Fusion reactor materials: Computational modelling of atomic-scale damage in irradiated metal

Project reference: 2202

Nuclear fusion is one of the most promising methods for generating large-scale sustainable and carbon-free energy. Since the 19^th century, the rapid rise of global energy consumption and the cumulative CO₂ emissions from burning fossil fuels have played a critical role in climate change. Mitigating the harmful effects of climate change is one of the most important challenges for humankind today, which motivates our search for clean energy sources. Fusion is the process that takes place in the sun and generates enormous quantities of heat and light. Therefore, creating a power plant that runs on fusion energy is a very exciting prospect that requires long-term research and development.

Since the 1950s, researchers have tried to replicate nuclear fusion on Earth, a process coined as “building the sun in a box.” However, the conditions in a fusion reactor need to be extremely harsh, with plasma temperatures of over 100 million °C, so that the hydrogen isotopes inside can fuse together and release energy. No design yet has achieved positive net energy gain (more energy generated than used to run the machine), making the optimization and improvement of all components of planned fusion reactors an open question.

In this project, we will use classical molecular dynamics simulations to study the fundamental properties of metals at the atomic scale.  Prior work by Summer of HPC 2021 students in this area will be continued and extended (http://fusion.bsc.es/index.php/2021/08/31/two-students-on-their-internship-in-the-fusion-group/). This line of investigation will help find suitable materials with desirable chemical and physical properties for use as protective layers within fusion reactor walls. Predicting the behaviour of candidate materials as they undergo damage from being near the burning plasma enables engineers to make reactor components that will last longer before needing to be replaced. Such improvements contribute to the goal of feasible industrial power plants by reducing maintenance costs. In examples like this, where experimental data are not available or difficult to obtain, computer simulations are critically important. Furthermore, the continual development of increasingly powerful computers makes discoveries in materials science more achievable than ever before. The outcomes from this study will be key for the continued development of more resistant materials to be used in fusion technologies.

Two examples of atomic-scale damage in tungsten under simulated fusion reactor conditions: an empty bubble (top), and a cascade (right).
These models were produced by Paolo Settembri and Eoin Kearney, SoHPC 2021 fellows at our BSC Fusion Group. View from inside the MareNostrum-4 supercomputer (background).

Project Mentor: Julio Gutiérrez Moreno

Project Co-mentor : Mary Kate Chessey, Mervi Johanna Mantsinen

Site Co-ordinator: Toni Gabaldón

Learning Outcomes:
The student will learn how to model and simulate materials at the atomic scale, using state-of-the-art simulation methods in one of Europe’s largest HPC platforms. The student will gain training and experience in a nuclear fusion research project. .

 Student Prerequisites (compulsory):
Background in Materials Science, Materials Engineering, Physics, Solid State Physics, Theoretical Chemistry, or Computational Chemistry.
Enthusiasm and willingness to learn from mistakes.

Student Prerequisites (desirable):
Organization and communication skills for productive research meetings.
Previous experience with materials simulations from density functional theory or molecular dynamics.
Familiarity with Linux.

Training Materials:
http://fusion.bsc.es/
http://fusion.bsc.es/index.php/2021/08/31/two-students-on-their-internship-in-the-fusion-group/
https://fusionforenergy.europa.eu/
https://lammps.sandia.gov/tutorials.html

Workplan:
The candidate will be part of the BSC Fusion group where they will work in close contact with the group members and the supervisor. Regular monitoring (daily / weekly) of the work is planned according to the student’s progress and the tasks available.

Work packages (weekly schedule):

1. Introduction to materials for fusion (W1)
2. Training and introduction to density functional theory, molecular dynamics simulations and visualization tools (W2)
3. Introductory problems with atomistic modelling code (W3)
4. Simulation of fusion materials, post-processing, and results analyses (W4-W7)
5. Report writing (W8)

Final Product Description:
The outcomes from the proposed project are key to improving our understanding of the fundamental properties of metals under irradiation and will show the possibility of simulating realistic large-scale metallic systems based on density functional theory (DFT) and molecular dynamics simulations (MD).

Adapting the Project: Increasing the Difficulty:
The project will evolve from relatively easy tasks which are already of high interest and that can be completed within a few weeks, towards doping in polycrystalline structures, which require larger atomic structures with more complex geometries.
Depending on the interest and previous experience, the student could also take active part in the development of interatomic potentials from density functional theory calculations. These simulations can start from simple polymorphs which can be reproduced with few atoms, and will progress towards complex amorphous and interfacial models of alloys and doped compositions.

Adapting the Project: Decreasing the Difficulty:
The range of materials and structures is quite broad, so the project can be readily adapted depending on the student’s interests and background experience. In case the analyses of dynamic models (time and temperature dependent) get too complicated or require too much time to converge, the study can be easily adjusted in scope to static models, from which we can extract valuable information like the equilibrium structure or the mechanical properties of the system. Working with static (frozen) models, we can make use of more complex and accurate interatomic potentials, and define real-scale structural models with a limited computing cost. Still, the study on the evolution of mechanical properties upon vacancy formation is an interesting topic and many structures can be analysed within the period allocated to this internship.

Resources:
The student will make use of BSC’s in-house resources like the MareNostrum supercomputer. We will preferentially use open source codes for modelling, simulation and analyses of the results.

Organisation:
BSC – Barcelona Supercomputing Center