JPH1048371A - Reactor plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion of zircaloy fuel clad for a long period by positively utilizing metal elements having corrosion suppression function. SOLUTION: Steam generated by the heat in the core 42 is sent via a steam line 43 to a steam turbine 44. The steam having worked in the turbine 44 is condensed in a condenser 45 to recover water. This water is sent to a condensate purification device 47, impurity is removed and then it is preheated in a water supply heater 48 to be fed back into a reactor pressure vessel 41. On the way of a bypass line 38 bypassing a metal element generator 30, a flow control valve 39 is provided, which is controlled for the opening by a concentration controller 61. Valves 35 and 37 for isolation are used for isolating the device 30 during maintenance. Metal ion generated in the generator 30 is supplied in the pressure vessel 41 together with the recirculation water and thereby, corrosion of zircaloy fuel clad is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear power plant having a zircaloy fuel cladding, and more particularly to a nuclear power plant capable of preventing corrosion of a zircaloy fuel cladding.

[0002]

2. Description of the Related Art In general, in light water reactors such as a boiling water reactor (BWR) and a pressurized water reactor (PWR), zircaloy, a kind of zirconium-based alloy, is used as a material for a fuel cladding tube. Zircaloy has a small neutron absorption cross section and excellent mechanical properties, and is a material suitable for a fuel cladding tube. However, it has a problem that it causes a corrosion reaction with light water as a coolant. Conventionally, the corrosion reaction between zircaloy fuel cladding and light water in a BWR has been mainly nodular corrosion, which produces lens-like oxides. It is changing to uniform corrosion, which forms a uniform oxide film on the entire surface. On the other hand, the corrosion reaction between the Zircaloy fuel cladding tube and light water in the PWR has not changed from the past, and the formation of a uniform oxide film is the main form of corrosion. However, under the current fuel use conditions in light water reactors, these corrosions (thickness of oxide film) are not serious problems that affect the life of the fuel from the viewpoint of the soundness of the fuel cladding tube.

[0003] However, there has been a demand for a reduction in the amount of spent fuel generated due to a recent rise in fuel reprocessing costs.
On the other hand, since the fuel cost accounts for a large proportion of the operating cost of a nuclear power plant, a higher burnup of fuel, that is, a longer life, is being planned to improve its economic efficiency. Therefore, there is a demand for an excellent fuel cladding tube having a sufficient margin against corrosion even during long-term use.
Under such circumstances, improvement of the corrosion resistance of Zircaloy fuel cladding has become one of the important research subjects at present.

[0004] Factors affecting the corrosion resistance of Zircaloy fuel cladding include material factors such as fuel cladding manufacturing history, heat treatment, alloying components, dissolved oxygen,
Environmental factors such as neutron irradiation and impurities in the coolant are considered, and studies are being actively conducted on these factors to improve corrosion resistance.

[0005]

SUMMARY OF THE INVENTION The present inventors have been conducting studies and studies on the effects of water quality environmental factors on the corrosion resistance of zircaloy fuel cladding tubes. It has been estimated that there is a possibility of suppression. Therefore, in order to confirm this, a corrosion test of zircaloy was carried out in the presence of trace metals under conditions simulating the environment of a zircaloy fuel cladding in a nuclear power plant. And the result of the corrosion test showed that the estimation was correct. In addition, the analysis results of the test pieces used in the corrosion test succeeded in elucidating the mechanism of the corrosion inhibition, and also obtained the preventive measures.

[0006] The present inventors have investigated the growth rate of a corrosion film on a Zircaloy fuel cladding tube in a nuclear power plant, and have found many cases that are difficult to explain only by the material factors. That is, despite the use of Zircaloy fuel cladding tubes of exactly the same production lot, many cases have been reported in which the thickness of the oxide film per the same operation time is completely different depending on the plant. We believe from this fact that the corrosion of Zircaloy fuel cladding is indeed affected by water quality conditions. Furthermore, it was presumed that these differences in corrosion rate depended on the presence or absence of trace impurities in the plant water, and the causal relationship between the impurity concentration and the oxide film thickness of the Zircaloy fuel cladding was investigated in detail. As a result, copper is affecting the corrosion rate of Zircaloy,
It was found that the coexistence of a small amount of copper suppresses the corrosion of Zircaloy.

[0007] In a light water reactor, light water, which is both a coolant and a moderator, undergoes radiolysis and undergoes generation, synthesis, and decomposition of various short-lived radical species, and finally, hydrogen, oxygen, and peroxides. Generates hydrogen. Each equilibrium concentration differs depending on the furnace type, the target site, and the water quality of the water supply system. For example, in a zircaloy fuel cladding portion of a BWR of normal water quality (when the oxygen concentration of the water supply system is not controlled), hydrogen: oxygen: Hydrogen oxide = 50: 400: 200p
pb, at the recirculation piping site, hydrogen: oxygen: hydrogen peroxide =
Values such as 25: 200: 50 ppb have been reported by simulation calculations. That is, it is shown that oxygen and hydrogen peroxide generated by this reaction are promoting the corrosion (generation of an oxide film) of the Zircaloy fuel cladding tube described below. Zr + O ₂ → ZrO _{2 In} a nuclear power plant, copper exists as monovalent or divalent ions in reactor water. on the other hand,
When it adheres to the surface of the fuel cladding tube, it may exist in a nuclear reactor, for example, when it exists in a metal state having zero valence or when it exists as cuprous oxide (Cu ₂ O) or cupric oxide (CuO). Is a unique element with an ionic valence of Therefore, the present inventors have found that when a zircaloy fuel cladding tube and copper coexist in an aqueous environment in which an oxidizing agent such as oxygen or hydrogen peroxide that promotes oxidation as described above is present, copper becomes a zircaloy fuel cladding tube. We thought that it might function as a buffer against the corrosion phenomenon. In other words, when oxygen and hydrogen peroxide approach the vicinity of the surface of the zircaloy fuel cladding tube and coexist with copper in a situation where the zircaloy is oxidized, the oxidizing agent oxidizes copper preferentially over zircaloy, and the oxidizing agent becomes oxidized. It was presumed that the loss of power would result in suppression of corrosion (growth of oxide film) of the Zircaloy fuel cladding tube. Further, it is considered that the oxidized copper circulates in the system as ions, is reduced in other parts, and approaches the vicinity of the surface of the fuel cladding again to control the same reaction. It is presumed that copper reduction easily proceeds at a site where an oxidation reaction is occurring, and can occur in a situation where an oxide film is growing on, for example, a pipe surface.

To prove the above hypothesis, a corrosion test of zircaloy was carried out under conditions simulating the environment of a zircaloy fuel cladding tube in a nuclear power plant, with copper coexisting as monovalent ions. As a result, a reliable corrosion inhibition phenomenon was found in the zircaloy simulated fuel cladding tube under the condition that the copper ion concentration was adjusted to 10 ppb in water and immersed for 1000 hours. In other words, the thickness of the uniform oxide film formed on the simulated Zircaloy fuel cladding tube under the condition of no copper ions was about 1 micron, but under the coexistence of copper ions, it was reduced by about 20 microns to about 0.8 micron. It was. In addition, copper oxide was slightly attached to the simulated fuel cladding,
This included not only cuprous oxide (Cu ₂ O) but also cupric oxide (CuO). This phenomenon means that copper was oxidized, and as a result, it was interpreted that oxidation of zircaloy was suppressed.

[0009] From the above series of estimation and confirmation tests, it was found that corrosion of the Zircaloy fuel cladding is suppressed by the coexistence of copper. In addition, the corrosion mechanism is presumed to be due to the fact that copper takes a plurality of ionic valences to function as a buffer for the corrosion phenomenon of the Zircaloy fuel cladding tube, as estimated by the inventors. I was convinced that the corrosion of the fuel cladding tube could be suppressed.

As described above, it has been found that coexistence of copper is effective for suppressing corrosion of the Zircaloy fuel cladding tube. However, in a conventional nuclear power plant, for example, BWR,
Brass, which is an alloy of copper and zinc, is used as the material of the condenser, and as a result, the copper concentration in the reactor water has increased, and the above-described corrosion inhibiting effect has only occurred.

An object of the present invention is to provide a nuclear power plant capable of preventing corrosion of a Zircaloy fuel cladding tube by positively utilizing a metal element having a corrosion inhibiting function.

[0012]

As described above, it has been found that the coexistence of copper suppresses the corrosion of the Zircaloy fuel cladding tube. Since there are elements that can have an ionic valence, it is considered that such elements other than copper can also suppress corrosion of the Zircaloy fuel cladding tube by the same mechanism as copper.

[0013] Then, when the potential-pH diagram of each element in the use environment of the fuel cladding tube was investigated, in addition to copper (Cu), cerium (Ce), titanium (Ti), vanadium (V), chromium (Cr) ), Tungsten (W), manganese (Mn), iron (Fe), tin (Sn), and lead (Pb).

FIG. 1 is a calculation example of a potential-pH diagram of a copper-water system at 300 ° C. Here, the reason why the temperature is set to 300 ° C. is based on the assumption of the use environment of the fuel cladding tube in the BWR. The potential-pH diagram shows, by a thermodynamic method, which form of copper is stable when copper is present in a specific environment defined by pH and potential. FIG. 1 is calculated under the condition that the copper concentration is 10 ⁻⁶ (mol / l). In FIG. 1, the horizontal axis indicates the pH at 300 ° C., which is about 5.5 in a system containing no impurities under the temperature condition of BWR. The vertical axis indicates the potential of the material with respect to the hydrogen reference electrode. Although different for each material, in a normal BWR reactor water environment, for example, values of 0 V to 0.1 V for stainless steel have been reported. In addition, although there has been no report on Zircaloy in the past, the present inventors have experimentally confirmed that it shows almost the same value as that of stainless steel. That is, on the surface of stainless steel or zircaloy in water at 300 ° C., copper exists as ions (Cu ⁺ ) or oxides (Cu ₂ O) as monovalent, or ions (Cu ²⁺ ) or oxides as divalent. Cu
It can be seen that it is near the boundary of whether it exists as O) or hydroxide (Cu (OH) ₂ ). In other words, copper is in a situation where the ionic valence easily changes depending on the potential. As a result, it is considered that when zircaloy and copper coexist, oxygen and hydrogen peroxide, which are oxidizing agents, preferentially oxidize copper and suppress corrosion of zircaloy. In addition, other elements other than copper are in almost the same situation, and the same effect can be obtained by the same mechanism.

By the way, the higher the concentration of the metal element coexisting with the Zircaloy fuel cladding tube, the more effective it is not necessarily. This is because it is defined by the solubility of the substance in high temperature water. That is, if they exist in the reactor water at a concentration exceeding the solubility of the substance, they cause a precipitation reaction. In particular, since the enrichment phenomenon occurs with boiling on the fuel surface of BWR, this precipitation phenomenon is remarkable. Here, not all data on the solubility data of each substance in high-temperature water has been obtained, and even with the data already obtained, their reliability is unfortunately not complete. Therefore, the inventor examined thermodynamic data in high-temperature water, calculated a concentration range in which precipitation did not occur even in an environment in which enrichment occurred on the fuel surface, and obtained a value of 5 ppb in view of a safety factor. . That is, if the concentration is not more than this, the Zircaloy fuel cladding tube and the metal element can coexist without depositing on the fuel surface.

The above-mentioned metal element which becomes a corrosion inhibitor of the Zircaloy fuel cladding tube by coexisting in the use environment of the fuel cladding tube has an isotope ratio in advance so as not to generate secondary radioactivity by activation. It is desirable that they be adjusted. Here, the meaning of “adjusting the isotope ratio” will be described by taking chromium as an example. Chromium is present in a proportion of each 4.3,83.8,9.5,2.4 percent ^{50 Cr, 52 Cr, 53 Cr} , 54 Cr in nature. Supplying chromium remains abundance of naturally nuclear plant, from ⁵⁰ Cr by radiation reaction ⁵¹ C
Each radioisotope from r, ⁵⁴ Cr ⁵⁵ Cr is generated. These radioisotopes are harmful substances that generate large amounts of high-energy gamma rays. Therefore, before supplying to the nuclear power plant, secondary radioactivity is generated by preliminarily isotopic separation by centrifugation, etc., and excluding ⁵⁰ Cr and ⁵⁴ Cr to only ⁵² Cr and ⁵³ Cr. Can be prevented. Such a method is defined herein as “adjustment of the isotope ratio”.

In a nuclear power plant according to the present invention, there is provided a nuclear power plant having a zircaloy fuel cladding tube, wherein the zircaloy fuel cladding tube is provided with a metal element which suppresses corrosion of the zircaloy fuel cladding tube in a use environment of the zircaloy fuel cladding tube. It is characterized in that it is made to exist near the surface of the cladding tube.

The nuclear power plant according to the second aspect of the present invention is characterized in that the metal element can have a plurality of ionic valences in an environment in which the zircaloy fuel cladding tube is used.

According to a third aspect of the present invention, in the nuclear power plant, the metal elements are cerium (Ce), titanium (T
i), vanadium (V), chromium (Cr), tungsten (W), manganese (Mn), iron (Fe), copper (C
u), tin (Sn), and lead (Pb).

In the nuclear power plant according to the present invention, the isotope ratio of the metal element capable of taking a plurality of ion valences is adjusted to suppress the generation of secondary radioactivity due to the activation of the metal element. It is characterized by doing.

A nuclear power plant according to a fifth aspect of the present invention is characterized in that the metal element is previously applied to the surface of the Zircaloy fuel cladding tube before using the Zircaloy fuel cladding tube.

In the nuclear power plant according to the present invention, the metal element may be formed by laser cladding, plating,
The Zircaloy fuel cladding is applied to the surface of the Zircaloy fuel cladding tube using one or more of dry plating, thermal spraying, ion implantation, and lining.

According to a seventh aspect of the present invention, in the nuclear power plant, when the metal element is injected into the surface of the Zircaloy fuel cladding tube by the ion injection technique, the injection amount is one.
× 10 ¹⁷ / cm ² or less.

The nuclear power plant according to the present invention is characterized in that a thin film of the metal element having a thickness of 100 μm or less is formed on the surface of the Zircaloy fuel cladding tube by the lining technique.

A nuclear power plant according to a ninth aspect of the present invention is characterized in that the nuclear power plant has a metal element generator for generating the metal element in a system of the nuclear power plant. The nuclear power plant according to the invention of claim 10, wherein the metal element generator includes a metal, an oxide,
A hydride or hydroxide, or a compound containing one or both of hydrogen and oxygen, such as a metal salt, is installed in the high-temperature system of the nuclear power plant and is allowed to pass high-temperature water to cause a corrosion release reaction. Thereby releasing the metal element into the high-temperature water.

In the nuclear power plant according to the present invention, the metal element generating device includes a column having a metal mesh screen, and the metal element is held inside the column by the metal mesh screen. It is characterized by. A nuclear power plant according to a twelfth aspect of the invention is characterized in that the metal element is finely divided and the particle size is adjusted so that the particle size is distributed between 0.1 mm and 1 mm.

A nuclear power plant according to a thirteenth aspect of the present invention is characterized in that the metal element whose particle size has been adjusted is fired at a temperature equal to or more than half the melting temperature to be in a sintered state.

According to a fourteenth aspect of the present invention, in the nuclear power plant, a bypass line is provided in parallel with the metal element generator, a flow control valve is provided in the middle of the bypass line, and the degree of opening and closing of the flow control valve is controlled. A concentration controller for controlling the flow rate of the high-temperature water flowing in the metal element generator and thereby controlling the amount of the metal element generated.

In the nuclear power plant according to the fifteenth aspect, a high-pressure pump is provided in series with the metal element generator, and the flow rate of the high-pressure pump is adjusted to control the flow rate of high-temperature water flowing in the metal element generator. And a concentration control device for controlling the amount of generation of the metal element.

The nuclear power plant according to the present invention is characterized in that the nuclear power plant is a boiling water reactor having a recirculation line, and the metal element generating device is a reactor of a system in the boiling water reactor. Water or reactor water is provided in a system in which high-temperature water that is substantially isothermal is flowing, the concentration control device measures the concentration of the metal element in the reactor water flowing through the recirculation line, and according to the measured value, Adjusting the opening / closing degree of the flow rate control valve or the flow rate of the high-pressure pump to control the concentration of the metal element in the reactor water.

In the nuclear power plant according to the seventeenth aspect of the present invention, the reactor water or the system through which high-temperature water having substantially the same temperature as the reactor water flows may be any one of a recirculation line, a water supply line, and a reactor water purification line. There is a feature.

The nuclear power plant according to the present invention is characterized in that the concentration controller measures the concentration of the metal element by ion chromatography.

The nuclear power plant according to the invention of claim 19 is characterized in that two said metal element generating devices are provided in parallel.

A nuclear power plant according to a twentieth aspect of the present invention is characterized in that the nuclear power plant has a metal element injection device for injecting the metal element into the system from outside the system of the nuclear power plant.

According to a twenty-first aspect of the present invention, in the nuclear power plant, the metal element injecting device may include one or both of hydrogen and oxygen, such as an oxide, a hydride or a hydroxide, or a metal salt. The raw material in any state of the contained compound is transformed into a solution state or a slurry state and then injected into the nuclear power plant system.

A nuclear power plant according to a twenty-second aspect of the present invention is characterized in that the raw material is in the form of fine powder of 1 micron or less.

According to a twenty-third aspect of the present invention, in the nuclear power plant, the metal element injection device includes a tank storing a liquid containing the raw material in the form of a fine powder, and the liquid in the tank is forcibly stirred. And an impeller for preventing sedimentation of the raw material.

In the nuclear power plant according to the present invention, the metal element injection device has a plurality of electrodes constituted by a metal plate made of the metal element or a metal plate partially containing the metal element. And applying a DC voltage to the electrode to ionize the metal element.

The nuclear power plant according to the twenty-fifth aspect of the present invention is characterized in that the polarity of the DC voltage applied to the electrodes is switched at predetermined time intervals so that the thinning of the plurality of electrodes is made uniform.

The nuclear power plant according to the twenty-sixth aspect is characterized in that carbon dioxide gas is dissolved in the electrolyte in the electrolytic cell in advance, and the electrode reaction is promoted by using the electrolyte as an electrolyte.

In the nuclear power plant according to the twenty-seventh aspect, a degassing gas is injected into the electrolytic solution after the electrode reaction to degas carbon dioxide gas dissolved in the electrolytic solution. I do.

In the nuclear power plant according to the twenty-eighth aspect, a flow rate control valve is provided in series with the metal element injection apparatus, and the opening degree of the flow rate control valve is adjusted to control the injection amount of the metal element. A concentration control device is provided.

In the nuclear power plant according to the invention, an injection pump is provided in series with the metal element injection device, and a concentration control device for controlling the injection amount of the metal element by adjusting the flow rate of the injection pump. Is provided.

In the nuclear power plant according to the present invention, the nuclear power plant is a boiling water reactor having a recirculation line, and the concentration control device is configured to control the concentration of the metal element in the reactor water flowing through the recirculation line. The concentration of the metal element in the furnace water is controlled by measuring the concentration and adjusting the opening / closing degree of the flow control valve or the flow rate of the high-pressure pump according to the measured value.

In the nuclear power plant according to the present invention, the metal element injection device may be any one of a high-temperature system such as a recirculation line, a water supply line, a reactor water purification line, or a low-temperature system such as a condensate purification line. A feature is that the metal element is injected into a system.

A nuclear power plant according to the invention of claim 32 is characterized in that the concentration of the metal element in the reactor water is limited to 5 ppb or less.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, a first embodiment of a nuclear power plant according to the present invention will be described with reference to the drawings. In the present embodiment,
The metal element serving as the above-described corrosion inhibitor is preliminarily applied to the surface of the Zircaloy fuel cladding tube using a technique such as laser cladding, plating, dry plating, thermal spraying, ion implantation, and lining.
Hereinafter, a method for providing the metal element to the surface of the Zircaloy fuel cladding tube will be described.

First, a construction method using laser cladding will be described. Laser cladding is a method of forming a clad alloy layer by dissolving a metal powder of the metal element in a binder, applying the paste to a target site, and then irradiating a laser beam. In order to enhance the corrosion prevention effect, it is most effective to form a thin alloy layer on the entire surface of the fuel cladding tube.However, even when the metal element is applied to a part of the surface of the fuel cladding tube, the corrosion prevention effect is obtained. Since it can be obtained, the alloy layer may be processed in a spot-like manner, or may be processed into one or several lines in the axial direction of the fuel cladding tube. In addition, YAG (Y
ttrium Aluminuim Garnet) lasers are currently the best. FIG. 2 conceptually shows a construction method using laser cladding. This method has a feature that it has little influence on a base material because it is a point source.

Next, an application method by plating will be described. Plating is a method of electrochemically depositing the metal element on a target portion, and the metal element can be applied to the entire surface of the fuel cladding tube. The metal element fills the plating tank as a sulfate, ammonium salt, cyanide, ethylenediamine compound, EDTA compound, etc.
The target member is immersed for construction. FIG. 3 shows an example of a plating tank, and a plating tank 1 includes an anode 2 made of the metal.
And the cathode 3 are inserted, and a predetermined voltage is applied between the anode 2 and the cathode 3. Further, a diaphragm 4 is interposed between the anode 2 and the cathode 3. Further, an air pipe 5 is provided below the plating tank 1 to make the plating layer uniform. Then, the construction target member is immersed inside the diaphragm 4 and processed.

Next, a construction method by dry plating will be described. Dry plating is a method in which the metal film is formed on a target portion by a dry method, and the metal element can be applied to the entire surface of the fuel cladding tube. The dry plating method is further classified into a vapor deposition method in which a metal is vaporized and condensed on a solid surface, an ion plating method in which a gas discharge is caused in an atmosphere gas, ionized vapor particles are activated by ionization, and a film is formed. There is a sputtering method in which a metal element is used as a target in a metal state, a high voltage is applied between the electrodes to cause a discharge, and a thin film is formed on a target portion. FIG. 4 is a conceptual diagram of a sputtering apparatus, and the sputtering apparatus 10 includes a target 11 formed of the metal. A holder 12 is arranged so as to face the target 11, and a target member 13 is placed on the holder 12. The target 11 and the holder 12 are insulated from the vacuum vessel 15 by an insulator 14, and a shield 16 is provided around the target 11 and the holder 12 to increase the sputtering efficiency. Then, a high voltage is applied to the target 11 by the DC power supply 17, and the metal constituting the target 11 is turned into plasma and adheres to the target member 13 to form a thin film.

Next, an application method by thermal spraying will be described. Thermal spraying is a method in which the metal is heated, melted or brought into a state close to it, and sprayed onto a substrate to form a film.
For thermal spraying on the fuel cladding tube, plasma spraying, which can obtain the highest temperature, is optimal. This plasma spraying has features such as a high density of the film to be formed and good adhesion. FIG. 5 is a conceptual diagram showing the principle of plasma spraying. A spraying apparatus 20 includes a plasma torch 21 as an anode, and a cathode 22 is provided in the plasma torch 21. Then, the metal M in powder form is supplied via the metal supply path 23, and the plasma gas P is jetted by the working gas G. The sprayed material adheres to the surface of the target member 24 to form a film. Further, the thermal spraying apparatus 20 uses the target member 24 as an anode in order to enhance the directivity of the plasma.

Next, a construction method by ion implantation will be described. The ion implantation utilizes a physical phenomenon in which the metal element is ionized, accelerated by an electric field, and colliding with and hitting the surface of the target member. This ion implantation technology has been reported to be applied to tool steel, for example, by using the suppression of material wear by nickel ion implantation, and to improve corrosion resistance by barium ion implantation into titanium alloys. Applied in various fields. In the ion implantation method, the number of implanted ions per unit area (pieces / cm
² ) is often used. As a guide, 1 × 10 ¹⁷ pieces / c
It is believed that the injection amount of m ² corresponds to a surface composition of about 10 atomic%. In applying the metal element to the fuel cladding tube, it is considered sufficient if a film containing the metal element of about 10% is formed on the surface. Therefore, when this method is used, 1 × 10 ¹⁷ / cm ² is the upper limit of the injection amount. At the time of ion implantation, a large number of point defects and secondary defects are introduced into the target member due to direct elastic collision of the implanted ions with atoms of the target member and cascade collision occurring after the direct elastic collision, resulting in so-called irradiation damage. Can be caused. Therefore, when applying this method, it is preferable to perform an annealing operation by heat treatment on the target member after ion implantation.

Next, the lining is a method in which the metal element is brought into a metal state, and a thin film produced by rolling is coated on the outside of the fuel cladding tube. It is considered that a thickness of the thin film of about 100 microns is sufficient.

As described above, according to the present embodiment, before the use of the zircaloy fuel cladding tube, the metal element functioning as a corrosion inhibitor is applied to the surface of the zircaloy fuel cladding tube in advance. Corrosion of the Zircaloy fuel cladding tube during use can be prevented.

Second Embodiment Next, a second embodiment of the nuclear power plant according to the present invention will be described with reference to the drawings. In the nuclear power plant according to the present embodiment, the metal element is in a state of a metal, an oxide, a hydride or a hydroxide, or a compound containing one or both of hydrogen and oxygen such as a metal salt,
Installed in the high-temperature system of a nuclear power plant to allow high-temperature water to flow,
It is characterized in that a predetermined concentration is obtained by a corrosion release reaction.

FIG. 6 shows a metal element generator 30 for generating a metal element that functions as a corrosion inhibitor in a use environment of a Zircaloy fuel cladding tube. The metal element generator 30 includes a column 31, and a metal mesh screen 32 is provided inside the column 31. Between the metal mesh screens 32, the metal element portions 33 filled with the metal in the form of particles are provided.
Is provided. The metal particles are from 0.1 mm to 1
The particle size is adjusted so as to have a particle size distribution of mm, the specific surface area is increased, and the packing density in the column 31 is improved. One end of the column 31 is connected to an inlet pipe 34 for introducing high-temperature water in the system of the nuclear power plant into the column 31.
In the middle of 4, a valve 35 is provided. An outlet pipe 36 for discharging the high-temperature water supplied into the column 31 is connected to the other end of the column 31. A flow rate adjusting function having a flow rate adjusting function is provided in the middle of the outlet pipe 36. A valve 37 is provided. In addition, the inlet pipe 34
A bypass pipe 38 is provided between the outlet pipe 36 and the outlet pipe 36 so as to bypass the column 31, and a flow control valve 39 having a flow control function is provided in the middle of the bypass pipe 38.

Then, in the metal element generator 30, high-temperature water in the system of the nuclear power plant is introduced into the column 31 via the inlet pipe 34, and passes through the metal element portion 33 made of the metal in the form of particles. I do. Then, the metal ions are dissolved in the high-temperature water, and the high-temperature water containing the metal ions is returned to the system of the nuclear power plant via the outlet pipe 36. Further, the concentration of the metal ion in the nuclear power plant is monitored by a concentration control device (not shown), and the opening and closing degree of the valves 37 and 39 is constantly adjusted to adjust the concentration. That is, when the concentration of the metal ion is lower than the predetermined value, the valve 39 of the bypass pipe 38 is throttled to increase the flow rate of the high-temperature water flowing in the column 31. On the other hand, when the concentration of the metal ion is higher than the predetermined value, the valve 37 of the outlet pipe 36 is throttled to decrease the flow rate in the column 31 and reduce the amount of the metal ion generated.

Further, in the metal element generating device 30, the metal is made into particles and the particle size is adjusted so as to have a particle size distribution of 0.1 to 1 mm. When it is fired and sintered, the sintered state is maintained even when high temperature water is passed, so that the sintered fine particles do not accidentally flow directly into the high temperature system of the nuclear power plant. Holding becomes easy.

FIG. 7 shows an example in which the metal element generator 30 is applied to a BWR. In FIG. 7, reference numeral 41 denotes a reactor pressure vessel, in which a reactor core 42 is provided. The steam generated by the heat from the core 42 is sent to a steam turbine 44 via a steam line 43 to perform work. The steam that has worked in the steam turbine 44 is condensed in the condenser 45 and returns to water. This water is condensed by a condensate pump 46 into a condensate purification device 47.
After the impurities are removed, the feed water is preheated by the feed water heater 48 and returned to the reactor pressure vessel 41. The reactor water is forcibly circulated in the reactor pressure vessel 41 by a recirculation line 50 having a recirculation pump 49 and a jet pump 51. A part of the reactor water flowing through the recirculation line 50 is cooled down by a regenerative heat exchanger 54 and a non-regenerative heat exchanger 55 through a reactor water purification line 53 having a reactor water purification system pump 52. The water is purified by the water purification device 56. The purified reactor water is returned to the reactor pressure vessel 41 via the water supply line 57.

In some BWRs, a reactor water purification system pump 52 is disposed downstream of the regenerative heat exchanger 54 or the non-regenerative heat exchanger 55. Further, a plant having no reactor water recirculation system and having a plurality of pumps called internal pumps in the reactor pressure vessel 41 and forcing reactor water to be stirred by these internal pumps (referred to as ABWR) Has been constructed, and the number of ABWR-type plants is increasing in the future.

A metal element generator 30 is attached to the outlet side of the recirculation pump 49, and an isolation valve 3 is provided upstream and downstream of the metal element generator 30.
5 and 37 are provided respectively. A flow control valve 39 having a flow control function is provided in the middle of a bypass line 38 that bypasses the metal element generating device 30, and the flow control valve 39 can be adjusted by a concentration control device 61 to adjust the degree of opening and closing. Has become. The concentration control device 61 measures the metal ion concentration on the downstream side of the recirculation pump 49 and adjusts the degree of opening and closing of the flow control valve 39 according to the measured value. here,
As the metal ion concentration measuring method (analyzing method) in the concentration control device 61, ion chromatography capable of continuously measuring the ion species concentration is the most suitable at present. The isolation valves 35 and 37 are used to isolate the metal element generator 30 during maintenance. As described above, according to the present embodiment, the metal ions generated in the metal element generator 30 are supplied into the reactor pressure vessel 41 together with the recirculated water, whereby the corrosion of the zircaloy fuel cladding tube is suppressed. .

First Modification FIG. 8 shows a first modification of the above embodiment. In this modification, the metal element generator 30 is provided on the upstream side of the recirculation pump 49, and the valves 35 and 37 are provided. Is connected to the recirculation line 50 by opening the Further, a high-pressure pump 71 is provided between the metal element generator 30 and the valve 35, and the high-pressure pump 71 compensates for pressure loss generated in the metal element generator 30. Further, the concentration control device 72 measures the metal ion concentration on the upstream side of the recirculation pump 49, and according to the measured value, the high-pressure pump 7
2 is adjusted. If the concentration of the metal ions is controlled by adjusting the flow rate of the high-pressure pump 72 by the concentration control device 72 as described above, the flow rate control valve 39 shown in FIG. 7 becomes unnecessary.

[0063] The second modification Figure 9 shows a second modification of the embodiment, provided a metal element generator 30 of 2 groups as shown in parallel in FIG 9, the respective metal elements generator 30 Isolation valves 73 and 74 may be provided on the upstream and downstream sides. With this configuration, even when the nuclear power plant is in operation, one metal element generator 30 supplies the metal element while the other metal element generator 30 supplies the metal element.
Can be isolated by the valves 73 and 74 to perform maintenance.

In the above embodiment, the metal element generator 3
0 is installed in the recirculation line 50, but the installation position of the metal element generator 30 is not limited to the recirculation line 50. For example, the water supply line 57, the outlet of the reactor water purification line 53, etc. Thus, it can be installed at a site where high-temperature water of the same level as the reactor water temperature flows.

Third Embodiment Next, a third embodiment of the nuclear power plant according to the present invention will be described with reference to the drawings. FIG. 10 shows a metal element implantation apparatus 80 according to the present embodiment. The metal element implantation apparatus 80 sets the metal element functioning as a corrosion inhibitor in a metal state, and converts the metal element in the metal state into a metal ion by an electrode reaction. Is generated, and the metal ions are injected into the system of the nuclear power plant using an injection pump.

In FIG. 10, reference numeral 81 denotes a carbon dioxide gas saturation tank. The carbon dioxide gas saturation tank 81 has a function of converting an electrolytic solution into an electrolyte so that metal ions can be easily generated by an electrode reaction. ing. By using the electrolyte as the electrolyte in this way, the electrolytic reaction can be caused at a low voltage, so that the DC power supply equipment for causing the electrode reaction can be downsized. A pure water supply line 82 is connected to the carbon dioxide gas saturation tank 81, and a flow control valve 83 for adjusting the pure water flow rate is provided in the middle of the pure water supply line 82. Further, inside the carbon dioxide gas saturating tank 81, a carbon dioxide gas discharge part 85 provided at the tip of the bubbling line 84 is arranged, and a carbon dioxide gas cylinder 86 is connected to the bubbling line 85. Also,
A seal pot 88 is connected to the carbon dioxide gas saturation tank 81 via a pipe 87 in order to release the excessively supplied carbon dioxide gas from the carbon dioxide gas saturation tank 81.

The carbon dioxide gas saturating tank 81 is connected to the electrolytic cell 90 via a connecting pipe 89. An electrolytic solution is put in the electrolytic cell 90, and a pair of plate-shaped electrodes 91 are immersed in the electrolytic solution. A DC power supply 93 is connected to these electrodes 91 via a lead wire 92. It is connected. These electrodes 91 are formed of a metal material containing the metal element functioning as a corrosion inhibitor, and may be formed of the metal element alone. Note that FIG.
Although two electrodes 91 are shown, the number of electrodes is increased to increase the amount of generated metal ions, or by attaching electrodes made of different metal species, different ion species are blended. It can also be generated. If the polarity of the DC power supply 93 is switched at regular intervals, the thickness of the plurality of electrodes can be equalized, and the metal material can be effectively used.

Further, the electrolytic cell 90 is connected to a carbon dioxide gas removing tank 95 via a connecting pipe 94. Inside the carbon dioxide gas removal tank 95, a degassing gas discharging portion 97 provided at a tip end of a bubbling line 96 is arranged, and a degassing gas cylinder 98 is provided in the bubbling line 96.
Is connected. The degassing gas discharge section 96 has a bubbler structure having a large number of fine outlets, and the bubbler structure allows the degassing gas to be injected efficiently. In the carbon dioxide gas removal tank 95, the collected carbon dioxide gas and excess degassed gas are stored in the carbon dioxide gas removal tank 95.
To release from the seal pot 1 via a pipe 99
00 is connected. Further, the carbon dioxide removal tank 9
5 is connected to a transport pipe 101 for sending the generated metal ion solution to a target site in the nuclear power plant.
Is provided.

Next, the operation of the metal element injection device 80 will be described. First, pure water adjusted to a constant flow rate by the flow rate adjusting valve 83 is continuously supplied to the carbon dioxide gas saturation tank 81 via the pure water supply line 82. The carbon dioxide gas from the carbon dioxide gas cylinder 86 is supplied to the bubbling line 84.
The carbon dioxide gas is supplied to the carbon dioxide gas releasing section 85 via the carbon dioxide gas releasing section 85, and the bubble-like carbon dioxide gas is released from the carbon dioxide gas releasing section 85 into the carbon dioxide gas saturation tank 81. The bubbled carbon dioxide gas released into the carbon dioxide gas saturation tank 81 is dissolved in pure water, and causes the following dissociation reaction to become an electrolyte, thereby promoting an electrode reaction in the electrolytic tank 90. _{CO 2 + H 2 O → H} 2 CO 3 H 2 CO 3 → H + + HCO 3 - HCO 3 - → H + + CO 3 2- Incidentally, excessively supplied carbon dioxide gas from the seal pot 88 via a pipe 87 Released outside the system.

Next, the solution in which the carbon dioxide gas is dissolved and the carbonate ions are in a dissociated state is sent to the electrolytic cell 90 via the connecting pipe 89. Since voltages having different polarities are applied to the pair of electrodes 91 in the electrolytic cell 90 by the DC power supply 93, an electrode reaction occurs in the electrodes 91, and the electrodes 9.
The metal constituting 1 dissolves in the solution as ions.

The electrolytic solution in which the metal ions are dissolved in the electrolytic cell 90 is sent to the carbon dioxide gas removing tank 95 via the connecting pipe 94. Inside the carbon dioxide gas removal tank 95, the degassing gas tank 9 is passed through a bubbling line 96.
The degassed gas supplied from 8 is discharged from the degassed gas discharge unit 97 in a bubble state. The released bubble-like degassed gas allows the carbonate ions dissolved in the solution to be recovered in a gaseous state by a reverse reaction of the dissociation reaction. The collected carbon dioxide gas is released from the seal pot 100 to the outside of the system via the pipe 99 together with the excessively supplied degassed gas.

The solution containing the metal ions generated by the metal element injection device 80 is pressurized by the injection pump 102 and sent to a target site in the nuclear power plant via the transport pipe 101.

As described above, according to the metal element implantation apparatus 80, the metal ion species is injected into the system of the nuclear power plant while producing the metal ion species. Therefore, the concentration in the tank is low, and the carbon ion in the electrolyte is reduced. Since the ions are removed by degassing, introduction of unnecessary ion species is suppressed, and only target metal ions can be implanted.

In addition, by degassing the carbon dioxide gas, a part of the dissolved metal ions is precipitated in the solution as hydroxide of fine particles, but when the fine particles are introduced into the high-temperature water, they become ionic again. . This is because the solubility of these metals is sufficiently high compared to the desired concentration (for example, 5 ppb), and as a result, the intended purpose can be obtained without introducing unnecessary ion species into the reactor. Can be achieved.

A metal plate made of the metal element alone;
Alternatively, since the electrode 91 is formed using a plurality of metal plates containing the metal element, the concentration of the metal ion species can be controlled to an arbitrary value by adjusting the current value of the electrode 91. In addition, fine adjustment can be performed accurately and unnecessary inflow of metal ion species can be prevented. Further, it is possible to change the ion species to be implanted by changing the composition of the metal forming the electrode 91, and if the electrode 91 is constituted by a plurality of metal plates having different metal compositions, the ion species to be implanted can be changed. Can be blended. Further, by increasing or decreasing the number of metal plates constituting the electrode 91, the amount of generated ionic species can be adjusted according to the scale of the target nuclear power plant.

FIG. 11 shows a case where the metal element implantation apparatus 80 shown in FIG. 10 is applied to a BWR. The outlet end of the transport pipe 101 is connected to the reactor water purification line 53, and a flow control valve 103 is provided in the transport pipe 101 downstream of the injection pump 102. The recirculation line 50 is provided with a concentration control device 104. The concentration control device 104 measures the metal ion concentration on the upstream side of the recirculation pump 49, and controls the opening / closing degree of the flow control valve 103 and the amount of metal ions generated by the metal element injection device 80 according to the measured value. Thereby, the metal ion concentration in the reactor water is controlled to a predetermined value. Here, as the metal ion concentration measurement method (analysis method) in the concentration control device 104, in-line ion chromatography that can continuously measure the ion species concentration is the most suitable at the present time. According to this method, the metal ion concentration in the reactor water can be measured at regular intervals.

In the above embodiment, the metal element injection device 8 is used.
0 is connected to the reactor water purification line 53, but the connection position of the metal element injection device 80 is not limited to the reactor water purification line 53. For example, the recirculation line 50, the water supply line 57, etc. It can also be connected to a low-temperature system in which low-temperature water flows, such as a site where high-temperature water at the same temperature as the reactor water flows, or an outlet of a condensate purification device (not shown).

Fourth Embodiment Next, a fourth embodiment of the nuclear power plant according to the present invention will be described with reference to the drawings. FIG. 12 shows a metal element implanting device 110 according to the present embodiment. The metal element implanting device 110 converts an object metal element into an oxide, hydride, or hydroxide in order to generate a target metal element. Or one of hydrogen and oxygen, such as metalates,
Alternatively, it is characterized in that it is in a compound state containing both, and is injected in a slurry state or a solution state to obtain a predetermined concentration.

The metal element injection device 110 has a tank 111, to which pure water is continuously supplied via a pure water supply line 112. Above the tank 111, a fine powder tank 113 is provided. In the fine powder tank 113, the metal element functioning as a corrosion inhibitor contains an oxide, hydride or hydroxide, or a metal salt. As described above, a compound containing one or both of hydrogen and oxygen is filled in a fine powder form. Then, the fine powder in the fine powder tank 113 is supplied to the tank 11 continuously or intermittently. The particle size of the fine powder is desirably on the order of submicron of 1 micron or less from the viewpoint of preventing sedimentation. In addition, an impeller 114 is provided in the tank 111.
, The sedimentation of the fine powder can be reliably prevented. The tank 111 is connected to a transport pipe 115 for sending the generated slurry turbid solution or solution to a target site in the nuclear power plant. Is provided. Then, the slurry supplied to the target site in the nuclear power plant via the transport pipe 115 is rapidly ionized by contact with high-temperature water in the plant system.

FIG. 13 shows a case where the metal element implantation apparatus 110 shown in FIG. 12 is applied to a BWR. The outlet end of the transport pipe 115 is connected to the water supply line 57,
The recirculation line 50 is provided with a concentration control device 117. The concentration control device 117 includes a recirculation pump 4
The metal ion concentration on the upstream side of 9 is measured, and the flow rate of the high-pressure pump 116 is controlled according to the measured value, thereby controlling the metal ion concentration in the reactor water to a predetermined value.

In the present embodiment, the slurry turbid liquid containing the metal element generated by the metal element injection device 110 is supplied via the transport pipe 115 to the water supply line 5.
7, and the supplied slurry is brought into contact with the high-temperature water flowing through the water supply line 57 to be metal-ionized. The generated metal ions are supplied into the reactor pressure vessel 41 to suppress corrosion of the Zircaloy fuel cladding tube.

In the above embodiment, the metal element injection device 110 is connected to the water supply line 57. However, the connection position of the metal element injection device 110 is not limited to the water supply line 57. 50, such as at the outlet of the reactor water purification line 53, where it can be installed at a location where high-temperature water at the same temperature as the reactor water temperature flows. Also,
Even in a low-temperature system in which low-temperature water flows, the metal element injection device 110 can be connected to a portion where the flow rate in the system is sufficiently large and sedimentation of the fine powder can be ignored.

In the first to fourth embodiments, a BWR of a type in which reactor water is forcibly circulated by a jet pump has been described as an example. However, application of the present invention is not limited to this type of BWR. Various types of nuclear power plants, including natural circulation BWRs without jet pumps, ABWRs with external recirculation lines, forced water circulation by internal pumps, and all light water reactors and heavy water reactors including PWRs Can be applied to

[0084]

As described above, according to the present invention, a metal element which suppresses corrosion of a Zircaloy fuel cladding tube in the use environment of the Zircaloy fuel cladding tube is present near the surface of the Zircaloy fuel cladding tube. Therefore, corrosion of the Zircaloy fuel cladding tube can be prevented for a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a calculation example of a potential-pH diagram of a copper-water system at 300 ° C.

FIG. 2 is a conceptual diagram showing a construction concept of a laser cladding method.

FIG. 3 is a conceptual diagram showing an example of a plating tank.

FIG. 4 is a conceptual diagram illustrating an example of a sputtering apparatus.

FIG. 5 is a conceptual diagram showing the principle of plasma spraying.

FIG. 6 is a longitudinal sectional view schematically showing a metal element generator according to a second embodiment of the present invention.

FIG. 7 is a system diagram showing a nuclear power plant according to a second embodiment of the present invention.

FIG. 8 is a system diagram showing a first modification of the second embodiment of the present invention.

FIG. 9 is a system diagram showing a second modification of the second embodiment of the present invention.

FIG. 10 is a longitudinal sectional view schematically showing a metal element implantation apparatus according to a third embodiment of the present invention.

FIG. 11 is a system diagram showing a nuclear power plant according to a third embodiment of the present invention.

FIG. 12 is a longitudinal sectional view schematically showing a metal element implantation apparatus according to a fourth embodiment of the present invention.

FIG. 13 is a system diagram showing a nuclear power plant according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating tank 10 Sputtering apparatus 20 Thermal spraying apparatus 30 Metal element generator 31 Column 32 Metal mesh screen 33 Metal element part 37, 39, 83, 103 Flow control valve 38 Bypass pipe 50 Recirculation line 53 Reactor water purification line 57 Water supply line 71 , 116 High-pressure pump 72, 104, 117 Concentration control device 80, 110 Metal element injection device 81 Carbon dioxide gas saturation tank 84, 96 Bubbling line 85 Carbon dioxide gas discharge part 86 Carbon dioxide gas cylinder 90 Electrolyzer 91 Electrode 93 DC power supply 95 Carbon dioxide gas tank 97 Desorption Gas gas discharge section 98 Degassing gas cylinder 102 Injection pump 111 Tank 113 Fine powder tank 114 Impeller

Claims (32)

[Claims] In a nuclear power plant having a Zircaloy fuel cladding, a metal element which inhibits corrosion of the Zircaloy fuel cladding in a use environment of the Zircaloy fuel cladding may be present near the surface of the Zircaloy fuel cladding. A nuclear power plant characterized in that: 2. The nuclear power plant according to claim 1, wherein said metal element can have a plurality of ionic valences in an environment in which said zircaloy fuel cladding tube is used. 3. The metal element includes cerium (Ce), titanium (Ti), vanadium (V), chromium (Cr), tungsten (W), manganese (Mn), iron (Fe), and copper (C).
The nuclear power plant according to claim 1, wherein the nuclear power plant is at least one element selected from the group consisting of u), tin (Sn), and lead (Pb). 4. The method according to claim 1, wherein an isotope ratio of said metal element capable of taking a plurality of ionic valences is adjusted to suppress generation of secondary radioactivity due to activation of said metal element. A nuclear power plant according to claim 2 or claim 3. 5. The zircaloy fuel cladding tube according to claim 1, wherein the metal element is applied to a surface of the zircaloy fuel cladding tube before using the zircaloy fuel cladding tube. Nuclear plant. 6. The method according to claim 1, wherein the metal element is laser cladding,
6. The nuclear power plant according to claim 5, wherein the nuclear power plant is applied to the surface of the Zircaloy fuel cladding using one or more of plating, dry plating, thermal spraying, ion implantation, and lining. 7. The method according to claim 6, wherein when the metal element is implanted into the surface of the zircaloy fuel cladding tube by the ion implantation technique, the implantation amount is set to 1 × 10 ¹⁷ / cm ² or less. Nuclear plant. 8. The nuclear power plant according to claim 6, wherein a thin film of the metal element having a thickness of 100 μm or less is formed on the surface of the Zircaloy fuel cladding tube by the lining technique. 9. The nuclear power plant according to claim 1, further comprising a metal element generator for generating the metal element in a system of the nuclear power plant. 10. The apparatus for generating a metal element according to claim 1, wherein the metal element is in a state of one of a metal, an oxide, a hydride or a hydroxide, and a compound containing one or both of hydrogen and oxygen such as a metal salt. 10. The nuclear power plant according to claim 9, wherein the metal element is installed in a high-temperature system of the nuclear power plant, water is passed through the high-temperature water, and the metal element is released into the high-temperature water by a corrosion release reaction. 11. The apparatus according to claim 10, wherein said metal element generator includes a column having a metal mesh screen, and wherein said metal element is held inside said column by said metal mesh screen. Nuclear plant. 12. The nuclear power plant according to claim 10, wherein the metal element is finely divided and the particle size is adjusted so that the particle size is distributed between 0.1 mm and 1 mm. 13. The nuclear power plant according to claim 12, wherein the metal element whose particle size has been adjusted is fired at a temperature equal to or higher than half the melting temperature to be in a sintered state. 14. A bypass line is provided in parallel with the metal element generator, a flow control valve is provided in the middle of the bypass line, and the degree of opening and closing of the flow control valve is adjusted so that the inside of the metal element generator is controlled. The nuclear power plant according to any one of claims 9 to 13, further comprising a concentration control device that adjusts a flow rate of the flowing high-temperature water and thereby controls an amount of the metal element generated. 15. A high-pressure pump is provided in series with the metal element generator, and the flow rate of the high-pressure pump is adjusted to adjust the flow rate of high-temperature water flowing in the metal element generator. The nuclear power plant according to any one of claims 9 to 13, further comprising a concentration control device for controlling an amount of generation of the gas. 16. The nuclear power plant is a boiling water reactor having a recirculation line, and the metal element generator includes:
Among the systems in the boiling water reactor, the system is provided in a system in which high-temperature water that is substantially equal to reactor water or reactor water flows,
The concentration control device measures the concentration of the metal element in the reactor water flowing through the recirculation line, and adjusts the opening / closing degree of the flow rate control valve or the flow rate of the high-pressure pump in accordance with the measured value, thereby controlling the flow rate of the reactor water. The nuclear power plant according to claim 14, wherein the concentration of the metal element is controlled. 17. The system through which the reactor water or high-temperature water having a temperature substantially equal to that of the reactor water flows is any one of a recirculation line, a water supply line, and a reactor water purification line. Nuclear power plant as described. 18. A nuclear power plant according to claim 16, wherein said concentration control device measures the concentration of said metal element by ion chromatography. 19. The nuclear power plant according to claim 9, wherein two metal element generators are provided in parallel. 20. The nuclear power plant according to claim 1, further comprising a metal element injection device for injecting the metal element into the system from outside the nuclear power plant. 21. The metal element injection device, wherein the metal element is a raw material in a state of one of an oxide, a hydride or a hydroxide, and a compound containing one or both of hydrogen and oxygen such as a metal salt. 21. The nuclear power plant according to claim 20, wherein after being transformed into a solution state or a slurry state, it is injected into a system of the nuclear power plant. 22. The nuclear power plant according to claim 21, wherein said raw material is in the form of fine powder of 1 micron or less. 23. The metal element injection device includes a tank storing a liquid containing the raw material in the form of fine powder, and an impeller for forcibly stirring the liquid in the tank to prevent sedimentation of the raw material. 23. The nuclear power plant according to claim 22, comprising a nuclear power plant. 24. The apparatus for injecting a metal element, comprising: an electrolytic bath having a plurality of electrodes constituted by a metal plate made of the metal element or a metal plate partially including the metal element. 21. The nuclear power plant according to claim 20, wherein a voltage is applied to ionize said metal element. 25. The nuclear power plant according to claim 24, wherein the polarity of the DC voltage applied to said electrodes is switched at predetermined time intervals so as to equalize the thickness reduction of said plurality of electrodes. 26. The electrode reaction according to claim 24, wherein carbon dioxide gas is dissolved in the electrolytic solution in the electrolytic cell in advance to promote the electrode reaction using the electrolytic solution as an electrolyte.
6. The nuclear power plant according to 5. 27. The nuclear power plant according to claim 26, wherein a degassing gas is injected into the electrolytic solution after the electrode reaction to degas carbon dioxide dissolved in the electrolytic solution. 28. A flow control valve provided in series with the metal element injection device, and a concentration control device for controlling the injection amount of the metal element by adjusting the opening / closing degree of the flow control valve. The nuclear power plant according to any one of claims 20 to 27, wherein 29. An injection pump is provided in series with the metal element injection device, and a concentration control device for controlling the injection amount of the metal element by adjusting the flow rate of the injection pump is provided. A nuclear power plant according to any one of claims 20 to 27. 30. The nuclear power plant is a boiling water reactor having a recirculation line, and the concentration control device measures the concentration of the metal element in the reactor water flowing through the recirculation line, and calculates the measured value. 30. The nuclear power plant according to claim 28, wherein the degree of opening and closing of the flow control valve or the flow rate of the injection pump is adjusted to control the concentration of the metal element in the reactor water. 31. The metal element injection device injects the metal element into a high-temperature system such as a recirculation line, a water supply line, a reactor water purification line, or a low-temperature system such as a condensate purification line. The nuclear power plant according to claim 30, wherein: 32. The method according to claim 32, wherein the concentration of the metal element in the reactor water is 5%.
The nuclear power plant according to any one of claims 1 to 31, wherein the nuclear power plant is limited to ppb or less.