CECAM workshop: " Challenges and perspective in computational modelling for fusion reactors"

You can find all the relevant information (speakers, abstracts, program,...) on the event website: https://www.cecam.org/workshop-details/challenges-and-perspective-in-computational-modelling-for-fusion-reactors-1293.

Registration is required to attend the full event, take part in the social activities and present a poster at the poster session (if any).  However, the EPFL community is welcome to attend specific lectures without registration if the topic is of interest to their research. Lectures will also be streamed on Zoom. Registrations are still mandatory to attend remotely (deadline 24.10), please visit the event website to apply. The Zoom link will be sent to accepted online attendees on Friday October 25th.
Do not hesitate to contact the CECAM Event Manager if you have any question.

Description
Fusion energy represents one of the most promising and sustainable options for providing mankind with a large-scale, carbon-free energy source [1]. However, achieving practical fusion requires addressing several critical challenges, with one of the key obstacles being the availability of suitable in-vessel plasma-facing materials (PFMs) capable of withstanding the severe operational conditions in fusion power plants [2]. PFMs must endure intense bombardment with 14.1 MeV neutrons and 1-100 eV plasma particles, along with fluctuating heat fluxes oscillating between MW/m2 and GW/m2, making their performance crucial for the overall success of fusion reactors.
One of the harshest regions in terms of heat fluxes is the divertor. The PFM designated to cover this role in ITER is tungsten (W) [3]. Despite its potential, the application of tungsten is not without limitations and its applicability in future tokamak-like reactors, such as DEMO, is still under debate [4,5]. It exhibits low recrystallization temperature and high ductile-brittle transition temperature, leading to increased brittleness and decreased thermal shock resistance and mechanical strength. Tungsten tiles also experience cracking, melting, and surface erosion during extreme events such as Edge Localized Modes. Furthermore, plasma-W interactions induce surface morphology changes, forming helium (He) bubbles and a fuzz layer, which can lead to spontaneous material melting, delamination, and decreased thermal properties. Neutron-induced damages and elemental transmutation affect both thermal and mechanical properties, while increase tritium retention in trapping sites.
Atomistic-level studies and Boltzmann plasma simulation play a key role in understanding and addressing these phenomena. However, both experimental and computational limitations have left many questions unanswered. The mechanisms underlying the generation of He bubbles and the fuzz layer resulting from interactions between tungsten, He, and hydrogen isotopes are yet to be fully elucidated [6]. Furthermore, neutron radiation damage significantly impacts these mechanisms, while the change in material composition due to elemental transmutation adds another layer of complexity. In the first wall blanked, tritium breeding materials face similar challenges, along with others, such as a good tritium release coupled with high mechanical integrity [7]. The only experimental facility able to evaluate PFM under operational conditions is ITER itself, which is expected to start the deuterium-tritium operation in 2035 [8]. Until then, first-principles calculations and modelling and simulation of plasma turbulence have the potential to play a key role in understanding PFM behavior under irradiation. Only with the recent advances in computational power and machine learning techniques a quasi-ab initio accuracy for MD simulations have become feasible for large-scale and long time-scale, which are essential for realistic modeling of PFMs' evolution, such as helium bubbles growth and its interaction with hydrogen isotopes and neutron-induced defects [9-12].
The interatomic potential choice is critical in high-energy irradiation simulations, affecting the quantity, distribution, and morphology of the produced defects. At the same time electronic stopping, electron–phonon interaction and short-distance interaction cannot be neglected [13-16]. The variety of atomistic species produced due to transmutation and the interaction between plasma and neutron-induced defects add additional complexity. Understanding the degradation processes of potential PFMs in fusion tokamak reactors requires interdisciplinary efforts combining experimental observations and advanced simulations.

References
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