VIII-Ⅱ-1. Project Research
Project 1

PR1

Irradiation Effects on Microstructural Evolution in Materials Irradiatedby Particles with High Energy

Q. Xu
Research Reactor Institute, Kyoto University
OBJECTIVES: Neutron irradiations in KUR have beenused to not only estimate degradation mechanical properties of materials but also develop new materials, such as
material for optoelectronic and high-power devices. In
addition, other irradiation facilities, such as ions, electrons and γ rays, have also been used in the present project research to clarify the damage structural development.
RESULTS: The allotted research subject (ARS) andthe name of co-researches in each ARS are listed below.
Ferritic steels containing Cr are expected to be used forthe first-wall component in fusion reactors. Neutron irradiation induced phase separation in Fe-30Cr binary alloy.
Transmutation of 14C, which related luminescence andnet carrier concentration, in GaN by a (n, p) reactionof 14N was reported. Others results are presented in detailin this progress reports.
ARS-1
Neutron-transmuted Carbon-14 in neutron-irradiatedGaN compensation of DX-like center(K. Kuriyama, T. Ida, K. Kamioka, K. Kushida, and Q.
Xu)
ARS-2
Neutron irradiation effects of superconducting magnet
materials at low temperature(T. Nakamoto, M. Yoshida, T. Ogitsu, Y. Makida, K. Yoshimura, S. Mihara, K. Sasaki, M. Sugano, H. Nishiguchi,
M. Iio, Y. Kuno, M. Aoki, A. Sato, T. Itahashi, Q. Xu, K.
Sato, Y. Kuriyama, Y. Mori and T. Yoshiie)
ARS-3
Study on formation and recovery processes of radiation
damage in crystalline materials(A. Kinomura, K. Sato, Q. Xu and T. Yoshiie)
ARS-4
Blue emission of natural calcite by gamma rays
(T. Awata, Y. Bando and Q. Xu)
ARS-5
Annealing behavior of thermal diffusivity in ceramics
irradiated by 30 MeV electron and neutron(M. Akiyoshi, I. Takagi, T. Yoshiie, Q. Xu, K. Sato)

採択課題番号 24P1

ARS-6
Annealing behavior of vacancy-type defects in Mg-Zn-Y
alloy
with
LPSO
structure
introducedbyelectron-irradiation at liqiud nitrogen temperature(Y. Nagai, K. Inoue, T. Toyama, Y. Matsukawa, Y.
Shimizu, A. Kuramoto, H. Takamizawa, Y. Kakubo, T.
Yoshiie, Q. Xu and K. Sato)
ARS-7
Radiation damage in bulk amorphous alloys by electron
irradiation(F.Hori, N. Onodera, A.Ishii, S.Mineno, A.Iwase, Y.
Yokoyama, Q.Xu, K.Sato and T.Yoshiie)
ARS-8Development of replica extraction method for vanadiumalloys and its application for neutron-irradiated ones
(K. Fukumoto and Q. Xu)
ARS-9
Damage evolution in neutron-irradiated metals during
neutron irradiation at elevated temperatures(I.Mukouda, K. Yamakawa, T. Yoshiie, Q. Xu)
ARS-10
Positron annihilation behavior of Fe-Cr alloys after neutron irradiation in KUR(R. Kasada, K. Sato, Q. Xu, T. Yoshiie)
ARS-11
Similarity of radiation resistance of nanocrystalline Ni by
ion and neutron irradiation(H. Tsuchida, A. Itoh, K. Sato, T. Yoshiie, Q. Xu)
ARS-12
Interaction between deuterium and defects in tungsten (2)(K. Sato, R. Tamiya, Q. Xu and T. Yoshiie)
ARS-13
Irradiation effects on stress loading property of refractory
metal at high temperature(K. Tokunaga, K. Araki, T. Ukita, Q. Xu, T. Yoshiie)
ARS-14
Effect of substrate temperature in nanocell fabrication of
GaSb(N. Nitta, K. Yokoyama and M. Taniwaki
ARS-15
Deuterium retention in electron-irradiated VPS-W
Y. Hatano. J. Shi, T. Nozaki, K. Masude, T. Tokunaga, H.
Watanabe, N. Yoshida, K. Sato and Q. Xu

材料の組織変化に及ぼす高エネルギー粒子線の照射効果（京大・原子炉）徐 虬

プロジェクトPR1-1

Neutron-Transmuted Carbon-14 in Neutron-Irradiated GaN:
Compensation of DX-like Center

K. Kuriyama, T. Ida, K. Kamioka, K. Kushida1 andQ. Xu2compensated by the transmuted 14C acceptor.

College of Engineering and Research Center of
Ion Beam Technology, Hosei University
1
Osaka Kyoiku University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: In our previous study [1], we reported that Ge atoms were transmuted into Ga in GaN by
a (n,γ) reaction of 69Ga and 71Ga, which acted as donors. 14C atoms would be also transmuted from 14N in
GaN by a (n,p) reaction of 14N. In the present study, we
report the transmutation of 14C in GaN by a (n,p) reactionof 14N. The transmuted 14C related luminescence and net
carrier concentration are studied by combining photoluminescence, liquid scintillation, and Raman scattering.
EXPERIMENTS: GaN single crystal films grown bymetalorganic-vapor-phase epitaxy were irradiated with
fast and thermal neutrons at fluxes of 3.9 x 1013 cm-2s-1
and 8.15 x 1013 cm-2s-1, respectively. Irradiation time was
48 hours. The calculated 72Ge and 14C concentrations
were 1.24 x 1018 cm-3 and 1.13 x 1018 cm-3, respectively.
RESULTS: The transmuted 14C was studied by the liquid scintillation method to detect β-rays emitted in theprocess of 14C decays from 14N. Tritium (3H) is also
emitted by a (n,t) reaction of 14N due to the neutron irradiation above 4.5 MeV. Figure 1 shows the liquid scintillation spectra of NTD-GaN. The transmuted 3H concentration is three orders of magnitude lower than that of 14C.
However, the radiation dose of the emitted 3H is ten
times higher than that of 14C. This attributes to the difference of the half-life, namely 14C has a half-life of 5730
years, but that of 3H is 12.33 years. The short half-lifeelements release more radiation.
As shown in figure 2, photoluminescence relating tocarbon [2], DX-like center of Ge [1], and yellow luminescence band (YL) relating to the crystal defects by fastneutron was observed in 1000 oC annealed NTD-GaN.
Figure 3 shows a Raman spectrum. The peaks at 421
cm-1 and 756 cm-1 are related to the sapphire substrate.
The spectra relating to the NTD-GaN are observed at 740
cm-1 and 575 cm-1. The free electron concentration (N)estimated from N = 1.1 x 1017 (ν max - 736) 0.764 [3], whereν max is the LO mode frequency, is 3.17 x 1017 cm-3. Thisvalue is lower than that from the transmuted Ge concentration. Therefore, the DX-like center of Ge [1] would be

Fig 1. Liquid scintillation spectra of NTD-GaN.

Fig 2. Photoluminescence spectra of 1000 oC annealed
NTD-GaN.

Fig 3. Raman spectra of 1000 oC annealed NTD-GaN.
REFERENCES:[1] K. Kuriyama, T. Tokumasu, J. Takahashi, H. Kondo,
and M. Okada, Appl. Phys. Lett. 80, (2002) 3328;[2] S. Fischer, C. Wetzel, and E. E. Haller, and B. K.
Meyer, Appl. Phys. Lett. 67, (1995) 1298.
[3] C. Wetzel, W. Walukiewicz, E. E. Haller, J. Ager Ⅲ, I.
Grzegory, S. Porowski, and T. Suski, Phys. Rev. B 53,(1996) 1322.
A part of this work was presented in 31th Int. Conf.
Physics of Semiconductors in Zurich (2012, July. 30 ~August. 2).

採択課題番号 24P1-1 化合物半導体の照射効果と電気的・光学的物性に関する研究（法政大院）栗山一男、伊田孝寛、上岡一馬（大阪教育大）串田一雅（京大・原子炉）徐 虬

プロジェクトPR1-2

Neutron Irradiation Effects of Superconducting Magnet
Materials at Low Temperature

T. Nakamoto, M. Yoshida, T. Ogitsu, Y. Makida,
K. Yoshimura, S. Mihara, K. Sasaki, M. Sugano,
H. Nishiguchi, M. Iio, Y. Kuno1, M. Aoki1, A. Sato1,
T. Itahashi1, Q. Xu2, K. Sato2, Y. Kuriyama2, Y. Mori2
and T. Yoshiie2
J-PARC Center, KEK
Department of Physics, Osaka University
2
Research Reactor Institute, Kyoto University
1

INTRODUCTION:
The superconducting magnets
will be subjected to a high neutron fluence of 1021 n/m2
or higher in the operation life time in the high energy
particle physics experiments, such as a high luminosity
upgrade of the LHC at CERN and the muon source for
the COMET experiment at J - P A R C. Since electricalresistivity of a stabilizer at low temperature, which isvery sensitive to neutron irradiation, is one of theimportant parameters for the quench protection of themagnet system. A series of electrical resistivity
measurement at neutron irradiation for the aluminumstabilizer with additives of yttrium taken from theprototype superconducting cable as well as copper
stabilizer was started in 2011. In 2012, the second
irradiation test with the same samples in 2011 was
performed to observe the effect of the multiple
irradiations and the thermal cycles to room temperature.
EXPERIMENTS: The irradiation tests have been
carried out at a low temperature irradiation facility (LTL)
at E-4 line of KUR. The aluminum stabilizer samples(RRR~350) with dimensions of 1 mm x 1 mm x 70 mm
were cut from the superconducting cable manufactured
by Hitachi Cable. The copper stabilizer sample(RRR~300) also has the same dimensions. The electric
resistance was measured by a 4-wire method employing a
Keithley 6221 current source and a Keithley 2182A
voltmeter. The temperature was determined by using athermocouple of Au(Fe) and Chromel, since the Cernox
sensor (CX-1050-SD) showed a temperature drift during
neutron exposure due to the irradiation damage. The
thermocouple and the Cernox sensor and placed justbehind the samples to measure the temperature of thehelium gas coolant.
RESULTS:
The second irradiation test for two
aluminum samples (Al-Y1, Al-Y2) and one copper
sample was carried out in Nov. 2012. The irradiation
condition is basically same as the first irradiation in 2011.
After cooling down to 13 K, the reactor was turned on toa power of 1 MW. The estimated fast neutron fluence in
52 hour operation is 2.6 x 1020 n/m2. Resistance of thesamples and temperature variations during the irradiation
are shown in Fig. 1. The temperature jumped from 13 K
to 15 K at the beginning due to radiation from the reactor

Fig.1. Electrical resistance of aluminum and copper
stabilizer samples during the neutron irradiation in 2012.

core. During exposure the thermocouple indicates stabletemperature while the Cernox sensor readout drifts up to
18 K due to irradiation damage. Behavior of the induced
resistance by the neutron irradiation is very similar to theprevious results in 2011: the resistance shows linear
increase with respect to the neutron fluence during theexposure. Degradation rates of the electrical resistivity at
the fluence of 1020 n/m2 are 2.7 x 101 pΩm and1.0 x 101 pΩm for the aluminum and the copper samples,
respectively.
Anneal effects of the samples due to the thermal cycle
to room temperature were observed. For the aluminum
samples, the induced resistance was fully recovered to be
the original resistance by the thermal cycles for the first
and the second neutron irradiations. For the copper
sample, however, the recovery of the resistance by thethermal cycle was imperfect. The recovery rates, defined
as how much induced electrical resistivity due to theirradiation is recovered by the thermal cycle, were 84 %and 96 % for the first and the second irradiations,
respectively. These results seem to be consistent with theprevious works.
SUMMARY: A series of neutron irradiation tests havebeen pursued at KUR, with the aim of R&D for radiation
hard superconducting magnets. The aluminum stabilizer
with yttrium additive and the copper stabilizer from thesuperconducting cable were irradiated in 2011 and 2012
in order to investigate the multiple irradiation effects andthe anneal effects by the thermal cycles on electricalresistivity. Each sample showed consistent resistivity
increase in the first and the second irradiation runs. A fullrecovery of the resistivity was confirmed in thealuminum sample while the copper sample indicated therecovery rate of around 90 %.

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PR1-3

Study on Formation and Recovery Processes of Radiation Damage
in Crystalline Materials

A. Kinomura, K. Sato1, Q. Xu1 and T. Yoshiie1
National Institute of Advanced Industrial Science andTechnology (AIST)
1
Kyoto University Research Reactor Institute (KURRI)

INTRODUCTION: Radiation effects of ion irradiation
have been extensively studied for various materials. In
general, radiation damage degrades crystallinity andgives harmful effects on material properties. However,under appropriate irradiation or annealing conditions, theradiation effects can induce interesting phenomena or
useful structures in materials. A typical example ofsuch effects is the ion beam annealing in Si, where
implantation-induced damage layers are recrystallized byother ion irradiation. Thus, it is important to investigate
the radiation effects of energetic particles (ions andneutrons) with materials.
EXPERIMENTS: Two types of experiments have been
performed so far. As the first experiment, neutron
enhanced annealing of ion-implantation induced damage
in single-crystalline Si was studied. Si ion implantation
to crystalline Si samples was performed at 200 keV todoses of 5×1014 – 2×1015 cm-2 to induce radiation damage
or amorphous phases. The damaged Si samples were
neutron-irradiated in the KUR (Kyoto University
Reactor) core or SSS irradiation facilities. The samples
with and without neutron irradiation were characterized
by Rutherford backscattering/channeling (RBS/C). As
the second exeriment, gettering of metal impurities tohydrogen-implanted multicrystalline Si was studied.
The multicrystalline Si was implanted with 50 keV H+ toa dose of 3×1016 cm-2 and annealed at 750 or 850 ºC for
1h. The gettering effect of metal impurities wascharacterized by neutron activation analysis using thecore or hydronuematic irradiation facilities of KUR.
RESULTS: In the neutron enhanced annealing
experiments, annealing effects were negligible in the caseof amorphized samples (with doses of 1 or 2×1015 cm-2).
The heavily damaged samples (with a dose of 5×1014
cm-2) showed sufficient annealing effects for the core and
SSS irradiations. The sample temperature of the SSS
irradiation was accurately controlled at 400 ºC. On theother hand, the sample temperature of the core irradiation
cannot be measured during the neutron irradiation,although the water temperature in the KUR core can bemeasured. Thus it is important to estimate the sample

temperature of the irradiation capsule. We numericallysolved one- or two-dimensional partial differential
equation of heat flow for the Si sample in a KUR coreirradiation capsule. The capsule consists of outer andinner sub-capsules made of Al. He gas was introducedin the capsule. The ambient temperature of the capsule
was adjusted to the water temperature of the reactor core
(49 ºC in this calculation). Such information together
with capsule and sample sizes was put in the calculation.
Figure 1 shows the calculated temperature distributions(cross-sectional views) of the core irradiation capsulewith Si samples. Fig. 1(a) and 1(b) assumed thecircular and the rectangular sample shape with the samecross-sectional area. The maximum temperatures in thecapsule were 85 and 81 ºC for Fig. 1(a) and 1(b),respectively.
From these calculations, the sample
temperature during the neutron irradiation at the KUR
core irradiation facility was estimated to be less than 90ºC. The RBS/C spectra of the control sample thermallyannealed at 90 ºC showed that the damage peak was
bigger than that of the neutron irradiated sample. We
confirmed that the neutron enhanced annealing occurredin the core irradiation as well as in the SSS irradiation at
400 ºC.
The specimen for cross-section TEM(transmission electron microscophy) for the getteringexperiment was prepared by the FIB milling machine.
The best milling condition was determined and thefurther sample preparation is in progress.
In summary, the sample temperature during neutron
irradiation of the core irradiation facility was calculated.
The FIB-milling condition for the multicrysalline Si
sample for the gettering experiment was determined.
ACKNOWLEDGMENT: We would like to thankcolleagues in AIST for their assistance on this study.
(a)

(b)

Fig. 1 Calculated temperature distributions (crosssectional views) inside the KUR core irradiation capsulewith Si samples. The circular (a) and rectangular (b)shapes of the samples were assumed.

採択課題番号 24P1-3 結晶材料における照射損傷形成と回復過程の研究（産総研）木野村淳（京大・原子炉）佐藤紘一、徐、義家敏正

プロジェクトPR1-4

Blue Emission of Natural Calcite by Gamma Rays

T. Awata, Y. Bando and Q. Xu1
Department of Physics, Naruto University of Education
1
Research Reactor Institute, Kyoto University
INTRODUCTION: The calcite (CaCO 3 ) has beenstudied since 1940’s because it has the possibility of radiation dosimeter [1]. In the past years, we reported
thermoluminescence of natural calcite irradiated by
gamma rays and it was shown that the spectra had only
one orange emission peak at 620nm and that may beoriginated from impurity Mn2+ [2-3]. In this study, we
have measured blue thermoluminescence emission of
Mexico natural calcite and also have performed trace
impurity elements analysis using NAA (Neutron Activation Analysis) and ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) to clear the relationship with blue emission bands and impurities.
EXPERIMENTS: The sample is natural calcite at
Mexico. It was irradiated 60Co gamma rays for 1h(20kGy) at KUR and also irradiated neutron at Pn-3 of
KUR for NAA. The gamma rays spectrum was taken by
Ge detector at KUR after 1day for short-lifetime element
and after two weeks for long-lifetime elements. ICP-AES(iCAP6300Duo, Themo Fisher) was also performed tomeasure impurity elements concentration of Mexico calcite at KUR.
RESULTS and DISCUSSION: Fi gur e 1 s ho ws t hethermoluminescence spectra of Mexico calcite irradiatedgamma rays at 77K which are measured 93K to 413K

the calcite. From ICP-AES results, impurities (ppm) of
Fe(0.335), Mn(0.216), Na(1.31), Pb (0.0967), Pr(3.19)
and Sm(0.0386) were contained in this calcite. A. Sidike
et. al. [4] showed that photoluminescence peak of calcite
at 487nm was related to impurity of Pb in calcite. Photoluminescence data reference [5] showed that emission
peak at 575nm for impurity Eu and 610nm for Sm. Fromthese results, peak at 487nm in figure 1 might be related
to origin of Pb, 600nm peak to origin of Sm. Other peaks
can not be assigned now.

Fig. 2 Gamma-ray energy spectrum of Mexico natural
calcite irradiated by neutron at Pn-3 for after 1 day.

Fig.3 Gamma-ray energy spectrum of Mexico natural
calcite irradiated by neutron at Pn-3 for after 14 days.
ACKNOWLEDGEMENT: We would like to thankProfessor Dr. S. Fukutani (KURRI) for using ICP-AES
on this study.
Fig. 1 Thermoluminescence spectrum of Mexico natural calcite irradiated by gamma rays.
with heating speed at 0.32K /sec. In this spectrum, there
are seven peaks at 440nm, 487nm, 575nm, 600nm (lineshape), 650nm, 675nm (line shape) and 760nm (doublet).
Figure 2 and 3 show the gamma rays energy spectrum of
Mexico natural calcite irradiated by neutron at Pn-3 forafter 1 day and for after 14days, respectively. These figures showed that Fe, Mn, Na, La and Eu are detected in

REFERENCES:[1] W. L. Medlin, J. Opt. Soc. Am. 53(1963) 1276-1285.
[2] T. Awata and Q. Xu, KURRI Progress Report 2010
p.183.
[3] T. Awata, T. Kishino, F. Maki and Q. Xu, KURRI
Progress Report 2011 p.143.
[4] A. Sidike, X. M. Wang, A. Sawuti, H. –J. Zhu, I.
Kusachi and N. Yamashita, Phys. Chem. Minerals, 33(2006) 559.
[5] Colin M. MacRae and Nicholas C. Wilson, Microsc.
Microanal. 14 (2008) 184.

採択課題番号 24P1-4
高エネルギー粒子線による絶縁体の照射効果（鳴門教育大学）粟田高明，板東康行（京大・原子炉）義家敏正，徐虬

プロジェクトAnnealing Behavior of Thermal Diffusivity in Ceramics
Irradiated by 30MeV Electron and Neutron

Faculty of Engineering, Kyoto University
1
Research Reactor Institute, Kyoto University

INTRODUCTION:
It is well known that neutron-irradiated ceramics
showed significant degradation in thermal diffusivity,
while thermal diffusivity during the irradiation is still notestimated. A temperature of a specimen is calculated fromthe thermal conductivity easily, but at an irradiation condition, thermal conductivity of specimen decreased, andthat rise the temperature of the specimen. The increased
temperature anneals the irradiation induced defects, andthat recover the thermal conductivity. To resolve thisproblem, kinetic analysis is required. In this analysis,
most important information is the behavior of point defects.
EXPERIMENTS:
Accordingly, in this work, 30MeV electron accelerator
KURRI-Linac is used to induce point-defects in bulk
specimens of typical structural ceramics (AlN and β-SiC)
to 1.5x1024e/m2 which correspond to 0.01dpa. The irradiation was performed in the water-cooled specimen holder
at around 80℃.
After the irradiation, isochronal annealing was conducted every 100℃ up to 1100℃ in vacuum using the
SiC furnace of TC-7000H. Specimens were annealed for
1 h at an objective temperature. After the annealing,
specimens were cooled in the furnace to the room temperature, and then thermal diffusivity was measured by
the laser-flash method using a specially ordered measurement system (ULVAC Techno. TC-7000H/Special),
and was analyzed with the t 1/2 method.
In addition, neutron-irradiations have been performed in
the experimental fast reactor JOYO using CMIR-4 rig inprevious works. The capsule T51 was irradiated to 28 dpa
at 502℃ and the capsule T57 was irradiated to 37 dpa at
738℃. These samples were also isochronal annealed up
to 1500℃ and measurements of thermal diffusivity were
performed at room temperature.
RESULTS:
Figs. 1 and 2 show recovery behavior of the thermal
diffusivity in the electron- and neutron-irradiated AlN
and β-SiC ceramic specimens with isochronal annealing.
The filled symbols in the figure represent the result fromelectron-irradiated specimen, and their thermal diffusivities were shown with left-side axis. The error bar shows
standard deviation among the values measured about 10
times. The open symbols represent the result from neutron-irradiated specimens.
All electron-irradiated specimen showed the recovery ofthermal diffusivity from 400-500℃, and AlN specimens
recovered linearly with the annealing temperature (Fig.1).
The electron-irradiated β-SiC specimen (Fig.2) showed
recovery from 400℃ with quadric curve.
In the case of neutron-irradiated AlN, the onset temperature of recovery ( 800-900℃ ) is higher than and independent of the irradiation temperature. On the other hand,the electron-irradiated specimen recovered from400-500℃, that is obviously lower than the onset temperature of recovery in neutron-irradiated specimens andhigher than the irradiated temperature. The neutron-irradiated β-SiC showed almost same behavior as
the electron-irradiated specimen at lower temperature.
While the neutron-irradiated and β-SiC recovered rapidly
with quadric curve above 1000℃.
This difference may arise from the difference in the
crystal structure discussed in a previous work, where thedefect structure was explained by the pileup model (AlN)
and nano-partition model (β-SiC).

Thermal Diffusivity / 10-4 m2/s

M. Akiyoshi, I. Takagi, T. Yoshiie1, Q. Xu1 and K. Sato1

0.70

0.20

0.60
0.10

0.50

Electron irradiated AlN (KURL-0708, 0.01dpa at 80℃)
Neutron irradiated AlN (T51, 28dpa at 502℃)
Neutron irradiated AlN (T57, 37dpa at 738℃)

0.40
0

500
1000
Annealing Temperature / ℃

01500

Fig.1 Recovery behavior of thermal diffusivity in electron-irradiated AlN ceramic with isochronal annealing.

Thermal Diffusivity / 10-4 m2/s

PR1-5

0.80

0.15

Electron irradiated β-SiC (KURL-0708, 0.01dpa at 80℃)
Neutron irradiated β-SiC (T51, 28dpa at 502℃)
Neutron irradiated β-SiC (T57, 37dpa at 738℃)

0.60
0.10
0.40
0.20
0
0

0.05
500
1000
Annealing Temperature / ℃

1500

Fig.2 Recovery behavior of thermal diffusivity in electron-irradiated β-SiC ceramic with isochronal annealing.

採択課題番号 24P1-5
電子線照射後セラミックス中の欠陥評価
プロジェクト（京大・工）秋吉 優史、高木 郁二（京大・原子炉）義家 敏正、徐 虫L、佐藤 紘一

PR1-6

Annealing Behavior of Vacancy-Type Defects in Mg-Zn-Y Alloy with LPSO
Structure Introduced by Electron-irradiation at Liquid Nitrogen Temperature

Y. Nagai, K. Inoue, T. Toyama, Y. Matsukawa, Y. Shimizu, A. Kuramoto, H. Takamizawa, Y. Kakubo, T. Yoshiie1,
Q. Xu1 and K. Sato1
Institute for Materials Research, Tohoku University
1
Research Reactor Institute, Kyoto University

INTRODUCTION: Mg alloys containing transition-metal (TM) and rare-earth (RE) elements(Mg-TM-RE) have received a considerable amount ofattention in recent years as a new-class of light-weight
structural material that exhibits high strength and highductility, simultaneously. A long-period stacking-ordered(LPSO) structure which is long period stacking variantsof hcp-Mg by introducing the TM/RE enriched layers
synchronized with stacking faults periodically have been
believed to play a critical role in endowing such attractive mechanical properties and high ductility with the
Mg-TM-RE alloys. In order to understand the detailed
mechanisms for the formation, it is important to investigate the behavior of vacancy-type defects in the material
with LPSO structure. Positron annihilation spectroscopy
is well known to detect vacancy-type defects in materials.
In this work we have investigated annealing behavior of
defects introduced by electron-irradiation at liquid nitrogen temperature.
EXPERIMENTAL: The samples used in this study are
Mg85Zn6Y9 alloy with almost 100% LPSO structure. The
samples were irradiated at 77K to a fluence of 4x1018
e/cm2 using the KUR-LINAC. The samples were set to asample chamber for positron annihilation (positron lifetime and coincidence Doppler broadening (CDB)) apparatus without temperature rise. The positron annihilation
measurements were performed at 77K. The isochronalannealing was done for 5 minutes at 10K intervals.
RESULTS & DISCUSSION: Figure 1 shows annealing
temperature dependence of mean positron lifetime. In
as-irradiated state, the mean positron lifetime is 283 ps,
which is much longer than the un-irradiated state (223ps). Almost all the positrons are trapped at vacancy-type
defects introduced by electron-irradiation in theas-irradiated state. Annealing behavior of the mean positron lifetime consists of several stages as shown in Fig. 1.
The lifetime starts to decrease above 120K and decrease
largely until 160K. It decreases gradually from 160K to
250K and is almost constant from 250K to 300K anddecreases again above 300K. It is reported that the divacancy and monovacancy can migrate at 130K and 160K

採択課題番号 24P1-6

in pure Mg, respectively [1]. Therefore, large decrease of
the mean positron lifetime above 120K to 160K probably
corresponds to the recovery of the divacancy in hcp-Mg
layer of the LPSO structure and gradual decrease from
160K to 250K corresponds to the recovery of the monovacancy in hcp-Mg layer of LPSO structure and formation of the higher order vacancy complexes.
The correlation between low momentum component
fraction (LMCF: |pL|<4×10-3mc) and high momentum
component fraction (HMCF: 14×10-3mc < |pL| <23×10-3mc) in CDB spectrum are shown in Fig. 2, wherepL denotes the momentum, m is the electron/positron rest
mass, and c is the speed of light. In the as-irradiated state,
LMCF-HMCF correlation point shift not toward lower-right direction from the point of Mg but toward thepoint of Y. Therefore, Y atoms probably exist next to thevacancy. The correlation points move slightly toward thepoint of Zn above 120K, indicating the formation of vacancy-Zn complexes during the migration, and thenmove toward the point of Mg.

Fig .1. Annealing temperature dependence of mean positron lifetime.

Fig. 2. Annealing behavior of LMCF-HMCF correlationin CDB spectrum.
REFERENCES:[1] P. Hautojarvi et al., Appl. Phys., A 27 (1982) 49-56.

陽電子消滅および 3 次元アトムプローブによるプロジェクト
低温照射効果の研究（東北大・金研）永井康介、井上耕治、外山健、松川義孝、清水康雄、蔵本明、高見澤悠、
鹿窪勇（京大・原子炉）義家敏正、徐虬、佐藤紘一Radiation Damage in Bulk Amorphous Alloys by Electron Irradiation

F. Hori, N. Onodera, K. Ishii, A. Iwase, Y.Yokoyama1,
Q.Xu2, K.Sato2 and T.Yoshiie2
Dept. of Mater. Sci., Osaka Prefecture University
2
Institute of Materials Research, Tohoku University
1
Research Reactor Institute, Kyoto University

INTRODUCTION: It is well known that theirradiation damage of the metal under high-energy
particles irradiation makes various effects with thealloy compositions. The amorphous alloys, which have
no long-range atomic periodicity, are expected to be
useful for various applications due to their superiormechanical properties such as hardness, strength,
corrosion resistance and micro-formability. We havebeen studying the radiation effects of various kinds ofhigh energetic particles irradiation, such as an electron,
proton and ions, irradiation on free volume andmechanical properties of ZrCuAl bulk glassy alloy. We
have measured X-ray diffraction, DSC, positronannihilation and bulk density measurements for before
and after an electron irradiated samples.

EXPERIMENTS: A samples of Zr 50 Cu 40 Al 10 bulk
metallic glass with 8 mm in diameter and 60 mm inlength was prepared by a tilt casting technique. For
positron annihilation measurements, alloy sample was cut
into the size of about 0.5 mm thickness. 8 MeV electron
irradiations with total doses from 4.0x1017 to 2x1018
e/cm2 was performed for these alloys at 300 K by LINAC
at Research Reactor Institute, Kyoto University.
Irradiated samples were examined by X-ray diffraction,
positron annihilation lifetime and coincidence Doppler
broadening measurements at room temperature. The
positron annihilation lifetime spectra consist of more than
3.0 x 106 counts. The positron lifetime spectra wereanalyzed by the POSITRONFIT and CONTIN-PALS II
program. The CONTIN program provides theannihilation probability density function f(λ).

function f(λ) of before and after electron irradiatedsample of Zr 50 Cu 40 Al 10 bulk metallic glasses. In thisfigure, peak position of positron lifetime distribution
increases and the shape of its profile becomes slightly
sharpen. In our previous work, mean positron lifetime
increases from 167 to 176 psec by 8 MeV electron
irradiation with the fluence of 2x1018 e/cm2 [1,2], i.e,their difference is about 9 psec. This value is consistent
with the shift of positron lifetime distribution peak by theirradiation. Also, no peak separation can be seen by theirradiation. These indicate that the electron irradiation
does not retain a vacancy type defect randomly, but thedamages have some interactions with intrinsic open
volume. Consequently, mean size of free volume grows.

30
Zr Cu AlAs-cast
18

25

Intensity (%)

PR1-7

-

2×10 e /cm

50

2

40

10

20
15
10
5
0
100

150

200

250

300

Positron lifetime (ps)Fig. 1 Positron annihilation probability density function of
as-prepared and after 8 MeV electron irradiated ZrCuAl bulk
glassy alloy.

REFERENCES[1] F.Hori et al., KURRI progress report 2011[2] Y.Fukumoto, A.Ishii, A.Iwase, Y.Yokoyama, F.Hori,
J. Phys.: Conf. 225 (2010) 012010

RESULTS: Figure 1 shows the change of thepositron annihilation probability density distribution

採択課題番号 24P1-7
金属合金における照射効果の研究（阪府大・工）堀史説、小野寺直利、石井康嗣、岩瀬彰宏(京大・原子炉)徐虫 L 、義家敏正、佐藤紘一

プロジェクトPR1-8Development of Replica Extraction Method for Vanadium Alloys and its Application
for Neutron-Irradiated Ones

K. Fukumoto and Q. Xu1

1

RINE, Univ. of Fukui
Research Reactor Institute, Kyoto University

INTRODUCTION:
Vanadium-base alloys are attractive candidates of low
activation structural materials for future fusion reactors.
Since small Ti(OCN) precipitates were the dominant microstructural feature in neutron-irradiated V-4Cr-4Ti alloys at elevated temperatures, the precipitation processesof Ti(OCN) should be well understood. For this purpose,
we have irradiated V-4Cr-4Ti alloy by neutrons to induce
defect clusters due to displacement cascades and havestudied the characterization of neutron-induced precipitates. Electron microscopy and microanalysis were employed to investigate the features and mechanisms ofprecipitation process in the V-4Cr-4Ti alloy under irradiation through knowledge the crystallography, chemicalcomposition and size distribution of precipitates. A carbon replica technique has been developed to extract precipitates from vanadium alloys. Using this technique,precipitation phases can be extracted from neutron-irradiated or thermal-aged V-4Cr-4Ti alloys.

RESULTS: Fig.1 shows the TEM micrographs of neutron-irradiated V-4Cr-4Ti alloy at 593C with 105dpa.
TEM micrographs reveal tangled dislocation structure
and bimodal distribution of irradiation-induced precipitates such as Ti-(CON) precipitate with {100} habit plane.
The crystal structure of precipitates could not be identified due to their fine size about few ten nm, but the previous work for neutron-irradiated V-Cr-Ti and V-Ti alloys
have already reported that precipitate with {100} habit
plane is identified to be the same structure as Ti-rich(CON) precipitate. Fig.2 shows the STEM image of tiny
irradiation-induced precipitate on carbon replica film andFig.6 shows the results of the chemical composition
analysis of their precipitates using X-EDX. The chemicalcomposition of titanium varied from 20% to 100% andvanadium and chromium consisted of the other composition. Thus the precipitate with {100} habit plane is nolonger type of Ti-(CON) but MX type with M=(Ti, V, Cr)
and X=(C, O, N). Even though the Ti-(CON) precipitateis in an equilibrium state, the MX type is in a metastablestate during irradiation circumstance.
100%
80%

EXPERIMENTS: The majority of test specimens forthis study were prepared from V-4Cr-4Ti alloys. Before
irradiation, all specimens were annealed in vacuum at
1000°C for 2hrs. Neutron irradiation experiments were
performed in the e JOYO reactor. Two irradiation conditions were selected to investigate the nature of irradiation-induced precipitates. The irradiation temperatures,
irradiation doses and displacement damages for 1/3CVN
specimen was intended to be 450°C, 2.3x10 26 n/m2
(E>0.1MeV) and 15dpa estimated for pure vanadium.
Those conditions for SSJ-3 specimen was intended to be
593°C, 1.7x1027 n/m2 (E>0.1MeV) and 107dpa. The
microstructural TEM observations were performed in
KUR/Kyoto Univ.
The carbon replica technique yielded measurementsof chemical compositions for irradiation-induced precipitates without matrix contribution. A mechanically polished surface of specimen was put into a chemical polishing solution for 30s. A carbon layer was sputtered on
the specimen surface and then, an electro-etching procedure was performed in order to collect the replicas.

Cr
V
Ti

60%
40%
20%
0%

1μ m

Fig.1. A set of (a) STEM bright image and spectrum of
EDS analysis of the precipitate in as received V-4Cr-4Ti
alloo

100%
80%
Cr
V
Ti

60%
40%
20%
0%

0.5μ m

Fig.2. A set of (a) STEM bright image and spectrum of
EDS analysis of the precipitate in neutron -irradiatedV-4Cr-4Ti alloy at 593C with damage of 107dpa.

採択課題番号 24P1-8 中性子・イオン照射を用いたバナジウム合金の熱処理による損傷回復過程（福井大院工）福元謙一 （京大・原子炉）徐虫 L

プロジェクトPR1-9

Damage Evolution in Neutron-Irradiated Metals
during Neutron Irradiation at Elevated Temperatures

I. Mukouda, K. Yamakawa1, T. Yoshiie2 and Q. Xu2
Hiroshima International University
1
Faculty of Engineering, Ehime University
2
Research Reactor Institute, Kyoto University
INTRODUCTION: Copper and nickel are used as
typical FCC metals in radiation damage studies. Many
studies have been carried out and reviewed by Singh andZinkle [1]. They concluded that there is a lack of
information on the microstructure of copper and nickel
irradiated to below 10-2 dpa at 100 to 300oC [1]. Zinkle
and Snead carried out fission neutron irradiation at 230oC
to damage levels between 10-2 and 10-1 dpa [2]. They
concluded that a high density of small SFT anddislocation loops was observed in copper and nickel, andsmall voids were observed in irradiated copper. Recently
Shimomura and Mukouda carried out fission neutron
irradiation of copper at 200 and 300oC at a similar rangeof dose, we reported dose dependence of voids and SFTs
previously. The present work is carried out to examine
the evolution of vacancy clusters and voids inneutron-irradiated copper of transient regime at elevatedtemperatures. To obtain precise results, the irradiation
was carried out at the temperature controlled irradiation
facility in the KUR.
EXPERIMENTAL PROCEDURES: The specimens
used in this study were pure copper and nickel.
Specimens were cold-rolled to 0.05 mm and punched out
to disks of 3mm in diameter, and annealed in vacuum.
Neutron irradiation was carried out in the temperature
controlled capsule at KUR reactor in SSS at 1MW. The
specimen temperature was kept at 300oC or 200oC during
irradiation. After radiation cooling, specimens were
electro-polished and using JEOL-2010 TEM at anaccelerating voltage of 200kV. Void images wereobserved by bright field technique of off-Bragg
diffraction condition (void contrast) and weak beam dark
field (WBDF) image.
RESULTS AND DISCUSSIONS: Figure 1 shows TEM
observation of neutron- irradiated copper at 300oC, 5.7 x1017 n/cm2, by bright field image. Large voids
were seldom observed in this specimen. Fig. 2 shows
TEM observation of same specimen by dark field image.
Large SFT and small interstitial clusters wereobserved. The number density of voids and point
defect clusters were smaller than irradiation at 5MW
300oC specimen [3]. Fast neutron flux was 1.7 x1013 at 5MW, 3.4 x 1012 n/cm2s. Another irradiation
conditions are progressing now.

採択課題番号 24P1-9

REFERENCES[1] B. N. Singh and S. J. Zinkle, J. Nucl. Mater., 206,
212 (1993).
[2] S. J. Zinkle and L. L. Snead, J. Nucl. Mater., 225,
123 (1995).
[3] I. Mukouda and Y. Shimomura, Mat. Res. Soc. Symp.
Proc., 650, R3.11.1-R3.11.6 (2001)

KUR 1MW 300oC 47h
Fig. 1. TEM observation of neutron- irradiatedcopper at 300oC, 5.7 x 1017 n/cm2, by brightfield image.

KUR 1MW 300oC 47h
Fig. 2. TEM observation of neutron- irradiatedcopper at 300oC, 5.7 x 1017 n/cm2, by dark
field image, (g,5g) g=200.

高温での中性子照射金属中の点欠陥集合体動的挙動と損傷組織発達過程（広島国際大学）向田一郎、（愛媛大）山川浩二、(京大原子炉) 義家敏正、徐プロジェクト虬PR1-10

Positron Annihilation Behavior of Fe-Cr Alloys after Neutron Irradiation in KUR

R. Kasada, K. Sato1, Q. Xu1 and T. Yoshiie1

Experimental Procedure: Materials used in the present
study is Fe-Cr binary alloys. Neutron irradiation on these

Institute of Advanced Energy, Kyoto University
1
Research Reactor Institute, Kyoto University
INTRODUCTION:

Ferritic steels containing Cr are

expected to be used for the first-wall component in thefusion reactors as well as the fuel pin cladding in thematerials was carried out at 300 °C up to 199 h in KUR.
The displacement damage is 2.1 × 10-3 dpa (5.1 × 1018
n/cm2).

Positronannihilation

coincidence

Dopplerbroadnening (CDB) measurement were performed at the
hot laboratory of KURRI.

Generation IV nuclear fission systems [1]. However,high-Cr steels may suffer from thermal aging embrittlement, which is well-known 475 °C embrittlement. This ismainly due to phase separation of Fe and Cr as shown in
the phase diagram (Fig.1). In the previous study [2], weapplied a positron annihilation spectrometry to detect thephase separation in the Fe-Cr alloys under “the Strategic
Promotion Program for Basic Nuclear Research by the
Ministry of Education, Culture, Sports, Science andTechnology of Japan”.
The present collaborative research has moved to investigate the neutron irradiation effect on the phase sep-

Results and Discussions: The CDB ratio curves to pure
Cr of Fe-30Cr alloy before and after the neutron irradiation is shown in Fig. 2. It should be noticed that thehigh-momentum region of the irradiated Fe-30Cr is close
to that of unirradiated Fe. This means that the most of
positron annihilates with the Fe electron in the irradiatedFe-30Cr. Considering with the positron annihilation behavior of the themally aged Fe-Cr alloys, the current irradiation condition may enhance the phase separation of
Fe-30Cr alloy. Further experiments on the Fe-Cr alloys
are now going.

aration of Fe-Cr ferritic alloys. In the FY2012 we have

1.6

unirradiated Fe
unirradiated Fe-30Cr
Fe-30Cr (300C, 200h)

the Fe-Cr binary alloys before and after the neutron irradiation in KUR.

Ratio to pure Cr

obtained the first result of positron annihilation study on
1.4
1.2
1
0.8
0.6
0

10

20
pL(10-3m0c)

3040Fig. 2 Positron CDB ratio-curves obtained for the ODS
steels and SUS430 before and after neutron irradiation at
300 °C up to 199 h.
REFERENCES:[1] A. Kimura, et al., Journal of Nuclear Science andTechnology, 44 (2007) 323-328.
[2] R. Kasada and K. Sato, to be submitted.

Fig. 1 Phase diagram of Fe-Cr binary system calculatedusing ThermoCalc software.

採択課題番号 24P1-10
鉄クロム系合金の相平衡に及ぼす照射影響（京大・エネ理工研）笠田竜太、（京大・原子炉）義家敏正、徐虬、佐藤紘一

プロジェクトSimilarity of Radiation Resistance of Nanocrystalline Ni by Ion
and Neutron Irradiation

H. Tsuchida, A. Itoh1, K. Sato2, T. Yoshiie2 and Q. Xu2
Quantum Science and Engineering Center, Kyoto University
1
Depertment of Nuclear Engineering, Kyoto University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: Nanocrystalline (NC) materials
are known to have high resistance to radiation damage
effects, because the grain boundaries act as effective
sinks that absorb radiation-induced defects. Up to thepresent, we have studied radiation damage in NC nickel
under ion or neutron irradiation using positron annihilation spectroscopy. In the ion irradiation study, we investigated the dependence of the grain size on the formationof transient vacancy defects that occurred during irradiation in a real-time measurement of Doppler-broadening
positron-annihilation spectroscopy [1]. It was found thatthe transient vacancies were unstable in NC materials andthey could be annihilated at grain boundaries or via recombination with freely migrating interstitials during
irradiation. In the neutron irradiation study, we investigated the grain size dependence on defect accumulation
using positron annihilation lifetime spectroscopy. The
results showed that for NC materials the defect accumulation is suppressed, whereas for coarse-grained materials,
the defect accumulation or defect clustering is occurredwith increasing the neutron fluence. These results suggestthat grain boundaries play an important role in themechanism of radiation resistance in NC materials.
In this work, we studied similarity of radiation resistance of NC Ni, in comparison between ion and neutron irradiation. It was found that defect accumulationnear grain boundaries is suppressed both for ion and neutron irradiation.
EXPERIMENTS: An NC Ni, obtained from theGoodfellow Company, UK, was used as a specimen. The
average grain size was 30 nm. The specimens were irradiated with neutron at the dpa 3.8 x 10-5-1.8 x 10-3. Vacancy defects produced in the irradiated specimens wereanalyzed by positron annihilation lifetime spectroscopy.
We also performed irradiation experiments withhigh-energy heavy ions. To measure vacancy defects
produced during irradiation, the specimens were analyzed
by in situ Doppler-broadening positron-annihilation spectroscopy.
RESULTS: We studied a change in microstructure NC
Ni for neutron irradiation, and measured values of positron annihilation lifetime as a function of the dpa. We
found that the value of the lifetime, corresponding to thepositron annihilation occurring near grain boundaries,
remain unchanged with increasing the dpa. This indicatesthat the suppression of defect accumulation at grainboundaries occurs under neutron irradiation.
Next, we investigated the transient vacancies formed
during irradiation via in situ observations of the positronannihilation Doppler broadening spectra. The annihilation line-shape parameter S was measured during andafter irradiation. Fig. 1 shows experimental results for thevariation of the line-shape parameter S measured alternately under irradiation (closed symbols) andnon-irradiation (open symbols) conditions, for (a) the NC
Ni irradiated with 0.5 MeV C ions, (b) the NC Ni irradiated with 2.5 MeV C ions, and (c) the coarse-grained Ni(annealed polycrystalline Ni) irradiated with 2.5 MeV C
ions. The variation of S for the NC specimen was different from that observed for the coarse-grained specimen.
For the coarse-grained specimens, the S measured during
irradiation was larger than that observed before/after irradiation, while for the NC specimens, the S value remained unchanged. The results for the coarse-grained
specimens indicated that the concentration of vacancies
during irradiation was high compared with that after irradiation. This is due to that transient vacancy defects were
produced during irradiation. In contrast, the results for
the NC specimens suggested that such transient vacancies
disappear, and the defect concentrations remain unchanged during irradiation. The results observed in theion irradiation experiments shows the same trend to thatin the neutron irradiation experiments. This similarity
may be related to the defect annihilation occurring neargrain boundaries.
0.5

Line-shape parameter S

PR1-11

(a)

(b)

(c)

0.49

0.48

0.47

0.46

1 2 3 4 5 6 7 8 910111213 1 2 3 4 5 6 7 8 910111213 1 2 3 4 5 6 7 8 910111213

Run number

Fig.1 Variation of the line-shape parameter S measured alternately under irradiation and non-irradiation

REFERENCES:[1] Tsuchida et al., “Radiation damage in nanocrystalline
Ni under irradiation studied using positron annihilation
spectroscopy”, J. Nucl. Mater., (2013) (accepted)

採択課題番号 24P1-11 ナノ結晶材料の照射欠陥緩和挙動の陽電子解析に関する研究 プロジェクト（京大院工）土田秀次、伊藤秋男（京大・原子炉）義家敏正、徐 虬、佐藤紘一

Interaction between Deuterium and Defects in Tungsten (2)K. Sato, R. Tamiya1, Q. Xu and T. Yoshiie
Research Reactor Institute, Kyoto University
1
Graduate School of Engineering, Kyoto University
INTRODUCTION: In a fusion reactor, plasma-facing
materials (PFMs) must withstand the damage producedby hydrogen and helium at up to 10 keV of energy andheat loads from the plasma, in addition, the neutrons withhigh energy, high flux and high fluence similar to thestructural components. Hydrogen isotopes retain in vacancy-type defects in PFMs, and this is a critical problem
for fusion reactors. To know the interaction between vacancy-type defects and hydrogen isotopes is very important. In this study, the size and density of vacancy-type defects in tungsten was obtained by positron annihilation lifetime (PAL) measurements. Next, thermal
desorption spectra of deuterium was obtained after deuterium charging. From these results, trapping site anddissociation energy of deuterium were identified.
EXPERIMENTS: The samples were 99.95% puretungsten (A.L.M.T. Corp.). The 0.2-mm-thick sheet waspunched to 5mm in diameter. These samples were annealed at 1773 K for 1 h in a vacuum of less than 10−4 Pa.
Electron and deuterium ion irradiations were carried out
to introduce defects. Electron irradiation was performedat Electron Linear Accelerator of Research Reactor Institute, Kyoto University. 8 MeV electrons were irradiatedup to 9.4×1017 /cm2 (1.3×10-4 dpa). A displacement
threshold energy used for irradiation dose calculation was
42 eV [1]. Deuterium ion irradiation was performed at
Low-energy ion irradiation system of Research Reactor
Institute, Kyoto University. 5 keV D 2 + ions were irradiated up to 1.0×1018 /cm2 (20 dpa at defect peak) at room
temperature (R.T.). Iron ion irradiation was performed at
2.0-MV tandem accelerator of Quantum Science and Engineering Center, Kyoto University. 6 MeV Fe3+ ionswere irradiated up to 2.3×1019 /cm2 (8.4 dpa at defectpeak) at 573 K. After that, 1 keV D 2 + ions, which do notform irradiation defects, were implanted by low-energy
ion irradiation system. Thermal desorption spectroscopy
was carried out from R.T. to 1523 K in order to detect
elimination behavior of deuterium from tungsten.
RESULTS: TDS spectra of electron-, 5 keV- D 2 + ionand 6 MeV-Fe3+ ion-irradiated samples are shown in Fig.
1. From PAL measurement, single vacancies are detectedin electron-irradiated sample. Therefore, peak around 550
K denotes elimination of deuterium from single vacancies.
Peak separation analysis was performed to spectra of 5
keV D 2 + ion- and 6 MeV Fe3+ ion irradiation by data
analysis software Origin, and the results were shown in
Figs. 2 and 3. Spectra of 5 keV D 2 + ion irradiation at R.T.
were resolved into three gauss functions. The peak ofthem was around 450 K, 560 K and 640 K. Spectra of 6
MeV Fe3+ ion irradiation at 573 K were also resolved into

three gauss functions. The Peak of them was around 460
K, 630 K and 840 K. 450 K peak denotes the eliminationof deuterium from surface. It is expected that 560 K peakdenotes the elimination of deuterium from single vacancies from result of electron-irradiated sample. 640 K peakdenotes the elimination of deuterium from dislocations.
840 K peak denotes the elimination of deuterium fromvoids. It is not clear that voids are formed during iron ion
irradiation or increase in temperature of TDS measurement.
D2 desorption rate [×1016/m2s]

PR1-12

Electronirr.
+
D23+5keV RT
Fe 573K

3

2

1

0

300

400

500

600

700

800

900

1000

110

Temperature [K]Fig. 1. TDS spectra of electron-, 5keV D2+ ion-, 6MeV
Fe3+ ion-irradiated samples

Fig. 2. Peak separation of TDS spectrum of sample
irradiated with 5 keV D2+ ions at R.T.

Fig. 3. Peak separation of TDS spectrum of sample
irradiated with 6MeV Fe3+ ions at 573 K.
REFERENCES:[1] F. Maury, M. Biget, P. Vajda, A. Lucasson and
P. Lucasson, Radiat. Eff. 38 (1978) 53.

採択課題番号 24P1-12 電子照射された金属の損傷組織の照射温度依存性の研究（京大・原子炉）佐藤紘一、徐虬、義家敏正（京大院・工）田宮怜

プロジェクトPR1-13

Irradiation Effects on Stress Loading Property of Refractory Metal
at High Temperature

K. Tokunaga, K. Araki, T, Ukita1,
Q. Xu2 andT. Yoshiie2

W have been obtained by the tensile testing used in the
FEA.

Institute for Applied Mechanics, Kyushu University
Interdisciplinary Graduate School of Engineering
Sciences, Kyushu University
2
Research Reactor Institute, Kyoto University

RESULTS: Figure 1 shows stress-strain curves of
ITER grade W (L-R type) with various temperatures.
Brittle fracture occurs both L-R and T-R type specimens
at RT. On the other hand, ductile fracture occurs on L-R
type specimen but not T-R type specimen at 200 oC. This
result means that DBTT of the specimen is around at 200o
C in the case of the strain rate. Yield strength decreases
and total elongation increases with increasing test temperature. There is difference of about 100 MPa between
L-R and T-R type specimens on tensile strength at RT and
200 oC, however, there is no difference between them
above 400 oC. The reason for this is considered that migration of dislocation do not occurs at low temperature,and shape of grain boundary for direction of stress influences tensile strength. On the other hand, there is difference between L-R and T-R type specimens on total elongation, even if high temperature which ductile fracture
occurs, and total elongation of L-R type specimen ishigher than that of T-R type specimen. The repeatedheating by electron beam irradiations of 20 times caused
surface roughening in the intragranular. The subsequent
repeated irradiations of totally 200 times caused significant surface roughening, cracking in the intragranular andgrain boundaries and surface exfoliation. The FEA indicated that compressive stress is generated in the electron beam irradiated area during the electron beam irradiation. On the other hand, tensile stress is generated duringcooling after the irradiation of the electron bean is ended.
In addition, plastic deformation occurs and residual stressremains in the W specimen. Those results suggest that thesurface roughening is considered to be caused due toplastic deformation by the thermal stresses. Irradiation
effect for stress loading property is planning to be investigated in the next stage.

1

INTRODUCTION: Tungsten (W) is the primary candidate for use as plasma facing materials/components(PFM/PFC). PFM/PFC will be subjected to heavy
thermal loads in the steady state or transient mode combined with high energy neutron irradiation that will cause
serious material degradation. It is necessary to clarify
mechanical strength to evaluate thermal behaviour oftungsten materials by high heat loading. In the present
works, the tensile testing of W material has been performed up to at 1600 oC to obtain stress-strain curves. In
addition, thermo elasto-plastic stress analyses of W
specimen have been carried out to evaluate modificationof the W specimen exposed to high heat loading. Furthermore, the calculated results have been compared tosurface modification of W specimen under cyclic thermalloading experiments using an electron beam to evaluate
thermo-mechanical performance of W.
EXPERIMENTS: W material used in the present work
was ITER grade W. Tensile testing was performed on
dog-bone shaped tensile test specimens with an overall
length of 16 mm, a gauge length of 5 mm and an effective cross section of 0.6 mm2. The orientation of thespecimens used were parallel (L-R type) and perpendicular (T-R type) directions to rolling direction along rollingsurface, respectively. The tests were conducted at RT, 200,
400, 650, 800, 1000, 1300, 1600 oC. The tests were performed at a strain rate of 2 x10-4 s-1. In addition, ITER
grade W was machined to the dimensions of 10 mm x 10mm x 1mm, followed by mechanical and electro polishing. The polished specimens were subjected to highheat load experiments by an electron beam irradiation test
simulator. The experiments were conducted at the irradiation conditions; repeated irradiations of 2 s-irradiation
and 7.5 s-rest with one cycle of 9.5 s for totally 200 times.
The surface temperature of the specimens changes frombelow 450oC to 1300oC by 2 s-irradiation. Before andafter the irradiation, the specimen surfaces were examined by SEM. The thermo elasto-plastic stress analyses
using a transient finite element analyses (FEA) have been
performed to evaluate the thermal behaviour and surface
modification of the W specimens during the high heatloading experiments. Stress-strain curves of ITER gradeFig. 1 Stress-strain curves of ITER grade
W (LT-R type) with various temperatures.

採択課題番号 24P1-13 高融点金属材料の高温下における応力負荷特性に及ぼす照射効果 プロジェクト（九大・応力研）徳永 和俊、荒木 邦明（九大・総理工）浮田 天志（京大・原子炉）徐 虬、義家 敏正

PR1-14

Effect of Substrate Temperature in Nanocell Fabrication of GaSb*

N. Nitta, K. Yokoyama and M. Taniwaki
Department of Environmental Systems Engineering, Kochi University of Technology
INTRODUCTION
The authors proposed a novel nanofabrication technique and have performed to fabricate nanocell lattices
by focused ion beam (FIB) at room temperature. In
their past studies, mainly the possible range of the cellinterval and ion dose yielding ordered nanocell lattices
has been obtained only at room temperature. However,
the mobility of the point defects, which dominates thenanocell formation, depends strongly on the temperature, then, the range of the parameters for successful
nanocell formation must differ so much by substratetemperature. Then, in this work, the authors investigated the effect of the substrate temperature by fabricating nanocell lattices on GaSb (100) surface at room
temperature and at lower temperature (130 K) andcomparing them.

EXPERIMENT
Nanocell lattices were fabricated using FIB Quanta 3D
200i by the nanofabrication technique that the authors
had proposed. In order to know the possible range ofthe cell interval for the ordered nanocell lattice, an
initial pattern consisting of nine matrices with a different void interval was created by the same ion dose
per one dot in box repairing mode of the FIB with 30
keV Ga+ and it was developed by a constant ion dose
per unit area in the image scanning mode of the same
FIB. Such processes were performed in variations ofinitial ion dose and developing ion dose at room temperature and 130 K. The ion doses per one dot in theinitial procedure were 1.13×104 - 2.25×106 ions/dot
and the ion doses per unit area in the second procedure
were 1.6×1013 - 2.9×1014 ions/cm2. The change ofthe pattern during irradiation was observed in situ by
FIB secondary electron image.

RESULTSThe lattice image of the pattern at 130K is observed
obscurely, which may be due to the gas adsorption on
the surface. The dot contrast is bright on the sample
fabricated at 130K in contrast to the dark image on thesample at room temperature. The bright contrast
means the elevation of the surface. This is due to thelow migration of vacancies at cryogenic temperature,
which retards the growth of void comparing at room
temperature and then the top surfaces of the voids
were not yet completely removed. The ordered image at 130 K was observed in the dot interval of 80 nm
which was not made at room temperature. The development of the pattern by scanning at 130 K was re-tarded comparing at room temperature, which is again
attributed to the difference in the migration of point
defects, especially vacancies. The cell diameter in
one scanned pattern was larger in larger dot interval,and 55 – 108 nm at 130 K and 90 – 125 nm at room
temperature. It increased monotonously with increasing scan times in every lattice at both temperatures, though it saturated to a critical value a little lessthan its dot interval. However, some difference isobserved between two substrate temperatures; thecurve of cell diameter against scan times is a convex
below at 130 K, and linear or a convex on the top at
room temperature. The increasing rate of the diameterto scan times at early scanning stage is 7.8 nm/one
scan at 140 K and 13.7 nm/one scan at room temperature. We consider that this difference may be causedby the difference of the nanocell development mechanisms (probably it contains two elementary mechanism at least) between at room temperature and at
cryogenic temperature. This detailed understanding
is our future issue.
CONCLUSION
The nanocell fabrication experiment on GaSb (100)using 30 keV Ga+ at room temperature is summarized
as follows. The appropriate ion dose for fabrication of
the initial void is 1.13 – 2.25×105 ions/dot, and nanocell lattice with 80 – 300 nm dot interval isachieved.The nanocell fabrication on GaSb surface at
low temperature has several advantages over that atroom temperature. One is to suppress the secondary
void formation. In the case of 130 K, secondary
voids formed first by 8 scans, though they formed by 5scans at room temperature and their size was smallerat 130 K. Another advantage at low temperature is tocreate the ordered nanocell lattice with smaller dot
interval. Nanocell formation mechanism at cryogenic
temperature is somewhat different from that at room
temperature. Fabrication at low temperature hassome advantages in application, that is, nanocell lattices are easily obtained in wider range of dot interval,
without secondary void formation.
*This report is summarized from “Nanocell fabrication
on GaSb at room temperature and cryogenic temperature (N. Nitta, K. Yokoyama, and M. Taniwaki, AIP
conf. Proc. 1496)

採択課題番号 24P1-14 半導体イオン照射によって導入される点欠陥挙動の解明と プロジェクト
ナノセル技術の開発（高知工科大）谷脇雅文，新田紀子 (京大原子炉)義家敏正，徐 虬Deuterium Retention in Electron-Irradiated VPS-W

Y. Hatano, J. Shi, T. Nozaki, K. Masuda, T. Tokunaga1,
H. Watanabe1, N. Yoshida1, K. Sato2 and Q. Xu2
Hydrogen Isotope Research Center, University of
Toyama1
Research Institute for Applied Mechanics, Kyushu
University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: Tungsten (W) is currently recognized as a primary candidate of plasma-facing material(PFM) for future fusion reactors. Vacuum plasma spraying is a technique to prepare W layers on structural materials such as reduced-activation ferritic/martensitic steels.
Tritium (T) is the radioisotope of hydrogen and used asfuel in fusion reactors together with deuterium (D). The
fusion reaction of D and T forms 3.5 MeV He and 14
MeV neutrons. PFMs are subjected to irradiation of thosehigh energy neutrons. Therefore, understanding of T retention in PFMs and effects of neutron irradiation is important issue for assessing safety margins of fusion reactors. Indeed, significant increase in D retention with neutron irradiation has been observed for bulk W fabricatedby powder metallurgy in Japan–US Joint Research Project TITAN [1–2]. From these viewpoints, effects of displacement damages on D retention in VPS-W were examined in this study with irradiation of 8 MeV electrons.
High energy electrons induce defects throughout the
thickness of materials like neutrons, while ions form defects only in a shallow region beneath the surface.
EXPERIMENTS: The specimens used were VPS-W
layers (0.6 mm thickness) prepared on carbon/carbon-fiber composite (CFC, CX-2002U) by Plansee Aktiengesllshaft. After removing CFC substrates bymechanical polishing, the VPS-W layers were exposed to
D 2 gas in a high-vacuum device at 100 kPa and 673 K for
10 hours under the following conditions:(1) As-received,(2) After heating in vacuum at 1273 K for 1.5 hours,(3) After irradiation with 8 MeV electrons up to 10−3
displacement per atom (dpa) following theabove-mentioned heat treatment in vacuum.
Exposure to D 2 gas under several different conditions
showed that the specimens were saturated with D under
the above-mentioned conditions. The D retention wasmeasured by thermal desorption spectroscopy (TDS) at
the temperature ramp rate of 0.5 K s−1. Desorption spectra were simulated with the program TMAP4 [3].
RESULTS: The retention of D in VPS-W layer under
as-received conditions was 1 × 10−5 in atomic ratio,[D]/[W]. It decreased to [D]/[W] = 1 × 10−6 by the heat
treatment in vacuum at 1273 K. During the heat treatment,

the desorption of CO was observed. Hence, the reductionin D retention by the heat treatment was ascribed to theremoval of impurities such as carbon and oxygen acting
as trapping sites against hydrogen isotopes. The electron
irradiation resulted in increase in D retention to [D]/[W]= 3 × 10−5. In other words, D retention increased by anorder of magnitude with irradiation as low as 10−3 dpa.
Such significant increase in D retention was ascribed totrapping by radiation defects. Damage levels in ITER anddemonstration reactors are expected to be far higher.
Hence, T retention could be dominated by trapping effects by radiation defects.
Fig. 1 shows TDS spectrum of D from the electron-irradiated specimen together with the result of simulation with the TMAP4 program. The desorption peakfrom the electron-irradiated specimen was broad and it
indicates long-range diffusion under trapping effects. The
maximum desorption rate was observed at 830 K. The
simulation roughly reproduced this peak temperature bysetting the activation energy of detrapping to 1.5 eV. Thisvalue corresponds to detrapping from vacancies [4]. It is
plausible that vacancies induced by the electron irradiation played dominant roles in trapping effects under thepresent conditions.

Desorption rate (1018 D m-2s-1)

PR1-152.0
1.5

Measured
TMAP4 simulation

1.0
0.5
0.0
300

500

700
900 1100
Temperature (K)1300

Fig. 1 TDS spectrum of D from electron-irradiated
VPS-W and the result of simulation with the
TMAP4 program, in which the activation energy
for detrapping was set to 1.5 eV.
REFERENCES:[1] Y. Hatano et al., Mater. Trans., 54 (2013) 437.
[2] Y. Hatano et al., J. Nucl. Mater., in press (doi:
10.1016/j.jnucmat.2013.01.018.)[3] G. R. Longhurst et al., TMAP4 User’s Manual,
EGG-FSP-10315, doi: 10.2172/7205576.
[4] H. Eleveld and A. van Veen, J. Nucl. Mater., 212-215(1994) 1421.

採択課題番号 24P1-15 タングステン中の照射欠陥による水素同位体捕獲機構（京大・原子炉）佐藤紘一、徐 虬（富山大・水素研）波多野雄治、野﨑天生

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