24P082-P
Hydrogen isotope removal in ion-damaged W
照射損傷を与えたタングステン中の水素同位体除去について
Takuya Karikawa1 ,Heun Tae Lee1 ,Yusuke Ohtsuka1 ,Yoshio Ueda1 ,Ikuji Takagi2 ,Takashi Inoue3
Masaki Taniguchi3 ,Keiji Sakamoto3
1
1
狩川拓也 ,Heun Tae Lee ,大塚裕介1,上田良夫1,高木郁二2,井上多加志3,谷口正樹3,坂本慶司31

Graduate School of Engineering, Osaka University,2-1Yamadaoka, Suita, Osaka 565-0871, Japan
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
2Graduate School of Engineering, Kyoto University: Yoshidahonmachi, Sakyo, Kyoto, Japan
京都大学大学院工学研究科 〒606-8501 京都市左京区吉田本町
３Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193, Japan
日本原子力研究開発機構 〒311-0193 茨城県那珂市向山801-1

The purpose of this study is to investigate an isotope exchange phenomena to remove tritium accumulated
in damaged tungsten. Tungsten specimens damaged by high energy hydrogen were irradiated by low
energy deuterium ion beam, then irradiated by hydrogen ion beam. The deuterium depth profiles weremeasured by NRA and SIMS. Experimental results and TMAP modeling results on isotope exchange
phenomena between deuterium and hydrogen were compared.

1. Introduction
Tungsten is one candidate for plasma facing
materials (PFM’s) in ITER and is planned for
future fusion reactors. PFMs are simultaneously
exposed to fuel particles and 14MeV neutrons
generated by DT reactions. The radiation damage
produced by the neutrons will increase tritium
retention in tungsten due to production ofhydrogen isotope trap sites. Increased tritium
retention will impact safety and operational limitsof ITER and future fusion reactors. Therefore, it
is important to assess the trap characteristics
produced in tungsten and develop the way toremove tritium trapped in these sites. It is known
that annealing is one way to remove tritium. In
this study, however, we study the effect ofisotope exchange because it could take place atlower temperatures than annealing temperatures.
2. Experiment
In this study, tungsten damage were produced byhigh energy negative hydrogen ions (~300keV and700keV) using MeV Test Facility (MTF) in JAEA.
This energy difference makes the damage depth
profiles different. All of the damaged specimens
were irradiated at 473K by a low energy(~1keV)
deuterium ion beam using HiFIT in Osaka Univ. tothe fluence of 1.5×1024D/m2. Then the irradiatedspecimens were irradiated at 473K by the sameenergy of hydrogen ion beam to the fluence of
5.0×1022~1.5×1024H/m2. in order to observe
removal of initially implanted deuterium by isotope
exchange reactions. The deuterium depth profiles inthe specimens were measured by Nuclear Reaction
Analysis(NRA) and Secondary Ion Mass

Spectrometry(SIMS). In our study, 300keVH
damaged specimens were used to see isotope
exchange only, and 700keV damaged specimens
were used to see isotope exchange for trapped
deuterium atoms at high energy trap sites. For thelatter experiment, the samples with deuterium
implanted were annealed at 573 K to desorb trapped
deuterium at relatively low energy trap sites.
3. Result300keV ion damaged specimens were firstly
irradiated to the fluence of 1.5×1024D/m2 deuterium,
which is enough for deuterium saturation atdamaged region [1], followed by hydrogen
irradiation to the fluences of 5.0×1022, 1.0×1023,
5.0×1023, 1.5×1024H/m2. Irradiation temperature
was 473K. There was no deuterium left in thespecimens irradiated by hydrogen to the fluence of
higher than 5.0×1023H/m2 from the SIMS data. This
result suggested that isotope exchange between
deuterium and hydrogen took place.
On the other hand, there should be left only
strongly trapped deuterium after annealing in
700keV damaged specimens. We will present
results on whether these strongly trapped deuterium
are removed by hydrogen isotope exchange at thetemperature where the strongly trapped deuterium
are not thermally desorbed. We will also show
simulation results by the TMAP7 code, which cansimulation hydrogen isotope retention and diffusion
in materials.
Reference[1]M.Fukumoto et al., Journal of Nuclear Materials
390–391 (2009) 572–575