Lab profile: Rudy Konings, Joint Research Centre EC

Materials that can withstand extreme environments are vital in a range of applications from nuclear power to supersonic flight. In the sphere of nuclear power, understanding the behavior of fuel materials is particularly critical, both to optimize operation and predict potential release of radioactive materials in the event of an accident.

Rudy J. M. Konings, who leads the Nuclear Fuel Safety Unit at the Joint Research Centre of the European Commission, has dedicated his career to the study of nuclear fuel – particularly actinide materials – under extreme conditions. After graduating from Utrecht University with an MSc in Earth Sciences in 1985, he joined the Netherlands Energy Research Foundation ECN researching the thermodynamics of nuclear materials, during which time he received a PhD from the University of Amsterdam. After a spell at NRG, the Nuclear Research and Consultancy Group, working on nuclear fuel-related issues, he joined the European Commission's Joint Research Centre in Karlsruhe (formerly the Institute for Transuranium Elements) in 1999. He also holds a professorial chair at the Delft University of Technology.

He has served as editor of the Journal of Nuclear Materials (2009-2012) and is editor-in-chief of the major reference work Comprehensive Nuclear Materials, the second edition of which is currently under preparation. Konings is currently a board member for the Open Access journal Materials Today Advances: for more information on the journal, including submission instructions, please visit https://www.journals.elsevier.com/materials-today-advances/.

Rudy talked to Materials Today about his current research and future plans.

How long has your group been running?

The unit in its present form is three years old and was formed after a merger of my former unit, which was focused on the study of high-temperature and structural properties of nuclear materials, and a unit involved in the synthesis of and irradiation programs for nuclear materials, traditional research fields for many years here. We see now a lot of synergy in the unit, which is good.

How many staff currently makes up your group?

We have about 35 staff and 10-15 scientific visitors, the latter consisting predominantly of PhD and MSc students from universities in EU member states.

What are the major themes of research in your group?

The central theme of our work is providing the scientific basis for evaluating the performance and safety of nuclear power sources, predominantly nuclear fuels, under normal operation and extreme conditions during incidents and accidents. The synthesis of materials, their characterization, and the study of temperature and radiation on their properties are the key elements of our work. The technical challenge is to measure radioactive material under extreme conditions, for which we develop new instruments. The scientific challenge is to develop basic understanding of the relation between physical properties and the structure of materials.

How and why did you come to work in these areas?

I studied geosciences, which gave me knowledge of material structures, thermodynamics, and material chemistry. When I finished my degree in 1985, I got the opportunity to pursue a PhD in nuclear fuel chemistry at a Dutch research institution, and have remained working in the field since then.

What facilities and equipment does your lab have?

The equipment of the unit falls in three groups: synthesis of nuclear materials for which we have powder preparation, compaction, fluorination and chlorination kit; material characterization using electron microscopy, microprobe analysis, X-ray analysis; and thermal property determination through calorimetry, laser-based melting and thermal diffusivity techniques, and mass spectrometry. The unique aspect of our facilities is that all these instruments are built in nuclear glove boxes, allowing us to work on plutonium and other actinide materials.

Do you have a favorite piece of kit or equipment?

I have always strongly appreciated the beauty of chemical thermodynamics, so I have a weak spot for our calorimetric and laser-based thermal instruments. I think we have done quite unique work with these. I also like transmission electron microscopy for looking into the structure of materials.

What do you think has been your most influential work to date?

Only a few organizations worldwide have the ability to work with highly radioactive materials, so our impact is generally limited to the nuclear fuel community. In my view, we have done some great work on the very high temperature properties of the actinide dioxides. For example, by using an in-house developed laser-based thermal analysis technique, we have demonstrated that the accepted melting temperatures of PuO₂ and NpO₂ were wrong by more than 300 degrees. This has attracted interest from other fields, and we are now using the technique for ultra-high-temperature ceramics as well.

I think we also excel in the area of molten salts for nuclear applications. Over the last 15 years, we have built experimental capabilities from scratch, which is far from trivial for salts containing actinides. We can now measure, with success, the phase diagrams and physical properties of salt mixtures with UF₄ and PuF₃, which are highly relevant for the safety analysis of nuclear reactors. There is a rapidly growing interest in this work because molten salt reactors are studied in many countries as flexible and safe systems. We see that molten salt reactors strongly appeal to students and young researchers at universities with which we collaborate because of their innovative character.        

What is the key to running a successful group?

Success depends on many factors; it is like an equation with many variables in which you have to find the maximum. I personally see good chemistry between people as essential in an international research laboratory like ours. It requires openness from everybody to different cultures and views. But working together efficiently, motivating each other, and sharing successes are key.

How do you plan to develop your group in the future?

Our organization is going through a change, which requires our work to bring an even stronger added value at the European level for the institutions of the European Union as well as EU Member States. For us, this means that we are more closely aligning our research in the nuclear safety field to that of member states, embarking on new research topics outside our core domain, and improving access to our facilities for visiting researchers.

In collaboration with the European Space Agency, for example, we have started working on radioisotope power sources based on the Americium-241 isotope. Through open access initiatives, we help students from universities and other research organizations to perform experiments with actinides, which they cannot do in their own laboratories. It offers them a unique opportunity to get work experience in a nuclear laboratory.

On the practical side, our competences on the high-temperature behavior of materials and the effects of radiation on materials will remain central, but we must modify and improve our instruments to answer to new challenges. We are nuclearizing a focused ion beam with a high temperature nanoindenter for structural and mechanical analysis of irradiated materials, spark plasma sintering equipment for special material synthesis, and a Knudsen effusion mass spectrometer for studying vaporization at very high temperatures. Our goal is to remain at the front of nuclear materials science. 

Key publications

1. J.F. Vigier, D. Freis, P. Pöml, D. Prieur, P. Lajarge, S. Gardeur, A. Guiot, D. Bouexiëre, R.J.M. Konings. Optimisation of uranium-doped americium oxide synthesis for space application. Inorg. Chem. 57 (2018) 4317. 
2. K. Popa, O. Walter, O. Dieste Blanco, A. Guiot, D. Bouëxière, J.-Y. Colle, L. Martel, M. Naji , D. Manara. A low-temperature synthesis method for AnO₂ nanocrystals (An = Th, U, Np, and Pu) and associate solid solutions. Cryst. Eng. Comm. 20 (2018) 4614. 
3. A. Tosolin, P. Soucek, O. Beneš, J.-F. Vigier, L. Luzzi, R.J.M. Konings. Synthesis of plutonium trifluoride by hydro-fluorination and novel thermodynamic data for the PuF₃-LiF system. J. Nucl. Mater. 503 (2018) 171. 
4. T. Pavlov, M.R. Wenman, L. Vlahovic, D. Robba, R.J.M. Konings, P. Van Uffelen, R.W. Grimes. Measurement and interpretation of the thermo-physical properties of uranium dioxide at high temperatures: the viral effect of oxygen defects. Acta Mater. 139 (2017) 138. 
5. O. Cedillos-Barraza, D. Manara, K. Boboridis, S. Grasso, D.D. Jayaseelan, R.J.M. Konings, M.J. Reece, W.E. Lee. Unveiling the highest melting temperature material: A laser melting study of the TaC-HfC system. Sci. Rep. 6 (2016) 37962. 
6. E. Capelli, O. Beneš, J.-Y. Colle, R.J.M. Konings. Determination of the thermodynamic activities of LiF and ThF₄ in the Li_xTh_1-xF_4-3x liquid solution by Knudsen Effusion Mass Spectrometry. Phys. Chem. Chem. Phys. 17 (2015) 30110. 
7. T. Wiss, O. Dieste Blanco, A. Tacu, A. Janssen, Z. Talip, J.-Y. Colle, R.J.M. Konings, P. Martin. TEM study of alpha-damaged plutonium and americium dioxides. J. Mater. Res. 30 (2015) 1544. 
8. A.L. Smith, P.E. Raison, L. Martel, D. Prieur, T. Charpentier, G. Wallez, E. Suard, A. Scheinost, C. Hennig, P. Martin, K.O. Kvashnina, A.K. Cheetham, R.J.M. Konings. A new look at the structural and thermodynamic properties of the trisodium uranate Na₃UO₄. Inorg. Chem. 54 (2015) 3552. 
9. R.J.M. Konings, O. Beneš, T. Wiss. Predicting material release during a nuclear reactor accident. Nature Materials 14 (2015) 247. 
10. R. Böhler, M.J. Welland, D. Prieur, P. Çakir, T. Vitova, T. Pruessmann, I. Pidchenko, C. Hennig, C. Guéneau, R.J.M. Konings and D. Manara. Recent advances in the study of the UO₂-PuO₂ phase diagram at high temperatures. J. Nucl. Mater. 448 (2014) 330.