Overview of PhD students, Postdocs and MSc students and their research topics within the SAMOSAFER project
Nicolò ABRATE – Politecnico di Torino
Ph.D. thesis title: “Methods for safety and stability analysis of nuclear system”
Short description of the activity: The objective of this PhD is to study and develop methods for the safety and stability analysis of innovative nuclear systems, like the Gen-IV reactors. The development of these reactors has introduced the need for more sophisticated computational tools for design and licensing purposes. The first part of the PhD, led in the framework of the SAMOFAR project, has concerned the study and application of advanced computational methods for propagating the uncertainty from the raw nuclear data to the main neutronic parameters for the main nuclides composing the fuel salt. Then, the research activity has concerned the development of reduced-order models to minimise the computational cost associated to the parametric evaluations needed to assess the reactor core operational stability. Finally, in the framework of the SAMOSAFER project, the third year will be devoted to develop incident detection methods in order to maximise the safety and operability of the molten salt reactor, improving the early detection of incidental or abnormal conditions, after the identification of the safety-relevant parameters.
Federico CARUGGI – Politecnico di Milano
MSc thesis title: “Multiphysics Modelling Approach for the Analysis of Xenon Removal via Helium Bubbling in the Molten Salt Fast Reactor”
Short description of the activity: The aim of this thesis is to develop a multiphysics solver in OpenFOAM and provide it with new functionalities useful for the analysis of the Molten Salt Fast Reactor (MSFR). The main objective is the modelling of Gaseous Fission Products (GFPs) inside the reactor and their interactions with a helium bubbling system aimed
at removing both GFP. In this way, the multiphysics tool can be employed to study the extraction capabilities of the bubbling system. The correct prediction of the behavior of gaseous fission products, and their interactions with the helium bubbling system represent a key aspect in the definition of the radioactive source term and in the analysis of the fuel cycle of this innovative nuclear system. Starting from an Euler-Euler two-phase solver able to model separately the liquid fuel salt and injected helium phases, a multi-component mixture approach will be implemented to model the evolution of GFP species within each phase, considering production, decay, consumption, intra-phase transport, inter-phase mass transfer and extraction mechanisms. The developed model will be employed to study the efficiency of GFP removal by means of the bubbling system in both 2D and 3D MSFR test cases.
Andrea DI RONCO – Politecnico di Milano
PhD thesis title: “Extension of multiphysics modelling of the Molten Salt Fast Reactor to the transport of metallic fission products”
Short description of the activity: The aim of this Ph.D. activity is to improve the multiphysics description of the Molten Salt Fast Reactor (MSFR) by integrating transport models for the solid noble metal fission products. Metallic fission products can interact with solid surfaces or liquid/gas interfaces, causing local accumulation and potential hazards such as heat exchanger fouling or local heat sources. This work will therefore investigate appropriate modelling approaches and their integration within well-established Finite Volume MSFR codes. Relevant parts of the activity include the analysis of particle-wall interaction and inertial transport mechanisms – and related numerical aspects – and the modelling of the precipitation source term, with input from thermochemical studies to be carried out within the SAMOSAFER project.
Thomas DUMAIRE – TU Delft
Ph.D. thesis title: “Thermochemistry and evaluation of the thermo-physical properties of key fission products and corrosion products in Molten Salt Reactor”
Short description of the activity: The goal of this PhD will be to improve the understanding of the behaviour of key fission products and corrosion products in MSR fuel. We will develop a thermochemical model to describe the chemistry of the fuel and the most important volatile fission products, noble metals and their fluoride phases, and corrosion products. The required structural and thermodynamic data for relevant sub-systems will be assessed coupling experimental measurements by calorimetry, X-ray absorption spectroscopy, atomistic simulations, and CALPHAD thermodynamic modelling. In addition, the retention capacity of the fuel salt for volatile fission products will be investigated as a measure to reduce the source term.
Bouke KAAKS – TU Delft
Ph.D. thesis title: “Melting and Solidification Phenomena of Salt in a Molten Salt Nuclear Reactor”
Short description of the activity: A good understanding of the melting and solidification phenomena of the LiF-ThF4-UF4 fuel in the Molten Salt Fast Reactor is required for the design of the freeze plug, a key safety component, and for the analysis of accident scenarios where solidification of the fuel might pose a risk. As such, the goal of this PhD thesis is to improve the melting and the solidification modelling capabilities. To this end, the effects of phase change will be included in a computational fluid dynamics (CFD) model based on the discontinuous Galerkin (DG) approach through the so-called enthalpy method, where the melting/solidification front is tracked implicitly. The coupling of the enthalpy method with the DG approach is new and is expected to lead to a higher accuracy of the predicted melting/solidification front, as compared to more diffusive discretization schemes such as the finite volume method (FVM). Experimental validation of the applied numerical models will be performed using a cylindrical vessel containing a phase-change material with a melting point close to room temperature and a Prandtl number matching the LiF-ThF4-UF4 salt (ESPRESSO), where the lid rotates at speeds capable of establishing both laminar and turbulent flows.
Giulia MERLA – Politecnico di Milano
MSc thesis title: “Improvement of continuous reprocessing and fuel composition adjustment capabilities in SERPENT-2 for Molten Salt Reactors”
Short description of the activity: Molten Salt Reactors allow not only the possibility of a continuous Fission Products (FPs) removal, but implies also the chance to perform
tailored intervention of the fuel isotopic composition, adjusting the mixture as needed. These peculiarities prevents the adoption of commonly available simulation tools,
which are designed for solid-fuelled reactors and lack in general the possibility to account for mass exchange processes within burn-up calculations. The objective of this MSc thesis is the development of a Serpent-2 extension to couple depletion calculations and material transfer, thus featuring the capability to simulate FPs removal and continuous composition adjustments for both reactivity and eutectic control in MSR. An additional assessment of the tool capabilities will be performed thanks to the dedicated benchmark of task 3.1 of the project. The benchmark represents a common effort among the partners to both verify each burn-up code functionalities and accurately quantify the radioactive source term. The capability of each code to reproduce the same results is to be confirmed for calculations with material exchange processes, thus constituting a solid starting point for following studies and analyses on MSR material evolution.
Yohannes MOLLA – CRNS/SUBATECH
PhD thesis title: “Decay heat uncertainty calculations with associated sensitivity studies. Impact of nuclear data”
Short description of the activity: The determination of decay heat is a major safety issue for a reactor in operation but also for the transport of burnt fuel and nuclear waste management. It is in particular a key parameter for the design of the Generation IV safety systems but also for the use of innovating fuels. The calculation of decay heat relies on the combination of reactor simulations to estimate the fuel inventory and on nuclear data : decay properties of the fission products and actinides, fission yields and cross sections. The objective of this PhD decay is to improve the uncertainty associated to decay heat calculations and especially the impact of nuclear data based on the Total-Monte Carlo method (TMC). The Total Monte Carlo method (TMC) is based on repeating many times a calculation with each time a different set of initial nuclear data. The first part of the PhD will be based on developing the TMC method coupled to the SERPENT code and will be applied on fast fission pulses and PWR assemblies. In the second part of the PhD lead in the framework of the SAMOSAFER project, this method will be used to calculate the decay heat uncertainties for the MSFR concept. In parallel, within the task 3.1 of the SAMOSAFER project, some studies will be performed to compare the different depletion codes (CEA, CNRS/LPSC, CNRS/SUBATECH, PSI, POLIMI) used in the benchmark for fuel inventories calculations.
Ies LAKERVELD – TU Delft
MSc thesis title: “Removal of solid fission products by He bubbling”
Short description of the activity: The goal of this MSc project is to measure the extraction of particles of the size of ~100 nm from a fluid by bubbling and to deliver the data (extraction efficiency as a function of time, local particle concentrations) to NRG for modelling purposes. Laser Induced Fluorescence will be used to track the particle concentration.
Thibault LE MEUTE – CNRS
Ph.D. thesis title: “Modeling of a reactivity insertion scenario in a Generation IV molten salt reactor”
Short description of the activity: The objective of this PhD is to study an accidental scenario likely to induce mechanical effects on the containment of a molten salt reactor and to characterize these effects. In a first phase of the PhD, the reactivity effects possibly involved in the different accident scenario families will be systematically studied. Their dynamics and respective influence on the power transient will be evaluated with a systematic dimensional analysis.
In a second step, taking into account effects that may be involved and their dynamics, studies will be carried out to insert reactivity ramps in order to study the natural behaviour of the reactor in the presence of these ramps. For these reactivity ramps, the consequences will be evaluated by performing, as part of this PhD, a modeling coupling neutronic effects to thermohydraulic effects in order to evaluate the calorific energy deposited in the salt. Given this energy, the phases formed when the salt is heated up to high temperature will have to be determined. Then, an adaptation of the vapour and gas expansion model developed at CEA will be carried out in order to evaluate the mechanical effects of expansion.
Finally, the capacity of the various mitigation measures (salt discharge system, depressurization devices, ect.) of the accident to reduce its consequences will be assessed for a preliminary design of the reactor. Depending on the main parameters driving the effectiveness of these provisions, design improvements in terms of mitigation will be proposed.”
Aske Chris NILSSON – Danish Technical University
BSc thesis title: “Dynamic burnup in a Molten Salt Reactor”
Short description of the activity:
Mateusz PATER – Danish Technical University
Ph.D. thesis title: “Advanced freeze valves for energy production and conversion systems using molten salts”
Short description of the activity:
Hugo PITOIS – CNRS Laboratoire de Physique Subatomique et Cosmologie (CNRS-LPSC)
Ph.D. thesis title: “Design and safety studies of the Molten Salt Fast Reactor concept”
Short description of the activity: This PhD has several objectives related to the design and the safety of the Molten Salt Fast Reactor (MSFR) concept with contributions to:
Nikolas SCURO – Ontario Tech University
Ph.D. thesis title: “Multi-physics coupling using OpenFoam and Thermochimica in a Molten Salt Nuclear Reactor”
Short description of the activity: This Ph.D. aims to develop a CFD model coupling the open-source libraries OpenFOAM and Thermochimica to better understand the fluid dynamics of the chemical equilibrium of molten salts. This multi-physics analysis aims to present the equilibrium composition and a more accurate transport properties calculation of a molten salt composition using the JRCMS database. The desired properties and functions for each compound are, the heat capacity, enthalpy, viscosity and density. The phase proportions of each material (solid deposition, molten salt phase and gas production) are also included in the objectives. This will allow the comparison with previous simulations that used average transport properties with fixed chemical composition and hope to present a more accurate model of the fluid transport of the future molten salt reactors. This thesis directly supports the SAMOSAFER project and will be performed in collaboration with the following organizations: JRC, PoliMi, TU Delft and PSI.”
Elias Pagh SENSTIUS – Danish Technical University
MSc thesis title: “Neutronics model of the Molten Salt Fast Reactor for nuclear heating assessment”
Short description of the activity:
Davide TARTAGLIA – Politecnico di Milano
MSc thesis title: “Numerical modelling and simulation of melting phenomena for freeze valves analysis in Molten Salt Reactors”
Short description of the activity: The aim of this M.Sc thesis is to identify the numerical models that can be adopted to achieve the quantitative insights needed for the design of the freeze valve of the Molten Salt Fast Reactor. After a review of the literature on the numerical modelling of melting and solidification, the most appropriate models will be selected based on a compromise between accuracy and computational efficiency. A critical look at the models will allow achieving a synthetic and consistent formulation of the numerical models and their implementation in the open-source software OpenFOAM. The code will be subsequently verified using analytical and numerical solutions already well-established in the literature.
Jesper VAN WINDEN – TU Delft
MSc thesis title: “Simulation of melting and solidification of fuel salts in natural circulation driven flows”
Short description of the activity: Short description of the activity: the goal of this MSc thesis is to study the applicability of the lattice-Boltzmann Method for the melting and solidification of fuel salts under natural circulation driven flow conditions. Moreover, the effect of the orientation of the freeze plug with respect to the gravity field will be studied.