This title appears in the Scientific Report :
2023
Please use the identifier:
http://dx.doi.org/10.34734/FZJ-2023-03599 in citations.
Joining of tungsten and steel for the first wall of a future fusion reactor
Joining of tungsten and steel for the first wall of a future fusion reactor
Nuclear fusion energy has the potential to be the future source of CO2-free clean energy. However, harnessing it needs overcoming significant engineering and scientific challenges. One major challenge is manufacturing a first wall (FW) that can withstand extreme thermal, particle, and neutron loadin...
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Personal Name(s): | Ganesh, Vishnu (Corresponding author) |
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Contributing Institute: |
Plasmaphysik; IEK-4 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2023
|
Physical Description: |
xxx, 142, a-v |
Dissertation Note: |
Dissertation, Univ. Bochum, 2023 |
ISBN: |
978-3-95806-715-8 |
DOI: |
10.34734/FZJ-2023-03599 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
ohne Topic |
Series Title: |
Schriften des Forschungszentrums Jülich Reihe Energie & Umwelt / Energy & Environment
614 |
Link: |
OpenAccess |
Publikationsportal JuSER |
Nuclear fusion energy has the potential to be the future source of CO2-free clean energy. However, harnessing it needs overcoming significant engineering and scientific challenges. One major challenge is manufacturing a first wall (FW) that can withstand extreme thermal, particle, and neutron loading. As per the current understanding, it would consist of protective tungsten (W) armour joined to the underlying structure. This structure is made of reduced activation ferritic/martensitic steel, like Eurofer 97. Presently, several literatures presume that the direct joining of W and Eurofer 97 cannot be foreseen, as the coefficient of thermal expansion (CTE) of Eurofer 97 is more than twice of W. This leads to macroscopic thermal stress at the bonding seam that might cause early failure of the joint during the operation of the reactor. One solution is redistributing the stresses by introducing a graded interlayer between them that can gradually change the CTE. This graded interlayer is known as functionally graded material (FGM), which is itself a mixture of W and steel with several layers, each with a gradually varying W/steel ratio; each layer is a W/steel-composite of a certain volume content of W. Thus, the goal was to investigate the feasibility of this concept. Three different manufacturing techniques have been explored: spark plasma sintering (SPS), electro discharge, and atmospheric plasma spraying (APS); their feasibility was investigated. First, the processing parameters of the manufacturing techniques were optimized to produce individual composites—consisting of three volume concentrations of W: 25 %, 50 %, and 75 %—with low porosity while minimizing the formation of brittle intermetallic compounds. It was found that the EDS was not the most unsuitable technique. Second, using the optimized parameters, composites were prepared. These were then characterized for their microstructure, mechanical, and thermophysical behaviour. The elastic modulus and flexural deformation behaviour were determined by resonant ultrasound spectroscopy and a miniature 4-point bending test. The thermophysical characterization was carried out by dilatometry, dynamic differential scanning calorimetry and laser flash analysis method. The composites produced by the SPS had the mostpromising and superior properties compared with that of APS. Third, post characterization, graded joint, directly bonded W-steel joint, and joint featuring a V interlayer were manufactured. Fourth, these joints were benchmarked by high heat flux (HHF) test at an electron beam facility to investigate their thermal fatigue response. This revealed an important finding; the most critical factor responsible for the lifetime of a graded joint is the bonding between the W and FGM, and not the properties of FGM itself. The thesis also concluded that none of the FGM concepts improved the lifetime of the joint. Finally, a thorough discussion led to recommendations for future work towards successfully realising the joining of W and steel. |