JPH10307197A - Reactor power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attempt no spacial dose and reduce exposure of workers by using materials of elements which are little activated by neutron to be radioactives for core structure material and the like. SOLUTION: For core structure materials and the like in high neutron irradiation field, materials with elements with little activated by neutron to be radioactives are used. That is, materials consisting of at least one of elements chosen from element group of Be, C, Si, P, S, Ca, Re, Pt, Tl, Pb and Bi are used. Or a material consisting of elements capable of reducing the fraction of isotope element activated by neutron to be radioactives are used. For example in laser cladding, powder of these elements is solved in binder to be pastelike, which is spread on an object part and melted by irradiation with laser beam 1 to form a clad alloy layer 2.

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, and in particular, to reduce the amount of radioactivity adhering to equipment and pipes, and as a result, it becomes possible to reduce the radiation dose to workers during periodic inspections and the like. Related to a nuclear power plant.

[0002]

2. Description of the Related Art Generally, in a nuclear power plant, 1) a core structural material under high neutron irradiation is activated,
A part of which is dissolved in the reactor water and released into the water; or 2) corrosion products generated from structural materials in the reactor, or corrosion of materials in the water supply system or condensate system, The corrosion products brought into the inside adhere to the fuel cladding surface,
It is converted into radioactive corrosion products by irradiation with neutrons and then released into the reactor water by dissolution or exfoliation; or 3) water quality control, etc., to suppress the generation and migration of radioactive corrosion products. The chemical species added for the purpose adheres to the fuel cladding surface in the same way as the corrosion products, and is converted into radioactive materials by neutron irradiation, and then released into the reactor water by dissolution or separation, etc. There are various types of radioactivity that have different generation processes. The radioactivity is mainly in the form of ions when released by the dissolution phenomenon, and is mainly in the form of neutral atoms or particles in the form of a compound when released by the exfoliation phenomenon.

[0003] Regarding the generation process of these radioactivity,
This will be described in more detail below.

[0004] 1) Regarding a process of generating radioactivity, a core structure material under high irradiation of neutrons is activated, a part of which is dissolved and released into reactor water, and a BWR (boiling water light water reactor) power plant In this regard, typical core structural materials that generate and emit such radioactivity include control-dedicated pins and roller materials. Control rods control reactor power,
This is a very important device for adjusting the power distribution, and the role of the pin and the roller material is to ensure that the control rod is inserted or pulled out reliably and smoothly. Pin and roller materials are required not only to have wear resistance and corrosion resistance in high-temperature and high-pressure water, but also to have impact resistance and thermal shock resistance. Stellite, which is a cobalt-based alloy having extremely excellent wear resistance, has been conventionally used.

However, the installation site of such pins and rollers material due to the high irradiation field neutrons, cobalt in stellite, the following nuclear reaction is converted to ⁶⁰ Co radioactive.

[0006] ^{59 Co (n, γ) 60} Co Meanwhile, ⁶⁰ Co in the pin and roller material is not only a portion thereof with use is released to the reactor water and dissolved by the drive of the control rod Since an impact force is applied, a part of the material may be peeled off due to “galling”.

[0007] Then, ⁶⁰ Co has a long half-life of 5.2 years,
In addition, since the energy of the emitted gamma rays is as high as 1.17 MeV and 1.33 MeV, it is the main radiation source to which workers are exposed in the current BWR and PWR (pressurized water reactor) power plants. Since Stellite, including the cobalt element 50 wt% or more, wetted area while small, are believed large ⁶⁰ Co sources become rate of.

[0008] 2) Corrosion products generated from structural materials in the reactor or corrosion products generated by corrosion of water supply and condensate materials brought into the reactor adhere to the surface of the fuel cladding tube. The process of generating radioactivity, which is converted into radioactive corrosion products by irradiation with neutrons and then released into the reactor water by dissolution and separation, is a typical example of the deposition and release of such radioactivity in a BWR power plant. Examples of suitable structural materials include carbon steel used for bleed pipes, condensers, and condensate piping, and stainless steel and nickel-based alloys that are frequently used for feed water heaters, structural materials in furnaces, and the like.

The process of generating radioactive corrosion products originating from these materials is described below.

That is, iron ions are emitted from carbon steel, nickel ions and cobalt ions are emitted from stainless steel, and nickel ions and cobalt ions are similarly emitted from nickel-based alloys. Then, when the water supply system or the condensate system is the generation site, these corrosion products released into the water migrate along the flow of the water and are brought into the reactor. Corrosion products brought into the reactor together with corrosion products generated from structural materials inside the reactor become complex oxides on the fuel surface by the following reaction. 2Fe ²⁺ + Ni ²⁺ + Η ₂ O → NiFe ₂ O ₄ + Η ₂ + 6Η ⁺ ... (I) 2Fe ²⁺ + Co ²⁺ + Η ₂ O → CoFe ₂ O ₄ + Η ₂ + 6Η ⁺ ... (II) In the case where iron ions do not coexist on the fuel surface, composite oxides cannot be generated in principle.

[0011] These composite oxides produced on the fuel surface are subjected to high neutron irradiation to become radioactive corrosion products containing ⁵⁸ Co, ⁶⁰ Co, ⁵⁴ Mn, etc. produced by the following nuclear reactions.

[0012] ⁵⁸ Ni (n, p) ⁵⁸ Co ⁵⁹ Co (n, γ) ⁶⁰ Co ⁵⁴ Fe (n, p) ⁵⁴ Mn 3) To control the generation and transfer of radioactive corrosion products, for water quality control, etc. The chemical species added as fuel adheres to the surface of the fuel cladding in the same way as the corrosion products, is converted into radioactive materials by neutron irradiation, and is then released into the reactor water by dissolution and exfoliation. Regarding the above, not only radioactivity is incidentally generated from the structural materials of the plant, but also radioactivity may be generated from chemical species added for the purpose of water quality control or the like.

[0013] For example, as a patent registration No. 1654414, "In a method for suppressing the attachment of radioactive ions to a structural material that comes into contact with a coolant containing radioactive ions, a metal ion contained in the coolant during operation of a nuclear power plant is disclosed. Is measured, and Mg, Cr, V, Ti, Cu, and so on are determined so that the amount of metal ions in the coolant becomes a predetermined value based on the measured value.
A method for suppressing the adhesion of radioactive ions, characterized by injecting at least one metal ion selected from the group consisting of Ni, Zn, and Cd into the coolant.

The present inventors conducted a similar test in accordance with the contents of this patent, and confirmed the effectiveness and elucidated the mechanism. As a result, this method is based on the principle that the rate of incorporation of radioactive ions is governed by a competitive reaction with coexisting metal ion species in the process where ionic radioactivity is incorporated into the corrosion film along with corrosion of structural materials. It became clear that we used. In other words, the incorporation of ions into the corrosion film is, to varying degrees, governed by the concentration ratio of radioactive ions and other coexisting ionic species in the solution. In addition, the amount of radioactive ions taken into the corrosion film is suppressed.

From such a principle, in a nuclear power plant, a chemical species may be intentionally added in order to suppress generation and transfer of radioactive corrosion products.

Furthermore, chemical species may be added for the following purposes. That is, generally, corrosion of a metal material is pΗ
Is known to decrease by increasing the pressure, but in the reactor type where the boiling phenomenon occurs on the fuel cladding tube surface,
Since the enrichment phenomenon occurs at the site, when the pΗ is increased, the water quality environment of the fuel cladding tube becomes extremely high pH condition as compared with that in the coolant, and there is a risk that the fuel cladding tube may be damaged by alkali cracking or the like.

Therefore, the present inventors have focused on the pΗ value in the water quality data during the operation of the nuclear power plant, and have collected enormous data accumulated on the correlation between the value and the damage example of the fuel cladding tube. It has been verified and concluded that "in BWR, alkaline water quality conditions where p 冷却 in the coolant is at least 8.6 or less in terms of 25 ° C. do not affect the soundness of the fuel cladding tube." Therefore, in order to maintain such alkaline water quality conditions, a chemical species may be added to the coolant.

[0018]

The above problems 1), 2),
The radioactivity generated through the process 3) reaches the entire primary system of the plant using the primary coolant as a medium and contaminates each system. In addition, since the liquid contact portion of the primary coolant is almost made of a metal material, if the contamination phenomenon is locally observed, it is nothing but a phenomenon in which radioactivity is taken into the metal material.

Here, the incorporation of particulate radioactivity is mainly carried out by physical adsorption on the surface of the metal material or adhesion by gravity sedimentation, while ionic radioactivity is produced when the metal material is corroded. It is eutectoid as an oxide in a corrosion film formed on the surface or is taken in by an isotope exchange reaction.

For example, it is considered that ⁶⁰ Co ²⁺ is taken into the corrosion film by the reaction represented by the following two formulas (III) and (IV) with the corrosion of the steel material.

[0021] ^{2Fe 2+ + 60 Co 2+ + Η} 2 O → 60 CoFe 2 O 4 + Η 2 + 6Η + ...... (III) 60 Co 2+ + CoFe 2 O 4 → Co 2+ + 60 CoFe 2 O 4 ...... ( IV) In this way, the metallic material in contact with the primary coolant takes up radioactivity, the amount of which increases over time due to the growth of the corrosion film, and the rate at which the incorporated radioactivity decreases due to radioactive decay. Will continue to increase until the balance is reached. When radioactivity accumulates on the surfaces of pipes and equipment, the air dose rate increases, the radiation dose to workers working nearby increases, and the total radiation dose during the periodic inspection of the plant (total man- Belt). As a result, not only does the number of required workers increase, thereby increasing the cost of periodic inspections and the inspection period, but also the exposure itself poses a serious social problem and hinders the construction of new plants. From such a background, methods for suppressing generation and adhesion of radioactivity and methods for removing radioactivity once adhered (decontamination method) have been energetically studied.

By comprehensively examining the behavior of the generation and transfer of the above-mentioned radioactivity, as a measure for suppressing an increase in the air dose rate due to the adhesion of the radioactivity to the primary system piping surface or equipment surface, (1) do not generate radioactivity, (2) stop the radioactivity at the site of generation, do not transfer to the reactor water, (3) remove the radioactivity transferred to the reactor water, do not increase the concentration in the reactor water,
It was found that (4) radioactivity could not be attached to the surfaces of pipes and equipment, and (5) the radioactivity that had adhered could be removed. Various proposals have been made for each of these methods, and some techniques have been applied to actual equipment.However, effective methods have yet to be obtained in order to achieve zero exposure, which is the ultimate goal of exposure reduction. There is no present.

The present invention has been made in view of these circumstances, and from the viewpoint of not generating radioactivity, a nuclear power plant capable of reducing the radiation dose to workers and the like by reducing the air dose rate to zero. The purpose is to provide.

[0024]

According to a first aspect of the present invention, there is provided a nuclear power plant comprising, as a core structural material in a high neutron irradiation field, a material comprising an element which is less likely to become radioactive by activation by neutrons. Is used.

In the nuclear power plant according to the second aspect of the present invention, when the corrosion product is introduced into a nuclear reactor, it becomes radioactive by neutron activation when the corrosion product is introduced into the nuclear reactor. It is characterized by using a material made of an element that rarely occurs. A nuclear power plant according to a third aspect of the present invention is characterized in that as a chemical species added to reactor water for the purpose of water quality control, a chemical species composed of an element that is less likely to become radioactive due to activation by neutrons is used.

In the nuclear power plant according to the fourth aspect of the present invention, as a core structural material in a high neutron irradiation field, a material composed of an element having a reduced proportion of an isotope element which becomes radioactive by activation by neutrons is used. It is characterized by.

In the nuclear power plant according to the fifth aspect of the present invention, when the corrosion product is introduced into a nuclear reactor, it becomes radioactive by neutron activation when the corrosion product is introduced into a nuclear reactor. It is characterized by using a material made of an element having a reduced isotope ratio.

The nuclear power plant according to the sixth aspect of the present invention comprises, as a chemical species added to reactor water for the purpose of water quality control, an element having a reduced proportion of an isotope element which becomes radioactive by activation by neutrons. It is characterized by using a chemical species.

In the nuclear power plant according to the present invention,
For each of the following radioactivity generation processes:
Appropriate generation suppression means are provided.

That is: 1) The core structural material under high neutron irradiation is activated,
Core structure materials under high irradiation of neutrons are activated, such as pin and roller materials that drive control rods for the process of generating radioactivity, part of which is released into the reactor water, There are the following two methods to suppress the generation of radioactivity due to a part of the radioactivity being dissolved in the reactor water and released into the reactor water. That is, one method is (i) a method using a material made of an element that is less likely to become radioactive due to activation by neutrons as a core structure material in a high neutron irradiation field, and another method is ( ii) A method using a core material in a high neutron irradiation field, which is made of an element in which the proportion (constituent ratio) of the isotope element that becomes radioactive by activation by neutrons is reduced by adjusting the isotope ratio. It is.

First, in the method (i), a target element can be selected by verifying a nuclear reaction with a neutron for each element by using an isotope handbook or the like. At this time, the selection criteria are that there is no (n, γ) reaction, or that the generated radioactivity emits low γ-ray energy, if any, or that the generated radioactivity has a short half-life. Becomes As a result of performing these screenings, Be, C, Si, P, S, Ca, as elements that are less likely to become radioactive due to activation by neutrons,
Ti, Re, Pt, Tl, Pb and Bi were selected. Therefore, it is desirable that the core structure material in the high neutron irradiation field, such as the control rod pin and the roller material, be made of a material composed of at least one element selected from these element groups.

Next, "adjustment of isotope ratio" in the method (ii) will be described by taking zinc as an example.

In nature, ⁶⁴ Zn, ⁶⁶ Zn, ⁶⁷ Zn, ⁶⁸
Five stable isotopes of Zn, Zn and ⁷⁰ Zn, respectively
It is present at 48.6, 27.9, 4.1, 18.8, and 0.6%. When a material containing Zn or Δn is used as a structural material in a reactor pressure vessel in a high neutron irradiation field, a radioactive substance ( ⁶⁵ Zn, ⁶⁹ Zn,
⁷¹ Zn) is newly generated.

⁶⁴ Zn (n, γ) ⁶⁵ Zn ⁶⁸ Zn (n, γ) ⁶⁹ Ζn ⁷⁰ Zn (n, γ) ⁷¹ Zn At this time, the isotope ratio is adjusted, and ⁶⁴ Ζn among the stable isotopes of Zn , ⁶⁸ Zn and ⁷⁰ Zn, respectively, ⁶⁶ Zn and ⁶⁷ Zn
If Zn composed of one or both of Zn is used, secondary radioactivity generated by using zinc as a structural material can be completely eliminated, and the intended purpose can be achieved.

Elements which can reduce the composition ratio of the isotope element which becomes radioactive by neutron activation by adjusting the isotope ratio include Li, B, Mg, V, and
Cr, Fe, Ni, Zn, Ge, Se, Sr, Zr, M
o, Ru, Pd, Cd, Sn, Sb, Te, Ba, L
a, Νd, Sm, Εr, Yb, Ηf, W, Os, Ηg, and in the present invention, the core structural material in the high irradiation field of neutrons is prepared from at least one element selected from these element groups. It is desirable to be composed of such materials. In application to an actual power plant, it is not always necessary to completely remove harmful isotopes that generate secondary radioactivity due to activation, due to the relationship between cost and the effect obtained.

1) In order to suppress the generation of radioactivity due to the activation of core structural materials under high neutron irradiation,
In the case of employing the methods i) and (ii), it is preferable that the entire target member is made of a material made of the above-described element (hereinafter, referred to as the material). Such a method can be applied only to a layer having a constant thickness. In that case, activation of the inner part is inevitable, but activation is very little or very little in the liquid contact part, so that the amount of radioactivity transferred into the reactor water is extremely small. The inner portion is not limited to a conventionally used material, but may be a less expensive material.

Here, the thickness from the liquid contact surface to which the material is applied varies depending on the material to be used. According to the result of a material corrosion test using a BWR core simulated water quality conducted by the present inventors, the thickness is 5 mm. It is desirable to have a thickness of the order.
This is a value calculated rationally considering that the life of the plant is 40 years and that the BWR core water quality is a considerably oxidizing atmosphere. In addition, as a method of applying the material to a portion having a certain thickness from the liquid contact surface, laser cladding, plating, dry plating, thermal spraying,
Examples of the method include ion implantation and lining.

Further, when the methods (i) and (ii) are applied during the construction of a plant, a great reduction in exposure can be expected from the initial operation of the plant. The same can be applied. In an existing plant that has passed a considerable period from the start of operation, for example, by performing the inspection at the time of a periodic inspection of the plant, an effect of reducing the exposure in the subsequent period can be expected.

2) Corrosion products generated from structural materials in the reactor, or corrosion products generated by corrosion of water supply and condensate materials and brought into the reactor, adhere to the surface of the fuel cladding tube. It is converted into radioactive corrosion products by irradiation of neutrons and then released into the reactor water by dissolution or exfoliation. In order to suppress the generation of radioactive corrosion products originating from the synthesized composite oxides (NiFe ₂ O ₄ , CoFe ₂ O ₄ ), it is important to suppress the introduction of iron ions or iron cladding into the reactor. It is.

In order to suppress the generation of radioactive corrosion products from carbon steel, stainless steel, nickel-base alloys, etc., which are structural materials in the reactor or water supply and condensate materials, these materials must be used. Then, there is a method using the following alternative materials. One method is to use (i) a material made of an element that is less likely to become radioactive due to activation of neutrons even when the corrosion product is brought into the reactor, as a structural material at the site where the corrosion product is generated. Another method is (ii) as a structural material at the site where corrosion products are generated, even if corrosion products are brought into the reactor by adjusting the isotope ratio, even if the corrosion products are brought into the reactor, the neutrons will activate the radioactivity. In this method, a material made of an element having a reduced proportion of an isotope element is used.

When these methods are employed, as in the case of suppressing the generation of radioactivity by the above-mentioned process 1), the elements which are less likely to become radioactive by activation by neutrons are Be and C. , Si, P, S, C
a, an element selected from the group consisting of Ti, Re, Pt, Tl, Pb, and Bi can be used. The decrease in the composition ratio of the isotope element which becomes radioactive by neutron activation can be determined by the isotope ratio The elements that can be adjusted by adjusting
i, B, Mg, V, Cr, Fe, Ni, Zn, Ge, S
e, Sr, Zr, Mo, Ru, Pd, Cd, Sn, S
b, Te, Ba, La, Νd, Sm, Εr, Yb, Η
An element selected from the group consisting of f, W, Os, and Δg can be used.

When the methods (i) and (ii) are applied to a site where a corrosion product is generated, it is desirable to apply the method only to a layer having a certain thickness from the surface in contact with the liquid of the target member. . That is, it is desirable in terms of cost to change the inner portion to a less expensive material if there is no problem in use. Here, the thickness from the liquid contact surface to which the material is applied is different depending on the material to be used and the application site. However, at a site other than the structural material inside the furnace, the BWR water supply system and the Based on the results of a material corrosion test using simulated water quality of the condensate system, it is desirable that the thickness be about 2 mm. This is a value calculated rationally considering that the life of the plant is 40 years and that the BWR feedwater and condensate water quality are mildly corrosive in comparison with the core water quality. In addition, since the water quality environment is slightly milder than the core water quality in the in-furnace structural materials, the same can be applied by applying the material to a thickness of about 2 mm from the surface in contact with the liquid. Examples of a method of applying the material to a portion having a certain thickness from the liquid contact surface include methods such as laser cladding, plating, dry plating, thermal spraying, ion implantation, and lining. In addition, when applying the methods (i) and (ii), when applied during the construction of a plant, a significant reduction in exposure can be expected from the early stage of operation. Can also.

3) In order to suppress the generation and migration of radioactive corrosion products, the chemical species added for the purpose of water quality control or the like adheres to the surface of the fuel cladding in the same manner as the corrosion products and becomes radioactive by neutron irradiation. In a nuclear power plant, chemical species may be intentionally added for various purposes to the process of generating radioactivity, which is converted into a substance and then released into the reactor water by melting or exfoliation. Can have side effects such as generation of radioactivity originating from the added chemical species. To avoid this,
The following two methods can be employed. That is,
One method is to use (i) a chemical species to be added for the purpose of water quality control or the like, which contains an element that rarely becomes radioactive by activation with neutrons,
The other method is (ii) a chemical species to be added for the purpose of water quality control, etc., which contains an element in which the proportion of the isotope element which becomes radioactive by neutron activation is reduced by adjusting the isotope ratio. It is a method using. When these methods (i) and (ii) are adopted, the element that is unlikely to become radioactive due to activation of neutrons is B
e, C, Si, P, S, Ca, Ti, Re, Pt, T
An element selected from the group consisting of l, Pb, and Bi can be used, and the composition ratio of an isotope element that becomes radioactive by neutron activation can be reduced by adjusting the isotope ratio. As Li, B, Mg, V, Cr,
Fe, Ni, Zn, Ge, Se, Sr, Zr, Mo, R
u, Pd, Cd, Sn, Sb, Te, Ba, La, Ν
An element selected from the group consisting of d, Sm, Δr, Yb, Δf, W, Os, and Δg can be used.

Then, in the nuclear power plant,
(I) and (i) for the radioactivity generation process of 3)
When the method of i) is adopted, an element generator capable of generating the above-described elements or an element injection apparatus capable of injecting these elements is attached to a plant, and the operation of these apparatuses is performed. The goal can be achieved.

Here, as the element generator, an element selected from the above-described element group (the element) is used as a simple metal,
Oxides, hydroxides, hydrides, or compounds containing one or both of hydrogen and metal salts, including metal salts, placed in a high-temperature system and passed through high-temperature water, A structure having a structure capable of obtaining a predetermined element concentration can be used.

Further, the element implanting device may be a device in which the element is a simple metal, an oxide, a hydroxide, a hydride, or a compound containing one or both of hydrogen and oxygen containing a metal salt. After transformation into a slurry state or a solution state, it is preferable to use a structure in which a predetermined amount is added by using an injection pump or the like to obtain a predetermined element concentration.

[0047]

Embodiments of the nuclear power plant according to the present invention will be described below.

In the embodiment of the nuclear power plant according to the present invention, (i) Be, C, Si, P, S, Ca,
A material consisting of at least one element selected from the group of elements that rarely become radioactive by activation by neutrons, such as Ti, Re, Pt, Tl, Pb, Bi, or (ii) Li, B, Mg , V, Cr, Fe, Ni, Z
n, Ge, Se, Sr, Zr, Mo, Ru, Pd, C
d, Sn, Sb, Te, Ba, La, {d, Sm,}
At least one selected from a group of elements capable of reducing the proportion of isotopes that become radioactive by activation with neutrons by adjusting the isotope ratio, such as r, Yb, Δf, W, Os, and Δg. A material consisting of a certain element is used as a core structure material in a high neutron irradiation field or a structure material constituting a site where a corrosion product is generated, and a material consisting of the element (the material) is used as a contact material. It is applied to a layer of a certain thickness from the liquid surface.

In the nuclear power plant of such an embodiment, a coating layer of a certain thickness made of the above-mentioned material is formed on the surface in contact with the structural material with the following laser cladding, plating, and drying. It is formed by any one of rating, thermal spraying, ion implantation, and lining.

First, a method of forming a layer made of the material having a constant thickness by laser cladding will be described.

In the laser cladding, as shown in FIG. 1, a powder of the element is dissolved in a binder, applied in the form of a paste, and then applied to a target portion, and then irradiated with a laser beam 1 to form a clad alloy layer 2. How to In addition, the code | symbol 3 in a figure shows a base material, 4 shows a fusion | melting part. The laser source is YAG (Yttrium Aluminum Garnet)
The use of a laser is most preferred. Further, such a laser cladding treatment is usually performed in an inert gas atmosphere, but may be performed at atmospheric pressure. When laser cladding is performed at atmospheric pressure,
The surface of the clad alloy layer 2 is oxidized by the heat input to form a film, and the oxide film thus generated at a high temperature is
When exposed to high-temperature water at a temperature equal to or lower than the film formation temperature, it has a function of suppressing dissolution. This laser cladding method
Since it is a point source, there is an advantage that the influence on the base material 3 is small.

Next, a method of forming a layer made of the material by plating will be described.

The plating is a method of electrochemically depositing the element on a target portion, and a layer made of the element can be formed on the entire surface of the target structural material. In this method, as shown in FIG. 2, the element (sulfate, ammonium salt, cyanide, ethylenediamine compound, EDTA compound, etc.) is filled in a plating tank 6 with a solution thereof (electrolyte 5), and The target member is immersed in the work. In the figure, an anode 7 and a cathode 8 made of the element are provided in a plating tank 6, and a predetermined DC voltage is applied between the anode 7 and the cathode 8. An insulating diaphragm 9 is interposed between the anode 7 and the cathode 8, and a target member such as a core structure material or a structural material at a site where a corrosion product is generated is located inside the insulating diaphragm 9. It is soaked and processed. Further, an air ejection pipe 10 is provided below the plating tank 6 in order to make the plating layer uniform.

Next, a construction method by dry plating will be described.

Dry plating is a method in which the element film is formed on a target portion in a dry manner, and the element can be applied to the entire surface of a target structural material. Dry plating can be further subdivided into two categories: vapor deposition in which metal is vaporized and condensed on the solid surface, gas discharge in atmosphere gas, ionization of evaporated particles to activate and form a film, and metal as a target. There is a sputtering method or the like in which a high voltage is applied between electrodes to cause a discharge to form a thin film on a target portion.

Among these dry platings, in the sputtering method, a thin film is formed by a sputtering apparatus having a target formed of the element.
In this apparatus, as shown in FIG.
1, a holder 12 is arranged, and a target member 13 is placed on the holder 12. The target 11 and the holder 12 are arranged so as to be insulated from the vacuum vessel 15 by the insulating member 14. To further increase the sputtering efficiency, a shield 16 is provided around the target 11 and the holder 12. Then, a high voltage is applied to the target 11 by a DC power supply 17, and the elements constituting the target 11 are turned into plasma and adhere to the target member 13 to form a thin film.

Next, an application method by thermal spraying will be described.

[0058] Thermal spraying is a method in which the element is heated to a molten state or a state close to it, and is sprayed on a target portion of the structural material to form a film. For thermal spraying on the target structural material, plasma spraying is most desirable, in which the highest temperature state can be obtained, and a film having high density and good adhesion can be obtained. In the plasma spraying method, as shown in FIG. 4, a spraying apparatus having a plasma torch 18 as an anode and a cathode 19 provided in the plasma torch 18 is used. In this thermal spraying apparatus, the powdered element 21 is supplied via the element supply path 20, the plasma jet 23 is jetted by the working gas 22, and the sprayed material adheres to the surface of the target member 24. A film is formed. Further, in this apparatus, the target member 24 is used 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 is a method in which the element is ionized, accelerated by an electric field, and colliding with the surface of the target member for implantation. In this method, the number of ions implanted per unit area (pieces / cm ² )
It is considered that an implantation dose of 1 × 10 ¹⁷ / cm ² corresponds to a surface composition of about 10 atomic%. If a film containing about 10 atomic% of the element is formed on the surface of the target structural material, the effect can be expected. Therefore, when the ion implantation method is used, about 1 × 10 ¹⁷ / cm ² It is desirable to use the injection amount as a guide. At the time of ion implantation, a large number of point defects and secondary defects are introduced into the sample due to direct elastic collision and cascade collision with sample atoms, which may cause so-called irradiation damage. Therefore, it is preferable to add an annealing operation by heat treatment after ion implantation.

Further, a construction method using lining will be described.

The lining is a method of coating a thin film produced by rolling the element in a metallic state on the outside of a target structural material. In consideration of workability, it is desirable to adopt a method of forming a thin film to a thickness of about 100 μm and stacking it in multiple layers to secure a constant thickness.

In the embodiment of the present invention, the core structure material in the high neutron irradiation field and the liquid contact surface of the structure material at the site where the corrosion product is generated are fixed by the above-mentioned construction method. A thick layer can be formed, and as a result, a nuclear power plant with less generation of radioactivity can be obtained.

Next, another 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 element is in the state of one of a single metal, an oxide, a hydroxide, a hydride, a compound containing one or both of hydrogen and oxygen including metal salts. And an element generator capable of obtaining a predetermined ion concentration by a corrosion release reaction by passing high-temperature water through.

FIG. 5 shows an example of the element generator.

As shown in FIG.
Has a column 27 in which a metal mesh screen 26 is disposed, and the space between the metal mesh screens 26 is filled with the element 28 in the form of particles. The particle size of the particles of the element is adjusted so as to have a particle size distribution from 0.1 mm to 1 mm, and by adjusting the particle size, the specific surface area is increased and the packing density in the column 27 is improved. . And at one end of the column 27,
A supply pipe 29 for introducing high-temperature water in the system of the nuclear power plant is connected, and a valve 30 is provided in the middle of the supply pipe 29. Column 27
A discharge pipe 31 for discharging the high-temperature water supplied into the column 27 is connected to the other end of the discharge pipe 31. In the middle of the discharge pipe 31, a flow control valve 32 having a flow control function is provided. Is provided. Further, a bypass pipe 33 is provided between the supply pipe 29 and the discharge pipe 31 so as to bypass the column 27, and a flow control valve 34 having a flow control function is provided in the middle of the bypass pipe 33. Have been.

In the element generator 25,
When high-temperature water in the system of the nuclear power plant is introduced into the column 27 through the supply pipe 29 and passes through the element 28 in the form of particles, ions of the element are dissolved in the high-temperature water, and the high-temperature water containing the element ion is dissolved. The water is circulated through the discharge pipe 31 into the system of the nuclear power plant. At this time, the concentration of the element ion in the nuclear power plant is monitored by a concentration control device (not shown), which will be described later, and the degree of opening and closing of the flow control valves 32 and 34 is constantly adjusted, so that an optimum concentration is obtained. Is controlled. That is, when the concentration of the element ion is lower than the predetermined value, the flow control valve 34 provided in the bypass pipe 33
To increase the flow rate of the high-temperature water flowing through the column 27. On the other hand, when the concentration of the element ion is higher than a predetermined value, the flow control valve 3 provided in the discharge pipe 31 is used.
By controlling the flow rate of No. 2 to decrease the flow rate in the column 27 and reduce the generation amount of the element ions, the concentration is controlled to the optimum concentration.

In the element generator 25, the element is converted into particles and the particle size is adjusted so as to have a particle size distribution from 0.1 mm to 1 mm.
It is also possible to heat and bake at a temperature of 1/2 or more. When provided in a sintered state in this way, the particles of the element remain in a sintered state even when high-temperature water is passed through, so that sintered fine particles may accidentally flow into the high-temperature system of a nuclear power plant. For example, holding in a high-temperature system becomes easy.

FIG. 6 shows that such an element generator 25 is
The embodiment attached to the WR power generation plant is shown.

In this figure, reference numeral 35 denotes a reactor pressure vessel, in which a reactor core 36 is provided. The steam generated by the heat from the core 36 is supplied to the steam line 3
After being sent to the steam turbine 38 via 7 for work, it is condensed in the condenser 39 and returns to water. Then, the water is sent to a condensate purification device 41 by a condensate pump 40 to remove impurities. Then, the water is preheated by a feedwater heater 42 and returned to the reactor pressure vessel 35. The reactor water is
A recirculation line 44 having a recirculation pump 43 and a jet pump 45 forcibly circulate inside the reactor pressure vessel 35. Further, a part of the reactor water flowing through the recirculation line 44 passes through a reactor water purification line 47 having a reactor water purification system pump 46, and is cooled by a regenerative heat exchanger 48 and a non-regenerative heat exchanger 49. The reactor water purified and purified by the water purification device 50 is returned to the reactor pressure vessel 35 via the water supply line 51.

In such a BWR power plant,
An element generator 25 is attached to the outlet side of the recirculation pump 43, and the upstream side of the element generator 25 (the supply pipe 2).
9) and the downstream side (discharge pipe 3)
The flow control valves 32 provided in 1) are configured to serve as isolation valves for isolating the element generator 25 during maintenance. As described above, the flow control valve 34 is provided in the middle of the bypass line (bypass pipe 33) that bypasses the element generator 25.
The flow control valve 34 can be adjusted in the degree of opening and closing by the concentration control device 52.
The concentration control device 52 functions to measure the concentration of elemental ions downstream of the recirculation pump 43 and adjust the opening / closing degree of the flow control valve 34 according to the measured value. here,
As a method for measuring (analyzing) the element ion concentration in the concentration controller 52, ion chromatography capable of continuously measuring the ion species concentration is optimal.

In the embodiment configured as described above,
The element ions generated by the element generator 25 are supplied together with the recirculated water into the reactor pressure vessel 35, whereby a nuclear power plant with less generation of radioactivity is achieved.

Next, another embodiment of the nuclear power plant according to the present invention will be described.

In the nuclear power plant shown in FIG. 7, the element generator 25 shown in FIG. 5 is provided on the upstream side of the recirculation pump 43, and the valves 30 and 3 for isolation are provided.
By opening 2, it is connected to the recirculation line 44. A high-pressure pump 53 is provided between the element generator 25 and the isolation valve 30, and the high-pressure pump 53 compensates for a pressure loss generated in the element generator 25. Further, the concentration control device 52 measures the concentration of the element ion on the upstream side of the recirculation pump 43, and adjusts the flow rate of the high-pressure pump 53 according to the measured value.

In the nuclear power plant configured as described above, the flow rate of the high-pressure pump 53 is adjusted by the concentration control device 52, thereby controlling the element ion concentration. Therefore, the flow rate in the recirculation line 44 shown in FIG. The adjustment valve 34 becomes unnecessary.

In the nuclear power plant shown in FIG. 8, two element generators 25 are provided in parallel, and isolation valves 54 are provided upstream and downstream of each element generator 25, respectively. . In the nuclear power plant configured as described above, even during the operation of the plant, the one element generator 25 supplies the element while the other element generator 25 is connected to the upstream and downstream valves 54. By closing and isolating,
The maintenance can be performed.

In each of the embodiments shown in FIGS. 6 to 8, the element generator 25 is installed in the recirculation line 44, but the installation position of the element generator 25 is not limited to the recirculation line 44. No, for example, water supply line 51
Such as the outlet of the reactor water purification line 47 or the like, it can be installed at a position where high-temperature water at the same level as the reactor water temperature flows.

Next, still another embodiment of the nuclear power plant according to the present invention will be described with reference to the drawings.

In the nuclear power plant of this embodiment, the element is in any state of a simple metal, an oxide, a hydroxide, a hydride, a compound containing one or both of hydrogen and oxygen including a metal salt. In addition, an element injection device capable of obtaining a predetermined element concentration by adding a certain amount by using an injection pump or the like after forming a slurry or a solution is provided.

FIG. 9 shows an element injection device 55 for generating element ions from the element in a metal state by an electrode reaction and injecting the ions into a system of a nuclear power plant using an injection pump.

In the drawing, reference numeral 56 denotes a carbon dioxide gas saturation tank, which has a function of converting an electrolytic solution into an electrolyte so that elemental ions are easily generated by an electrode reaction. In addition, since the electrolytic reaction can be caused at a low voltage by converting the electrolytic solution into an electrolyte by the carbon dioxide gas saturation tank 56, the DC power supply equipment can be downsized.

A bubbling line 58 provided with a carbon dioxide emission part 57 at the tip is provided inside the carbon dioxide gas saturation tank 56.
Is disposed, and a carbon dioxide gas cylinder 59 is connected to the other end of the bubbling line 58. The carbon dioxide release section 57 has a bubbler structure having a number of fine outlets, and the bubbler structure allows carbon dioxide gas to be efficiently injected into the tank. In addition, a seal pot 60 is connected to the carbon dioxide gas saturation tank 56 via a pipe in order to release an excessively supplied carbon dioxide gas. Further, a pure water supply line 61 is connected to the carbon dioxide gas saturation tank 56, and in the middle of the pure water supply line 61, a flow control valve 62 for adjusting a pure water flow rate is provided.

Further, such a carbon dioxide gas saturation tank 56 is
It is connected to an electrolytic cell 64 via a connection pipe 63. An electrolytic solution is contained in the electrolytic bath 64, and in the electrolytic solution,
A pair of plate-like electrodes 65 made of the element alone or a metal material containing the element is immersed, and a DC power supply 66 is connected to these electrodes 65. In addition,
In FIG. 9, two plate-like electrodes 65 are immersed in the electrolytic cell 64. However, by increasing the number of the electrodes 65, the generation amount of the element ions can be increased, or an electrode made of a different element can be used. A different ionic species can also be generated in a blended state by attaching. Also,
By switching the polarity of the DC power supply 66 at regular intervals, it is possible to equalize the thickness reduction of the plurality of electrodes 65 and to effectively use the element.

Further, such an electrolytic cell 64 is connected to a carbon dioxide gas removing tank 68 via a connecting pipe 67. Inside the carbon dioxide gas removal tank 68, a bubbling line 70 provided with a degassing gas discharge section 69 at the tip is disposed, and a degassing gas cylinder 71 is connected to the other end of the bubbling line 70. I have. The degassing gas discharge section 69 has a bubbler structure having a large number of fine blowout ports, and the bubbler structure allows the degassing gas to be injected efficiently. Further, a seal pot 72 is connected to the carbon dioxide gas removing tank 68 via a pipe in order to release the collected carbon dioxide gas and excess degassed gas. Further, a transportation pipe 73 is connected to the carbon dioxide gas removal tank 68 to send the generated element ions to a target site in the nuclear power plant. Is provided.

In the element injection device 55, first, pure water adjusted to a constant flow rate by the flow control valve 62 is
It is continuously supplied to the carbon dioxide gas saturation tank 56 via the pure water supply line 61. Further, carbon dioxide gas is supplied from the carbon dioxide gas cylinder 59 to the carbon dioxide gas discharge unit 57 via the bubbling line 58, and the carbon dioxide gas discharge unit 57 releases bubble-like carbon dioxide gas into the tank. The carbon dioxide gas released into the carbon dioxide gas saturation tank 56 dissolves in pure water, causes the following dissociation reaction, becomes an electrolyte, and promotes an electrode reaction in the electrolytic tank 64. Further, the excessively supplied carbon dioxide gas is discharged from the seal pot 60 to the outside of the system via a pipe.

[0087] _{CO 2 + H 2 O → H} 2 CO 3 Η 2 CO 3 → Η + + ΗCO 3 - ΗCO 3 - → Η + + CO 3 2- Next, a solution of carbonate ions and carbon dioxide gas dissolved is in dissociated state ( The electrolytic solution is sent from the carbon dioxide gas saturation tank 56 to the electrolytic tank 64 via the connection pipe 63. Since a DC voltage is applied between the pair of electrodes 65 in the electrolytic bath 64 by the DC power supply 66, an electrode reaction is performed, and the element constituting the electrode 65 is dissolved in the electrolyte as ions.

The electrolytic solution in which the element ions are dissolved in the electrolytic cell 64 is sent to the carbon dioxide gas removing tank 68 via the connecting pipe 67. In the carbon dioxide gas removal tank 68, the degassed gas supplied from the degassed gas cylinder 71 via the bubbling line 70 is discharged in a bubble state from the degassed gas discharge part 69, and The carbonate ions dissolved in the solution are converted into carbon dioxide gas by the reverse reaction of the above-described dissociation reaction, and are collected. The recovered carbon dioxide gas is released from the seal pot 72 to the outside of the system via a pipe together with the excessively supplied degassed gas. And
The solution containing the element ions generated by the element injection device 55 is pressurized by an injection pump 74 and sent to a target site in a nuclear power plant via a transport pipe 73. According to the element implanting device 80, the ion species of the element are manufactured and injected into the system of the nuclear power plant while producing the ion species. Is configured to be removed by degassing, the introduction of unnecessary ion species is suppressed, and only target element ions can be implanted.

Further, by degassing the carbon dioxide gas, a part of the dissolved element ions precipitates as hydroxides in the form of fine particles, but when the fine particles are introduced into high-temperature water, they become ionic again. This is because the solubility of these elemental ions is sufficiently high compared to the target concentration (for example, 5 ppb), and as a result, unnecessary ion species are not brought into the reactor without incidentally. It is possible to achieve the purpose of the period. Further, a plate-shaped body composed of the element alone,
Alternatively, since the electrode 65 is formed by using a plurality of plate bodies made of a metal material containing the element, the concentration of the element ion species can be arbitrarily controlled by adjusting the current value of electrolysis. In addition, the fine adjustment of the element ion concentration can be accurately performed, and the inflow of unnecessary element ion species can be prevented. Further, by using a plurality of metal plates having different element compositions as the electrode 65, it is possible to blend ion species to be implanted into the system. Further, by increasing or decreasing the number of metal plates constituting the electrode 65, the amount of generation of the element ion species can be adjusted in accordance with the scale of the target nuclear power plant.

FIG. 10 shows an embodiment in which such an element implantation device 55 is attached to a BWR power plant.

In this embodiment, the element implantation device 55
The outlet end of the transport pipe 74 connected to the furnace water purification line 47 is connected to the reactor water purification line 47, and a flow control valve 75 is provided downstream of the injection pump 74. Further, a concentration control device 76 is provided in the recirculation line 44. The concentration control device 76 measures the element ion concentration on the upstream side of the recirculation pump 43, and controls the opening / closing degree of the flow control valve 75 and the amount of the element ions generated in the element injection device 55 according to the measured value. Thereby, the concentration of the element ion in the reactor water is adjusted to a predetermined value. Here, as a method (analysis method) of measuring the element ion concentration in the concentration controller 76, an in-line ion chromatography that can continuously measure the ion species concentration is optimal. The element ion concentration in the reactor water can be measured every time.

In this embodiment, the element implantation device 55
Is connected to the reactor water purification line 47. However, the connection position is not limited to the reactor water purification line 47. For example, as in the recirculation line 44 and the water supply line 51, the connection position is substantially the same as the reactor water temperature. It can be connected to a portion where high-temperature water flows, and further can be connected to a low-temperature system where low-temperature water flows, such as an outlet of the condensate purification device 41.

Next, another element implantation apparatus will be described with reference to FIG.
It will be described based on.

As shown in the figure, the element injection device 77 includes a tank 79 to which pure water is continuously supplied via a pure water supply line 78. This tank 79
In the upper part of the fine powder, the element is filled in a fine powder state as a simple substance, an oxide, a hydride or a hydroxide, or a compound containing one or both of hydrogen and oxygen such as a metal salt. A tank 80 is provided, and the fine powder in the fine powder tank 80 is supplied to the tank 79 continuously or intermittently. The particle size of the fine powder containing the element is desirably in the submicron order of 1 μm or less from the viewpoint of preventing sedimentation. Further, an impeller 81 is provided in the tank 79, and sedimentation of the fine powder is prevented by the forced stirring action of the impeller 81. Further, the tank 79 has a transport pipe 8 for sending the generated slurry suspension or solution to a target site in the nuclear power plant.
2 is connected, and a high-pressure pump 83 is provided in the middle of the transport pipe 82. Then, the slurry supplied to the target portion in the nuclear power plant via the transport pipe 82 is quickly ionized by contacting the high-temperature water in the plant system.

FIG. 12 shows an embodiment in which such an element implantation apparatus 77 is attached to a BWR power plant.

In this embodiment, the element implantation device 77
The outlet end of a transport pipe 82 connected to the water supply line 51 is connected to the water supply line 51, and a concentration control device 84 is provided in the recirculation line 44. The concentration control device 84 measures the concentration of element ions on the upstream side of the recirculation pump 43, controls the flow rate of the high-pressure pump 83 according to the measured value, and thereby controls the concentration of the element ions in the reactor water to a predetermined value. Is controlled. And the element implantation device 7
The slurry suspension containing the element generated in step 7 is
The slurry supplied to the water supply line 51 via the transport pipe 82 is contacted with high-temperature water flowing through the water supply line 51 to be ionized, and the ions of the generated element are supplied to the reactor pressure vessel 35. Thus, the original purpose is achieved.

In this embodiment, the element implantation device 77
Was connected to the water supply line 51, but the connection position of the element injection device 77 is not limited to the water supply line 51. For example, like the outlet of the recirculation line 44 and the reactor water purification line 47, the reactor water temperature and It can be installed in a part where the same high temperature water flows. Further, even in a low-temperature system in which low-temperature water flows, an element injection device 77 can be connected to a portion where the flow rate in the system is sufficiently large and sedimentation of fine powder can be ignored.

Further, in all the embodiments described above, the BWR power generation plant of the type in which the reactor water is forcibly circulated by the jet pump 45 has been described as an example. However, the present invention is limited to such a type of BWR. Instead, it can be applied to all reactors configured to extract thermal energy from nuclear fuel material using thermal neutrons. That is, a natural circulation BWR without the jet pump 45 or the external recirculation line 44
The present invention can be applied to all light water reactors and heavy water reactors including an ABWR of a type in which reactor water is forcibly circulated by an internal pump without an internal pump, and a pressurized water nuclear power plant (PWR). In addition, the current BW
In R, there is a plant in which a reactor water purification system pump 46 is installed downstream of the regenerative heat exchanger 48 or the non-regenerative heat exchanger 49, and can be applied to such a power plant.

[0099]

As is apparent from the above description, in the present invention, the core material added in the high neutron irradiation field, the structural material in the site where the corrosion product is generated, or the water added for the purpose of water quality control or the like. As a chemical species, a material consisting of a specific element group that has a low ratio of becoming radioactive by neutron activation, or by adjusting the isotope ratio,
Since a material composed of a specific element group in which the composition ratio of the isotope element which becomes radioactive by activation by neutrons is reduced is used, a nuclear power plant with less generation of radioactivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a method of forming a layer having a constant thickness by laser cladding in an embodiment of a nuclear power plant of the present invention.

FIG. 2 is a view showing a method for forming a layer of the material by a plating method in the same embodiment.

FIG. 3 is a diagram showing a method for forming a layer of the material by a sputtering method in the same embodiment.

FIG. 4 is a view showing a method for forming a layer of the material by a plasma spraying method in the embodiment.

FIG. 5 is a longitudinal sectional view showing an element generator used in the embodiment of the nuclear power plant according to the present invention.

FIG. 6 is a diagram schematically showing a second embodiment of the nuclear power plant according to the present invention.

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

FIG. 8 is a diagram schematically showing a fourth embodiment of the nuclear power plant according to the present invention.

FIG. 9 is a diagram schematically showing an element injection device used in the embodiment of the nuclear power plant of the present invention.

FIG. 10 is a diagram schematically showing a fifth embodiment of the nuclear power plant according to the present invention.

FIG. 11 is a view schematically showing another element implantation apparatus used in the embodiment of the nuclear power plant according to the present invention.

FIG. 12 is a diagram schematically showing a sixth embodiment of the nuclear power plant according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser beam 2 ... Clad alloy layer 6 ... Plating tank 9 ... Insulating diaphragm 11 ... Target 12 ... Holder 13,24 ... Target member 15 ... Vacuum container 18 Plasma torch 23 Plasma jet 25 Element generator 27 Column 28 The element 30, 54 Valve 32, 34, 62, 75 Flow control valve 35 Reactor pressure vessel 36 Reactor core 37 Steam line 38 Steam turbine 43 Recirculation pump 44 Recirculation line 45 Jet pump 47 Furnace Water purification line 51 Water supply line 52, 76, 84 Concentration control device 53, 83 High pressure pump 55, 77 Element injection device 56 Carbon dioxide saturation tank 58, 70 … Bubbling line 59 Carbon dioxide cylinder 60, 72 Seal pot 61, 78 Pure water supply line 64 Electrolyzer 65 Electrode 66 DC power supply 68 Carbon dioxide removal Tank 71 Degassing gas cylinder 73, 82 Transport pipe 74 Injection pump 79 Tank 80 Fine powder tank

Claims (19)

[Claims] 1. A nuclear power plant, wherein a material made of an element that is less likely to become radioactive due to activation by neutrons is used as a core structural material in a high neutron irradiation field. 2. A material comprising an element which is less likely to become radioactive due to activation by neutrons when the corrosion product is introduced into a nuclear reactor, as a structural material constituting a corrosion product generation site. A nuclear power plant characterized by being used. 3. A nuclear power plant, wherein a chemical species composed of an element that rarely becomes radioactive by activation by neutrons is used as a chemical species added to reactor water for the purpose of water quality control. 4. An element that is less likely to become radioactive by activation by neutrons is Be, C, Si, P, S, Ca,
The nuclear power plant according to any one of claims 1 to 3, wherein the nuclear power plant is at least one element selected from the group consisting of Ti, Re, Pt, Tl, Pb, and Bi. 5. A nuclear power plant, characterized in that as a core structure material in a high neutron irradiation field, a material made of an element having a reduced proportion of isotopes that become radioactive by activation by neutrons is used. 6. As a structural material constituting a site where a corrosion product is generated, when the corrosion product is brought into a nuclear reactor, the proportion of an isotope element which becomes radioactive by activation by neutrons is reduced. A nuclear power plant characterized by using a material made of different elements. 7. A chemical species to be added to reactor water for the purpose of water quality control, wherein a chemical species composed of an element having a reduced proportion of an isotope element which becomes radioactive by activation by neutrons is used. Nuclear power plant. 8. The element in which the proportion of the isotope element which becomes radioactive by activation by neutrons is reduced to Li, B, M
g, V, Cr, Fe, Ni, Zn, Ge, Se, Sr,
Zr, Mo, Ru, Pd, Cd, Sn, Sb, Te, B
a, La, Nd, Sm, Er, Yb, Δf, W, Os,
The nuclear power plant according to any one of claims 5 to 7, wherein the nuclear power plant is at least one element selected from the group consisting of Ηg. 9. In the core structural material, a material made of an element that is less likely to become radioactive by activation by neutrons or a material that has a reduced proportion of isotope elements that become radioactive by activation by neutrons is used, 6. The nuclear power plant according to claim 1, wherein a coating layer having a constant thickness is formed from a surface in contact with the liquid. 10. The nuclear power plant according to claim 9, wherein the thickness of the coating layer in the core structural material is 5 mm. 11. The core structure material, wherein the coating layer is formed by a combination of at least one of laser cladding, plating, dry plating, thermal spraying, ion implantation, and lining. The nuclear power plant according to claim 9 or 10, wherein: 12. As a structural material at a site where the corrosion product is generated, the proportion of an element that is less likely to become radioactive by activation by neutrons or a proportion of an isotope element that becomes radioactive by activation by neutrons is reduced. 7. The nuclear power plant according to claim 2, wherein a coating layer having a constant thickness is formed from a surface of the liquid by using a material made of an element. 13. The nuclear power plant according to claim 12, wherein the thickness of the coating layer in the structural material at the site where the corrosion product is generated is 2 mm. 14. In the structural material at the site where the corrosion product is generated, the coating layer is formed by combining one or more of laser cladding, plating, dry plating, thermal spraying, ion implantation, and lining. 14. The image forming device according to claim 12, wherein
Nuclear power plant as described. 15. A chemical species consisting of an element that is less likely to become radioactive by activation by neutrons or an element in which the proportion of isotopes that become radioactive by activation by neutrons is reduced to a simple metal, an oxide, or the like. , Hydroxides, hydrides,
The nuclear power plant according to claim 3 or 7, wherein a compound containing one or both of hydrogen containing metal salt and oxygen is used as a starting material and used in a slurry state or a solution state. 16. An element generator for generating a chemical species comprising an element which is less likely to become radioactive by activation by neutrons or an element having a reduced proportion of isotopes which become radioactive by activation by neutrons is provided. The nuclear power plant according to claim 3, wherein the nuclear power plant is provided. 17. The method according to claim 17, wherein the element generator is configured to convert an element that is less likely to become radioactive by activation with neutrons or an element that reduces the proportion of an isotope element that becomes radioactive by activation with neutrons into a simple metal, Oxides, hydroxides, hydrides, compounds containing one or both of hydrogen and oxygen, including metal salts, through which water is passed through high-temperature water to obtain a predetermined ion concentration by a corrosion release reaction 17. The nuclear power plant according to claim 16, wherein the nuclear power plant is configured. 18. An element injection device for injecting a chemical species consisting of an element that is less likely to become radioactive by activation by neutrons or an element in which the proportion of isotopes that become radioactive by activation by neutrons is reduced. The nuclear power plant according to claim 3, wherein the nuclear power plant is provided. 19. The element implantation apparatus according to claim 1, wherein the element that is less likely to become radioactive due to activation by neutrons or the element in which the proportion of the isotope element that becomes radioactive due to activation by neutrons is reduced to a simple metal, Oxides, hydroxides, hydrides, compounds containing one or both of hydrogen and oxygen, including metal salts, in the form of a slurry or a solution, are injected by a pump and added, and 19. The nuclear power plant according to claim 18, wherein the plant is configured to obtain a concentration.