Fast local motions and their transitions in polybutadiene across the glass transition

Kikuchi, Tatsuya*; Mashita, Ryo*; Masui, Tomomi*; Kanaya, Toshiji*; Kishimoto, Hiroyuki*; Nakajima, Kenji

Physical Review E, 113(6), p.065418_1 - 064518_10, 2026/06

https://doi.org/10.1103/tg7v-hw13

We investigated the local dynamics of polybutadiene over a wide temperature range, using quasielastic neutron scattering combined in the modified mode distribution analysis. Among these processes, the subpicosecond fast process was analyzed using a local diffusion model, which characterizes the dynamics via two physically meaningful parameters: the local diffusion coefficient and the harmonic potential stiffness. Temperature-dependent analysis revealed a distinct dynamic transition near the glass transition, which is interpreted as the disappearance of cooperative diffusion involving multiple segments. Furthermore, an additional relaxation mode, termed the extra-fast process, was identified and interpreted as a higher-order mode within the local diffusion model. These findings suggest a unified physical framework for the evolution of local motions across the glass transition and establish a robust methodology for quantifying polymer dynamics at subnanometer and subpicosecond scales.

Compliance measures at the Radioactive Waste Treatment Facilities at the Nuclear Science Research Institute; Aseismic reinforcement of the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility

Iketani, Shotaro; Suzuki, Takeshi; Yokobori, Tomohiko; Sugawara, Satoshi; Yokota, Akira; Kikuchi, Genta; Muraguchi, Yoshinori; Kitahara, Masaru; Seya, Manato; Kurosawa, Tsuyoshi; et al.

JAEA-Technology 2025-001, 169 Pages, 2025/08

JAEA-Technology-2025-001.pdf:14.22MB

The radioactive waste treatment facilities at the Nuclear Science Research Institute includes the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility. These three facilities come under the purview of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, and are included under Class C of the act based on the seismic requirements specified in the Act. We assessed the seismic capacity of these three radioactive waste treatment facilities based on the current Building Standards Act, to verify whether they comply with the new regulatory requirements enforced by the Nuclear Regulation Authority (NRA) in the aftermath of the 2011 nuclear accident at the Fukushima Daiichi Nuclear Power Station operated by the Tokyo Electric Power Company. We found that the allowable stress of a few structural members used in the construction of the facilities did not meet the regulatory requirements. After studying the approval granted by the NRA for the construction plans, including the design and construction methods (design and construction plans) of the three facilities on March 5, 2021, we made aseismic reinforcement at these facilities between 2021 and 2022. This report presents an overview of the seismic design of these facilities and an outline of the aseismic reinforcement conducted, management system existing, safety measures adopted, and the preoperational inspections conducted at these facilities.

Experiment and numerical simulation of pulsation flow in single channel for Li-7 enrichment technology development by MCCCE method

Horiguchi, Naoki; Yoshida, Hiroyuki; Kitatsuji, Yoshihiro; Hasegawa, Makoto*; Kishimoto, Tadafumi*

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

From the viewpoint of energy security in Japan and reduction of the environmental load, continuous operation of light water reactors is essential. Since a pH adjuster with enriched Li-7 ions is required for water quality control on PWR, the development of Li-7 enrichment technology is one of the key issues. The multi-channel counter-current electrophoresis (MCCCE) method has been developed as the technology with a low environmental load. To put this method into practical use, it is necessary to understand Li-7 ion behavior in the channel flow and optimize the experimental condition to separate Li-7 and its isotope. In this paper, to understand Li-7 ion behavior in a single channel of the experimental apparatus, a numerical simulation method based on a computational fluid dynamics (CFD) code with a particle tracking method, TPFIT-LPT, was developed. In the method, the motion of multiple ions under the electric field was simulated as a particle with an added velocity by the electric field. The difference in the isotopes was represented by changing of the magnitude of the added velocity. We also considered that although it is impossible to measure the behavior of each ion, it is important to measure the flow velocity of the bulk fluid for the validation of the numerical simulation. We developed a lab-scale experimental apparatus in which the single channel of the actual apparatus was simplified to measure the flow velocity by Particle Image Velocimetry (PIV). We set a pulsation flow condition on the lab-scale experiment, which is one of difficult conditions for the numerical simulation, and measured the velocity. As the result, we confirmed that the pulsation flow was reproduced. We set the measured data as the inlet boundary condition of the numerical simulation and conducted it. As the numerical result, we confirmed the ions affected by the electric field moved upstream with pulsation. We also confirmed the effect of the electric field on the motion of the isotope.

Detecting halfmetallic electronic structures of spintronic materials in a magnetic field

Fujiwara, Hidenori*; Umetsu, Rie*; Kuroda, Fumiaki*; Miyawaki, Jun*; Kashiuchi, Toshiyuki*; Nishimoto, Kohei*; Nagai, Kodai*; Sekiyama, Akira*; Irizawa, Akinori*; Takeda, Yukiharu; et al.

Scientific Reports (Internet), 11, p.18654_1 - 18654_9, 2021/09

https://doi.org/10.1038/s41598-021-97992-z

Safety measures in the melting facilities of The Advanced Volume Reduction Facilities; Document collection of discussion meetings related to melting facilities

Iketani, Shotaro; Yokobori, Tomohiko; Ishikawa, Joji; Yasuhara, Toshiyuki*; Kozawa, Toshiyuki*; Takaizumi, Hirohide*; Momma, Takeshi*; Kurosawa, Shingo*; Iseda, Hirokatsu; Kishimoto, Katsumi; et al.

JAEA-Review 2018-016, 46 Pages, 2018/12

JAEA-Review-2018-016.pdf:12.79MB

Japan Atomic Energy Agency (JAEA) adopts melting process for the waste processing and packaging method of radioactive miscellaneous solid waste in NSRI because melting process is effective in radioactivity evaluation, volume reduction, and stabilization treatment. Metal melting processing facilities, Incinerator, and Nonmetal melting processing facilities (hereinafter referred to as melting process facilities) have taken lots of safety measures, including measures for preventing the recurrence of the fire accidents. To exchange opinions and discuss the validity of these measures and so on with internal personnel and external experts, "Discussions on Melting Process Facilities" was held. As a document collection, this paper summarizes presentation materials of discussion meetings. Presentation materials describe "Outline of AVRF", "Safety measures in the melting facilities in WVRF", "Operation management of the melting facilities in WVRF", "Comparison of the past accident cases between facilities in and outside Japan and WVRF", and "Introduction of past accident cases and safety measures in other facilities from each committee".

Pretreatment works for disposal of radioactive wastes produced by research activities, 1

Ishihara, Keisuke; Yokota, Akira; Kanazawa, Shingo; Iketani, Shotaro; Sudo, Tomoyuki; Myodo, Masato; Irie, Hirobumi; Kato, Mitsugu; Iseda, Hirokatsu; Kishimoto, Katsumi; et al.

JAEA-Technology 2016-024, 108 Pages, 2016/12

JAEA-Technology-2016-024.pdf:29.74MB

Radioactive isotope, nuclear fuel material and radiation generators are utilized in research institutes, universities, hospitals, private enterprises, etc. As a result, various low-level radioactive wastes (hereinafter referred to as non-nuclear radioactive wastes) are produced. Disposal site for non-nuclear radioactive wastes have not been settled yet and those wastes are stored in storage facilities of each operator for a long period. The Advanced Volume Reduction Facilities (AVRF) are built to produce waste packages so that they satisfy requirements for shallow underground disposal. In the AVRF, low-level beta-gamma solid radioactive wastes produced in the Nuclear Science Research Institute are mainly treated. To produce waste packages meeting requirements for disposal safely and efficiently, it is necessary to cut large radioactive wastes into pieces of suitable size and segregate those depending on their types of material. This report summarizes activities of pretreatment to dispose of non-nuclear radioactive wastes in the AVRF.

Observation of the inhomogeneous spatial distribution of MeV ions accelerated by the hydrodynamic ambipolar expansion of clusters

Kanasaki, Masato; Jinno, Satoshi; Sakaki, Hironao; Faenov, A.*; Pikuz, T.*; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kando, Masaki; Sugiyama, Akira; Kondo, Kiminori; et al.

Radiation Measurements, 83, p.12 - 14, 2015/12

https://doi.org/10.1016/j.radmeas.2015.06.011

An inhomogeneous spatial distribution of laser accelerated carbon/oxygen ions produced via the hydrodynamic ambipolar expansion of CO clusters has been measured by using CR-39 detectors. An inhomogeneous etch pits spatial distribution has appeared on the etched CR-39 detector installed on the laser propagation direction, while homogeneous ones are appeared on those installed at 45 and 90 from the laser propagation direction. From the range of ions in CR-39 obtained by using the multi-step etching technique, the averaged energies of carbon/oxygen ions for all directions are determined as 0.78 0.09 MeV/n. The number of ions in the laser propagation direction is about 1.5 times larger than those in other directions. The inhomogeneous etch pits spatial distribution in the laser propagation direction could originate from an ion beam collimation and modulation by the effect of electromagnetic structures created in the laser plasma.

Quasielastic neutron scattering study on polymer nanocomposites

Masui, Tomomi*; Kishimoto, Hiroyuki*; Kikuchi, Tatsuya; Kawamura, Seiko; Inamura, Yasuhiro; Koga, Tadanori*; Nakajima, Kenji

Journal of Physics; Conference Series, 502(1), p.012057_1 - 012057_4, 2014/04

https://doi.org/10.1088/1742-6596/502/1/012057

By using a quasielastic neutron scattering technique (disk-chopper-type spectrometer AMATERAS at J-PARC), we have investigated the microscopic dynamics of polybutadiene (PB) in which silica particles were embedded. The experimental results gave us both a damped vibration mode of PB and jumped diffusion motion of the segments. It was found that these dynamical features remain unaffected by the presence of the silica particle, while the residence time of the jumped diffusion motion becomes longer at the high filler loading.

NMR determination of noncollinear antiferromagnetic structure in TbCoGa

Tokunaga, Yo; Saito, Yo*; Sakai, Hironori; Kambe, Shinsaku; Sanada, Naoyuki*; Watanuki, Ryuta*; Suzuki, Kazuya*; Kawasaki, Yu*; Kishimoto, Yutaka*

Physical Review B, 84(21), p.214403_1 - 214403_7, 2011/12

https://doi.org/10.1103/PhysRevB.84.214403

We report NMR studies of TbCoGa, which has the tetragonal HoCoGa structure and exhibits two antiferromagnetic (AF) transitions at =36.2 K and =5.4 K. From a symmetry analysis of internal magnetic fields at orthorhombic Ga sites, we have successfully determined the magnetic structures in the AF-I () and AF-II () phases. The AF-I phase is a collinear AF order with a propagation vector and ordered moments parallel to the [001] direction. In the AF-II phase, on the other hand, we found a non-collinear AF structure described by double propagation vectors and , where the moments tilt away from the [001] direction toward [100], keeping a constant value along the [001] direction. In the context of these results we discuss the possible presence of magnetic frustration in this system.

Source development and novel applications of laser-driven plasma X-ray lasers in JAEA

Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Oba, Toshiyuki; Kaihori, Takeshi; Kishimoto, Maki; Ochi, Yoshihiro; Tanaka, Momoko; et al.

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.15 - 24, 2011/12

http://ci.nii.ac.jp/ncid/BB05543208

This paper reviews recent improvement in the source development of laser-driven X-ray lasers and the applications in the research fields of material science, laser processing, X-ray imaging, and radiation damage in biological cells. In the application for material science, we have firstly observed temporal correlation between the domain structures of ferro-electric substance under the Curie temperature. In the laser processing, new X-ray laser interferometer reveals us the nano-scale surface distortion of substance pumped by a femto-second optical pulse. In the X-ray diffraction image, we have taken several static images of micro-structure of samples: now we are trying to extend the objective to nano-scale dynamics using pump and probe method. In the radiation damage of biological cells, we observed double strand break in DNA using X-ray laser exposure; this results are compared with the case using incoherent several KeV X-ray exposure.