Study of the corrosion behaviour in NaCl-MgCl2-CeCl3 of a nickel-based alloy in the presence of fission products (Te, S) for molten salt reactor
Access to clean and affordable energy seems more crucial than ever in the current context of climate emergency. Several avenues have been explored for years, but many technological barriers remain to be overcome in order to realise them, as they represent significant technological breakthroughs. Whether it's for energy storage or 4th generation nuclear reactors, the molten salt medium used as a heat transfer fluid and/or fuel is highly corrosive, making the choice of structural materials very complex.
The objective of the proposed PhD project within the Service of Corrosion and Material Behaviour (S2CM) is the comprehensive study of the behaviour of promising nickel-based alloys in the NaCl-MgCl2-CeCl3 ternary system, representative of the salt used in the French molten salt reactor concept, at 600°C. By "comprehensive", this refers to everything from specimen preparation to the multi-scale and multi-technique characterisation of corrosion products. This topic has therefore a strong experimental character and focuses on understanding corrosion mechanisms. The influence of fission products, such as tellurium or sulphur, on corrosion mechanisms will be specifically studied.
Luminescent functional materials developed by additive manufacturing for corrosion monitoring
As part of the energy transition, extending the lifetime of metallic components exposed to corrosive environments is crucial, especially in the nuclear industry, where aggressive conditions lead to rapid degradation. Current maintenance methods, such as non-destructive testing using ultrasounds, are limited in detecting localized corrosion. To address this issue, luminescence-based techniques have been developed for in situ monitoring of material loss. Recent research has demonstrated the integration of luminescent materials into metallic components through additive manufacturing, providing optical properties and the potential to serve as corrosion markers. However, their behavior in corrosive environments and their luminescent characteristics require further exploration.
This thesis project aims to incorporate various luminescent candidates into metallic matrices using laser powder bed fusion (L-PBF) while studying the interplay between microstructure and corrosion. Corrosion will be assessed in NaCl and nitric acid environments to identify corrosive mechanisms and the optimized application. The experiments, accompanied by microstructural observations, will evaluate how long the phosphors remain fixed to the structure before migrating into the medium, an essential piece of information for defining detection devices and maintenance intervals. A test bench will also be established to monitor corrosion in situ.
Development of a lensless microfluidic instrument for in-situ measurement of facies-dependent dissolution kinetics
This thesis is part of an ambitious program designated as a priority research program. This project identifies the subsoil as a major reservoir of resources necessary for the energy transition.
One of the major issues is the dissolution of ores in the context of mining and extractive metallurgy. In particular, with the objective of process industrialization, the dissolution kinetics of ores must be compatible with the footprint of the installations, biocompatibility and the volume of reagents consumed.
The observation today is the very strong mismatch between the volume of experimental data produced and those necessary to model the chemical processes essential to demonstrate the viability of industrial processes.
This thesis proposes to develop a millifluidic prototype bench for mass kinetic data acquisition using lensless imaging techniques. This will make it possible to measure dissolution reaction kinetics using 3D reconstitution techniques, in-situ, under stable chemical conditions and with statistical representativeness allowing the original properties of the solid to be taken into account.
A large part of the research will be directed towards the development of the lensless optical technique in a millifluidic device and the mass production of chemical kinetic data for catalytic dissolution models.
The desired profile is that of a general physics and chemistry student, with a strong desire to learn in areas they are least familiar with, such as microfluidics or optics. At the end of this thesis, the student will acquire solid professional experience in applied research and will learn to evolve in a multithematic environment.