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(1), p.18654_1 - 18654_9, 2021/09
Kirihara, Yoichi; Nakashima, Hiroshi; Sanami, Toshiya*; Namito, Yoshihito*; Itoga, Toshiro*; Miyamoto, Shuji*; Takemoto, Akinori*; Yamaguchi, Masashi*; Asano, Yoshihiro*
Journal of Nuclear Science and Technology, 57(4), p.444 - 456, 2020/04
no abstracts in English
Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.
Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12
The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.
Iida, Kazuki*; Kajimoto, Ryoichi; Mizuno, Yusuke*; Kamazawa, Kazuya*; Inamura, Yasuhiro; Hoshikawa, Akinori*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Ishigaki, Toru*; Kawamura, Yukihiko*; et al.
Journal of the Physical Society of Japan, 86(6), p.064803_1 - 064803_6, 2017/06
Onuki, Yusuke*; Hoshikawa, Akinori*; Sato, Shigeo*; Xu, P. G.; Ishigaki, Toru*; Saito, Yoichi*; Todoroki, Hidekazu*; Hayashi, Makoto*
Journal of Applied Crystallography, 49(5), p.1579 - 1584, 2016/10
Ito, Hiromichi*; Ota, Katsu; Kawahara, Hirotaka; Kobayashi, Tetsuhiko; Takamatsu, Misao; Nagai, Akinori
JAEA-Technology 2016-008, 87 Pages, 2016/05
In the experimental fast reactor Joyo, as a part of the restoration work of a partial dysfunction of fuel handling, the replacement of the upper core structure (UCS) was started from March 2014, and was completed in December 2014. In the jack-up test, the UCS was jacked-up to 1000 mm without significant sodium shearing resistance and interference. In the replacement of the UCS, a procedure was prepared with the use of wire-jack equipment assuming the interference. As a result, with the procedure and wire-jack were effectively functioned, the work was successfully completed.
Takamatsu, Misao; Kawahara, Hirotaka; Ito, Hiromichi; Ushiki, Hiroshi; Suzuki, Nobuhiro; Sasaki, Jun; Ota, Katsu; Okuda, Eiji; Kobayashi, Tetsuhiko; Nagai, Akinori; et al.
Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(1), p.32 - 42, 2016/03
In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly of "MARICO-2" (material testing rig with temperature control) had been broken and bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). This paper describes the results of the in-vessel repair techniques for UCS replacement, which are developed in Joyo. UCS replacement was successfully completed in 2014. In-vessel repair techniques for sodium cooled fast reactors (SFRs) are important in confirming its safety and integrity. In order to secure the reliability of these techniques, it was necessary to demonstrate the performance under the actual reactor environment with high temperature, high radiation dose and remained sodium. The experience and knowledge gained in UCS replacement provides valuable insights into further improvements for In-vessel repair techniques in SFRs.
Ito, Hiromichi; Suzuki, Nobuhiro; Kobayashi, Tetsuhiko; Kawahara, Hirotaka; Nagai, Akinori; Sakao, Ryuta*; Murata, Chotaro*; Tanaka, Junya*; Matsusaka, Yasunori*; Tatsuno, Takahiro*
Proceedings of 2015 International Congress on Advances in Nuclear Power Plants (ICAPP 2015) (CD-ROM), p.1058 - 1067, 2015/05
In the experimental fast reactor Joyo (Sodium-cooled Fast Reactor (SFR)), it was confirmed that the top of the irradiation test sub-assembly had bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). There is a risk of deformation of the UCS and guide sleeve (GS) caused by interference between them unless inclination is controlled precisely. To mitigate the risk, special jack-up equipment for applying three-point suspension was developed. The existing damaged UCS (ed-UCS) jack-up test using the jack-up equipment was conducted on May 7, 2014. As a result of this test, it was confirmed that the ed-UCS could be successfully jacked-up to 1000 mm without consequent overload. The experience and knowledge gained in the ed-UCS jack-up test provides valuable insights and prospects not only for UCS replacement but also for further improving and verifying repair techniques in SFRs.
Saito, Akinori*; Tsuji, Hiromi*; Shimoyama, Iwao; Shimizu, Kenichi*; Nishina, Yuta*
Chemical Communications, 51(27), p.5883 - 5886, 2015/04
no abstracts in English
Ito, Hiromichi; Takamatsu, Misao; Kawahara, Hirotaka; Nagai, Akinori
JAEA-Technology 2014-024, 28 Pages, 2014/07
Because the gap between the UCS and rotation plug's guide sleeve is 5 mm in minimum, there is a risk of deformation of the UCS and guide sleeve with interference between UCS and guide sleeve in the UCS replacement work. In order to reduce the risk, R&D for below subjects is required.(1) UCS jack-up equipment with strict control of inclination, (2) Detection and escape method for interference between UCS and guide sleeve. In order to solve above (1), the jack-up equipment with applying three-point suspension is developed. Then, in the aspect of above (2), load-measuring devices are installed on three jacks of jack-up equipment. By means of detection eccentric load with interference, deformation of UCS and guide sleeve are prevented. And also, the location of interference can be investigated based on eccentric loads of three jacks. The performance is verified in the ex-vessel mock-up test using full-scale dummy of UCS.
Tokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*
Physical Review B, 89(21), p.214416_1 - 214416_8, 2014/06
The magnetic phase transition near K in AmO has been investigated microscopically by means of O NMR. To avoid complexities arising from sample aging associated with the alpha decay of Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO is very sensitive to disorder. We have also confirmed the loss of O NMR signal intensity over a wide temperature range below , and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below . In the paramagnetic state, strong NMR line broadening and spatially inhomogeneous spin fluctuations have been observed. The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.
Takamatsu, Misao; Ashida, Takashi; Kobayashi, Tetsuhiko; Kawahara, Hirotaka; Ito, Hideaki; Nagai, Akinori
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Safe Technologies and Sustainable Scenarios (FR-13) (USB Flash Drive), 10 Pages, 2013/03
In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test Sub-Assembly (S/A) of "MARICO-2" (material testing rig with temperature control) had bent onto the in-vessel storage rack (IVS) as an obstacle and had damaged the Upper Core Structure (UCS). This incident necessitates the replacement of the UCS and the retrieval of MARICO-2 S/A for Joyo re-start. Along with four stages involving jack-up and retrieval of the existing damaged UCS (ed-UCS), retrieval of the MARICO-2 S/A, and installation of the new UCS (n-UCS) in the restoration work plan, current conditions at Joyo are being carefully investigated, and the results are applied to the designs of special handling equipment, which is being manufactured and scheduled for operation in 2014.
Asano, Atsushi*; Takano, Katsuyoshi*; Chiba, Atsuya; Saito, Yuichi; Marui, Hiromi*; Omichi, Masaaki*; Maeyoshi, Yuta*; Honsho, Yoshito*; Saeki, Akinori*; Yamada, Keisuke; et al.
JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 163, 2013/01
Kikuchi, Kenji*; Rivai, A. K.*; Saito, Shigeru; Bolind, A. M.*; Kogure, Akinori*
Journal of Nuclear Materials, 431(1-3), p.120 - 124, 2012/12
The oxide layer on the 12Cr steel, HCM12A, is investigated using a scanning probe microscope (SPM), which was formed in lead bismuth eutectic (LBE) at 450500C, during 5500 hrs. Hitherto oxide formation mechanisms were studied from viewpoints of the location of original base metal surface, the pass for oxygen travel and Fe diffusion to understand the stability of oxide layer. The new findings in this research are that surface potential measurement detected the boundary between (FeCr)O and FeO, which is not found at the topographic mode measurement. The spinel layer can be distinguished from the bulk area with lower surface potential profile, but near the boundary between the spinel and magnetite layers the surface potential profile seems to be continuous except for the narrow path corresponding to the boundary line. The band structure penetrating magnetite and spinel layer was found, which was not found at the topography.
Mizuta, Yoshio*; Hosokai, Tomonao*; Masuda, Shinichi*; Zhidkov, A.*; Makito, Keigo*; Nakanii, Nobuhiko*; Kajino, Shohei*; Nishida, Akinori*; Kando, Masaki; Mori, Michiaki; et al.
Physical Review Special Topics; Accelerators and Beams, 15(12), p.121301_1 - 121301_10, 2012/12
Imaizumi, Kazuyuki; Saito, Takakazu; Tobita, Shigeharu; Nagai, Akinori; Kitamura, Ryoichi; Okazaki, Yoshihiro
JAEA-Technology 2012-027, 49 Pages, 2012/08
In-Vessel Observations (IVO) techniques for Sodium cooled Fast Reactors (SFRs) are important in confirming its safety and integrity. In order to secure the reliability of IVO techniques, it was necessary to demonstrate the performance under the actual reactor environment with high temperature, high radiation dose and remained sodium. During the investigation of an incident occurred in Joyo, the following observation systems were specifically developed for Joyo. And the following two observations were conducted. (1) Simple overhead observation using a standard video camera for the top of the sub-assemblies and the in-vessel storage rack (2) Narrow space observation using remote handling device equipped with radiation-resistant fiberscope for the bottom face of the upper core structure. As a result, the observations under the actual reactor environment were successfully made even in the narrow space in the reactor vessel and the results provided useful information on incident investigations and planning of restoration work.
Naito, Hiroyuki; Itagaki, Wataru; Okazaki, Yoshihiro; Imaizumi, Kazuyuki; Ito, Chikara; Nagai, Akinori; Kitamura, Ryoichi; Shamoto, Naoki*; Takeshima, Yoshiyuki*
JAEA-Technology 2012-009, 100 Pages, 2012/05
The radiation characteristics of image fiber and light guide fiber were evaluated to develop a high radiation resistant fiberscope for the fast reactor in-vessel observation. It is known that a pure silica core fiber has a high radiation resistance and radiation resistance is influenced with impurities in silica. Moreover it is necessary to change the clad material of the light guide fiber because that of the current light guide fiber is acrylate, which is weak against radiation. Hence the improved fibers consist of a pure silica core with 1,000 ppm OH and fluorine-doped silica clad. As a result of a irradiation test, we confirm that OH inhibits the generation of the precursor by irradiation. About the clad material, we confirmed that the transmission loss of the fluorine-doped silica clad fiber is smaller than that of the acrylate clad fiber. About the mechanical strength of a fiber, we confirmed that there is no weakening the strength of the fiber and no exfoliation of the coating from the glass. In this study, we discovered the fiber which consists of a pure silica core with 1,000 ppm OH and fluorine-doped silica clad has a high radiation resistance and it is possible to observe using this fiber under the 200 C after 510 Gy irradiation.
Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Chudo, Hiroyuki; Osaka, Masahiko; Miwa, Shuhei; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori; Homma, Yoshiya*
Materials Research Society Symposium Proceedings, Vol.1444, p.149 - 158, 2012/00
Besides the importance of AnO series (An; U, Np, Pu, Am) as a nuclear fuel, the magnetic properties of these compounds at low temperatures are particularly interesting. Their surprisingly varied physical properties continue to be of interest for both theory and experiment. In this study, we have performed NMR studies for the series of actinide dioxides. On the basis of O-NMR studies, exotic magnetic orderings associated with multipole degrees of freedom on 5 electrons have been identified in UO (dipolar + quadrupolar ordering) and NpO (octupolar + quadrupolar ordering), in contrast with the non-magnetic ground state of PuO. In AmO, our O-NMR data provide the first microscopic evidence for a phase transition as a bulk property in this system.
Nishi, Tsuyoshi; Ito, Akinori*; Ichise, Kenichi; Arai, Yasuo
Journal of Nuclear Materials, 414(2), p.109 - 113, 2011/07
The thermal diffusivities of AmO and AmO were measured using a laser flash method. The heat capacities of AmO and AmO were measured using a drop calorimetry. The thermal conductivity was determined from the measured thermal diffusivity, heat capacity and bulk density. In these results, the heat capacity of AmO was larger than that of AmO and close to those of UO and NpO. The thermal conductivities of AmO and AmO were found to decrease with increasing temperature in the temperature range investigated. The thermal conductivity of AmO from 473 to 773 K was slightly smaller than those of UO and PuO and close to that of NpO. On the other hand, the thermal conductivity of AmO with A-type rare earth oxide structure was smaller than that of AmO with fluorite structure and larger than that of non-stoichiometric AmO.
Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Ito, Akinori; Akabori, Mitsuo; Hirata, Masaru
Journal of Nuclear Materials, 401(1-3), p.138 - 142, 2010/06
XAFS studies were performed in a study of americium sesquioxide (AmO) with A-type rare earth oxide structure and americium dioxide (AmO) with fluorite structure. EXAFS results for Am-L absorption edge of AmO and AmO were good agreement with the crystallographic data from X-ray diffraction analysis. In order to characterize XANES in aspect of the electronic states, the theoretical assignments for the AmO and AmO were performed with the all-electron full potential linearized augmented plane wave (FP-LAPW) method. The theoretical XANES spectra of AmO and AmO well reproduced the experimental ones. In addition, it was found that the white line peak was created due to the interaction between Am-d and O-p components, and the broad peak and the tail peak were created due to the interaction between Am-d and O-d component.