Actinide production

Abstract

The invention provides a process for reducing to metallic form oxides of uranium, or metals more noble than uranium, present in spent nuclear fuel comprising a mixture of metal oxides, the process comprising cathodically electrolysing the oxide in the presence of a molten salt electrolyte, the potential of the cathode being controlled so as to favour oxygen ionisation over deposition of the metal from the cations present in the molten salt, and to ensure than reduction of metals other than uranium or metals more noble than uranium does not occur. The invention allows for the reduction of uranium or metals more than uranium present in spent nuclear fuel comprising mixed metal oxides to a metallic form by the use of a single electrochemical process, with oxygen being produced as the only by-product.

1 . A process for reducing to metallic form oxides of uranium, or metals more noble than uranium, present in spent nuclear fuel comprising a mixture of metal oxides, comprising: 
 cathodically electrolysing the metal oxides in the presence of a molten salt electrolyte; and    controlling the potential of a cathode so as to favour oxygen ionisation over deposition of the metal from the cations present in the molten salt, and to ensure that reduction of metals other than uranium or metals more noble than uranium does not occur.    
     
     
         2 . A process according to  claim 1  wherein the metal oxides comprise fuel pellets which include uranium oxide, irradiated uranium oxide and/or of mixed uranium/plutonium oxide.  
     
     
         3 . A process according to  claim 2  wherein the uranium oxide comprises uranium dioxide.  
     
     
         4 . A process according to  claim 1  wherein the metal oxides are located in a mesh basket which forms the cathode.  
     
     
         5 . A process according to  claim 1  wherein the molten salt electrolyte comprises at least one chloride salt.  
     
     
         6 . A process as claimed in  claim 5  wherein the chloride salt is CaCl 2  or BaCl 2 .  
     
     
         7 . A process according to  claim 1  wherein an anode is a carbon anode.  
     
     
         8 . A process according to  claim 1  wherein the fuel is treated together with its cladding.  
     
     
         9 . A process according to  claim 8  wherein the cladding is removed from the fuel prior to treatment.  
     
     
         10 . A process according to  claim 1  wherein a metal/metal oxide mixture resulting from the process is used as the feed for an electrorefining process.  
     
     
         11 . A process according to  claim 1  wherein the potential applied during the electrorefining process is such that only uranium metal enters the salt.  
     
     
         12 . A process according to  claim 11  wherein the electrorefining process is carried out in the same electrolytic cell as an electrolytic reduction process.