Decontamination of radioactively contaminated scrap metals from discs

Abstract

A decontamination method and system wherein contaminated nickel anodes are obtained by cutting cylindrical nickel ingots into wafers having a disc shape. Each of the disc-shaped wafers is then used as the anode in an electro-refining process. The anode is dissolved in the process, thereby generating nickel ions and pertechnetate ions in solution. The anolyte chamber of the electro-refining cell is in fluid communication with a technetium trap that removes pertechnetate ions from solution. The wafer anode is of substantially pure nickel that has typically been cut from a larger cylindrical ingot to a thickness of approximately 2.5 inches.

What is claimed is:  
     
         1 . A method of removing technetium from a contaminated metal comprising: 
 providing a disc-shaped metal wafer as an anode in an electro-refining cell having a cathode and an anolyte solution; and    energizing the anode and cathode to dissolve the anode and deposit metal dissolved from the anode upon the cathode.    
     
     
         2 . The method of  claim 1  further comprising the operation of cutting one or more disc-shaped wafers from a contaminated metal ingot.  
     
     
         3 . The method of  claim 1  further comprising selectively preventing pertechnetate ions from collecting upon the cathode.  
     
     
         4 . The method of  claim 3  wherein pertechnetate ions are selectively prevented from collecting upon the cathode by cationic membrane filtering.  
     
     
         5 . The method of  claim 1  further comprising the operation of flowing said anolyte solution through a technetium trap outside of said electro-refining cell to remove pertechnetate ions from the anolyte solution.  
     
     
         6 . The method of  claim 5  wherein the anolyte solution is flowed through the technetium trap by a fluid pump.  
     
     
         7 . The method of  claim 5  further comprising the operation of flowing the anolyte solution through a particulate filter to remove particulate matter.  
     
     
         8 . The method of  claim 5  wherein the technetium trap comprises an electrolytic cell that collects technetium upon a second cathode.  
     
     
         9 . The method of  claim 1  wherein the metal comprises nickel.  
     
     
         10 . A method of decontaminating a cylindrical metal ingot contaminated with technetium comprising: 
 cutting an ingot to provide one or more disc-shaped wafers;    providing one of said wafers as an anode in an electro-refining cell having an anolyte solution, and a cathode chamber containing a catholyte solution with a cathode disposed therein;    dissolving the anode within the anolyte solution; and    depositing metal dissolved from the anode upon the cathode.    
     
     
         11 . The method of  claim 10  further comprising the operation of filtering technetium from the anolyte solution.  
     
     
         12 . The method of  claim 11  wherein the operation of filtering technetium from the anolyte solution comprises flowing the anolyte solution outside of the electro-refining cell, through a technetium trap to remove pertechnetate ions from solution, and then returning the anolyte solution to the electro-refining cell.  
     
     
         13 . The method of  claim 11  wherein the operation of filtering technetium from the anolyte solution comprises filtering out pertechnetate ions through a cationic membrane.  
     
     
         14 . The method of  claim 10  wherein the cathode comprises a rectangular plate.  
     
     
         15 . The method of  claim 10  further comprising the operation of securing the wafer anode to a supporting header plate by welding.  
     
     
         16 . The method of  claim 10  wherein the operation of depositing metal dissolved from the anode further comprises transmitting metal ions through the catholyte solution to the cathode.  
     
     
         17 . A method for removing technetium from nickel and other transition metals comprising: 
 providing substantially pure nickel in the form of a substantially cylindrical ingot;    cutting at least one disc-shaped wafer from the ingot;    providing said wafer as an anode in an electro-refining cell having a cathode and an anolyte solution;    dissolving the anode within the anolyte solution; and    depositing metal dissolved from the anode upon the cathode.    
     
     
         18 . The method of  claim 17  wherein the ingot is formed by molding and cooling of the ingot from the radial outer surface and progressing radially inwardly.  
     
     
         19 . The method of  claim 16  further comprising the operation of removing technetium from the anolyte solution by transmitting the anolyte solution through a technetium trap.  
     
     
         20 . The method of  claim 17  wherein the operation of depositing metal upon the cathode further comprises transmitting metal ions from the anolyte solution to a catholyte solution through a membrane.