03pC6
チタン酸リチウムにおけるトリチウム滞留挙動に及ぼす照射損傷影響

Effect of irradiation damages on tritium retention behavior
in lithium titanate戸田 健介1)、小林 真1)、内村 大道1)、佐藤 美咲1)
藤井 俊行2)、山名元2)、大矢 恭久1)、奥野 健二1)
Kensuke Toda1), Makoto Kobayashi1), Hiromichi Uchimura1), Misaki Sato1)
Toshiyuki Fujii2), Hajimu Yamana2), Yasuhisa Oya1) and Kenji Okuno1)
1

静岡大学大学院理学研究科 2京都大学原子炉実験所
1
Graduate School of Science, Shizuoka University, 2 Research Reactor Institute, Kyoto Universityby -ray irradiation, where E’-center is known as thetrapping site of hydrogen isotopes. It was considered thatmost of deuterium dissolved in Li2TiO3 grains wastrapped by oxygen vacancy. Figure shows the deuterium
TDS spectra for -ray irradiated sample with the dose of
1 MGy and unirradiated sample. Three deuterium
desorption stages were observed at around 400, 550 and650 K, attributing to the desorption stage of deuterium
adsorbed on the surface, trapped by oxygen vacancy andbound to oxygen as O-D bonds. FT-IR measurement
revealed that there were two types of O-D bonds, namely
O-D bond affected by Li vacancy and interstitial O-Dbond. The deuterium retention as O-D bond wassignificantly enhanced, but the deuterium retention
trapped by oxygen vacancy was clearly reduced by -rayirradiation. It was reported that the potential energy
barrier of deuterium trapped by Li vacancy with bound tooxygen was lower than that retained in interstitial sites,
considering that deuterium retained in Li2TiO3 would
react with the dangling bond of oxygen, near the site
such as Li vacancy, resulting the formation of O-D bond.
It was clarified that the tritium retention as O-T bond inneutron irradiated Li2TiO3 was also increased with theirradiation damages as the case with -irradiated sample.
Therefore, it was founded that the formation of O-T bondby irradiation damages would be significantly contributeto the tritium inventory

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Desorption rate / 10 D gLithium titanate (Li2TiO3) is one of the candidates as
the tritium breeding material for the test blanket moduleof ITER due to its good tritium recovery efficiency andchemical stability. Elucidation of migration processes oftritium produced by nuclear reaction, such as 6Li (n, ) Tin Li2TiO3, is important to establish the effective blanket
system in fusion reactor. In actual condition, it isexpected that irradiation damages will be introduced
during neutron irradiation, and tritium retention
behaviors will be affected by the interaction between
tritium
andirradiation
damages.
Therefore,
understanding of correlation between recovery ofirradiation damage and tritium retention behaviors isrequired. In this study, deuterium exposed Li2TiO3 wasirradiated by -ray or neutron in order to introduce
irradiation damages. Then, the deuterium release
behavior and the annihilation behavior of irradiation
damages were evaluated by thermal desorption
spectroscopy (TDS) and electron spin resonance (ESR),respectively. In addition, fourier transform infrared
spectroscopy (FT-IR) measurement was also performedfor -ray irradiated sample to investigate the state of O-Dbond. The effect of the irradiation damages on tritium
retention behaviors was discussed.
Powder of Li2TiO3 purchased from Furuuchi Chemical
Corporation was preheated at 1173 K for 3 hours underhigh vacuum. Then, the sample was exposed todeuterium gas at 673 K with the pressure of 2.0 × 10 5 Pa
for 24 hours to introduce deuterium homogeneously. Thedeuterium gas exposed sample was introduced intoquartz tubes and vacuum-encapsulated. Thereafter,  -rayirradiation was performed at room temperature with thedoses of 1 MGy using Co-60 -ray irradiation facility at
Shizuoka University. For the other samples, thermal
neutron irradiation was performed with the fluence of 3.3
× 1015 n cm-2 at Research Reactor Institute, Kyoto
University (KURRI). TDS experiments were carried out
for these samples to investigate the deuterium retentionbehavior from room temperature to 1173 K with theheating rate of 5 K min−1. The ESR and FT-IR
measurements were performed to elucidate the stabilityof irradiation damages and O-D bonds.
The ESR measurement showed that the amounts ofoxygen vacancy (E’-center) and dangling bonds ofoxygen such as O--center and O2-center were increased

unirradiated sample
1 MGy g-irradiated sample

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Temperature. / KFig. Deuterium TDS spectra for deuterium exposed Li2TiO3with or without -ray irradiation at 1 MGy.