An overview of tritium retention in dust particles from the JET-ILW divertor
Physica Scripta 97 (2022) 024008
T Otsuka1, S Masuzaki2, N Ashikawa2,3, Y Torikai4, Y Hatano5, M Tokitani2,3, Y Oya6, N Asakura7, T Hayashi7, H Tanigawa7, Y Iwai7, A Widdowson8, M Rubel9 and JET Contributors10
1 Department of Electric and Electronic Engineering, Kindai University, Higashi-Osaka, Japan
2 National Institute for Fusion Science, Toki, Japan
3 The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
4 Graduate School of Science and Engineering, Ibaraki University, Mito, Japan
5 Hydrogen Isotope Research Center, University of Toyama, Toyama, Japan
6 College of Science, Shizuoka University, Shizuoka, Japan
7 National Institutes for Quantum and Radiological Science and Technology, Rokkasho, Japan
8 Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, United Kingdom
9 KTH Royal Institute of Technology, Stockholm, Sweden
Author note
10 See author list: J. Mailloux et al 28th IAEA Fusion Energy Conference, 2021.
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.
Accepted:17 December 2021