A Study on accuracy of analysis of the radiation-induced component in the ESR spectra of teeth

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

KEK Proceedings 2022-2, p.120 - 125, 2022/11

We investigate the effect of sample's anisotropy and measurement condition to obtain the higher reproducibility for the shape of the ESR spectrum and the intensity of CO radical.

Determination of site occupancy of boron in 6H-SiC by multiple-wavelength neutron holography

Hayashi, Koichi*; Lederer, M.*; Fukumoto, Yohei*; Goto, Masashi*; Yamamoto, Yuta*; Happo, Naohisa*; Harada, Masahide; Inamura, Yasuhiro; Oikawa, Kenichi; Oyama, Kenji*; et al.

Applied Physics Letters, 120(13), p.132101_1 - 132101_6, 2022/03

https://doi.org/10.1063/5.0080895

Development of cesium trap material for coated fuel particles in high temperature gas-cooled reactors

Sasaki, Koei; Miura, Shuichiro*; Fukumoto, Kenichi*; Goto, Minoru; Ohashi, Hirofumi

Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 6 Pages, 2021/08

https://doi.org/10.1115/ICONE28-61765

Cs-Bi and Cs-Sb absorbed graphite samples (Cs-Bi/graphite and Cs-Sb/graphite) were synthesized and their high temperature chemical stabilities were tested up to 1500C by TG and analyzed by TEM-EDS for the development of Cs trap material in high temperature gas-cooled reactor (HTGR) fuel particles. It was observed that Cs was stabilized by Sb but not by Bi in the specimens after the TG test. A rapid weight loss from 800 to 1000C may be caused by evaporation of Cs (boiling point: 671C) was seen in the TG result of both specimens. Precipitated Cs-Sb substance in the graphite matrix were not resolved even after the 1500C heating. The chemical composition of the Cs-Sb was specified as CsSb. The experimental results suggest that Sb have potential to be a Cs getter material in graphite matrix. Long term heating test should be performed to confirm adaptability of Sb for Cs trap material in HTGR fuel particles.

Analyzing the cross slip motion of screw dislocations at finite temperatures in body-centered-cubic metals; Molecular statics and dynamics studies

Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*

Modelling and Simulation in Materials Science and Engineering, 27(6), p.064001_1 - 064001_15, 2019/08

https://doi.org/10.1088/1361-651X/ab235e

Plasticity of body-centered-cubic (BCC) metals at low temperatures is determined by screw dislocation kinetics. Because the core of screw dislocation in these metals has non-planar structure, its motion is complex and unpredictable. For example, although density functional theory (DFT) predicts slip on a { 110 } plane, the actual slip plane at elevated temperatures departs from the prediction, its mechanism having been a mystery for decades. Here we conduct a series of molecular dynamics simulations to track the screw dislocation motion and successfully reproduced the transition of the slip plane. We then devised an algorithm to scrutinize the activation of dislocation jump over the Peierls barrier and discovered the possible origin of this unexpected phenomenon, i.e., a large fluctuation leads to the kink-pair nucleation for the cross-slip jump without transition of dislocation core structure.

Development of irradiation capsules in liquid metal environment in Joyo and their application to irradiation creep measurement of vanadium alloys

Fukumoto, Kenichi*; Narui, Minoru*; Matsui, Hideki*; Ito, Kazuhiro; Yano, Yasuhide

Journal of Nuclear Science and Technology, 45(2), p.171 - 178, 2008/02

https://doi.org/10.3327/jnst.45.171

In order to perform irradiation experiments under liquid metal environment in a nuclear reactor, an irradiation technique with sodium bonding irradiation capsules has been developed and a series of neutron irradiation experiments with sodium bonding irradiation capsule were performed in Joyo. The design and fabrication of sodium bonding capsule, sodium filling into capsules, capsule loading to Joyo, irradiation experiments, dismantling for irradiated capsule, removing the irradiated specimens from sodium filled capsules, and sodium cleaning the irradiated specimens were established through this study. Using the Joyo irradiation with the sodium bonding capsules where irradiation temperature was distributed uniformly, the irradiation creep experiment for highly purified V-4Cr-4Ti alloys, NIFS-Heat was carried out and the knowledge about the irradiation creep behavior of the alloys was obtained.

An Energy spread minimization system for microbeam generation in the JAERI AVF cyclotron

Fukuda, Mitsuhiro; Kurashima, Satoshi; Miyawaki, Nobumasa; Okumura, Susumu; Kamiya, Tomihiro; Oikawa, Masakazu*; Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; et al.

Nuclear Instruments and Methods in Physics Research B, 210, p.33 - 36, 2003/09

https://doi.org/10.1016/S0168-583X(03)01012-7

A heavy ion microbeam with energy of hundreds MeV is a significantly useful probe for research in biotechnology. A single-ion hitting technique using a 260 MeV Ne microbeam is being developed at the JAERI AVF cyclotron facility for biofunction elucidation. Production of a microbeam with a spot size of one micro-meter in diameter requires reducing the energy spread of the beam to 0.02 % to minimize an effect of chromatic aberrations in focusing lenses. The typical energy spread of the cyclotron beam is around 0.1 % in an ordinary acceleration mode using a sinusoidal voltage waveform. The energy spread can be reduced by superimposing the fifth-harmonic voltage waveform on the fundamental one to generate a flattop waveform for uniform energy gain. We have designed an additional coaxial cavity to generate the fifth-harmonic voltage, coupled to the main resonator of one-fourth wavelength coaxial type. In a power test we successfully observed the fifth-harmonic voltage waveform by picking up an acceleration voltage signal.

Prepulse effects on the interaction of intense femtosecond laser pulses with high-Z solids

Zhidkov, A. G.; Sasaki, Akira; Utsumi, Takayuki*; Fukumoto, Ichiro; Tajima, Toshiki; Saito, Fumikazu*; Hironaka, Yoichiro*; Nakamura, Kazutaka*; Kondo, Kenichi*; Yoshida, Masataka*

Physical Review E, 62(5), p.7232 - 7240, 2000/11

https://doi.org/10.1103/PhysRevE.62.7232

no abstracts in English

Sample preparation procedure for ESR dosimetry using teeth of wild animal

Oka, Toshitaka; Mitsuyasu, Yusuke*; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Sekine, Tsutomu*; Okutsu, Kenichi*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Releases of the radioactive materials from the Fukushima Daiichi Nuclear Power Plant accident result in a low dose exposure to wild animals. The external dose of wild animals is commonly estimated by the external dose rate of the captured point, but the estimated exposure dose has huge uncertainties because the size of the habitat and/or the movement of the wild animals are not included in the estimation. To estimate the external dose precisely, we utilize electron spin resonance (ESR) dosimetry. In this work, we investigated the sample preparation procedure of wild animals. The ESR spectrum of enamel of racoon captured in Namie-town, Fukushima has a broad ESR signal due to metal components. The linear relationship between the Co intensity and the absorbed dose that we can apply ESR dosimetry for racoon teeth. Using this relationship, the external exposure dose was estimated.

External exposure dose estimation using ESR dosimetry technique

Oka, Toshitaka; Takahashi, Atsushi*; Mitsuyasu, Yusuke*; Koarai, Kazuma; Kino, Yasushi*; Okutsu, Kenichi*; Yamashita, Takuma*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Electron spin resonance (ESR) dosimetry technique is a powerful tool that has been used in the study of external exposure dose assessment of human by measuring CO radicals of teeth. In this work, we applied this technique for wild monkey and wild racoon captured in Fukushima prefecture, and estimated the external exposure dose.

Molecular dynamics studies on interaction between a screw dislocation and a void in pure Fe, 2

Onitsuka, Takashi*; Okubo, Manabu*; Suzudo, Tomoaki; Fukumoto, Kenichi*

no journal, , 

Reactor structural materials such as pressure vessels become brittle under neutron irradiation. It is widely known that a cause of such phenomenon could be formation of extended lattice defects under irradiation such as voids that become obstacles for dislocation motion, but we do not know the strength of these obstacles accurately enough for establishing a quantitative model. In the present study, we choose pure iron as a substitute of steel and numerically simulate the interaction between screw dislocation and a void using molecular dynamics method. Especially, we analyze the critical shear stress.