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Tobita, Minoru*; Haraga, Tomoko; Sasaki, Takayuki*; Seki, Kotaro*; Omori, Hiroyuki*; Kochiyama, Mami; Shimomura, Yusuke; Ishimori, Kenichiro; Kameo, Yutaka
JAEA-Data/Code 2019-016, 72 Pages, 2020/02
JAEA-Data-Code-2019-016.pdf:2.67MB
In the future, radioactive wastes which generated from research and testing reactors in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes by the time it starts disposal. In order to contribute to this work, we collected and analyzed the samples generated from JRR-2, JRR-3 and Hot laboratory facilities. In this report, we summarized the radioactivity concentrations of 25 radionuclides (
H, 
C, 
Cl, 
Co, 
Ni, 
Sr, 
Nb, 
Mo, 
Tc, 
Ag, 
Sn, 
I, 
Cs, 
Eu, 
Eu, 
U, 
U, 
U, Pu, 
Pu, 
Pu, 
Pu, Am, 
Am, 
Cm) which were obtained from radiochemical analysis of those samples.
Seki, Yusuke*; Takayanagi, Toshiyuki*; Shiga, Motoyuki
Physical Chemistry Chemical Physics, 19(21), p.13798 - 13806, 2017/06
Times Cited Count：8 Percentile：35.36(Chemistry, Physical)Ring-polymer molecular dynamics (RPMD) simulations have been performed to understand the photoexcitation dynamics of the Ag atom embedded in a low-temperature cluster consisting of 500 helium atoms, after the electronic excitation of the Ag atom. Along the RPMD trajectory the time evolution of the electronic wavefunction within the spin-orbit 
P manifold is calculated, whereby the time-dependent Schr
dinger equation and the RPMD equation of motion are coupled, 
la Ehrenfest mean field approach. It is found from the simulations that the Ag atom is mostly ejected from the helium cluster with the average time of 100 ps after photoexcitation. The average velocity of the ejected Ag atom is estimated to be 60-70 m/s. These results are qualitatively in line with previous experimental findings.
Haraga, Tomoko; Tobita, Minoru*; Takahashi, Shigemi*; Seki, Kotaro*; Izumo, Sari; Shimomura, Yusuke; Ishimori, Kenichiro; Kameo, Yutaka
JAEA-Data/Code 2016-017, 53 Pages, 2017/02
JAEA-Data-Code-2016-017.pdf:3.17MB
Fugen Nuclear Power Station was shut down and now is under decommissioning. Many radioactivity concentration data of dismantled materials have to be accumulated to calculate the scaling factors of radioactive wastes and to verify that the cleared dismantled materials conform to the clearance levels. A simple and rapid radioactivity determination method for radioactive waste samples was developed by Department of Decommissioning and Waste Management. For its demonstration, the simple and rapid radioactivity determination method was applied to metal samples, which were taken from dismantled pipes in contact with heavy water or carbon dioxide gas of Fugen. This report summarizes the radioactivity data obtained from the analysis of those samples.
Minoshima, Yusuke*; Seki, Yusuke*; Takayanagi, Toshiyuki*; Shiga, Motoyuki
Chemical Physics, 472, p.1 - 8, 2016/06
Times Cited Count：2 Percentile：6.19(Chemistry, Physical)The dynamical process of electron attachment to a guanine-cytosine pair in the normal (h-GC) and deuterated (d-GC) forms has been studied theoretically by semiclassical ring-polymer molecular dynamics (RPMD) simulations using the empirical valence bond model. The initially formed dipole-bound anion is converted rapidly to the valence-bound anion within about 0.1 ps in both h-GC and d-GC. However, the subsequent proton transfer in h-GC occurs with a rate five times greater than the deuteron transfer in d-GC. The change of rates with isotopic substitution and temperature variation in the RPMD simulations are quantitatively and qualitatively different from those in the classical molecular dynamics (MD) simulations, demonstrating the importance of nuclear quantum effects on the dynamics of this system.
Sakasai, Akira; Masaki, Kei; Shibama, Yusuke; Sakurai, Shinji; Hayashi, Takao; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Yokoyama, Kenji; Seki, Yohji; Shibanuma, Kiyoshi; et al.
Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03
The JT-60SA vacuum vessel (VV) and divertor are key components for the performance requirements. Therefore the manufacturing and development of VV and divertor are in progress, inclusive of the superconducting magnets. The vacuum vessel has a double wall structure in high rigidity to withstand electromagnetic force at disruption and to keep high toroidal one-turn resistance. In addition, the double wall structure fulfills originally two functions. (1) The remarkable reduction of the nuclear heating in the superconducting magnets is made by boric-acid water circulated in the double wall. (2) The effective baking is enabled by nitrogen gas flow of 200
C in the double wall after draining of water. Three welding types were chosen for the manufacturing of the double wall structure VV to minimize deformation by welding. Divertor cassettes with fully water cooled plasma facing components were designed to realize the JT-60SA lower single null closed divertor. The divertor cassettes in the radio-active VV have been developed to ensure compatibility with remote handling (RH) maintenance in order to allow long pulse high performance discharges with high neutron yield. The manufacturing of divertor cassettes with typical accuracy of *1 mm has been successfully completed. Brazed CFC (carbon fiber composite) monoblock targets for a divertor target have been manufactured by precise control of tolerances inside CFC blocks. The infrared thermography test of monoblock targets has been developed as new acceptance inspection.
Tanabe, Yusuke*; Nishikawa, Hiroyuki*; Seki, Yoshihiro*; Sato, Takahiro; Ishii, Yasuyuki; Kamiya, Tomihiro; Watanabe, Toru*; Sekiguchi, Atsushi*
Microelectronic Engineering, 88(8), p.2145 - 2148, 2011/08
Times Cited Count：9 Percentile：47.34(Engineering, Electrical & Electronic)Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.
JAEA-Research 2010-019, 194 Pages, 2010/08
JAEA-Research-2010-019-01.pdf:48.47MBJAEA-Research-2010-019-02.pdf:19.4MB
This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.
Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.
Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07
Times Cited Count：137 Percentile：97.72(Physics, Fluids & Plasmas)Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).
Kamiya, Tomihiro; Takano, Katsuyoshi; Ishii, Yasuyuki; Sato, Takahiro; Oikawa, Masakazu*; Okubo, Takeru; Haga, Junji*; Nishikawa, Hiroyuki*; Furuta, Yusuke*; Uchiya, Naoyuki*; et al.
Nuclear Instruments and Methods in Physics Research B, 267(12-13), p.2317 - 2320, 2009/06
Times Cited Count：7 Percentile：47.15(Instruments & Instrumentation)Tanabe, Yusuke*; Nishikawa, Hiroyuki*; Watanabe, Toru*; Seki, Yoshihiro*; Sato, Takahiro; Ishii, Yasuyuki; Kamiya, Tomihiro
no journal, ,
no abstracts in English
Saga, Ryusuke*; Naganawa, Akihiro*; Seki, Takeshi*; Oka, Kiyoshi; Yoshino, Junji*
no journal, ,
no abstracts in English
Shinohara, Takenao; Kai, Tetsuya; Oikawa, Kenichi; Hiroi, Kosuke; Su, Y. H.; Nakatani, Takeshi; Seki, Yoshichika; Tsuchikawa, Yusuke; Hayashida, Hirotoshi*; Parker, J. D.*; et al.
no journal, ,
The Energy-Resolved Neutron Imaging System, RADEN, in the Materials and Life Science Experimental Facility (MLF) of J-PARC, has been constructed as the world's first dedicated instrument to the pulsed neutron imaging. RADEN is designed to conduct energy-resolved neutron imaging experiments like Bragg edge, resonance absorption and pulsed polarized neutron imaging by fully utilizing the short-pulsed neutron's nature, together with the conventional neutron radiography and tomography. The construction of RADEN was completed in 2014, and user operation was started from April 2015 after commissioning studies using the neutron beam. In addition to the user programs, the instrument group continues further technical developments for advanced energy-resolved neutron imaging and improving the performance of devices, especially the counting type imaging detectors.
