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 . A method for suppressing corrosion of carbon steel, comprising the steps of:
 adsorbing iron (II) ions on a surface of a carbon steel members composing a nuclear power plant; and   forming a ferrite film on said surface of said carbon steel members by oxidizing the absorbed iron (II) ions.   
   
   
       2 . The method for suppressing corrosion of carbon steel according to  claim 1 , wherein the formation of said ferrite film is performed under a temperature condition from 60° C. to 100° C. 
   
   
       3 . A method for suppressing corrosion of carbon steel, comprising the steps of:
 contacting a first chemical including iron (II) ions, a second chemical for oxidizing at least one part of the iron (II) ions to iron (III) ion, and a third chemical for adjusting pH of a solution including the first chemical and the second chemical to be 5.5 to 9.0 with a surface of a carbon steel members composing a nuclear power plant, and forming a ferrite film on the surface.   
   
   
       4 . The method for suppressing corrosion of carbon steel according to  claim 3 , wherein the first chemical contains nickel ions. 
   
   
       5 . The method for suppressing corrosion of carbon steel according to  claim 3 , wherein the first chemical is formic acid including the iron (II) ions. 
   
   
       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. 
   
   
       7 . The method for suppressing corrosion of carbon steel according to  claim 3 , 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 3 , wherein the third chemical is hydrazine. 
   
   
       9 . The method for suppressing corrosion of carbon steel according to  claim 3 , wherein the formation of the 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 3 , 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:
 comprising the steps of preparing a second chemical that oxidizes at least one part of iron (II) ions into iron (III) ion, a third chemical that contains nickel ion,   contacting a first chemical including iron (II) ions, a second chemical for oxidizing at least one part of the iron (II) ions to iron (III) ion, a third chemical including nickel ion, and a forth 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 with a surface of a carbon steel members composing a nuclear power plant, and   forming a ferrite film on the surface.   
   
   
       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 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 . A ferrite film formation apparatus for the method of suppressing corrosion of carbon steel members comprising;
 a surge tank for storing processing solution,   a circulation pump for sucking the processing solution from the surge tank;   a processing solution supply pipe for supplying the processing solution exhausted from the circulation pump to piping that the film is to be formed;   a first chemical tank for storing iron (II) ions to be added to the processing solution that flows through the processing solution supply pipe;   a second chemical tank for storing oxidizing agent to be added to the processing solution;   a third chemical tank for storing a pH adjustment agent to adjust pH of the processing solution in the range of 5.5 to 9.0;   a processing solution return pipe for returning the processing solution from the piping to the surge tank; and   a heating apparatus for heating the processing solution to a temperature of 60° C. to 100° C.   
   
   
       18 . The ferrite film formation apparatus according to  claim 17 , wherein a fourth chemical tank for storing nickel ions is provided. 
   
   
       19 . The ferrite film formation apparatus according to  claim 17 , wherein the first chemical tank stores a chemical including the iron (II) ions prepared by dissolving iron in formic acid. 
   
   
       20 . A method for suppressing deposit of radionuclide onto carbon steel members composing a nuclear power plant comprising the steps of:
 preparing a first chemical including iron (II) ions, a second chemical for oxidizing the iron (II) ions into iron (III) ion, and a third chemical for adjusting pH;   mixing the first chemical and the second chemical under a temperature condition of ordinary temperature to 100° C.;   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 and the second chemical and the third chemical; and   forming a ferrite film on the surface of the carbon steel members by using the processing solution.   
   
   
       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 ferrite film.   
   
   
       22 . The method for suppressing deposit of radionuclide 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 radionuclide 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 radionuclide onto carbon steel members composing a nuclear power plant according to  claim 20 , wherein the first chemical is prepared by solving iron in formic acid. 
   
   
       25 . The method for suppressing deposit of radionuclide onto the carbon steel members composing a nuclear power plant according to  claim 21 , wherein the formation of the ferrite film is carried out after in 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 radionuclide onto carbon steel members composing a nuclear power plant, comprising the steps of
 preparing a first chemical including iron (II) ions prepared by dissolving iron in organic acid, a second chemical for oxidizing the iron (II) ions into iron (III) ion, and a third chemical for adjusting pH;   mixing the first chemical and the second chemical under a temperature condition of ordinary temperature to 100° C.;   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 and the second chemical and the third chemical; and   forming a ferrite film on the surface of the carbon steel members by using the processing solution.   
   
   
       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 . A apparatus for forming ferrite film onto the surface of carbon steel members in the pipings of a nuclear power plant, comprising
 a surge tank for storing processing solution;   a circulation pump for sucking the processing solution from the surge tank;   a processing solution supply pipe for supplying the processing solution exhausted from the circulation pump and transfers the processing solution to piping that the film is to be formed;   a first chemical tank for storing iron (II) ions to be added to the processing solution that flows through the processing solution supply pipe;   a second chemical tank for storing oxidizing agent to be added to the processing solution;   a third chemical tank for storing a pH adjustment agent to adjust pH of the processing solution in the range of 5.5 to 9.0,   a processing solution return pipe for returning the processing solution from the pipes that require film formation to the surge tank; and   a heating apparatus for heating the processing solution to a temperature of 60° C. to 100° C.,   wherein the position for injecting the third chemical into the processing solution is provided inside the reactor containment vessel.