27E14P
ヘリウム混合照射におけるW中のトリチウムリテンションモデリング
Modeling tritium retention in tungsten under mixed helium irradiation
遠藤博史, Heun Tae Lee, 大塚裕介, 上田良夫
Hiroshi Endo, Heun Tae Lee, Yusuke Ohtsuka, Yoshio Ueda
大阪大学大学院工学研究科 〒565-0871 大阪府吹田市山田丘 2-1
Graduate School of Engineering Osaka University, 2-1Yamadaoka, Suita, Osaka, 565-0871, JapanThe detail of the benchmarked experiments is shown.
Specimens used in the permeation experiment werepolycrystalline W with thickness of 30 µm supplied by
A.L.M.T. Corp., Japan. D ion irradiation (D-only case)as well as mixed D-He ion irradiation (D-He case) at 1
keV was performed at 550 K ≤ T ≤ 1050 K. The
incident flux varied from 1019- 1020 m-2s-1. The Heconcentration was fixed at 2 %.
To model the experimental data, the parameters weredetermined as below. Diffusivity, D, and solubility, S,
were taken from Frauenfelder [4]. Initially, Anderl’s[5] recombination coefficient was used. However, to fit
the experimental data for D-only case, the front
segment recombination coefficient, K1, needed to bevaried. Modification of hydrogen transport during
mixed He-D irradiation was modeled by varying thefront segment recombination coefficient, K2, anddiffusivity, D2.
Finally, Simulation of ITER-like conditions was doneby assuming full W divertor and first walls.

3. Result
Tritium retention with and without He irradiation
under ITER-like condition was estimated using
TMAP7 code. The surface temperature of W divertor
and W first wall were taken as 500 K and 400 K,
respectively [6]. The incident flux of W divertor and W
first wall were set to be 2.0 x 1023 m-2 s-1 and 1.4 x 1019m-2 s-1, respectively. The hydrogen transport parameters
were benchmarked against ion driven permeation
experiments.
Fig. 5 shows the calculated T retention with andwithout He irradiation. Without He irradiation, the T
retention estimated in this work was lower byapproximately two orders of magnitude than previous
estimate by Roth et al. [6]. This was due to different
trap parameters resulting in different trap filling
dynamics and due to traps filled sequentially (strongtrapping) using 1.8 eV traps. With He irradiation, x 5
reduction in T retention observed compared to D-onlycase. The calculations were in good agreement with aprevious estimate by Wampler et al.[7]1028Retained amount (T-atoms)

1. Introduction
Tungsten (W) is a plasma facing material in ITER
divertor and candidate armor material for DEMO. The
evaluation of tritium (T) retention is important due toits impact on safety and operation. T retention in ITER
has been estimated by the previous studies. In the caseof D-T phase, neutrons and He ash will be present. On
the one hand, neutrons create additional trap sites
resulting in an increase in T retention. On the otherhand, He can strongly reduce hydrogen retention in W
[1] by limiting T diffusion.
In this paper, T retention in W under mixed Heirradiation is modeled using TMAP7. In contrast to
previous studies, simulations were performed usinghydrogen transport parameters benchmarked frompermeation experiments [2]. First, the recombination
coefficient was determined from D-only irradiation
case. Next, recombination coefficient and diffusivity
required for mixed D-He irradiation case was fitted.
Finally, the benchmarked transport parameters and trap
parameters from recent neutron damage study [3] wereused to estimate T inventory in ITER-like conditions.
2. Procedure

Roth&Ogorodonikova
700g limit （D-only)

1027
1026
1025

This work(D-only)

1024
This work (D-He)
1023
1022

Wampler (D-He)
104

105

106

107

time (s)Fig.1 Estimate of T retention in ITER (All W case). The solid lines
indicate T retention with and without He irradiation. Plotted indashed line are previous studies by Roth et al [6] and Wampler andDoerner [7].

Reference[1] V. Kh. Alimov et al., J. Nucl. Mater. 420 (2012)
370-373.
[2] H.T. Lee et al., J. Nucl. Mater. 415 (2011)
S696-S700.
[3] Yuji Hatano et al., 20th Int. Conf. PSI (2012).
[4] R. Frauenfelder, J. Vac. Sci. Technol. 6 (1969)
388.
[5] R.A. Anderl et al., Fusion Tech. 21 (1992) 745.
[6] Roth J. et al., J. Nucl. Mater. 390-391 (2009) 1-9.
[7] Wampler W R and Doerner R, Nucl. Fusion 49(2009) 115023.