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

Verlinden Bart


Binnemans Koen, (KULeuven), koen.binnemans@chem.kuleuven.be

SCK•CEN Mentor

Van Hecke Karen
+32 14 33 32 75

SCK•CEN Co-mentor

Verwerft Marc
+32 14 33 30 48

Expert group


PhD started


Short project description

During the last decades, significant scientific and technical progress was made in Europe for R&D on the selective extraction of minor actinides from spent fuel. The chemical similarity of the actinides and lanthanides and their unfavourable relative abundances in the PUREX Highly Active Raffinate (HAR) solution made this work really challenging. A lot of extractants and hydrometallurgical separation processes have been developed and extensively studied, first under impulse of the French and later on in the framework of European collaborative research (EU Framework Programmes 3-7). This work resulted in the technical demonstration (on laboratory scale) of several new processes like DIAMEX, SANEX, GANEX and EXAm which use mainly extractants of the following families: malonamides, diglycolamides (DGAs), bis-triazinyl-pyridine derivates (BTPs),… which are compliant with the CHON principle, i.e. they consist of only the elements C, H, N and O, and are thus completely incinerable at the end of life, which is important to keep the amounts of secondary waste as low as possible [1-3]. The expertise gathered in the FP3-7 projects and the results obtained at laboratory scale with genuine waste solutions are so encouraging that during the next years the R&D focus in this field will shift more and more towards aspects that are important for the future industrialization. One of the main aspects to be further elaborated is the effect on ionizing radiation on the extraction system, which is exposed to a high bèta/gamma radiation field and is in contact with alpha-emitters and acidic solutions. Therefore, complexing agents (ligands) together with the organic solvent should be reasonably stable against hydrolysis and radiolysis to allow long-term operation of the extraction system. Radiation degradation of the extraction system can affect the ligand concentration in the organic phase, produce interfering degradation products and affect physicochemical properties of the organic phase that influence the phase separation and/or flow characteristics [1,6]. Furthermore, the degradation of the solvent system usually also has an impact on the amounts of secondary waste that is produced. Possibilities for cleaning and recycling of the solvent system and options for the management of the secondary waste should also be investigated with regard to industrialization of the processes.


The aim of this project is to study the effect of ionizing radiation on extraction systems (ligand and organic solvent) used for selective extraction of minor actinides. The focus will be on SANEX and GANEX extraction systems selected in the frame of the past two EU FP7 projects ACSEPT and SACSESS [1-3].

The extraction systems will be irradiated in the gamma irradiation facilities of BR2 (Co-60 sources as well as spent fuel elements), with dose rates ranging from 1 Gy/h up to 50 kGy/h. In most currently available literature, only Co-60 irradiations were performed [4,5]. However, the gamma spectrum originating from spent fuel is more resembling the spectrum of a PUREX HAR solution and thus, more suitable to investigate radiolysis of the partitioning extraction systems. Furthermore, relatively high dose rates were used in most studies [2,3], while long-term irradiation at lower dose rates up to the same cumulative doses could have different effects.

The availability of BRIGITTE, RITA, CAL and GEUSE II for gamma irradiations offer a nice asset to perform a comparative study of the gamma irradiation effects caused by irradiations under different dose rates and with different gamma spectra. These irradiations can be performed on neat organic samples, samples pre-equilibrated with acid, samples in contact with the aqueous phase (acidic biphasic system) and on aerated as well as deaerated samples. This will enable us to investigate the influence of parameters such as dose rate, total cumulative dose, contact with aqueous phase and contact with oxygen, on the extraction behaviour.

Distribution ratios of minor actinides and europium (as representative for the trivalent lanthanides) will be evaluated before and after irradiation to assess the effect of radiation on extraction characteristics. Distribution ratios will be determined using ICP-MS, alpha and gamma spectrometry. Extraction experiments will be done on tracer level amounts up to experiments with (diluted) genuine spent fuel solutions, which are available from burn-up determinations on spent fuels. The first extraction studies will be directed towards radiotracers of americium, curium, and europium respectively, because they can be easily measured by gamma spectrometry.

The decomposition of the extraction systems will be evaluated using multiple techniques such as NMR,  HPLC-ESI-MS and HPLC-DAD (diode array detector).

This project is subdivided in four work packages (WPs).

WP1: Irradiation of selected solvent extraction systems under various conditions and analysis of the extraction system degradation (analysis of decomposition products).

WP2: Simplified extraction experiments on radiotracer solutions using non-irradiated and irradiated extraction systems.

WP3: Extraction experiments on genuine spent fuel solutions using non-irradiated and irradiated extraction systems.

WP4: Investigation of the role of the decomposition products in the extraction process and evaluation of options for their removal to regenerate the organic phase.


[1]     Modolo, G., Geist, A., Miguirditchian, M., Chapter 10: Minor Actinide separations in the reprocessing of spent nuclear fuels: recent advances in Europe, In: Reprocessing and Recycling of Spent Nuclear Fuel, Eds. Robin Taylor, Woodhead Publishing, Sawston, Cambridge (2015).

[2]     Modolo, G., Untersuchungen zur Abtrennung, Konversion und Transmutation von langlebigen Radionukliden, Habilitationsschrift, RWTH Aachen (2014).

[3]     Wilden, A., Modolo, G., Schreinemachers , C., Sadowski, F., Lange, S., Sypula, M., Magnusson, D., Geist, A., Lewis, F.W., Harwood, L.M. & Hudson, M.J., Direct Selective extraction of Actinides (III) from PUREX Raffinate using a Mixture of CyMe4BTBP and TODGA as 1-cycle SANEX Solvent Part III: Demonstration of a Laboratory-Scale Counter-Current Centrifugal Contactor Process, Solvent Extraction and Ion Exchange, Vol 31, Issue 5-6, 519-537 (2013).

[4]     Berthon, L., Morel, J. M., Zorz, N., Nicol, C., Virelizier & Madic, C., DIAMEX Process for minor actinide partitioning: hydrolytic and radiolytic degradations of malonamide extractants, Separation Science and Technology, Vol 35, Issue 5-6, 709-728 (2001).

[5]     Mincher, B.J., Modolo, G. & Mezyk S.P., Review article: The Effects of Radiation Chemistry on Solvent Extraction 3: A Review of Actinide and Lanthanide Extraction, Solvent Extraction and Ion Exchange, Vol 27, Issue 5-6, 579-606 (2009).

[6]     Mincher, B.J., Modolo, G. & Mezyk S.P., Review article: The Effects of Radiation Chemistry on Solvent Extraction 4: Separation of the Trivalent Actinides and Considerations for Radiation-Resistant Solvent Systems, Solvent Extraction and Ion Exchange, Vol 27, Issue 5-6, 579-606 (2009).