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  4. Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns
 
research article

Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns

Jepu, I
•
Matthews, G. F.
•
Widdowson, A.
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August 1, 2019
Nuclear Fusion

Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2).

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Type
research article
DOI
10.1088/1741-4326/ab2076
Web of Science ID

WOS:000472804000005

Author(s)
Jepu, I
Matthews, G. F.
Widdowson, A.
Rubel, M.
Fortuna-Zalesna, E.
Zdunek, J.
Petersson, P.
Thompson, V
Dinca, P.
Porosnicu, C.
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Date Issued

2019-08-01

Publisher

IOP Publishing Ltd

Published in
Nuclear Fusion
Volume

59

Issue

8

Article Number

086009

Subjects

Physics, Fluids & Plasmas

•

Physics

•

jet

•

iter-like wall

•

beryllium

•

erosion

•

melt layer motion

•

operation

•

inventory

•

limiters

•

tokamaks

•

divertor

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
Available on Infoscience
October 22, 2019
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/162208
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