Speaker
Irina Borodkina
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O2.106.pdf
Isotope wall content control strategy in the upcoming D, H and T
experimental campaigns in JET-ILW
I. Borodkina1,2, D. Douai3, D. Borodin1, S.Brezinsek1, D.Alegre4,5, E.de la Cal5, Y. Corre3,
A.Drenik6 J. Gaspar3, C.C. Klepper7, T. Loarer3, G.Sergienko1, S. Vartanian3, T. Wauters8,
and JET Contributors*
1
, IEK – Plasmaphysik, TEC , Germany
2
National Research Nuclear University MEPhI, 31, Kashirskoe sh., 115409, Moscow, Russia
3
CEA, IRFM, F-13108 Saint Paul Lez Durance, France
4
D p d I í E é , UNED, C/ d R 1 , 80 0 M d d, Sp
5
Laboratorio Nacional de Fusion, CIEMAT, Avda. Complutense 22, 28040 Madrid, Spain
6
Max-Planck-I f p y k, D-85748 Garching, Germany
7
Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6169, USA
8
Laboratory for Plasma Physics, ERM/KMS, 1000 Brussels, Belgium, TEC Partner
* See the author list of X. Litaudon et al., Nucl. Fusion 57 (2017) 102001
JET is the largest tokamak in use and currently the only one capable of handling tritium (T).
Equipped with the ITER-like wall (ILW), a tungsten (W) divertor and beryllium (Be) main
chamber, JET will soon operate with pure hydrogen isotopes in order to prepare scenarios for
ITER [1]. The total budget of 1020 14 MeV fusion neutrons for the upcoming isotope
campaigns in JET being consumed in 250 high power plasma pulses (40MW/5s) with only
1%D in the T campaign (or 1%T in the following D campaign), a strategy for reducing the D
(T) wall inventory below this level before the T (D) campaign is mandatory.
In this paper, we present the elaborated strategy to control and measure the D wall inventory.
The efficiency of the different methods which are composing it are evaluated, as well as their
combination aiming at maximizing access to different D retention areas in the JET-ILW. We
also discuss the review of experimental data and diagnostics (divertor spectroscopy, sub-
divertor Rest Gas Analysis) undertaken in order to reliably assess the isotope ratio and thus
the strategy efficiency. The strategy includes one week vacuum vessel baking at 320°C,
combined with isotopic exchange by hydrogen Glow Discharge and Ion Cyclotron Wall
Conditioning, preferentially accessing D retained in the main chamber. Post-mortem analysis
of JET PFCs after the first two ILW campaigns revealed however that the majority of the fuel
is retained in Be deposited layers at the inner divertor top [2] with thickness up to 40µm, and
that complete thermo-desorption of the co-deposited fuel requires surface temperatures
beyond 550°C [3]. Analysis of IR measurements in plasma discharges with inner strike point
raised to the inner divertor top shows that such temperatures and beyond can be reached.
Whereas spectroscopy in these shots reveals the enhancement of Dα, Be I and Be II emission
intensities at the strike point, BeD emission intensity is almost absent, consistently with the
fact that chemical sputtering of the co-deposited layers is inhibited if surface temperature is
higher than 270ºC [4]. Similarly, another scenario designed with strike points on vertical
targets will aim at depleting D stored in the outer divertor.
[1] X. Litaudon et al. Nucl. Fusion 57 (2017) 102001; [2] A. Widdowson et al, Nucl. Fusion 57 (2017) 086045
[3] K. Heinola et al. Nucl. Fusion 57 (2017) 086024; [4] R.P. Doerner et al, J. Nucl. Mater.681 (2009) 390–391
