Method and apparatus for suppressing corrosion of carbon steel, method for suppressing deposit of radionuclide onto carbon steel members composing a nuclear power plant, and film formation apparatus

Abstract

The present invention is a method for suppressing corrosion of carbon steel members composing a nuclear power plant. That is, the processing solution contains a chemical including iron (II) ions, an oxidizing agent for oxidizing at least one part of the iron (II) ions into iron (III) ion, and a pH adjustment agent for adjusting pH. The pH of the processing solution is adjusted in the range of 5.5 to 9.0 by the pH adjustment agent. The processing solution is introduced into a purifying system pipe having the carbon steel members. The iron (II) ions are adsorbed on an inner surface of the purifying system pipe, namely, a surface of the carbon steel members. The ferrite film is formed on the surface of the carbon steel members by oxidizing the absorbed iron (II) ions. Therefore, corrosion of the carbon steel members is suppressed by the ferrite film.

1 .- 3 . (canceled) 
   
   
       4 . A method for suppressing corrosion of carbon steel, comprising the steps of:
 preparing a solution having a first chemical including iron (II) ions and nickel ions, a second chemical for oxidizing at least one part of the iron (II) ions to iron (III) ions, and a third chemical for adjusting the pH of a solution including the first chemical and the second chemical to be 5.5 to 9.0; and   contacting the solution with a surface of carbon steel members composing a nuclear power plant, in a state of shutdown of the nuclear power plant, sufficiently for a nickel ferrite film to form on the surface in the state of the shutdown of the nuclear power plant.   
   
   
       5 . (canceled) 
   
   
       6 . The method for suppressing corrosion of carbon steel according to  claim 4 , wherein the first chemical is formic acid including the iron (II) ions and the nickel ions. 
   
   
       7 . The method for suppressing corrosion of carbon steel according to  claim 4 , wherein the second chemical contains at least one of hydrogen peroxide solution, oxygen, and ozone. 
   
   
       8 . The method for suppressing corrosion of carbon steel according to  claim 4 , wherein the third chemical is hydrazine. 
   
   
       9 . The method for suppressing corrosion of carbon steel according to  claim 4 , wherein the formation of the nickel ferrite film is performed under a temperature condition from 60° C. to 100° C. 
   
   
       10 . The method for suppressing corrosion of carbon steel according to  claim 4 , wherein a gas portion of a tank for storing the first chemical is purged with inert gas. 
   
   
       11 . A method for suppressing corrosion of carbon steel, comprising the steps of:
 preparing a second chemical that oxidizes at least one part of iron (II) ions into iron (III) ions, and a third chemical that contains nickel ions,   preparing a solution having a first chemical including iron (II) ions, the second and third chemicals, and a fourth chemical for adjusting pH of a solution including the first chemical, the second chemical and the third chemical to be 5.5 to 9.0; and   contacting the solution with a surface of carbon steel members composing a nuclear power plant in a state of shutdown of the nuclear power plant, sufficiently for a nickel ferrite film to form on the surface in the state of shutdown of the nuclear power plant.   
   
   
       12 . The method for suppressing corrosion of carbon steel according to  claim 11 , wherein the first chemical is formic acid including the iron (II) ions. 
   
   
       13 . The method for suppressing corrosion of carbon steel according to  claim 11 , wherein the second chemical contains at least one of hydrogen peroxide solution, oxygen, and ozone. 
   
   
       14 . The method for suppressing corrosion of carbon steel according to  claim 11 , wherein the fourth chemical is hydrazine. 
   
   
       15 . The method for suppressing corrosion of carbon steel according to  claim 11 , wherein the formation of the nickel ferrite film is performed under a temperature condition from 60° C. to 100° C. 
   
   
       16 . The method for suppressing corrosion of carbon steel according to  claim 11 , wherein the gas portion of a tank for storing the first chemical is purged with inert gas. 
   
   
       17 .- 19 . (canceled) 
   
   
       20 . A method for suppressing deposit of radionuclides onto carbon steel members composing a nuclear power plant, comprising the steps of:
 preparing a first chemical including iron (II) ions and nickel ions, a second chemical for oxidizing the iron (II) ions into iron (III) ions, and a third chemical for adjusting pH, in a state of shutdown of the nuclear power plant;   mixing the first chemical and the second chemical under an ordinary temperature condition of 100° C., in the state of shutdown of the nuclear power plant;   preparing a processing solution whose pH is adjusted in the range of pH 5.5 to pH 9.0 by mixing the mixture including the first chemical, the second chemical, and the third chemical in the state of shutdown of the nuclear power plant; and   forming a nickel ferrite film on the surface of the carbon steel members by using the processing solution, in the state of the shutdown of the nuclear power plant.   
   
   
       21 . The method for suppressing deposit of radionuclide onto carbon steel members composing a nuclear power plant according to  claim 20 , further comprises a step of:
 removing contaminants including oxide films from the surface of the carbon steel members before forming the nickel ferrite film, in the state of the shutdown of the nuclear power plant.   
   
   
       22 . The method for suppressing deposit of radionuclides onto carbon steel members composing a nuclear power plant according to  claim 21 , wherein removal of the contaminant is performed by a chemical decontamination containing at least one reducing removal. 
   
   
       23 . The method for suppressing deposit of radionuclides onto carbon steel members composing a nuclear power plant according to  claim 20 , wherein the position to inject the third chemical into the mixture is inside the reactor containment vessel. 
   
   
       24 . The method for suppressing deposit of radionuclides onto carbon steel members composing a nuclear power plant according to  claim 20 , wherein the first chemical is a formic acid solution including the iron (II) ions and the nickel ions. 
   
   
       25 . The method for suppressing deposit of radionuclides onto the carbon steel members composing a nuclear power plant according to  claim 21 , wherein the formation of the nickel ferrite film is carried out after a period between the finish of removal of the contaminants and the start of the operation of the nuclear power plant. 
   
   
       26 . A method for suppressing deposit of radionuclides onto carbon steel members composing a nuclear power plant, comprising the steps of
 preparing a first chemical including iron (II) ions and nickel ions prepared by dissolving iron and nickel in organic acid, a second chemical for oxidizing the iron (II) ions into iron (III) ions, and a third chemical for adjusting pH, in a state of shutdown of the nuclear power plant;   mixing the first chemical and the second chemical under an ordinary temperature condition of 100° C., in the state of shutdown of the nuclear power plant;   preparing a processing solution whose pH is adjusted in the range of pH 5.5 to pH 9.0 by mixing the mixture including the first chemical, the second chemical, and the third chemical, in the state of shutdown of the nuclear power plant; and   forming a nickel ferrite film on the surface of the carbon steel members by using the processing solution, in the state of shutdown of the nuclear power plant.   
   
   
       27 . The method for suppressing deposit of radionuclide onto carbon steel members composing a nuclear power plant according to  claim 26 , wherein the organic acid is formic acid. 
   
   
       28 . (canceled)