Surface chemistry of neutron irradiated tungsten in a high-temperature multi-material environment
Nuclear Materials and Energy 34 (2023) 101323
Chase N. Taylor a,*, Masashi Shimada a, Yuji Nobuta b, Makoto I. Kobayashi c, Yasuhisa Oya d,
Yuji Hatano e, Takaaki Koyanagi f
a Fusion Safety Program, Idaho National Laboratory, Idaho Falls, ID, 83415, USA
b Laboratory of Plasma Physics and Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Japan
c National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
d Graduate School of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan
e Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555, Japan
f Materials Science and Technology Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6138, USA
Abstract
Tritium (T) retention characteristics in dust collected from the divertor in JET with ITER-like wall (JET-ILW) after the third campaign in 2015–2016 (ILW-3) have been examined in individual dust particles by combining radiography (tritium imaging plate technique) and electron probe micro-analysis. The results are summarized and compared with the data obtained after the first campaign in 2011–2012 (ILW-1). The dominant component in ILW-1 dust was carbon (C) originating from tungsten-coated carbon fibre composite (CFC) tiles in JET-ILW divertor and/or legacy of C dust after the JET operation with carbon wall. Around 85% of the total tritium retention in ILW-1 dust was attributed to the C dust. The retention in tungsten (W) and beryllium (Be) dominated particles was 100 times smaller than the highest T retention in carbon-based particles. After ILW-3 the main component contributing to the T retention was W. The number of small W particles with T increased, in comparison to ILW-1, most probably by the exfoliation and fragmentation of W coatings on CFC tiles though T retention in individual W particles was smaller than in C particles. The detection of only very few Be-dominated dust particles found after ILW-1 and ILW-3 could imply stable Be deposits on the divertor tiles.
https://doi.org/10.1016/j.nme.2022.101323
Accepted:Accepted 29 November 2022