Material migration in tokamaks: Erosion-deposition patterns and transport processes
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]
Controlled thermonuclear fusion may become an attractive future electrical power source. The most promising of all fusion machine concepts is called a tokamak. The fuel, a plasma made of deuterium and tritium, must be confined to enable the fusion process. It is also necessary to protect the wall of tokamaks from erosion by the hot plasma. To increase wall lifetime, the high-Z metal tungsten is foreseen as wall material in future fusion devices due to its very high melting point. This thesis focuses on the following consequences of plasma impact on a high-Z wall: (i) erosion, transport and deposition of high-Z wall materials; (ii) fuel retention in tokamak walls; (iii) long term effects of plasma impact on structural machine parts; (iv) dust production in tokamaks.
An extensive study of wall components has been conducted with ion beam analysis after the final shutdown of the TEXTOR tokamak. This unique possibility offered by the shutdown combined with a tracer experiment led to the largest study of high-Z metal migration and fuel retention ever conducted. The most important results are:
- transport is greatly affected by drifts and flows in the plasma edge;
- stepwise transport along wall surfaces takes place mainly in the toroidal direction;
- fuel retention is highest on slightly retracted wall elements;
- fuel retention is highly inhomogeneous.
A broad study on structural parts of a tokamak has been conducted on the TEXTOR liner. The plasma impact does neither degrade mechanical properties nor lead to fuel diffusion into the bulk after 26 years of duty time. Peeling deposition layers on the liner retain fuel in the order of 1g and represent a dust source. Only small amounts of dust are found in TEXTOR with overall low deuterium content. Security risks in future fusion devices due to dust explosions or fuel retention in dust are hence of lesser concern.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , p. 109
Series
TRITA-EE, ISSN 1653-5146 ; 2017:060
Keywords [en]
TEXTOR, fusion, plasma physics, transport, migration, tracers, tokamak, limiter, divertor, high-Z, ion beam analysis, Rutherford backscattering, Nuclear reaction analysis, Elastic recoil detection analysis
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-209758ISBN: 978-91-7729-461-0 (print)OAI: oai:DiVA.org:kth-209758DiVA, id: diva2:1114187
Public defence
2017-09-19, F3, Lindstedtsvägen 26, Stockholm, 14:59 (English)
Opponent
Supervisors
Note
QC 20170630
2017-06-302017-06-222022-09-05Bibliographically approved
List of papers