Program > 13th SPCA

The schedule of the 13^th SPCA is available in the "planning" menu.

Please click the link below to join the webinar:

https://univ-rennes1-fr.zoom.us/j/99920295530

passcode: SPCA

Lecture 1: The synthesis of actinide-based materials - Monday 22 March - 16h00-17h00

Antonio Pereira goncalves -C2TN, DECN, Instituto Superior Técnico, Universidade de Lisboa (Portugal)

Abstract 

Actinide compounds often show complex magnetic structures and unique ground states. This behavior derives from the 5f strong spin-orbit coupling and the complex interactions between the 5f states and the states of the ligands. Theoretical work on actinide compounds is extensive and a great evolution in computational tools to calculate their electronic structure took place in recent times.  However, the experimental work is still fundamental not only to confirm theory, but also to identify new exciting ground states and physical behaviors. Nevertheless, there is an increasing lack of experimental work in this field, which is related with the difficulties on handling such materials, that leads to the central issue of making good samples with the minimum quantities and efforts. 

In this talk, a brief description of the main methods for the synthesis and crystal growth of actinide solid compounds is given. It will start with an introduction on the challenges on dealing with the preparation of such samples. It will continue stressing the importance of phase diagram studies for the identification of new compounds and delineation of the best preparation and crystal growth methods. Finally, the main methods for the synthesis and crystal growth of actinide solid compounds will be presented. 

This work was partially supported by FCT, Portugal, through the program UID/Multi/04349/2019. 

Lecture 2: Magnetism and electronic structures of actinides - Monday 22 March - 17h15-18h15

Ladislav Havela -Charles University, Department of Condensed Matter Physics (Czech Republic)

Abstract

This lecture will introduce basic features  of 5f electrons in metallic states and their implications on magnetic and other electronic properties (heat capacity, electronic transport) in various  5f systems (elements, alloys, compounds). The formation of magnetic moments and their interaction will be discussed from the viewpoints of localized and itinerant electronic states, considering the specific strong spin-orbit interaction.

Lecture 3: X-ray Magnetic Circular Dichroism Studies of 5f-based Magnetic Systems - Tuesday 23 March - 16h00-17h00

Fabrice Wilhelm -European Synchrotron Radiation Facility (France)

Abstract

 Over the last 25 years, x-ray absorption near edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) spectroscopy¹ have proven to be particularly valuable tool to study the electronic and magnetic properties of actinide-based compounds². Application of  of magneto-optical sum rules to XMCD spectra recorded at the M_4,5 edges offer a possibility to disentangle the spin and orbital contributions to the total magnetic moment carried by the 5f electrons of actinide atom. Monitoring XMCD signal as a function of applied magnetic field affords element selective magnetization curve. In this lecture, use of XANES/XMCD techniques in physics and chemistry of actinides will be illustrated by a number of selected examples, such as molecular magnets, strongly correlated electron systems and uranium-based multilayers.

References

1) Magnetic Circular Dichroism in the Hard X-ray Range, A. Rogalev and F. Wilhelm, The Physics of Metals and Metallography, Vol. 116, No. 13, pp. 1285–1336 (2015).

2) Magnetism of uranium compounds probed by XMCD spectroscopy, F. Wilhelm, J.-P. Sanchez and A. Rogalev, ournal of Physics D: Applied Physics, Vol. 51, No. 33, 333001 (2018).

Lecture 4: X-ray Spectroscopy for Actinide Science - Tuesday 23 March - 17h15-18h15

Kristina Kvashnina -European Synchrotron Radiation Facility (France)

Abstract

X-ray spectroscopy is a widely used technique at synchrotron radiation sources for analyses of the electronic and structural parameters of materials. This includes the determination of the oxidation state and local symmetry of the absorbing atom. This lecture aimed at PhD students and postdocs who are interested in learning about the principles and practicalities of X-ray spectroscopy, as applied to actinide science. Experimental measurements can be performed on materials in a variety of states, including liquids and solids. The high intensity and tunability of X-rays allow the investigation of a wide range of materials, including thin films, nanoparticles, amorphous materials, solutions, disordered minerals and soils. Moreover, I will provide an overview of the advanced spectroscopic techniques, such as resonant inelastic X-ray scattering (RIXS) and high-energy-resolution fluorescence detected (HERFD) absorption spectroscopy (XAS) that are available at the synchrotrons for studies of actinide systems. I will cover basic principles of X-ray spectroscopy theory and instrumental setups and I will show several examples of the studies performed on the uranium, thorium and plutonium containing materials in the hard and tender X-ray range.

Lecture 5: Basics of radioprotection - Wednesday 24 March - 16h00-16h30

Stéphanie Fryars -Univ Rennes, Institut des Sciences Chimiques de Rennes - UMR6226 (France)

Abstract

Radiation protection is to prevent the occurrence of harmful deterministic effects and to reduce the probability of occurrence of stochastic effects (cancer, hereditary effects...). Ionising radiation may produce deterministic and stochastic effects. In this lecture, we’ll go through the definition of ionising radiation, its ways of exposure, its biological effects, regulations, the characteristics of some actinides and the radiation safety rules.

Lecture 6: From solution to solid: precipitation and crystallization - Wednesday 24 March - 16h45-18h15

Murielle Rivenet -Unité de Catalyse et Chimie du Solide, Centrale Lille (France)

Abstract

Hydrometallurgy is a process commonly encountered throughout the nuclear fuel cycle. As an example, the purification of uranium compounds from mines and the recovery of valuable material from spent nuclear fuel goes through a preliminary step consisting in the solids dissolution. The recovery of the elements of interest then requires a crystallization / precipitation step on which the properties of the final powders will partly depend. We will discuss some laws which govern crystallization / precipitation and some means of modulating crystal growth.

Lecture 7: Chemical speciation modeling of f-elements in the environment - Thursday 25 March - 13h50-14h50

Rémi Marsac -Univ Rennes, CNRS, Géosciences Rennes - UMR6118 (France)

Abstract

Actinides are contaminants of special concern given the severe threats they may cause to human health, ecosystems, and the environment. Natural systems are characterized by a high degree of chemical and physical heterogeneities. Therefore, once released to the environment, actinides can dissolve in water, form complexes with various (in)organic ligands, precipitate with hydroxides or carbonate, adsorb onto “immobile” large particles or “mobile” colloidal phases, undergo redox reactions… Because the distribution of actinides among these different chemical forms (so-called “speciation”) strongly affect their mobility and biotoxicity, it is necessary to develop numerical tools to predict their fate in the environment, which can be used for risk assessment of contaminated sites or potential nuclear waste disposal, or to propose innovative remediation strategies.

This lecture will introduce various (bio)(geo)chemical reactions that can affect actinides speciation in the environment, some analytical and spectroscopic methods to characterize, and numerical tools to predict actinide speciation. Particular focus will be given to (i) redox processes and (ii) complexation processes occurring on mineral surfaces^1,2 because of the key role they play in the fate of actinides in natural systems. A comparison with lanthanides analogues of actinides will also be made.³

 References

(1)          Geckeis, H.; Lützenkirchen, J.; Polly, R.; Rabung, T.; Schmidt, M. Mineral-Water Interface Reactions of Actinides. Chem. Rev. 2013, 113 (2), 1016–1062. https://doi.org/10.1021/cr300370h.

(2)          Marsac, R.; Banik, N. L.; Lützenkirchen, J.; Buda, R. A.; Kratz, J. V.; Marquardt, C. M. Modeling Plutonium Sorption to Kaolinite: Accounting for Redox Equilibria and the Stability of Surface Species. Chem. Geol. 2015, 400, 1–10. https://doi.org/10.1016/j.chemgeo.2015.02.006.

(3)          Marsac, R.; Réal, F.; Banik, N. L.; Pédrot, M.; Pourret, O.; Vallet, V. Aqueous Chemistry of Ce(IV): Estimations Using Actinide Analogues. Dalton Trans. 2017, 46 (39), 13553–13561. https://doi.org/10.1039/C7DT02251D.

Lecture 8: Fuels and Uranium alloys used for nuclear research reactors -Thursday 25 March - 15h00-16h00

Bertrand Stepnik - Framatome-CERCA, Romans-sur-Isère (France)

Abstract

Uranium is one of the major actinide elements. It is used in nuclear fuel reactors. Two types of nuclear reactors exist. Power plant nuclear reactors, such as EDF reactors in France; they use Uranium Oxides pellets in the state of ceramics and they are dedicated to electricity production. Research nuclear reactors, such as RJH and RHF in France; they use metallic alloys of Uranium and they are used by the scientific community to produce neutrons for science, industry and medicine.

This lecture will be dedicated to fuels used in research nuclear reactors. What they stand for? How they are produced? And what are the Uranium alloy properties for their manufacturing? I will briefly present the R&D performed in Framatome in Uranium metallurgy.

Lecture 9: Importance of correlations effects, spin-orbit coupling in heavy elements vs. actinides using Density Functional Theory approach- Thursday 25 March - 16h10-17h10

Dominik Legut - Technical University of Ostrava (Czech Republic)

Abstract

 Thermal expansion and thermal conductivity are the key properties for nuclear reactor fuel design. This considers the actinides and actinide compounds mainly. Those are formed from heavy elements and its physics of complex behavior of the 5f electronic shell. In this lecture we learn how to treat relativistic effects using quantum-mechanical calculations and lattice dynamics (atomic vibrations) in order to determine thermal expansion and thermal conductivity, i.e the electron as well as phonon contributions to these quantities. Success of the approach depends how accurate one can determinate the electronic structure of given system with respect to the physical quantity (phenomena) of interest, here often complicated by the physics of itinerant vs. localized behavior of the 5f shell. Here we tackle the effects of electron correlations as well as the effect of the the role of relativistic effects (e.g. spin-orbit coupling) and determine to which extent and for which material they play a decesive role for such usefull and measureable quantities like thermal expansion and thermal conductivity.  More details and for the future reference of the described phenomena could be found in Ref. [1-5].

 References:

[1]  D. Legut, M. Friák and M. Šob: Why is polonium simple cubic and so highly anisotropic?, Phys. Rev. Lett. 99, 016402 (2007).

[2] D. Legut, M. Friák and M. Šob: Phase stability, elasticity, and theoretical strength of polonium from first principles, Phys. Rev. B 81, 214118 (2010).

[3] U. D. Wdowik, P. Piekarz, D. Legut, and G. Jaglo, Effect of spin-orbit and on-site Coulomb interactions on the electronic structure and lattice dynamics of uranium monocarbide, Phys. Rev. B 94, 054303 (2016).

[4] L. Kývala and D. Legut, Lattice dynamics and thermal properties of thorium metal and thorium monocarbide, Phys. Rev. B 101, 075117 (2020).

[5]  U.D. Wdowik, V. Buturlim, L. Havela, and D. Legut, Effect of carbon vacancies and oxygen impurities on the dynamical and thermal properties of uranium monocarbide, J. Nucl. Mat. 545 , 152547 (2021).

 Lecture 10: Neutrons: a soft quantum probe for magnetism - Thursday 25 March - 17h20-18h20

Roberto Caciuffo - European Commission, Joint Research Centre, Karlsruhe (Germany)

Abstract

Neutron Scattering provides information on crystallographic and magnetic structures at different spatial distances, from atomic to mesoscopic scales. Combined with spin polarization analysis, neutron diffraction, small angle scattering and neutron reflectometry allow one to determine orientation and amplitude of magnetic moments in bulk samples, thin films, and interfaces. On the other hand, inelastic neutron scattering, accounts for the detailed atomic motions and magnetic excitations - individual or collective - within a many-body system in vastly different time and length scales, typically ps to ms and sub-nm to mm.

After a brief introduction on the properties of neutrons as quantum probe for magnetism in condensed matter, I will describe the most common experimental setups used in continuous and pulsed neutron sources, discussing characteristics and limits of the various components of a neutron spectrometer, including devices for selecting and analysing neutron energy, momentum, and spin polarization states. The master formula providing the neutron scattering amplitude probability will be derived in a simple way and applied to different cases. In particular, I will focus on the scattering amplitude associated with the interaction of neutrons with the magnetic field distribution generated by electrons spin and currents in a material and I will show how the magnetic neutron scattering cross section provides information on the correlation between the magnetization components, that is how the magnetization on a given site influence the magnetization of the surrounding.

References

1) Introduction to the Theory of Thermal Neutron Scattering, G. L. Squires, Cambridge University press (2012)

2) Magnetic Scattering from Magnetic Materials, Tapan Chatterji Ed., Elsevier BV (2006).

3) Theory of Magnetic Neutron and Photon Scattering, E. Balcar and S. W. Lovesey, Clarendon Press (1989)

4) Neutron Scattering in Condensed Matter Physics, A. Furrer, J. F. Mesot, T. Strässle; World Scientific (2009)

5) Elements of Slow neutron Scattering, J. M. Carpenter and C.-K. Loong, Cambridge University Press (2015)