Bringing nuclear safety to the next level
Overview of PhD students, Postdocs and MSc students and their research topics within the SAMOSAFER project
Nicolò ABRATE – Politecnico di Torino
Ph.D. thesis “Methods for safety and stability analysis of nuclear system”
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 “Multiphysics Modelling Approach for the Analysis of Xenon Removal via Helium Bubbling in the Molten Salt Fast Reactor”
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 “Extension of multiphysics modelling of the Molten Salt Fast Reactor to the transport of metallic fission products”
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 “Thermochemistry and evaluation of the thermo-physical properties of key fission products and corrosion products in Molten Salt Reactor”
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 “Melting and Solidification Phenomena of Salt in a Molten Salt Nuclear Reactor”
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.
Yohannes MOLLA – CRNS/SUBATECH
PhD thesis “Decay heat uncertainty calculations with associated sensitivity studies. Impact of nuclear data”
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.
Jonas Sebastian NARVAEZ ARRUA – Politecnico di Milano
PhD thesis “Numerical and experimental study of the dynamic behaviour of natural circulation systems using molten salts for heat removal”
The aim of this Ph.D. project is to develop a comprehensive methodology for the evaluation, study and design of natural circulation systems using molten salt as work fluid, for its application in Molten Salt Fast Reactors (MSFR), focused primarily on decay heat removal systems. The use of natural circulation driven systems allows achieving safety functions without active control measures, but a detailed description is required for the behavior of the system, the transition between possible states and the corresponding stability. The purpose of the work is to implement and couple the different models required for such analysis within a single numerical methodology, including Computational Fluid Dynamic (CFD) simulations, study of stability and bifurcation phenomena and the use of Reduced Order Models (ROM). The methodology is then used for the design of a natural circulation experiment; numerical simulations are carried out to evaluate different possible configurations, selecting an optimal case that enhances the studied phenomena expected to be encountered in a real application. Finally, the experimental campaign is carried out and the proper performance of the methodology is verified through the comparison between the numerical and experimental results.
Thibault LE MEUTE – CNRS
Ph.D. thesis “Modeling of a reactivity insertion scenario in a Generation IV molten salt reactor”
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.”
Mateusz PATER – Technical University of Denmark
Ph.D. thesis “Advanced freeze valves for energy production and conversion systems using molten salts”
This PhD project intends to develop advanced freeze valves to be used in molten salt based systems, with the primary focus on Seaborg Technologies’ Compact Molten Salt Reactor. Different designs of freeze valves will be tested in thermal convection loop facilities circulating molten salts and modelled numerically. The combination of modelling and simulation and experiments will allow for improvement of physical models for melting and solidification of salts. Overall research objectives of the entire project are to: (1) identify and assess mechanical and freeze valve design candidates for industrial development while being optimized for high performance, compatibility with molten salts, and reliability; (2) improve the understanding of salt phase change physics; (3) experimentally validate computational fluid dynamics models of salt phase change in a freeze valve integrated with a molten salt loop.
Hugo PITOIS – CNRS Laboratoire de Physique Subatomique et Cosmologie (CNRS-LPSC)
Ph.D. thesis “Design and safety studies of the Molten Salt Fast Reactor concept”
This PhD has several objectives related to the design and the safety of the Molten Salt Fast Reactor (MSFR) concept with contributions to:
Franco QUINTEROS – CNRS
Ph.D. thesis “Conceptual design of a nuclear electric propulsion reactor for space exploration”
The use of nuclear power for space propulsion has been gaining significant attention in recent years due to potential advantages of nuclear reactors for these applications. Two main approaches are usually considered: Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP). In this project, we are investigating a NEP concept based on a Molten fuel Salt Reactor (MSR). In a NEP the nuclear thermal energy is converted into electricity that powers an Electrical Propulsion (EP) system. The main objective of this doctoral thesis is to build a full multi-physics numerical model to carry-out the design of a nuclear space fission reactor based on a Molten Salt Reactor (MSR) and for electric propulsion. The nuclear reactor model is being built from the multi-physics tool already developed by the LPSC Grenoble Reactor Physics team based on the codes OpenFOAM and SERPENT. This tool includes the three main areas of reactor physics: neutronics, thermo-hydraulics and thermo-mechanics. This tool has been developed based on the numerical coupling between the codes OpenFOAM (C++ toolbox for the development of numerical solvers for continuum mechanics problems, including Computational Fluid Dynamics) and SERPENT (multi-purpose three-dimensional continuous-energy Monte Carlo particle transport code). The modeling work performed in this PhD thesis will contribute to optimize the engine design, identify potential problems and solutions, and contribute to the definition of the future experiments that would be needed to validate the propulsion concept.
Nikolas SCURO – Ontario Tech University
Ph.D. thesis “Multi-physics coupling using OpenFoam and Thermochimica in a Molten Salt Nuclear Reactor”
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.”
Thomas SORNAY – Framatome/CNRS
Ph.D. thesis “Cliff-edge effects identification on design, safety and operating aspect for alternative versions of the MSFR”
This thesis will investigate small modular design of the Molten Salt Fast Reactor in a chloride version and Uranium/Plutonium fuel cycle. To do so, a coupled neutronics and thermal-hydraulics code called TFM-STAR is currently developed to simulate the fuel circuit of the MSFR. It is an adaptation of the TFM-OpenFOAM code developed at CNRS, implemented in the Computational Fluid Dynamics code Star-CCM+ used at Framatome. It can simulate steady state and various transients (reactivity insertion, load following, pump loss…) and can be adapted to any geometry thanks to Computational Aided Design tools including in Star-CCM+.One important objective of this work is to establish links between the calculation results and the safety issues or the plant operation issues, characterizing the phenomena that could appear in the reactor. Moreover, the work will lead to some design optimizations, for example the number of loops in the fuel circuit, including safety and operating considerations.In the framework of the SAMOSAFER project, this thesis work can study for instance some initial events for different sizes of the reactor and different levels of power, in relation with Task 6.6.
Bachelor and Master students
Ies LAKERVELD, TU Delft, MSc thesis “Removal of solid fission products by He bubbling”, Supervisor: Martin Rohde (TU Delft), Contact: firstname.lastname@example.org
Giulia MERLA, Politecnico di Milano, MSc thesis title: “Improvement of continuous reprocessing and fuel composition adjustment capabilities in SERPENT-2 for Molten Salt Reactors”, Supervisors: Antonio Cammi (POLIMI), Stefano Lorenzi (POLIMI), Contact: email@example.com
Tomas MOLINA, CNRS, MSc thesis “Thermal-hydraulic modeling of a molten salt flow in a closed square channel”, Supervisor: Pablo Rubiolo (CNRS), Contact: firstname.lastname@example.org
Aske Chris NILSSON, Danish Technical University, BSc thesis “Dynamic burnup in a Molten Salt Reactor”, Supervisor: Jacob Groth-Jensen (DTU)
Elias Pagh SENSTIUS, Danish Technical University, MSc thesis “Neutronics model of the Molten Salt Fast Reactor for nuclear heating assessment”, Supervisor: Bent Lauritzen (DTU), Contact: email@example.com
Davide TARTAGLIA, Politecnico di Milano, MSc thesis “Numerical modelling and simulation of melting phenomena for freeze valves analysis in Molten Salt Reactors”, Supervisors: Antonio Cammi (POLIMI) and Stefano Lorenzi (POLIMI), Contact: firstname.lastname@example.org
Jesper VAN WINDEN, TU Delft, MSc thesis “Simulation of melting and solidification of fuel salts in natural circulation driven flows”, Supervisor: Martin Rohde (TU Delft), Contact: email@example.com