Method for protecting components of a primary system of a boiling water reactor in particular from stress corrosion cracking

Abstract

A method for protecting the components of the primary system of a boiling water reactor, especially against stress cracking corrosion, includes feeding a reducing agent into the primary coolant in order to reduce the number of substances having a oxidizing effect or in order to modify the electrochemical potential of the component surfaces covered with an oxide layer to negative values. An alcohol that can be oxidized in the conditions of a reactor is fed in as a reducing agent, preferably in a liquid form, into the primary coolant. The component surfaces are provided with a blank coating or a single intrinsic oxide coating.

1 - 7 . (canceled)  
   
   
       8 : A method for protecting a primary system of a boiling water reactor having a pressure vessel and a feedwater line opening out into the pressure vessel, the method comprising: 
 continuously feeding methanol into a primary coolant to maintain a methanol concentration of from 0.1 to 300 μmol/kg in a downcomer, the downcomer extending downward at an opening of the feedwater line.    
   
   
       9 : The method as recited in  claim 8  wherein the methanol concentration is maintained at 0.1 to less than 10 mol/kg in the downcomer.  
   
   
       10 : The method as recited in  claim 8  wherein the feeding occurs via the feedwater line.  
   
   
       11 : The method as recited in  claim 8  wherein the pressure vessel is covered with a native oxide layer during the feeding.  
   
   
       12 : The method as recited in  claim 8  further comprising doping the pressure vessel with a precious metal.  
   
   
       13 : The method as recited in  claim 12  wherein the precious metal is platinum.  
   
   
       14 : The method as recited in  claim 8  further comprising doping a section of the reactor using a precious metal.  
   
   
       15 : The method as recited in  claim 14  further comprising reducing the methanol concentration as a function of the doping.  
   
   
       16 : The method as recited in  claim 8  wherein the methanol is fed while in a liquid phase.  
   
   
       17 : A method for protecting a primary system of a boiling water reactor having a pressure vessel and a feedwater line opening out into the pressure vessel, the method comprising: 
 doping the reactor with a precious metal; and    continuously feeding an alcohol into a primary coolant to establish a desired concentration, the desired concentration being reduced as a function of the doping.    
   
   
       18 : The method as recited in  claim 17  wherein the alcohol is methanol.  
   
   
       19 : The method as recited in  claim 17  wherein the continuously feeding maintains an alcohol concentration of from 0.1 to 300 μmol/kg in a downcomer, the downcomer extending downward at an opening of the feedwater line.  
   
   
       20 : The method as recited in  claim 19  wherein the alcohol concentration is maintained at 0.1 to less than 10 μmol/kg in the downcomer.  
   
   
       21 : The method as recited in  claim 19  wherein the pressure vessel is covered with a native oxide layer maintained during the feeding.  
   
   
       22 : A method for protecting a primary system of a boiling water reactor having a pressure vessel and a feedwater line opening out into the pressure vessel, the method comprising: 
 continuously feeding a protecting liquid consisting essentially of an alcohol into the primary system.    
   
   
       23 : The method as recited in  claim 20  wherein the alcohol is methanol.  
   
   
       24 : The method as recited in  claim 20  wherein the continuously feeding maintains an alcohol concentration of from 0.1 to 300 μmol/kg in a downcomer, the downcomer extending downward at an opening of the feedwater line.  
   
   
       25 : The method as recited in  claim 24  wherein the methanol concentration is maintained at 0.1 to less than 10 μmol/kg in the downcomer.  
   
   
       26 : The method as recited in  claim 25  wherein the pressure vessel is covered with a native oxide layer during the feeding.