Technetium (Tc), an artificial radioactive element, makes up about 6% of the fission products in spent nuclear fuel. The PUREX process is used to separate uranium and plutonium from other fission products. However, Tc is co-extracted with these actinides, requiring an additional stripping step. In this stage, a stabilizing agent, hydrazinium nitrate (NH), is used, but due to its toxicity and CMR classification (Carcinogenic, Mutagenic, Reprotoxic), it is being replaced by less toxic alternatives such as oximes. Although promising, oximes exhibit slower stripping kinetics compared to NH. In the context of the PUMAS process, this thesis aims to understand the complex redox mechanisms of Tc and the kinetic differences between oximes and NH. The PhD student will study the reduced forms of Tc and analyze the reduction kinetics in the presence of U(IV) and anti-nitrous agents. A methodology will be developed to characterize the oxidation states of Tc, and reaction rate constants will be determined as a function of temperature and reactant concentrations.
The candidate will work closely with the supervising team to develop autonomy, adaptability, and the ability to propose innovative ideas. By the end of this journey, the candidate will have gained not only advanced technical skills but also abilities in project management, collaborative work, and scientific writing and communication. These competencies will provide strong prospects for a career in academic research or industry.