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Reduction of the radiotoxicity of high level radioactive waste (Partitioning)

Partitioning

 

The long-term potential danger of high level radioactive waste may be significantly reduced by the separation of long-lived radionuclides (Partitioning) and fission of those nuclides in special reactors into shorter lived or stable products (Transmutation). In addition to the technical realization of transmutation, selective separation of the minor actinide elements from high level radioactive waste presents a special challenge in nuclear chemistry research.

The main focus of work at KIT-INE in this sector lies in the separation of americium and curium from the lanthanide elements (fission products). Due to the chemical similarity of these element groups (trivalent 4f-/5f-element ions with similar ion radii), high demands are placed on the selective extractants used.

 

Activities cover the following areas:

 

Synthesis of new N Donor-extractants

None of the selective partitioning extractants presently internationally discussed fulfill all demands for technical application. Therefore, extraction ligands with potentially improved qualities are designed, synthesized and characterized.

 

Identification and understanding the selectivity

To target optimization of improved extraction ligands, the reason behind the selectivity for actinides over lanthanides of extraction ligands at a molecular level must be understood. We carry out investigations into the structure and speciation of actinide-and lanthanide complexes in solution. The experimental program primarily consists of EXAFS, TRLFS and NMR investigations, supported by quantum-chemical calculations.

 

Process development

To evaluate the process suitability of new extraction ligands, continuous tests are carried out in a hollow fiber-microplant. Based on equilibrium and kinetic data of the extraction system, process-flow sheets are calculated.