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Reference : UPR3079-MARBAR1-002
Workplace : ORLEANS
Date of publication : Friday, June 4, 2021
Scientific Responsible name : Maqrie-France Barthe
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Title: Combination of experimental techniques for the fine characterization of the primary radiation damage in model metallic systems of interest for the nuclear energy industry.
In order to extend the lifetime of the current nuclear power plants, or to develop new reactors, a significant research effort must be devoted to improve and/or develop ad hoc materials. For this purpose, specific to the nuclear energy field is the crucial prerequisite of a perfect knowledge of those materials in extreme environments that includes irradiation from energetic particles (neutrons, alpha particles, fission fragments). Interactions of those projectiles with solids usually leads to defect creation that eventually alter the physical properties of the materials. The post-mortem (i.e. after a significant irradiation time) examination of the irradiated materials should allow to connect the physical properties changes to the actual microstructure. However, a precise description of these microstructures is not straightforward (and frequently relies on phenomenological models). Furthermore, the primary damage develops in the range of the picosecond, so no technique can be used to capture those events. Therefore, determining the exact nature of the primary damage and the fundamental mechanisms at the origin of the evolution of this damage requires to develop ad hoc, innovative investigation approaches that combine experimental and computational efforts. This imperious necessity defines the framework of the proposed PhD research work. More precisely, the approach we want to develop relies on the close comparison of the microstructures obtained, in very controlled and perfectly defined conditions, by both atomistic simulations and extensive experimental characterizations. It must be mentioned that the feasibility of this approach has been recently demonstrated for several experimental techniques [1-3].
The main aim of the PhD research work will thus be to finely characterize the primary radiation damage. This ultimate goal will first require to draw up a map of the complementarity and sensitivity of several characterization techniques mastered by the labs involved in the project. This crucial work has never been carried out before, although it clearly appears today as a major task to carry out in order to improve our use of those techniques for the specific aim of studying radiation damage in nuclear materials. For this purpose, we will examine a broad range of damages, in terms of both disorder level and nature, and we will use several techniques allowing to probe various types of defects at different length-scales: resistivity recovery (RR), sensitive to a wide panel of defects (and implemented at low temperature, which reduces the primary defect evolution), positron annihilation spectroscopy (PAS), specific for small vacancy-type defects, Rutherford backscattering spectrometry in channeling mode (RBS/C), well suited for extended, interstitial-type defects, X-ray diffraction (XRD) and X-ray scattering, sensitive to most of crystalline lattice perturbations, and finally, transmission electron microscopy (TEM) and associated spectroscopy techniques, optimal for large defects at the local scale (and for chemical perturbations). Beside, we plan to upgrade our skills in diffuse scattering techniques, essentially Huang scattering to determine defect size distributions . In a second time, after this systematic work, the actual identification and description of the primary damage will be realized using two ways, both guided by the map of the potentialities of the techniques previously drawn up. First, we will use the proper techniques to probe the early damage stages; second, we will examine microstructures originating from the evolution of the primary damage using here also the most suited techniques. The rationalization of the whole set of data should allow characterizing the primary damage. The experimental part of the work will be supported as much as possible by atomistic calculations. In order to limit the variable parameters, we will focus on model systems (ideally, single-crystals), such as pure Ni and Fe, but also fcc alloys of those elements. This work should pave the way for the study of more complex materials like austenitic stainless steels using in actual reactors.
The doctoral student will participate in the testing of RR and PAS devices, their coupling as well as the coupling with RBS / C and DRX. He or she will also contribute to the interpretation of the experimental data via the modeling results.
 Coupled experimental and DFT+U investigation of positron lifetimes in UO2, Julia Wiktor, Marie-France Barthe, Gérald Jomard, Marc Torrent, Michel Freyss, and Marjorie Bertolus, Phys. Rev. B 90, 184101 (2014)
 Early stages of irradiation induced dislocations in Urania, A. Chartier, C. Onofri, L. Van Brutzel, C. Sabathier, O. Dorosh, and J. Jagielski, Appl. Phys. Lett. 109, 181902 (2016)
 Analysis of strain and disordering kinetics based on combined RBS-channeling and X-ray diffraction atomic-scale modelling, Xin Jin, Alexandre Boulle, Alain Chartier, Jean-Paul Crocombette, Aurélien Debelle, Acta Materialia 201, 63-71 (2020)
 Raina J. Olsen, Ke Jin, Ch Lu, L K. Beland, L Wang, H Bei, E D. Specht, B C. Larson, Journal of Nuclear Materials 469, 153-161 (2016)
The doctoral thesis will be conducted at CEMHTI (Extreme Conditions for Materials: High Temperature and Irradiations, https://www.cemhti.cnrs-orleans.fr) in Orléans in collaboration with the IJCLab in Orsay and IRCER in Limoges laboratories. The doctoral student will join the team "Defects, Impurities, Radiotracers: Properties, Materials, Imaging (DEFIR)" based on the cyclotron site of CEMHTI and will be attached to the theme "Properties of defects: Nuclear materials and ICT". He / she will carry out experimental campaigns in the IJCLab and IRCER laboratories.
The CEMHTI is a CNRS research unit spread over two nearby sites (High Temperature and Cyclotron) and bringing together around 110 people. The laboratory develops expertise and original tools on a national and international level to study, in particular in situ, the physicochemical properties of materials under extreme conditions. It has a "particle beams" platform that manages and develops accelerators for irradiating (Pelletron) and characterizing materials (slow positron accelerators). Other means of characterization are also available on the Orleans campus, such as the scanning or transmission electron microscopes (MACLE platform).
The Irène Joliot-Curie 2 Infinite Physics Laboratory, or IJCLab, is a Joint Research Unit of the CNRS, the University of Paris Saclay and the University of Paris, located on the campus of the Faculty of Sciences of Orsay (https://www.ijclab.in2p3.fr/). Among the scientific themes developed in this laboratory, the Energy & Environment Pole deals in particular with issues related to materials for nuclear energy, and in particular those related to their behavior under irradiation. For this, the Pole has access to a platform of ion accelerators coupled to a transmission electron microscope. These accelerators allow irradiating materials, and implementing ion beam characterization techniques, including RBS / C, for which the Pole has great expertise and ad hoc modeling codes.
IRCER, Institute for Research on Ceramics (https://www.ircer.fr/), has been working for more than 10 years in close collaboration with IJCLab on the characterization of damage in materials induced by irradiation, in particular in relying on IRCER's expertise in terms of crystallography, X-ray diffraction / scattering and digital signal simulations. IRCER has several high-resolution diffractometers, capable of operating under different conditions (temperature, atmosphere) and for different types of materials (single crystals, thin films, polycrystals, etc.).
The thesis will be supervised by Marie-France Barthe (CEMHTI-Orléans) and Aurélien Debelle (IJCLab-Orsay) and will also benefit from the mentoring of Alexandre Boulle (IRCER-Limoges) and Pierre Desgardin (CEMHTI-Orléans).
The PhD student will actively participate in all experimental measurements, and in the development of the combined RR and PAS setup. He/she will have to gather and confront the results from the different techniques, and propose interpretations with the support of atomistic calculations.
Constraints and risks
Frequent work trips to Orsay and Limoges will be mandatory, as well as trips to experimental facilities such as synchrotron and ion accelerators facilities. Work in ionizing environments will necessarily happen, so a dedicated training will be offered at the very beginning of the contract.
The PhD candidate must have a Master degree (Master or Engineering School) covering a broad panel of topics related to solid-state chemistry. The work required solid knowledge in materials science (crystalline lattices and defects, defect properties, electronic structure), and also some expertise in characterization techniques (XRD, microscopies). Some knowledge in the field of ion/solid interactions and ion beam analysis would be appreciated. Real skills, or a desire to acquire those skills in numerical tools for data analysis, as well as a strong attraction for experimental science are mandatory. Skills for oral and writing communication, in English and, potentially, in French, are required. To finish, we are seeking for a fellow showing scientific curiosity, a relative autonomy and a desire to get really involved in his/her research work.
Application files will mandatorily include:
-- A detailed CV
- Contact details and recommendation letters of two referees
- A one-page motivation letter adapted to the subject
- A one-page summary of the Master thesis manuscript
- Transcripts (scores and ranks) of the Master-level past two years
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