PhD Thesis in Molten Salt Reactor Physics (M/F)

Job Description

Thesis Subject

Molten Salt Reactors (MSR) present a very interesting potential in terms of safety and flexibility. Such reactor is based on a liquid salt circulating between the core and the heat exchangers and playing the role of both the fuel to produce heat and the coolant to evacuate the heat produced. Due to its inherent features, and its flexible applications (power generation (from small modular reactors up to high power, burning actinides that may not be used as fuel in present Pressurized Water Reactors, etc.), since some times, there is renewed interest in these reactors in France, Europe, and over the world. In the past twenty years, the MSFR team of LSPC (Laboratoire de Physique Subatomique et de Cosmologie) drives studies of such reactors for all these applications and especially the reference MSFR version, breeder reactor in the Thorium fuel cycle and based on a fluoride fuel salt.
Given the renewed interest in this promising technology, new collaborations have been established, and new studies are underway on other applications and versions of the MSFR concept, particularly as a small modular reactor (SMR) with reduced power and/or volume, notably using the U/Pu fuel cycle, which corresponds to the fuel cycle in France. Such a reactor could thus have applications in energy production or for the incineration of nuclear waste, with a strategic interest for France in closing its fuel cycle. Framatome, in collaboration with the MSFR team at LPSC, aims to develop a project based on research in reactor physics and nuclear safety to assess the feasibility of molten salt reactors.
Actually, numerous unfinalized MSR concepts exist, with significant uncertainties regarding optimal design, whether concerning the choice of salt, fuel, component arrangement, or stability during normal operation. Indeed, regarding this last point, the state-of-the-art shows that even under nominal conditions, variations associated with the salt movement impact power output, causing it to oscillate around an equilibrium point. Other unsteady phenomena (such as shock waves) can also disrupt operation, both under nominal and accidental conditions. The overall objective of this thesis is to understand the impacts of certain disturbances on reactor efficiency and safety, primarily through three approaches.
The first approach concerns the impact of unsteadiness during normal operation on the fuel and intermediate circuits. This analysis will be performed using a coupling between neutronics and CFD and between CFD and a system code. The neutronics and CFD coupling aims to represent the fuel circuit as realistically as possible, while the CFD-system code coupling allows us to represent the impact of changes in fuel circuit parameters on the intermediate circuit.
The second approach concerns the impact of phenomena associated with pressure waves during fast transients on mechanics and neutronics. This issue will be addressed using a triple neutronics-CFD-FEM coupling. This triple coupling allows us to consider the deformation effect of pressure waves in the reactor vessel and the impact of this deformation on neutronics and thermohydraulics.
Finally, the third approach consists of finding a way to design a molten salt reactor prototype that is as representative as possible of the two previous phenomena. This involves core design and estimating the representativeness of different feasible experiments based on the physical phenomena being studied.
This work will draw on past developments in multi-physics modeling at both LPSC and Framatome, and will be carried out primarily within the framework of the European ENDURANCE project, with potential contributions to other European or national projects on molten salt reactors in which members of the MSFR team are involved.

Your Work Environment

The thesis under CNRS contract will take place at Framatome Lyon during the first part of the PhD and then at LPSC Grenoble for the second part of the work. The studies to be done are interdisciplinary, going from reactor physics to safety analysis.
The candidate must have a Master degree in reactor physics or in nuclear physics. He/she will have to:
• Have a good knowledge about reactor physics (neutronics, thermohydraulics, safety…)
• Be able to work in a team and in various collaborations
• Be able to develop a simulation/calculation tool, especially with the Java and Python language
• Master a large production of data
• Master the French and English languages, both written and spoken.

Constraints and risks

None

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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