Suppression method of radionuclide deposition on reactor component of nuclear power plant and ferrite film formation apparatus

Abstract

A method of suppressing deposition of radionuclides on components of a nuclear power plant comprises forming a ferrite film by contacting a first chemical including iron (II) ions, a second chemical for oxidizing the iron (II) ions to iron (III) ions, and a third chemical for adjusting the pH of a processing solution containing a mixture of the first and second chemicals to be 5.5 to 9.0 with the metal member surface in a time period from a finishing stage in decontamination step of removing contaminants formed on the surface of metal member composing the nuclear power plant, and suppressing deposition of radionuclides on the metal member by the ferrite film.

1 . A method of suppressing deposition of radionuclides on components of a nuclear power plant, comprising the steps of: 
 adsorbing iron (II) ions on a surface of a metal member composing the nuclear power plant;    forming a ferrite film by oxidizing the adsorbed iron (II) ions under the temperature condition from a normal temperature to 200° C.; and    suppressing deposition of the radionuclides on the metal member by the ferrite film.    
   
   
       2 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 1 , wherein the film formation processing of a ferrite film is conducted after removing contaminants including an oxide film deposited on the metal member surface.  
   
   
       3 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 2 , wherein removing processing of the contaminants is chemical decontamination repeating oxidative removing and reductive removing.  
   
   
       4 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 1 , wherein the film formation processing of a ferrite film is conducted under the temperature condition from 60° C. to 100° C.  
   
   
       5 . A method of suppressing deposition of radionuclides on components of a nuclear power plant comprising the steps of: 
 forming a ferrite film by contacting a first chemical including iron (II) ions, a second chemical for oxidizing the iron (II) ions to iron (III) ions, and a third chemical for adjusting the pH of a processing solution containing a mixture of the first and second chemicals to be 5.5 to 9.0 with the metal member surface in a time period from a finishing stage in decontamination step of removing contaminants formed on the surface of metal member composing the nuclear power plant; and    suppressing deposition of radionuclides on the metal member by the ferrite film.    
   
   
       6 . A method of suppressing deposition of radionuclides on components of a nuclear power plant comprising the steps of: 
 forming a ferrite film by contacting a first chemical including at least one of iron (II) ions and iron(III) ions, a second chemical for reducing the iron (III) ions, and a third chemical for adjusting the pH of a processing solution containing a mixture of the first and second chemicals to be 5.5 to 9.0 with the metal member surface in a time period from a finishing stage in decontamination step of removing contaminants formed on the surface of metal member composing the nuclear power plant; and    suppressing deposition of radionuclides on the metal member by the ferrite film.    
   
   
       7 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 5 , wherein the first chemical is a solution in which metal iron is dissolved in organic acid.  
   
   
       8 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 7 , wherein the first chemical is prepared by dissolving the metal iron in the solution containing organic acid to iron (II) ions after bubbling by inert gas or vacuum deaeration of said solution.  
   
   
       9 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 5 , wherein the first chemical is a solution in which iron carbonate is dissolved in carbonic water or organic acid.  
   
   
       10 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 5 , wherein inert gas is bubbled in at least one of a tank storing the first chemical, a tank storing the third chemical and a surge tank storing the processing solution.  
   
   
       11 . A method of suppressing deposition of radionuclides on components of a nuclear power plant according to  claim 6 , wherein the second chemical is ascorbic acid.  
   
   
       12 . An apparatus for forming a ferrite film on a surface of component composing a nuclear power plant, comprising: 
 a surge tank for storing a processing solution;    a recirculation pump sucking the processing solution in the surge tank;    processing solution supply piping for supplying the processing solution sucked by said recirculation pump to piping for film formation;    a first chemical tank for storing iron (II) ions injected into the processing solution in said processing solution piping;    a second chemical tank for storing oxidizer injected in the processing solution in said processing solution supply piping;    a third chemical tank for storing pH adjuster adjusting the pH of the processing solution in said processing solution supply piping to 5.5 to 9.0;    processing solution return piping for returning the processing solution returned from said piping for film formation to said surge tank; and    a heating means for heating the processing solution to be a temperature of 60-100° C.    
   
   
       13 . An apparatus for forming a ferrite film according to  claim 12 , wherein a chemical tank for oxidizer and reducer is fluidly communicated with said processing solution piping.  
   
   
       14 . An apparatus for forming a ferrite film according to  claim 13 , wherein an ion exchange resin tower and a mixed bed resin tower each for removing contaminants in the processing solution are inserted in said processing solution return piping.  
   
   
       15 . An apparatus for forming a ferrite film according to  claim 14 , wherein a filter for removing solid substances contained in the processing solution is installed in said processing solution supply piping or said piping for film formation.  
   
   
       16 . An apparatus for forming a ferrite film according to  claim 14 , wherein the oxidizer stored in said second chemical tank generates oxygen-containing bubbles in the solution.  
   
   
       17 . An apparatus for forming a ferrite film according to  claim 14 , wherein decomposition equipment for at least a part of organic acid and nitrogen compound contained in the processing solution in said processing solution return piping.  
   
   
       18 . An apparatus for forming a ferrite film according to  claim 17 , wherein said decomposition equipment is a decomposer employing at least one of active carbon catalyst, hydrogen peroxide, ultraviolet rays, and ozone.  
   
   
       19 . An apparatus for forming a ferrite film according to  claim 14 , wherein a chemical tank for storing noble metal or compound containing noble metal is connected to said processing solution supply piping.