Extraction behavior of radiolytic degradation compounds of methylated tetradecyl diglycolamide (mTDDGA)

SCK•CEN Mentor

Verlinden Bart, bverlind@sckcen.be, +32 (0)14 33 82 00

Expert group

Radiochemistry

Introduction

When fuel rods from nuclear power plants are removed, the irradiated nuclear fuel has become highly radioactive. It significantly radiates heat and poses high radiotoxicity levels.[1] These effects are on the long-term mainly caused by the presence of actinides such as Pu, Np, Am and Cm. By recycling the actinides from spent nuclear fuel, both the necessary deep geological repository space and the amount of required mined material (U) could be drastically reduced.

One of the different strategies for the reprocessing of spent nuclear fuel is the Grouped Actinide Extraction (GANEX).[2] Here, several actinides (Np, Pu, Am and Cm) are extracted together, which avoids a separate stream of plutonium. In the EURO-GANEX process,[3-7] the lanthanide fission products are co-extracted together with the previously mentioned actinides in the first step. In the second step, the actinides are separated from the lanthanides. This first step of the EURO-GANEX process is based on two extractants: N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and N,N’-(dimethyl-N,N’-dioctylhexylethoxy malonamide (DMDOHEMA). The latter ligand is necessary to deal with high metal concentrations, in this case Pu, and avoids the formation of a third phase.[7] However, DMDOHEMA also extracts unwanted fission products. A new diglycolamide ligand that can replace both TODGA and DMDOHEMA was engineered and it simplifies the extraction system. This new ligand concerns a methylated tetradecyl diglycolamide (mTDDGA).[8] By omitting the use of DMDOHEMA also the extraction of unwanted fission products is minimized.

Objective

After promising first extraction experiments,[8] the question rises how well this new ligand resists ionizing irradiation. Because the solvent is exposed to highly active solutions of dissolved nuclear fuel, it will undergo degradation and react with radicals formed in the solution. The first fundamental irradiation studies using gamma irradiation were already conducted at SCK CEN, to identify the main degradation compounds of mTDDGA. In the next step, degradation compounds were synthesized at the University of Twente and distributed via a European collaboration in the frame of the GENIORS project. The following step, which is the objective of this master thesis, is to screen and characterize the extraction behavior of these degradation compounds. Here, a parametric study will be performed by changing the acid concentration, the concentration of the ligand, the temperature and extraction time. In addition to the parametric study, the removal of degradation compounds from the irradiated solvent will be studied. This can be achieved by an alkaline washing step, which deprotonates acidic degradation compounds, and makes them water soluble. The evaluation of the extractions will be conducted using techniques such as α-spectrometry, γ-spectrometry and Inductively Coupled Mass Spectrometry (ICP-MS).

1.            Taylor, R., Reprocessing and Recycling of Spent Nuclear Fuel.  Taylor, R. (Ed.); Woodhead Publishing United Kindom, 2015.

2.            Miguirditchian, M.; Chareyre, L.; Sorel, C.; Bisel, I.; Baron, P.; Masson, M. Development of the GANEX process for the reprocessing of Gen IV spent nuclear fuels, ATALANTE, 2008.

3.            Carrott, M.; Bell, K.; Brown, J.; Geist, A.; Gregson, C.; Hères, X.; Maher, C.; Malmbeck, R.; Mason, C.; Modolo, G.; Müllich, U.; Sarsfield, M.; Wilden, A.; Taylor, R. Development of a New Flowsheet for Co-Separating the Transuranic Actinides: The “EURO-GANEX” Process. Solvent Extraction and Ion Exchange 2014, 32, 5, 447-467. DOI:10.1080/07366299.2014.896580.

4.            Carrott, M.; Geist, A.; Hères, X.; Lange, S.; Malmbeck, R.; Miguirditchian, M.; Modolo, G.; Wilden, A.; Taylor, R. Distribution of plutonium, americium and interfering fission products between nitric acid and a mixed organic phase of TODGA and DMDOHEMA in kerosene, and implications for the design of the “EURO-GANEX” process. Hydrometallurgy 2015, 152, 139-148. DOI:10.1016/j.hydromet.2014.12.019.

5.            Malmbeck, R.; Magnusson, D.; Bourg, S.; Carrott, M.; Geist, A.; Hérès, X.; Miguirditchian, M.; Modolo, G.; Müllich, U.; Sorel, C.; Taylor, R.; Wilden, A. Homogenous recycling of transuranium elements from irradiated fast reactor fuel by the EURO-GANEX solvent extraction process. Radiochimica Acta 2019, 107, 9-11, 917-929. DOI:10.1515/ract-2018-3089.

6.            Taylor, R.; Carrott, M.; Galan, H.; Geist, A.; Hères, X.; Maher, C.; Mason, C.; Malmbeck, R.; Miguirditchian, M.; Modolo, G.; Rhodes, C.; Sarsfield, M.; Wilden, A. The EURO-GANEX Process: Current Status of Flowsheet Development and Process Safety Studies. Procedia Chemistry 2016, 21, 524-529. DOI:10.1016/j.proche.2016.10.073.

7.            Bell, K.; Carpentier, C.; Carrott, M.; Geist, A.; Gregson, C.; Hérès, X.; Magnusson, D.; Malmbeck, R.; McLachlan, F.; Modolo, G.; Müllich, U.; Sypula, M.; Taylor, R.; Wilden, A. Progress Towards the Development of a New GANEX Process. Procedia Chemistry 2012, 7, 392-397. DOI:10.1016/j.proche.2012.10.061.

8.            Malmbeck, R.; Magnusson, D.; Geist, A. Modified diglycolamides for grouped actinide separation. Journal of Radioanalytical and Nuclear Chemistry 2017, 314, 3, 2531-2538. DOI:10.1007/s10967-017-5614-2.

The minimum diploma level of the candidate needs to be

Academic bachelor

The candidate needs to have a background in

Chemistry