Method for Depositing Noble Metal to Carbon Steel Member of Nuclear Power Plant and Method for Suppressing Radionuclide Deposition on Carbon Steel Member of Nuclear Power Plant

Abstract

A film forming apparatus is connected to a carbon steel purification system piping of a BWR plant (S1). Formic acid (surface purification agent) is injected into a circulation piping of the film forming apparatus (S4). A surface purification agent aqueous solution containing 30000 ppm of formic acid is contacted with the inner surface of the purification system piping, and a large amount of Fe²⁺ is dissolved from the purification system piping, and a large amount of electrons are generated by this dissolution. Thereafter, a formic acid Ni aqueous solution is injected into the surface purification agent aqueous solution to produce a film forming aqueous solution (S5). The film forming aqueous solution storing the electrons is contacted with the inner surface of the purification system piping, and Ni ions incorporated into the inner surface are reduced by the electrons, and a Ni metal film is formed on the inner surface. Platinum ions and a reducing agent are injected into the circulation piping (S9, S10), and an aqueous solution containing the platinum ions and the reducing agent is supplied to the purification system piping to deposit platinum on the surface of the Ni metal film.

Description

CLAIM OF PRIORITY[0001]The present application claims priority from Japanese Patent application serial No. 2019-019704, filed on Feb. 6, 2019, the content of which is hereby incorporated by reference into this application.BACKGROUND OF THE INVENTION1. Field of the Invention[0002]The present invention relates to a method for depositing a noble metal on a carbon steel member of a nuclear power plant and a method for suppressing radionuclide deposition on a carbon steel member of a nuclear power plant, and more particularly, to a method for depositing a noble metal on a carbon steel member of a nuclear power plant and a method for suppressing radionuclide deposition on a carbon steel member of a nuclear power plant, suitable for application in a boiling water type nuclear power plant.2. Description of Related Art[0003]The nuclear power plant such as, for example, a boiling water type nuclear power plant (hereinafter referred to as a BWR plant) and a pressurized water nuclear power plan...

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Benefits of technology

[0018]According to the first noble metal deposition method and the second noble metal deposition method, dissolution of iron ions from the carbon steel member is increased by the action of the surface purification agent, and the amount of electrons generated with the increased dissolution of iron ions is also increased, and accordingly, the substitution reaction between the iron (II) ions and the nickel ions contained in the film forming solution is promoted, and the amount of nickel ions incorporated into the surface of the carbon steel member is increased. The nickel ions incorporated into the surface of the carbon steel member are reduced by the electrons mentioned above into a nickel metal. For this reason, the formation of the nickel metal film on the surface of the carbon steel member is promoted, and the time required for forming the nickel metal film is remarkably shortened.

[0019]The object described above can also be achieved by a method for suppressing the deposition of radionuclides on a carbon steel member of a nuclear power plant, which, after the first noble metal deposition method or the second noble metal deposition method is performed to form the nickel metal film on the surface of the carbon steel member, contacts oxygen-containing water of a temperature range of 130° C. or more and 330° C. or less with the surface of the nickel metal film on which a noble metal is deposited.

[0020]Since the nickel metal film can be converted into a stable nickel ferrite film by contacting oxygen-containing water having a temperature range of 130° C. or more and 330° C. or less with the surface of the nickel metal film on which the noble metal is deposited, the surface of the carbon steel member is further covered with the stable nickel ferrite film, and deposition of radionuclides on the carbon steel member can further be suppressed over a long period of time.

[0021]According to the present invention, the time required for forming a nickel metal film on the surface of a carbon steel member of a nuclear power plant can be shortened.

Problems solved by technology

However, despite the corrosion prevention measures described above, there are traces of metal impurities inevitably present in the reactor water, and some of the metal impurities are deposited as metal oxides on the outer surface of the fuel rod contained in the fuel assembly.

However, the radionuclide that has not been removed accumulates on the surface of the structural member in contact with the reactor water while circulating in the recirculation system together with the reactor water.

As a result, radiation is emitted from the surface of the structural member, which causes radiation exposure of workers during regular inspection work.

However, in recent years, with this specified value lowered, it is necessary to make the exposure dose of each person as low as economically possible.

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