The development of plasma facing materials (PFMs) able to withstand the harsh conditions (large thermal loads and radiation-induced damage) in reactors is one of the key parameters for nuclear fusion to upscale to commercial power plants both, in inertial confinement fusion (ICF) and in the magnetic confinement fusion (MCF) approaches.
The radiation environment that PFMs will face in nuclear...
In a fusion reactor, tungsten will be exposed to high heat flux, neutrons, helium ash, and tritium-containing fuel plasma. Neutron irradiation generates defects in tungsten, and the migration of these defects under irradiation leads to their clustering and annihilation. These irradiation-induced defects serve as strong trapping sites for hydrogen isotopes. Therefore, predicting the...
This study explores the diffusion of hydrogen (H) across the tungsten (bcc) - copper (hcp) W(001)/Cu(11-20) interface [1-3]. It combines DFT electronic structure calculations and kinetic modeling based on diffusion coefficients and macroscopic rate equations (MRE). The copper lattice reconstructs significantly near the interface, inducing complex energetics for hydrogen atoms inserted at the...
The general problem of first principles force fields is to create surrogate models for quantum mechanics that yield the energy of a configuration of atoms in 3D space, as we would find them in reality for materials or molecules. Over the last decade significant advances were made in the attainable accuracy, and today we can model materials and molecules with a per-atom energy accuracy of up to...
In nuclear fusion environments, structural materials must withstand severe thermal loads and high-energy particle bombardment. Accurately simulating these conditions requires large-scale atomistic models capable of capturing complex grain and interface arrangements. PolyPal provides a big solution by generating massive polycrystalline specimens—scaling to tens of billions of atoms—in only a...
Excess lattice point defects can drive phase transformations, alter phase selection, or even lead to the formation of new phases. The removal of these defects serves both as a mechanism for accommodating precipitate eigenstrain and as a driving force for semi-coherent precipitation [1].
We present a thermodynamic framework for point-defect-induced precipitations, considering both...
D. Nguyen-Manh a)*, K. Starkey b), M. Christensen b),
E. Wimmer b), C. Geller b) and M..R. Gilbert a)
a) Materials Division, United Kingdom Atomic Energy Authority, Culham Campus, Abingdon, OX14 3DB, United Kingdom
b) Materials Design, 42 Avenue Verdier, 92120 Montrouge, France
Tungsten is a promising plasma-facing material for future fusion power plants owing to several favourable...
Due to their advantageous properties, tungsten (W) and steels are the main candidates for plasma-facing and structural materials for future fusion reactors. However, exposure to 14 MeV neutrons from D-T fusion reaction in nuclear environment will introduce significant displacement damage, altering the crystal structure of the materials and affecting their physical properties. To examine...
Tungsten has been selected as the divertor material for ITER and is also considered for the first wall in fusion reactors due to its exceptional properties, including a high melting point, excellent thermal conductivity, low thermal expansion, high strength at elevated temperatures, and a high sputtering threshold energy. In these environments, tungsten will be exposed to neutron irradiation,...
In future fusion devices, the tritium retention and permeation in plasma facing components (PFCs) are important safety concerns. In order to predict the tritium retention and permeation during operation of a reactor, numerical modelling of tritium transport and trapping at defects can be done. This allows to know how much tritium atoms are retained in the wall and how much permeate to the...
Hydrogen adsorption and absorption at solid surfaces is a prototype surface reaction, where fundamental concepts of gas-surface interaction are embodied. As such, hydrogen interaction with solid surfaces has been extensively studied in the surface science community [1]. To investigate the behavior of hydrogen at surfaces, our group has developed nuclear reaction analysis (NRA), which allows us...
With tungsten (W)-copper (Cu) bonding potentially used in the plasma-facing components (PFCs) in fusion devices, hydrogen isotope (HI) transport through the W/Cu interface is a key concern for tritium self-sustainment and operation safety.
To investigate HI permeation through W/Cu interface, a series of low-energy deuterium (D) plasma-driven permeation (PDP) experiments were performed on...
Molecular dynamics (MD) is a powerful materials simulation approach whose accuracy is limited by the interatomic potential (IAP). The quest for improved accuracy has resulted in a decades-long growth in the complexity of IAPs, many of which are implemented in the LAMMPS MD code.[1] Traditional physics-based IAPs are now being rapidly supplanted by machine-learning potentials (MLIAPs). The SNAP...
A fundamental description of gas transport and retention in plasma-facing materials is crucial for tritium inventory modelling. During future reactor operations, the material microstructure is expected to evolve and reveal defects which act as “traps” for diffusing gas atoms, thereby compromising material performance. The classical formalism for gas diffusion and trapping is given by the...
Classical molecular dynamics (MD) is in principle an ideal tool to investigate the long-time evolution of materials in extreme environments, as ab initio-based MD simulations remain limited to very short time. While modern machine learning MD potentials report errors on the order 1 meV/atom, these errors are only typical of configurations that are similar to those found in the training set...
In fusion reactors, the control of plasma parameters in the edge plasma plays a crucial role in maintaining high core plasma performance and achieving efficient burning conditions. The edge plasma is in direct contact with the reactor wall, where complex interactions occur due to plasma irradiation. This interaction leads to the release of neutral hydrogen atoms and molecules from the wall...
The transport and retention of hydrogen isotopes, deuterium and tritium, in materials affect the economics and sustainability of the fusion fuel cycle, as well as the integrity of materials due to the detrimental effects of hydrogen and helium produced by the alpha decay of tritium. Therefore, accurately predicting the behavior and effects of hydrogen in materials used as reactor components...
Universal interatomic potentials parameterize the interactions between all chemical elements in the periodic table simultaneously. In my talk I will introduce the Graph Atomic Cluster Expansion (GRACE). GRACE builds on a complete set of graph basis functions and can be viewed to generalize equivariant message passing neural networks and other machine learning interatomic potentials. I will...
Developing materials resistant to neutron irradiation is one of the key challenges in fusion energy applications. Due to the lack of fusion neutron sources for irradiation experiments, computational simulations provide valuable information and references for addressing such challenges. Multiscale simulation methods through a hierarchical, information-passing paradigm are often employed to...
Trap-diffusion modelling is of fundamental importance for the analysis of plasma-material interaction experiments (e.g. to extract information about hydrogen isotope trapping energies using thermal effusion spectroscopy) and is also indispensable to estimate tritium retention/permeation in future fusion devices.
Thus in the recent years a number of simulation codes have been developed...
The molecular dynamics (MD) simulations of successive collision cascades (SCC) within a single simulation domain have recently been employed to predict radiation damage at varying dpa levels [1,2]. We carry out SCC simulations with different primary knock-on atoms (PKAs) and interatomic potentials (IPs)—namely, traditional EAM and machine learning potentials (MLIPs). Since dpa serves as the...
To simulate neutron-induced defects, materials have been irradiated with Fe ions with an energy of 5.6 MeV at a temperature range of 250-500C and dose range of 3-50 dpa. The radiation defects have been investigated by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDXS), atom probe tomography (APT) and positron annihilation spectroscopy (PALS). To decorate...
This contribution summarizes experimental and modeling studies of hydrogen retention in ion-implanted beryllium, focusing on the role of vacancy and self-interstitial atoms (SIA) dynamics during the implantation process. As the main modelling tool macroscopic rate equations (MRE) implemented in the CRDS code [1] and supported by density functional theory (DFT) calculations are used to simulate...
Tungsten (W) is considered as a promising plasma-facing material for future fusion reactors. W components will be subjected to an intense flux of 14 MeV neutrons. This will result in the production of displacement damage and material transmutation. W components will operate at elevated temperatures (673-1300 K), which will favor the formation of irradiation-induced voids. These voids will act...
Temperature plays a critical role in the behavior of deuterium (D) in tungsten (W), a key material for plasma-facing components in fusion reactors. This study investigates the effects of temperature variation on D retention, surface blistering, and defect evolution in W. Two sets of temperature rising (TR) and temperature declining (TD) irradiation experiments were conducted in the temperature...
Tungsten will be used as the plasma facing material in fusion reactors, and will be subjected to irradiation, which will affect its properties. Fusion fuels, such as hydrogen isotopes, will be implanted into the material, which will affect the material properties and be a problem as radioactive tritium is retained. Experimentally it has been seen that having deuterium present during...
Tungsten, a candidate for nuclear fusion reactor armour, is susceptible to helium contamination. Such impurities are believed to interfere with the movement of screw dislocations, which typically propagate by nucleation and migration of kink pairs. Modelling this requires large simulations cells that are well beyond the limits of density functional theory, with a few heroic exceptions [1]....
This study focuses on using a combination of surface characterization techniques to assess the response of advanced tungsten alloys and ultra-high temperature ceramics (UHTCs) to high-flux plasmas. While these materials are at an early stage of development, they potentially offer superior thermomechanical properties and microstructural stability relative to other existing candidate materials....
Fcc NixFe1-x single-crystal alloys are key model systems for studying defect evolution under self-ion irradiation at room temperature, with fluences ranging from 4 × 10¹³ to 2 × 10¹⁵ ions/cm² [1,2]. This study investigates the effects of irradiation-induced defects on the nanomechanical response of NiFe alloys through a combination of experimentally guided nanoindentation and atomistic...
Five widely used interatomic potentials (IAP) for tungsten were used to simulate collision cascades in crystal tungsten. Three of the IAP were embedded atom model (EAM) based [1,2,3] whilst the other two were machine learning (ML) based [4,5]. The molecular dynamics (MD) simulations were carried out for primary knock-on atoms (PKA) having energies 5, 10, 20, 50, 75, 100 and 150 keV. The PKA...
Machine-learned interatomic potentials (MLIPs) are a promising new approach that allow us to make atomistic material predictions with close to first principles DFT accuracy at a fraction of the cost. The new developments of foundation model MLIPs over the last year [1,2] are especially promising for modelling alloys. In this poster, I will benchmark an iron MLIP that we have developed using...
Tungsten due to its superior properties is suggested to be used for both the divertor and the first wall of fusion reactor. As a plasma facing material, tungsten has to face high heat loads and bare intense flux of hydrogen/helium ions and neutral particles which degrade its properties and change its surface morphology. To improve the properties of tungsten, vanadium with different...
The impetus behind this abstract comes in relation to studies in experimental nuclear reactors with walls made up of materials containing simple atoms (e.g., Be, C, N), referred to as PFPs or plasma-facing materials, that may react with the fuel atoms (H, D, T) producing BeH, CH, NH, and their cations, all this related to the long-time elusive quest for controlled nuclear fusion energy...
Tungsten (W) is a promising candidate material for the plasma-facing surfaces of nuclear fusion devices. The interaction of helium (He) with W is of interest because the wall of a nuclear fusion device will be subject to high fluxes of He produced in the DT-fusion reaction. Furthermore, neutron irradiation will create He in the bulk by nuclear reactions.
Simulations on the atomic level...
Understanding the impact dynamics of high-velocity tungsten (W) dust on helium-implanted W targets is crucial for predicting material degradation in fusion reactor environments. In this study, we employ large-scale molecular dynamics (MD) simulations to investigate the interaction mechanisms governing the response of W surfaces under extreme impact conditions. The simulations reveal the...
Fusion within Inertial Electrostatic Confinement (IEC) devices occurs through three primary mechanisms, primarily influenced by plasma conditions and the electrodes material: beam-beam interactions, beam-background gas collisions, and beam-target interactions with electrode surfaces. Beam-background and beam-target fusion mainly contribute to neutron production. The rate of beam-background...
Plasma-facing materials (PFM) play crucial role in fusion reactors. It has been estimated that fusion energy, once commercially available, would contribute as much as 5% of the total electricity production in ASEAN. If one-tenth of such a fusion cost were from fusion materials, advanced fusion materials could constitute about 7.6 x 10⁸ USD with a possible four percent annual growth rate....
Cu-W metallic multilayers are promising candidates for the first wall of future fusion nuclear reactors due to their high melting point, excellent thermal conductivity, and defect-annihilating properties. However, the accumulation of impurities generated during neutron irradiation can weaken the interface, leading to operational failure over time. Enhancing the interfacial properties of these...
Inertial Electrostatic Confinement (IEC) fusion systems incorporating Lattice Confinement Fusion (LCF) techniques serve as compact neutron sources, capable of sustained neutron fluxes exceeding 1×10¹¹ neutrons per second, and beyond. These reactors produce neutrons primarily through Deuterium-Deuterium (DD, approximately 2.45 MeV) and Deuterium-Tritium (DT, approximately 14.1 MeV) fusion...
Ensuring the efficient performance of fusion devices requires a comprehensive understanding of plasma-facing materials and components under extreme operational conditions and neutron fluxes, particularly in the EU DEMO system. Neutrons with energies up to 14 MeV play a dual role in tritium breeding and energy production but also interact with in-vessel materials, causing activation, decay...
The study of plasma-material interaction (PMI) in fusion devices relies critically on understanding and controlling the properties of the edge or boundary plasma, which bridges the hot core plasma and the plasma-facing components (PFCs). The accurate modelling of the boundary plasma is a valuable tool to support the interpretation of experimental results and to guide the design of plasma...
Assessing the amount, type, and energy of radiation encountered requires knowledge of the radiation source and the shielding effect of the type of material between the radiation source and the area of interest.
The choice of elements in structural materials such as stainless steel can reduce the radiation levels due to particle activation. The dose rate to workers and electrical components is...
Non-axisymmetric magnetic field ($B$) configuration is present in linear fusion devices,particularly, those contain minimum-$B$ magnetic field configuration as MHD stabilizer [1,2]. Non-axisymmetric $B$ configuration is also present in toroidal fusion devices, such as, in helical devices [3]. Localized components of non-axisymmetric magnetic field can introduce radial transport of plasma...
Plasma-wall interaction (PWI) is a key topic to be addressed for the safe operation of
nuclear fusion reactors. Non-hydrogenic species, like helium (He) produced by D-T
fusion reactions or argon (Ar) injected in tokamaks as a seeding impurity, need special
attention. Their large mass may enhance the erosion of plasma facing components
(PFCs), but they also increase radiation cooling, which...
Historically, atomistic simulations of plasma–wall interactions (PWI) have been carried out using methods such as binary collision approximation, molecular dynamics (MD), and density functional theory. In these approaches, an incident particle from the plasma to the wall has been generally substituted by neutral atoms instead of ions due to the limitation of simulation models. However, the...
Controlling plasma-wall interactions (PWI) is a key challenge in the field of nuclear fusion, as it directly impacts the efficiency, safety, and operational reliability of future reactors. Linear Plasma Devices (LPDs), such as GyM, play a crucial role in studying PWIs by replicating charge-exchange neutral fluences characteristic of ITER's main chamber. Projectile energy is tuned via...
