01Dp06
ガンマ線照射と同位体交換反応によるセラミック被覆からのトリチウムの除去
Tritium removal from ceramic coating by gamma-ray irradiation with isotopic exchange
中澤章太*1，波多野雄治2，芦川直子3, 4，居波渉1，川田善正1，近田拓未1
Shota Nakazawa1, Yuji Hatano2, Naoko Ashikawa3, 4, Wataru Inami1, Yoshimasa Kawata1, Takumi Chikada1
1

静岡大学、2富山大学、3核融合科学研究所、4総合研究大学院大学
1
Shizuoka Univ., 2Univ. Toyama, 3 NIFS, 4SOKENDAI

1. Introduction
In a D-T fusion reactor blanket system, precise
prediction and evaluation of hydrogen isotopes (HI)retention into structural materials are needed toestablish appropriate HI handling in terms of fuelefficiency as well as radiological hazard. Anotherindispensable prerequisite in the reactor is to clarify
neutron and gamma-ray irradiation effects, which
may have an impact in the HI retention behavior.
Besides, it is expected that an interaction of
gamma-ray irradiation with HI exchange may affectthe HI retention since deuterium and tritium exist in
the blanket at the same time during the operation. In
this study, a new method of tritium removal wasinvestigated through the measurements of HI
concentrations in ceramic-coated samples after
exposure to HI with and without gamma-ray
irradiation under different atmospheres.
2. Experimental
Reduced activation ferritic/martensitic steel
F82H (Fe-8Cr-2W, F82H-BA07 heat) plates wereused as substrates. In this work, two kinds ofceramic coating were selected: zirconium oxide(ZrO2) and yttrium oxide (Y2O3) coatings. The ZrO2
coating with a thickness range of 700‒900 nm andthe Y2O3 coating with thicknesses of 650 nm and3.7 μm were fabricated by metal organic
decomposition and radio-frequency magnetron
sputtering, respectively. These samples wereexposed to 8.9-Torr tritium for 3 hours at 500 ºC.
After tritium exposure, the samples were separately
stored under argon gas at atmospheric pressure and80-kPa deuterium for about a month. After that, theamount of tritium retained in the ceramic-coatedsamples were examined by tritium imaging plate(T-IP) technique and β-ray induced X-ray
spectrometry (BIXS). As another measurement ofhydrogen isotope retention without tritium, thecoated samples were exposed to 80-kPa deuteriumfor 50 h at 500 ºC, and then were irradiated by
gamma-ray with the dose rate of 0.45‒2.0 Gy/s atroom temperature using a 60Co gamma-ray source.
After that, the concentrations of deuterium andprotium in the samples were analyzed using a

nuclear reaction analysis with(15N-NRA).

15

N ion beam

3. Results and discussion
Table shows T-IP results for the samples
exposed to tritium. From the obtained β-ray signals,
the ZrO2-coated samples possessed an activity
concentration of approximately 140 GBq/cm3, andthe concentration was 4 times higher than that of
the Y2O3-coated samples. After two months, theactivity concentration decreased in the samples
stored under argon gas rather than those stored
under D2 gas, suggesting that the retention behavior
varied with hydrogen isotope partial pressure in theenvironment.
The 15N-NRA results showed that detected HI
signals from ZrO2-coated samples decayed with 15N
ion dose, regardless of gamma-ray irradiation. That
indicates the amount of HI decreased due todiffusion, which was promoted by energy transferfrom 15N ions. In addition, the amount of movable
HI increased for all the gamma-ray irradiatedsamples, suggesting that gamma-ray made retained
HI in the ZrO2 coatings movable. This effect may
contribute to the development of tritium removal
technology in D-T fusion reactors.
In the presentation, the results of BIXS will bealso discussed.
Table T-IP on standard samples, ZrO2- andY2O3-coated with and without tritium exposure