PhD Defense | Bart Verlinden | Effect of ionizing radiation on solvent extraction systems for the separation of minor actinides | KU Leuven

Effect of ionizing radiation on solvent extraction systems for the separation of minor actinides

With the use of nuclear power, inevitably highly radiotoxic waste is produced. The irradiated nuclear fuel contains many different radionuclides which contribute to the radiotoxicity and heat production. The most determining elements for these undesired properties are the minor actinides and plutonium, which are the result of a combination of neutron absorption and radioactive decay processes. Historically, uranium and plutonium can be recovered from the used nuclear fuel and made into new nuclear fuel elements (Mixed Oxide (MOX) fuel). Nowadays, research is focusing on increasing resource efficiency and reducing the amount of nuclear waste to optimize the capacity of the highly expensive underground repositories. Minor actinides and plutonium are aimed to be burned in fast neutron Gen IV nuclear reactors. However, to be able to succeed in this closure of the fuel cycle, suitable separation processes are essential.

In the past, many hydrometallurgical solvent extraction processes were evaluated to achieve this goal. A new diglycolamide extractant, 2,2'-oxybis(N,N-di-n-decylpropanamide) (mTDDGA) was proposed to replace the current two extractants in a previously developed process with one. This means a huge simplification of the process, which on its turn reduces synthesis costs and the complexity of solvent regeneration. The challenges for using this single extractant are mainly situated in the plutonium loading capacity and fission product extraction. Early reported results are very promising and strongly motivate further in-depth study, which was conducted in this research. The focus of this doctoral thesis is on the radiolytic stability of mTDDGA, since ionizing radiation in nuclear fuel solutions causes degradation of the extractant.

Promotor:

• Koen Binnemans (KU Leuven)

• Thomas Cardinaels (KU Leuven)

SCK CEN mentors:

• Karen Van Hecke (SCK CEN)

• Marc Verwerft (SCK CEN)

Click here for a list of obtained PhD degrees.