4. Material Science and Radiation Effects

概要

CO4-1

Study on HPLC Elution Behavior of Heavy Lanthanide Metalloufullerenes

K. Akiyama1, D. Nakamura1, T. Kuroda1, K. Takamiya2,
and S. Kubuki1
Department of Chemistry, Tokyo Metropolitan Univer-sity
2
Institute for Integrated Radiation and Nuclear Science,
Kyoto University
1

INTRODUCTION:
Metallofullerene (EMF) is a
clathrate compound encapsulating metal atom in fullerene molecule. Lanthanide (Ln) EMFs: Ln@C82 have two
or three charge transferred electrons on the C82 cage from
the encapsulated Ln atom, and their electronic states reflecting the number of charge transfer electrons [1]. From
the view point of inorganic chemistry, It is interesting to
know that the effect of the electronic state for a series of
the encapsulated 10 lanthanide elements (La, Ce, Pr, Nd,
Gd, Tb, Dy, Ho, Er, Lu) with the electronic states of
(Ln3+)@(C823-) on the electronic state of the Ln@C 82
molecule from the difference in interaction with pylenyl
stationary phase. So far, we have made clear the retention
time in the pyrenyl stationary phase for five types of
Ln@C82 from La to Gd by the thermal neutron activation
method. On the other hand, the high-performance liquid
chromatography (HPLC) retention time of Ln@C82 with
heavy lanthanide elements have not been obtained because the half-life of the radio nuclide produced by thermal neutron irradiation such as Dy and Er is very short,
and the interference by the production of Ln2@C82 and
Ln2C2@C80, whose production rate increase competitively with Ln@C82 as the increase of the atomic number of
Ln. In previous work, we used already purified Ln@C82
of heavy lanthanide by HPLC column of a 5PBB for the
neutron activation and developed at three different temperature using newly developed column cooler to obtained detailed HPLC retention time of these Ln@C82s
and successively evaluated the adsorption-desorption
enthalpy (H) at room temperature (RT), 0 oC, and -10 oC
for Ln@C82 of La, Ce, Pr, Tb, Dy, Ho, and Er on a
pyrenyl stationary phase [2]. However, obtained HPLC
retention time and evaluated H for Ce and Tb were
slightly larger than that for other lanthanide considering
about the similarity of chemical properties of lanthanide
elements. In the previous experiment, we had to develop
Ln@C82 for short half-life (La, Pr, Dy, Ho, and Er) and
long half-life radioisotopes (Ce and Tb) by HPLC separately due to the limitation of the half-life. In this time,
we used HPLC-separated samples of mixed Ln@C82 solution regardless of their half-lives as irradiated samples
in order to confirm the reproducibility of the retention
times previously obtained.
EXPERIMENTS: Already isolated La@C82, Tb@C82
and Dy@C82 were dissolved in toluene and mixed to
prepare samples for HPLC development. These samples
were injected into a Buckyprep column and the eluate
was fractionated every 20 seconds at RT and every 1 mi-

nute at -10 oC. These fractionated eluates were evaporated to dryness and re-dissolved to carbon disulfide and
then dropped onto paper filters with 12 mm diameters
and dried. These samples were sealed into polyethylene
bags and irradiated in ethylene vial and activated by a
thermal neutron in the KUR of the Institute for Integrated
Radiation and Nuclear Science, Kyoto university. After
the irradiation, the g rays emitted from the samples were
measured by a Ge detector.
RESULTS: Figure 1 show HPLC elution behavior of
Ln@C82s studied in this work obtained at room temperature and -10 oC. HPLC retention time (tR) of these
Ln@C82 were evaluated from the least square fitting with
extreme function and determined as 60.41, 62.41, and
61.36 for La, Tb, and Dy at RT and 86.53, 90.24, and
88.58 for La, Tb, and Dy at -10 oC, respectively. The
separation coefficient () of Tb@C82 and Dy@C82 to
La@C82 were evaluated from obtained tR and Tb@C82 at
-10 oC was found to be quite smaller than that obtained
in previous work. From these results, it was clarified that
the retention time of Tb@C82 at -10 oC obtained in the
previous study was overestimated, as well as that of Ce
determined using long half-life nuclides.

Fig. 1. HPLC elution behavior of Ln@C82s studied
in this work obtained at a) room temperature and b).
-10 oC.
REFERENCES:
[1] H. Shinohara, Rep. Prog. Phys., 63 (2000) 843-892.
[2] K. Akiyama et al., KURNS Prog. Rep. 2021, CO4-20.

R4006
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CO4-2

Radiation Tolerance of SiC p+n Junction-Diodes for High-Energy Physics Experiments

T. Kishishita, H. Yashima1, R. Kosugi2

(protons and pions) or gamma-rays were not evaluated in
this measurement, however, the number of primary
defects is reported as low as that of diamond. Thus, we
conclude that the bulk defects introduced by irradiation at
the 1012 neutron equivalent fluence is ignorable, even
with the reverse bias of 1 kV.

High Energy Accelerator Research Organization, KEK
1
Institute for Integrated Radiation and Nuclear Science,
Kyoto University
2
National Institute of Advanced Industrial Science and
Technology
INTRODUCTION: Silicon carbide (SiC) has been
considered as a potential alternative to Si for the
manufacture of dosimeters, spectrometers, and charge
particle detectors in high energy physics experiments, by
virtue of its operation capability in strong radiation
and/or high-temperature environments. To take
advantage of such properties for future radiation detectors
with a comparable size of silicon, we investigated the
influence of the bulk defects on the radiation sensor
characteristics under the reverse-bias condition, by
irradiating neutrons at Institute for Integrated Radiation
and Nuclear Science, Kyoto University.
EXPERIMENTS: The reverse blocking characteristics
and leakage current characteristic are primary concerns
of the radiation effects. The radiation-induced effects are
generally divided into bulk and surface defects. The
formers are caused by the displacement of crystal atoms,
introducing to the increase of the leakage current and
degraded reverse blocking characteristics. The latter
include all effects in the covering dielectrics and the
interface region. Since the bulk damage caused by the
elastic nuclear scattering of the lattice nuclei has a
profound effect in our device, we irradiated fast neutrons
to SiC pn-diodes under the bias condition of 1 kV [1].
The irradiation test was conducted at KUR. Fig. 1 shows
the photograph of the measurement setup. We installed
two SiC sensors at the front of the rail-instrument. After
the 1MW operation, we carried out measurements of the
leakage current and compared with those of the
pre-irradiation samples.
RESULTS: The typical I-V characteristics before
irradiation is shown in Figure 2. The data before the
irradiation are plotted in white and black, while those
after the irradiation are shown in colors. We note that the
data around 1 kV are overlapped and the leakage current
characteristics is not changed in the irradiation. The
reverse blocking property was also retained up to 1 kV,
which is required for full depletion of the SiC devices.
Irradiation tests at higher fluences are performed in
FY-2023. We note that the 1 MeV neutrons have the
same efficiency in the detector degradation as 24 GeV
protons at a comparable neutron equivalent fluence. The
theoretical nonionizing energy loss (NIEL) calculation
performed on SiC can be found in Lee et al. [2]. The
primary radiation defects produced by single particles

Fig. 1.

Photograph of the measurement setup.

Fig. 2. Leakage currents before (plotted in white
and black) and after (plotted in colors) 1 MeV
neutron irradiation of 1012 neq/cm2.

REFERENCES:
[1] T. Kishishita et al., IEEE Trans. Nucl. Sci., 68 (2020)
2787-2793.
[2] K. K. Lee et al., Nucl. Instrum. Methods Phys. Res. B,
210 (2003) 489-494.

R4008
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CO4-3

Positron Annihilation Spectroscopy in Neutron-irradiated Fe-Cr Alloys

K. Sato, Y. Noshita, R. Kasada1, Q. Xu2, A. Yabuuchi2, A.
Kinomura2
Graduate School of Science and Engineering, Kagoshima
University
1
Institure for Materials Research, Tohoku University
2
Institute for Integrated Radiation and Nuclear Science,
Kyoto University

INTRODUCTION: Ferritic stainless and heat resistant
steels used as nuclear reactor peripheral materials have
high Cr content [1]. In these materials, ductility and
toughness remarkably decrease, and hardness and tensile
strength increase by aging from 593 to 813 K. This phenomenon is caused by the formation of Fe-rich and
Cr-rich phase, and is called 475˚C embrittlement [2].
These changes in mechanical properties are an important
issue in terms of evaluation of aged deterioration when it
was used as a reactor structural material. The phase separation process of Fe-Cr binary alloys have studied by the
small angle neutron scattering method [3], Mossbauer
spectroscopy [4] and atom probe field ion microscopy [5]
etc. Chen et al. detected phase separation in Fe-9.7%Cr
irradiated with neutrons at 573 K by atom probe tomography [6], and reported that irradiation-induced excessive
defects promote phase separation even at a temperature
of less than 593 K.
Positron annihilation spectroscopy (PAS) is very
powerful tool to obtain the information of vacancy-type
defects (even single vacancies) and precipitates. Xu et al.
reported the positron annihilation lifetimes of vacancy
clusters and the change in spectra of coincidence Doppler
broadening (CDB) in association with the formation of
Cu precipitates in neutron-irradiated Fe-Cu alloys [7]. In
Fe-Cu alloys, positron affinity of Cu is lower than that of
Fe [8], and the formation of Cu precipitates leads to the
change in spectra of CDB. In Fe-Cr alloys used in this
study, positron affinity of Fe is lower than that of Cr [8].
Therefore, we can detect the formation of Fe-rich phase
in phase separation of Fe-Cr alloys using PAS. The purpose of this study is to detect the progress of phase separation using PAS, and to obtain the correlation between
the hardness and phase separation in Fe-Cr binary alloys
irradiated with neutrons at 473K and 573 K. ...