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Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Kristo, M. J.*; Williams, R.*; Gaffney, A. M.*; Kayzar-Boggs, T. M.*; Schorzman, K. C.*; Lagerkvist, P.*; Vesterlund, A.*; Ramebck, H.*; Nelwamondo, A. N.*; Kotze, D.*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.425 - 434, 2018/02
Times Cited Count:17 Percentile:79.90(Chemistry, Analytical)In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched uranium oxide samples, providing 12 analytical results using three different parent-daughter pairs serving as independent chronometers. The vast majority of the results were consistent with one another and consistent with the known processing history of the materials. In general, for these particular samples, mass spectrometry gave more accurate and more precise analytical results than decay counting measurements. In addition, the concordance of the U-
Pa and
U-
Th chronometers confirmed the validity of the age dating assumptions, increasing confidence in the resulting conclusions.
Ho, D. M. L.*; Nelwamondo, A. N.*; Okubo, Ayako; Ramebck, H.*; Song, K.*; Han, S.-H.*; Hancke, J. J.*; Holmgren, S.*; Jonsson, S.*; Kataoka, Osamu; et al.
Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.353 - 363, 2018/02
Times Cited Count:2 Percentile:18.04(Chemistry, Analytical)The Fourth Collaborative Material Exercise (CMX-4) of the Nuclear Forensics International Technical Working Group (ITWG) registered the largest participation for this exercise in nuclear forensics, with seven of the 17 laboratories participating for the first time. In this paper, participants from five of the first-time laboratories shared their individual experience in this exercise, from preparation to analysis of samples. The exercise proved to be highly useful for testing procedures, repurposing established methods, exercising skills, and improving the understanding of nuclear forensic signatures and their interpretation trough the post-exercise review meeting.
Okubo, Ayako; Shinohara, Nobuo; Magara, Masaaki
Journal of Radioanalytical and Nuclear Chemistry, 314(1), p.231 - 234, 2017/10
Times Cited Count:3 Percentile:25.14(Chemistry, Analytical)The model date of two enriched uranium materials were determined using a new method for nuclear forensics investigation. In this method, the Th/
U ratio was calculated without spike addition from measured ratios of
Th/
Th and
U/
U, and calculated
Th/
U ratio in secular equilibrium. The obtained model date for the low-enriched uranium material was agreed with the known production date within uncertainty. For the highly enriched uranium material, slightly younger model date than the known production date was obtained. The
U interference on
Th counting in thermal ionization mass spectrometry measurement was suspected as a potential cause.
Tamai, Hiroshi; Okubo, Ayako; Kimura, Yoshiki; Shinohara, Nobuo; Tazaki, Makiko; Shimizu, Ryo; Suda, Kazunori; Tomikawa, Hirofumi
Proceedings of INMM 58th Annual Meeting (Internet), 6 Pages, 2017/07
Nuclear forensics is a technical measure to analyse and collate samples of illegally used nuclear materials, etc., to clarify their origins, routes, etc. and contribute to criminal identifications. Close collaboration with police and judicial organizations is essential. The national response framework is being built up with international cooperation. Discussions on promoting technical capability and regional cooperation are presented.
Tamai, Hiroshi; Okubo, Ayako; Kimura, Yoshiki; Kokaji, Lisa; Shinohara, Nobuo; Tomikawa, Hirofumi
Dai-37-Kai Kaku Busshitsu Kanri Gakkai Nihon Shibu Nenji Taikai Rombunshu (CD-ROM), 8 Pages, 2017/02
Nuclear Forensics capability has been developed under the international collaborations. For its effective function, technical development in analysis of seized nuclear materials as well as the institutional development in comprehensive response framework are required under individual national responsibility. In order to keep the "chain of custody" in the proper operation of sample collection at the event scene, radiological analysis at the laboratory, storage of the samples, and further inspection and trial, close cooperation and information sharing between relevant organisations are essential. IAEA issues the Implementing Guide to provide the model action plan and assists individual national development. International cooperation for the technical improvement and awareness cultivation is promoted. Examples in such national developments will be introduced and prospective technical/institutional prerequisite for nuclear forensics response framework will be studied.
Gaffney, A.*; Hubert, A.*; Kinman, W. S.*; Magara, Masaaki; Okubo, Ayako; Pointurier, F.*; Schorzman, K. C.*; Steiner, R. E.*; Williams, R. W.*
Journal of Radioanalytical and Nuclear Chemistry, 307(3), p.2055 - 2060, 2016/03
Times Cited Count:26 Percentile:90.18(Chemistry, Analytical)In and inter-laboratory measurement comparison study, four laboratories (LLNL, LANL, CEA, JAEA) determined Th-
U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. These model ages are concordant with to slightly older than the known production age of NBL U050, indicating unsufficient purification of U050.
Kimura, Yoshiki; Shinohara, Nobuo; Okubo, Ayako
Nihon Genshiryoku Gakkai-Shi ATOMO, 57(12), p.782 - 786, 2015/12
no abstracts in English
Eguchi, Shohei; Takemoto, Noriyuki; Tanimoto, Masataka; Kubo, Ayako; Ishitsuka, Etsuo; Nakamura, Jinichi; Ito, Haruhiko
JAEA-Review 2015-005, 38 Pages, 2015/06
Since fiscal 2011, a practical training course using the JMTR and other research infrastructures has been provided by Neutron Irradiation Testing Reactor Center for foreign young researchers and engineers in Asian and other countries which are planning to introduce power reactors. The aim of this course is to contribute to the human resource development in nuclear research field and to increase the future use the JMTR. On the other hand, a training course for Japanese young researchers and engineers has been conducted since fiscal 2010. In fiscal 2014, these two separate courses were integrated into one and it was conducted for 3 weeks for young researchers and engineers at home as well as abroad. Nineteen persons from seven countries participated and they studied about the general outline of nuclear research, current status and R&D of nuclear energy, irradiation test facilities and technologies, nuclear characteristics of the reactor and safety and operation management of nuclear reactors. At the end of the course, we had an active discussion about the current status and future of energy mix. The content of this training course in fiscal 2014 are reported in this paper.
Okubo, Ayako; Kimura, Yoshiki; Shinohara, Nobuo; Toda, Nobufumi; Funatake, Yoshio; Watahiki, Masaru; Sakurai, Satoshi; Kuno, Yusuke
JAEA-Technology 2015-001, 185 Pages, 2015/03
Nuclear forensics is the analysis of intercepted illicit nuclear or radioactive material and any associated material to provide evidence for nuclear attribution by determining origin, history, transit routes and purpose involving such material. Nuclear forensics activity includes sampling of the illicit material, analysis of the samples and evaluation of the attribution by comparing the analyzed data with database or numerical simulation. Because the nuclear forensics technologies specify the origin of the nuclear materials used illegal dealings or nuclear terrorism, it becomes possible to identify and indict offenders, hence to enhance deterrent effect against such terrorism. Worldwide network on nuclear forensics can contribute to strengthen global nuclear security regime. In this paper, the results of research and development of fundamental nuclear forensics technologies performed in Japan Atomic Energy Agency during the fiscal term of 2011-2013 were reported.
Okubo, Ayako; Obata, Hajime*; Magara, Masaaki; Kimura, Takaumi; Ogawa, Hiroshi*
Analytica Chimica Acta, 804, p.120 - 125, 2013/12
Times Cited Count:2 Percentile:6.97(Chemistry, Analytical)This work introduces a novel method of recovery of iron hydroxide using a DIAION CR-20 chelating resin column to determine Th isotopes in seawater with a sector field (SF) inductively coupled plasma mass spectrometer (ICP-MS). Thorium isotopes in seawater were coprecipitated with iron hydroxide, and this precipitate was sent to chelating resin column. The chelating column quantitatively collected Th with iron hydroxide in seawater at flow rates of 20-25 mL/min. Based on this flow rate, a 5 L sample was processed within 3-4 h.
Okubo, Ayako; Takeda, Shigenobu*; Obata, Hajime*
Atmospheric Research, 129-130, p.20 - 32, 2013/07
Times Cited Count:41 Percentile:69.76(Meteorology & Atmospheric Sciences)To understand the atmospheric input of trace metals to surface seawaters, the total deposition samples were collected simultaneously from three coastal station in Japan. The observed flux was within the lower limit of the previous estimation based on a model. Except for Sc and Fe, all the elements showed a increasing tendency toward dissolution with decreasing the pH. We calculated the Sc-normalized enrichment factors. The increasing tendency toward dissolution with decreasing the pH was higher for Al than that of Fe.
Okubo, Ayako; Obata, Hajime*; Gamo, Toshitaka*; Yamada, Masatoshi*
Earth and Planetary Science Letters, 339-340, p.139 - 150, 2012/07
Times Cited Count:45 Percentile:72.06(Geochemistry & Geophysics)Vertical distributions of total Th and dissolved
Th were determined in the mid-latitudes of the North Pacific Ocean. Th in the Pacific Ocean have been described well using the reversible-scavenging model. However, we observed the depletion of total Th. The enhanced vertical eddy diffusion derived from the complex topography of the western Pacific Ocean might promote bottom scavenging and transport of the low Th in deep water to the upper layers.
Kimura, Yoshiki; Okubo, Ayako; Tomikawa, Hirofumi; Matsumoto, Tetsuya*; Umino, Yuji*; Hosoi, Masaharu*
no journal, ,
Tomikawa, Hirofumi; Kimura, Yoshiki; Okubo, Ayako
no journal, ,
Okubo, Ayako; Mayer, K.*
no journal, ,
Under the collaboration between EC-JRC and JAEA, the in-situ age dating method was subject to joint validation, and six different uranium materialswere used for this purpose. The age dating result by in-situ isotope method was consistent with known production dates of the respective samples. The uncertainty evaluation according to GUM for the in-situ isotope method indicates that the measured Th/
Th ratio provides the highest contribution. The accuracy of in-situ isotope method can be improved by higher precision in
Th/
Th measurement.
Okubo, Ayako
no journal, ,
no abstracts in English
Kips, R.*; Lindvall, R.*; Marks, N.*; Gluschenko, V.*; Okubo, Ayako; Szeles, E.*
no journal, ,
Kimura, Yoshiki; Tsuchiya, Kenichi*; Okubo, Ayako*; Tanabe, Kosuke*; Kakuda, Hidetoshi*; Akiba, Norimitsu*; Tomikawa, Hirofumi
no journal, ,
Shinohara, Nobuo; Kimura, Yoshiki; Okubo, Ayako
no journal, ,
Nuclear forensics is the analysis of intercepted illicit nuclear or radioactive material and any associated material to provide evidence for nuclear attribution by determining origin, history, transit routes and purpose involving such material. Because the nuclear forensics methodologies provide hints of the origin of the nuclear materials used in illegal dealings or nuclear terrorism, it contributes to identify and indict offenders, hence to enhance deterrent effect against such terrorism. In the 59th Symposium on Radiochemistry, the results of research and development of fundamental nuclear forensics technologies (analysis of isotopic composition, impurity analysis, age dating of nuclear material, particle shape analysis by electron microscope, and nuclear forensics library) performed in Japan Atomic Energy Agency are reported. Japan's capability and the role of radiochemistry on nuclear forensics are also discussed in the Symposium.