S-P1-5
Tritium accumulation in plasma facing walls
プラズマ曝露した核融合炉材料へのトリチウムの蓄積
Yuji Torikai1), Akira Taguchi1), Masao Matsuyama1), Nobuaki Noda1) and Yukio Nakumura2)
鳥養 祐二1), 田口 明1)，松山 政夫1)，野田 信明1)，中村 幸男2)
1) Hydrogen Isotope Research Center, University of Toyama
Gofuku3190, Toyama 930-8555, Japan1) 富山大学 水素同位体科学研究センター 〒930-8555 富山市五福3190
2) National Institute for Fusion Science
Oroshi-cho, Toki-city, Gifu 509-5292, Japan2) 核融合科学研究所 〒509-5292 岐阜県 土岐市 下石町322-6

Accumulation of tritium on the surface and in the bulk (at depths up to 1 mm) in poloidal divertor tiles
exposed to D-T plasma shots in JET was measured by β-ray-induced X-ray spectroscopy (BIXS).
Additionally, tritium accumulation in tungsten preliminary exposed to TEXTOR core plasmas andsubsequently loaded with tritium was determined by IP method. Tritium distributions were highly
non-uniform over the plasma-facing wall surface.

1. Introduction
During an operation of fusion machines with
D-T plasma, tritium (T) is accumulated inplasma-facing components (PFCs). To improvethe understanding of tritium behavior in PFCs
under plasma exposure, various techniques wereused to measure a tritium accumulation anddistribution in those components.
In this study, a complete set of 10 poloidal
divertor tiles (Mark IIA configuration) retrieved
from JET after the first Deuterium-Tritium
Experiment campaign (DTE1) was analyzed by
β-ray-induced X-ray spectroscopy (BIXS) [1].
Additionally, the tritium accumulation in tungsten
preliminary exposed to the TEXTOR plasmas andsubsequently loaded with tritium was examined byusing IP technique.
2. Experimental
2.1 Measurement of tritium distribution in JET
divertor tiles by BIXS
A complete set of 10 poloidal divertor tiles
numbered from IN1 to ON10 was investigated byBIXS. X-ray spectra from the tiles were measured
at Tritium Laboratory of Karlsruhe Institute ofTechnology (KIT) by using a portable germanium
X-ray detector.
2.2 Measurement of tritium accumulation tungsten
preliminary exposed to the TEXTOR plasma
Tungsten samples were prepared from W rods
provided by Dr. Philipps (FZ Jülich) by mechanicalcutting. The samples were cleaned and placed into atritium exposed apparatus. First, the samples werepre-evacuated up to 10-6 Pa at 573 K for 3 h, andthen were loaded at 573 K with tritium from theD-T mixed gas at 1.2 kPa for 3 h. Tritium
concentration distribution over the samples surface
was measured by the Imaging Plate technique (IP).
3. Results
3.1 Tritium distribution in JET divertor tiles
Figure 1 shows a map of tritium distribution overthe surfaces for 10 JET tiles. One can see that thetritium concentrations on the surface are highly
non-uniform both in the toroidal and poloidal
directions. The maximum Ar(Kα) intensity areabout 120 times higher than the minimum intensity.
Analysing X-ray spectra with the use ofcomputer simulation, tritium depth profiles weredetermined. Four types of the depth profile wereobtained by BIXS analysis over the divertor surface(Figure 2).
There are many factors which influence on
tritium depth profile and the amount of tritium.
Tritium can be retained in the co-deposition layers
on the surface, and the tritium content depends on
the rate of co-deposition, rate of erosion, flux oftritium particles, power loads and etc. Tritium canbe implanted from plasma into the co-deposition,and in this case the tritium amount depends on theplasma flux, tritium ion energy, tile temperature,and properties of the tile in the near surface region.
Tritium can desorb from the surface and canmigrate into the bulk. The competition between
these two processes determines the T accumulationand the depth profile.

Figure 3 shows tungsten specimens mounted on
the TEXTOR limiter (a), the specimens and IP
images after tritium loading both for specimen set
exposed to the TEXTOR plasmas (b) and forspecimen set without plasma exposure (c). High
content of tritium was observed on the specimen
placed on the central part of the limiter. The tritium
accumulation in the central specimen can be
explained by carbon deposition. It is well know thatcarbon impurities deposited on the surface act astritium trapping sites.
4. Conclusions

Tritium accumulations in a complete set of 10
poloidal divertor tiles retrieved JET after DTE 1
and in tungsten rods exposed TEXTOR core plasma
were investigated. Tritium distributions were highly
non-uniform and very complicated on theplasma-facing wall.
References[1] M. Matsuyama et. al., J. Nucl. Mater. 290-293,(2001) 437.

Intensity of X-ray, I / counts sec-1

3.2 Tritium accumulation in tungsten preliminary
exposed to TEXTOR plasmas
4030
20
100

Inner
OuterDivertor Base Divertor Divertor
left

30
20
100

center30
20
100rigft

12IN IN

43IN BN

57689BN BN BN ON ON

10NOFig. 1. Intensities of Ar(Kα) measured by BIXS.