Conditioning and characterization of ionic liquid waste streams in nuclear research applications

SCK•CEN Mentor

Van de Voorde Michiel, mvdvoord@sckcen.be, +32 (0)14 33 31 07

Expert group

Radiochemistry

SCK•CEN Co-mentor

Zsabka Peter, pzsabka@sckcen.be, +32 (0)14 33 32 14

Introduction

Reprocessing of spent nuclear fuel is an important step in closing the nuclear fuel chain. Recovered uranium and plutonium can be used in mixed-oxide (MOX) fuel and re-enters the fuel cycle in the current generation of light water reactors. Advanced reprocessing strategies are being studied to further separate the minor actinides (MAs) to reduce the long-term radiotoxicity of the raffinate. Over the last few years, ionic liquids (ILs) have found their way into spent nuclear fuel reprocessing research. ILs are frequently regarded as safer alternatives to organic solvents in solvent extraction processes because of their negligible vapour pressure, low flammability and high thermal and chemical stability. However, no universally applicable method exists to condition radioactive IL waste streams for safe disposal so far. Conventional incineration is often impossible because of the formation of harmful compounds. Hence, solidification followed by super-compaction and permanent storage is the only remaining option.

Objective

The objective of this project is to elaborate and optimize a cementation method to solidify radioactive IL waste and assure its reproducibility and durability. The use of additives on the homogenization process will be studied. The addition of water, surfactants (e.g. superplasticizers) or other additives to the ionic liquid-cement mixture might enhance uniform cementation. Every mixture will be evaluated by small-scale super-compaction tests, in which any free-flowing liquid will be determined. In addition, the leachability of the ionic liquid from the final cement mixture will be studied by means of dynamic and static leaching methods. Any loss of ionic liquid will be quantified by total organic compound (TOC) analysis. After all, it must be ensured that no ionic liquid is released in case the mixture is contacted with water. The solidified samples will be analysed by different available techniques (e.g. UV-Vis and IR spectroscopy) to study the chemical and physical interactions between the IL and the cement matrix.

The minimum diploma level of the candidate needs to be

Academic bachelor , Professional bachelor

The candidate needs to have a background in

Chemistry