24P060-P
Temperature dependence on retention of hydrogen isotope in tungsten material
タングステン材料中水素リテンションの温度依存性
Takahiro Kenmotsu, Motoi Wada
剣持貴弘, 和田 元
Doshisha University, Life and Medical Sciences
1-3, Tatara-Miyakodani, Kyotanabe, Kyoto 631-0321, Japan
同志社大学生命医科学部 〒4631-0321 京田辺市多々羅都谷1－3
The ACAT-DIFFUSE code has been modified so as to calculate the amount of retained hydrogen isotopes
in wall material under exposure to high heat flux of edge localize mode (ELM). The temperature gradientsnear the surface of wall materials due to ELM condition are calculated by the one dimensional finite
element method (FEM). The effect of the temperature gradients of wall materials for the retention ofhydrogen isotopes has been calculated with the ACAT-DIFFUSE code which includes heat transfer
calculation as a subroutine.

2. Calculation model
The ACAT-DIFFUSE code has been used to
calculate the amount of retained hydrogen isotopes inwall material but with homogeneous temperature
profile so far. The ACAT-DIFFUSE has been
modified to take into account of the diffusion andtrapping of hydrogen isotopes under ELM condition
by including subroutines of heat transfer calculation
based on the finite element method (FEM).

3. Result
Figure 1 shows the amount of deuterium atoms
retained in tungsten during a time sequence of l00 eV D +bombardment with temperatures 300 K and 473 K
calculatedwith
ACAT-DIFFUSE
under
the
homogeneous temperature model. The calculation results
have indicated the amount of retained hydrogen isotopes
in tungsten at 300 K is larger than that at 473 K. The
increase of trapped hydrogen isotopes in tungsten atlower temperature results in the enhancement of theamount of retained hydrogen isotopes compared withthat for higher temperature. The temperatures of target
materials play a decisive role for the retention of the18wall+

100 eV DW+

2

Flux=2.0x1015 (D /cm /s)
24. Discussion

101710

100 % trapped

Thelarge
10temperature
gradient near thesurface of wall
10300 K
materials due to473 K
high heat flux of
100 % trapped
10ELM
condition
1010requires inclusion
Fluence (D+/cm2)
of a subroutine toFig. 1. Amounts of deuterium
calculatetheatoms in tungsten at 300 K and
precise temperature
473 K
gradients of wallin tungsten.
materials for accurate calculation of the retention ofhydrogen isotopes during a fusion device operation. The
one dimensional FEM method is applied to calculate thetemperature gradients of wall materials for theACAT-DIFFUSE code. The amount of trapped hydrogenisotopes and diffusion of the isotopes in wall material arelargely modified due to the temperature gradientscompared with those under a homogeneous temperaturemodel. These changes directly affect the amount ofretained hydrogen isotopes in wall material. The effect ofthe temperature gradients near surface of wall materials
for retention of hydrogen isotopes has been calculatedwith ACAT-DIFFUSE. Some initial results of the code
will be introduced.
+Wall materials in a fusion device are exposed tointense bombardments of energetic hydrogen isotopes
and high heat flux as observed in edge localized mode(ELM). They lead to the retention of hydrogenisotopes and at the same time cause large temperature
gradient near the surface in wall materials. The
resulting temperature gradient due to high heat flux
should largely alter the transport of hydrogen isotopes
in wall material, which affects the amount of retainedhydrogen isotopes. To realize the capability forclarifying the effect of the temperature gradient due tohigh heat flux for the retention of hydrogen isotopes,
the dynamic Monte Carlo simulation code
ACAT-DIFFUSE [1] have been modified and used
under ELM conditions.

isotopes inmaterials.

Retention (D /cm )1. Introduction

1615

1416

17

Acknowledgments
This work was partly supported by Grand-in-Aid for
Scientific Research, MEXT, Japan, Priority area 467,
‘Fusion Tritium’.
References[1] Y. Yamamura: Nucl. Instrum. Meth. B28 (1987) 17.