UDTR — Radar mondial des droits de la Nature

The effects of thermal history and composition on the thermodynamic behaviour of helium in tungsten and tungsten-based alloys

Identification

Clé publique

doi:10.25911/027g-8378

Auteurs

Teo, Bryan

Année déclarée

2026

Langue déclarée

und · en_AU

Type source

Thesis (PhD)

Première détection

2026-11-09T19:08:23.879677+00:00

Dernière observation des métadonnées

2026-11-09T19:08:23.879677+00:00

Dernière vérification HTTP

Non effectuée

Résumé documentaire — langue originale

Nuclear fusion power is the promise of clean energy generation to meet the demands of the new century. However, containing a plasma with a core temperature ten times hotter than that of the sun is no easy task. The confinement vessel must be constructed from resilient materials that can withstand both the heat and the bombardment of the plasma species. ITER is the first proof-of-concept reactor in constructed. This thesis aims to assist in ITER's goals of understanding the complex fundamental plasma-material interactions and developing materials resilient to the harsh reactor conditions in the global push for nuclear fusion energy. The first goal of the thesis aims to investigate the thermodynamic properties of helium (He) bubbles to contribute to the existing understanding and models of He PMI expected in ITER. Bulk W samples were exposed to a low-energy (25 eV) He plasma at 573 K (LT) and 1050 K (HT). After plasma exposure, these samples were subject to TDS, ERDA, SEM, and in-situ TEM annealing. Structures comprised of a network of bubbles were stable up to 998 K during in-situ TEM annealing of the LT sample. He desorption from the LT sample was inferred to stem from interstitial He rather than these bubbles. Bubbles in the HT sample were found to be thermally active up to 998 K, resulting in an increase in the average bubble size and a loss of number density. GISAXS analysis on the effects of annealing on bubble radius distribution produces results consistent with the TEM. An "Ostwald ripening-like" model was proposed to explain the differences in annealing behaviours of the LT and HT samples. In-situ TEM annealing of a HT bulk W sample at 1073 K showed a reconfiguration of lattice atoms to reduce the surface area of large voids left behind after plasma exposure. It is suggested that lattice effects also contribute to the formation of fuzz and require more investigation. The results provided a deeper understanding of the bubble formation mechanism and subsequent thermodynamics based on the plasma exposure temperature. The differences in behaviour observed from these experiments can be used to help explain temperature-dependent effects such as recrystallisation suppression and form a wide set of consistent experiments for computational models to be compared to. The second goal of the thesis is to characterise the He-PMI of three alloys for possible use as a divertor material in future fusion reactors. Four sputter-deposited materials: sputtered pure W (WS), W-5%(wt)Ta, W-3%(wt)Cr, and W-5%(wt)Ta-3%(wt)Cr were exposed to 25 eV He plasma at LT and HT. After plasma exposure, these materials were subject to TDS, ERDA, SEM and TEM. The addition of Ta to Ws and WCr has been shown to inhibit the formation of He bubbles. This may be a case of increasing the fluence threshold for fuzz rather than the complete prevention of fuzz. Additionally, the addition of Ta slows grain growth of both Ws and WCr. This property is intrinsic to Ta rather than from an emergent W-Ta interaction and could potentially be used to delay the undesired but inevitable onset of recrystallisation. The electrical resistivities of the four sputtered films were measured as a surrogate for its thermal conductivity to characterise how this property changes with alloying and He exposure. The alloying of Ta significantly increases the resistivity of W, much more than that of Cr. As expected, He plasma exposure degrades the resistivity regardless of the material. WTaCr has the largest electrical resistivity and suffers the largest increase after He plasma exposure likely due to the presence of both alloying impurities deforming the lattice and serving as trapping sites. Both effects increase probability of electron scattering. The reduction in thermal conductivity from both alloying and He plasma irradiation, especially for alloys with more elements, will have to be considered alongside its other benefits when determining its viability for fusion reactors.

Identifiants

DOI

10.25911/027g-8378

HANDLE

1885/733797176

OAI

oai:openresearch-repository.anu.edu.au:1885/733797176

Repères documentaires

Famille documentaire

Thèse

Types déclarés par les sources

Thesis (PhD)

Entités naturelles mentionnées

Espèce

Les mentions d’entités ne constituent pas une preuve de reconnaissance juridique. La juridiction étudiée est distincte du pays d’affiliation des auteurs.

Sources

Repository · Document 1 · Document 2

• DOI · https://doi.org/10.25911/027g-8378
• Document · https://hdl.handle.net/1885/733797176

Statut documentaire

Pertinence à examiner

Bibliothèque

Cette identité n’est pas encore intégrée à la Bibliothèque juridique.