical cell according to claim 9, comprising a three-electrode system including a counter electrode. 11. The electrochemical cell according to claim 10, comprising a two-electrode system in which the reference electrode functions as a counter electrode and also includes a working electrode. 12. An electrochemical cell according to claims 10 and 11, comprising an electrode electrically shorted to the structural material as a counter electrode. 13. In any one of claims 9 to 12, in the structure of the reference electrode and the working electrode, the counter electrode surrounds the reference electrode and the working electrode, and the reference electrode and the working electrode are provided in a cell constituted by the counter electrode. An electrochemical cell characterized by: 14. An electrochemical cell according to any one of claims 9 to 13, comprising the reference electrode, the working electrode, the counter electrode, and four types of electrodes exhibiting pH response. 15. In claim 14, the reference electrode has a reference electrode that also serves as a counter electrode, and the working electrode has a pH response.
An electrochemical cell characterized by comprising an electrode.