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Journal Articles

Overall approaches and experiences of first-time participants in the Nuclear Forensics International Technical Working Group's Fourth Collaborative Material Exercise (CMX-4)

Ho, D. M. L.*; Nelwamondo, A. N.*; Okubo, Ayako; Rameb$"a$ck, 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:0 Percentile:0.01(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.

Journal Articles

The Application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Kristo, M. J.*; Williams, R.*; Gaffney, A. M.*; Kayzar-Boggs, T. M.*; Schorzman, K. C.*; Lagerkvist, P.*; Vesterlund, A.*; Rameb$"a$ck, H.*; Nelwamondo, A. N.*; Kotze, D.*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.425 - 434, 2018/02

 Times Cited Count:6 Percentile:72.04(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 $$^{235}$$U-$$^{231}$$Pa and $$^{234}$$U-$$^{230}$$Th chronometers confirmed the validity of the age dating assumptions, increasing confidence in the resulting conclusions.

Journal Articles

Uranium age-dating using in-situ isotope ratios by thermal ionization mass spectrometry for nuclear forensics

Okubo, Ayako; Shinohara, Nobuo; Magara, Masaaki

Journal of Radioanalytical and Nuclear Chemistry, 314(1), p.231 - 234, 2017/10

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

The model date of two enriched uranium materials were determined using a new method for nuclear forensics investigation. In this method, the $$^{230}$$Th/$$^{234}$$U ratio was calculated without spike addition from measured ratios of $$^{230}$$Th/$$^{234}$$Th and $$^{234}$$U/$$^{238}$$U, and calculated $$^{234}$$Th/$$^{238}$$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 $$^{234}$$U interference on $$^{234}$$Th counting in thermal ionization mass spectrometry measurement was suspected as a potential cause.

Journal Articles

Prospective features for integration of nuclear forensics capability in national framework

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.

Journal Articles

Technical/institutional prerequisite for nuclear forensics response framework

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.

Journal Articles

Round-robin $$^{230}$$Th-$$^{234}$$U age dating of bulk uranium for nuclear forensics

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:15 Percentile:89.35(Chemistry, Analytical)

In and inter-laboratory measurement comparison study, four laboratories (LLNL, LANL, CEA, JAEA) determined $$^{230}$$Th-$$^{234}$$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.

Journal Articles

Current status and achievements on nuclear forensics technology developments for nuclear security

Kimura, Yoshiki; Shinohara, Nobuo; Okubo, Ayako

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 57(12), p.782 - 786, 2015/12

no abstracts in English

JAEA Reports

Report on research and development of nuclear forensics technologies

Okubo, Ayako; Kimura, Yoshiki; Shinohara, Nobuo; Toda, Nobufumi; Funatake, Yoshio; Watahiki, Masaru; Sakurai, Satoshi; Kuno, Yusuke

JAEA-Technology 2015-001, 185 Pages, 2015/03

JAEA-Technology-2015-001.pdf:56.65MB

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.

Journal Articles

Rapid collection of iron hydroxide for determination of Th isotopes in seawater

Okubo, Ayako; Obata, Hajime*; Magara, Masaaki; Kimura, Takaumi; Ogawa, Hiroshi*

Analytica Chimica Acta, 804, p.120 - 125, 2013/12

 Times Cited Count:2 Percentile:8.87(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 $$^{232}$$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.

Journal Articles

Atmospheric deposition of trace metals to the western North Pacific Ocean observed at coastal station in Japan

Okubo, Ayako; Takeda, Shigenobu*; Obata, Hajime*

Atmospheric Research, 129-130, p.20 - 32, 2013/07

 Times Cited Count:34 Percentile:73.29(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.

Journal Articles

$$^{230}$$Th and $$^{232}$$Th distributions in mid-latitudes of the North Pacific Ocean; Effect of bottom scavenging

Okubo, Ayako; Obata, Hajime*; Gamo, Toshitaka*; Yamada, Masatoshi*

Earth and Planetary Science Letters, 339-340, p.139 - 150, 2012/07

 Times Cited Count:34 Percentile:73.65(Geochemistry & Geophysics)

Vertical distributions of total $$^{230}$$Th and dissolved $$^{232}$$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.

Oral presentation

Vertical distributions of $$^{230}$$Th in the Pacific Ocean and their relation to advection and diffusion

Okubo, Ayako; Obata, Hajime*; Gamo, Toshitaka*; Yamada, Masatoshi*

no journal, , 

We investigated the vertical distribution of total $$^{230}$$Th in mid latitudes of the Pacific Ocean. The west to east section of $$^{230}$$Th shows a strong gradient in the deep waters around 170 degree east and 110 degree west. At depths of 2000 to 4000 m and 4000 m to bottom within the time-scale of scavenging residence time of $$^{230}$$Th, the horizontal eddy diffusion could reach 1100 to 1400 km and 400 to 700 km, respectively. The horizontal eddy diffusion transport is too weak to affect Th distribution in the deep layers between each station in this study area.

Oral presentation

Present status of R&D on nuclear forensics at JAEA

Sakurai, Satoshi; Kimura, Yoshiki; Sato, Kaneaki; Toda, Nobufumi; Shinoda, Yoshiharu; Okubo, Ayako; Magara, Masaaki; Watahiki, Masaru; Kuno, Yusuke

no journal, , 

The national statement made by the Japan Government at 2010 Nuclear Security Summit (Washington D.C., U.S.A.) was to develop its nuclear forensics detection and analysis technologies in a three-year period and to share them with the international community to contribute to strengthening the nuclear security regime. The Japan Atomic Energy Agency, the organization that possesses analytical capabilities with the potential to fulfill this nuclear forensics mission, started R&D on nuclear forensics technology from JFY 2011. The main areas of development are isotopic ratio analysis, impurity analysis, uranium age determination, etc. The cooperation with US-DOE and EC-JRC were also started to effectively promote the technical development. In the presentation reported will be progress in R&D to establish nuclear forensics analytical capabilities and international cooperation.

Oral presentation

Development of uranium dating for nuclear forensics

Okubo, Ayako; Magara, Masaaki; Shinohara, Nobuo

no journal, , 

The database of nuclear forensics information (composition, physical and chemical characteristic) is expected to work as deterrent against crimes concerning nuclear and radioisotope materials. However, quality of analysis on nuclear forensics is unknown between countries. To establish a fundamental skill of analysis is required for inter comparison between countries. The age of nuclear material is essential information to identify the source of the material, and $$^{234}$$U-$$^{230}$$Th chronometer is widely applied. Japan Atomic Energy Agency (JAEA) concluded Project Action Sheets between Department of Energy (DOE) of US and JAEA. We conducted procedure exchange and inter-laboratory comparison exercise on uranium age dating. We will report the outline of the project and the results of age determination on uranium oxide standard.

Oral presentation

Rapid collection of iron hydroxiedes for determination of Th isotopes in seawater using polyamin type chelating resin

Okubo, Ayako; Obata, Hajime*; Magara, Masaaki; Kimura, Takaumi; Ogawa, Hiroshi*

no journal, , 

This work introduces a novel method of recovery of iron hydroxide with thorium 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 co-precipitated with iron hydroxide, and this precipitate was sent to chelating resin column. The chelating column quantitatively collect $$^{232}$$Th with iron hydroxide in seawater at flow rate of 20-25 mL/min. Based on this flow rate, 5 L sample was processed within 3-4 h. The aging of iron hydroxide tends to reduce the recovery of $$^{232}$$Th. The rapid collection method was successfully applied to the determination of$$^{230}$$ Th and $$^{232}$$Th in open-ocean seawater samples.

Oral presentation

R&D on nuclear forensics, 4; Progress and future prospects of nuclear forensics technology development project at JAEA

Shinohara, Nobuo; Kimura, Yoshiki; Okubo, Ayako; Toda, Nobufumi; Funatake, Yoshio; Watahiki, Masaru; Kuno, Yusuke

no journal, , 

no abstracts in English

Oral presentation

Age-dating of single particle of uranium standard material for nuclear forensics and safeguards

Okubo, Ayako; Esaka, Fumitaka; Magara, Masaaki; Shinohara, Nobuo

no journal, , 

To elucidate the final purification date of uranium material namely age-dating is important subject on nuclear forensic analysis. Age-dating of uranium using $$^{234}$$U-$$^{230}$$Th nuclide pair was established in the field of geochemical science, and has been applied for nuclear forensics. Recently, safeguard analysis also demand age-dating of uranium materials. In order to measure a small amount of $$^{230}$$Th by ICP-MS, anion exchange column separation is commonly conducted to eliminate U tailing effect. However, column separation step could raise procedural blank of $$^{230}$$Th. In contrast, TIMS can separately ionize U and Th in filament heating step using the difference of optical ionization temperature of these elements. We developed analytical method for age-dating of single particle uranium material by TIMS.

Oral presentation

Technology and development for nuclear forensics; Result of ITWG collaborative materials exercise

Okubo, Ayako; Shinohara, Nobuo; Toda, Nobufumi; Kataoka, Osamu; Matsumoto, Tetsuya

no journal, , 

no abstracts in English

Oral presentation

Nuclear forensics and radiochemistry

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.

Oral presentation

Development of uranium age-dating using $$^{234}$$Th/$$^{230}$$Th ratios

Okubo, Ayako; Shinohara, Nobuo; Magara, Masaaki

no journal, , 

The uranium age-dating is a nuclear forensics analysis techniques, by measuring the $$^{230}$$Th / $$^{234}$$U isotope ratio in uranium sample, to estimate the elapsed time from being separated and purified. We have determined $$^{230}$$Th and $$^{234}$$U using isotope dilution mass spectrometry method, it has conducted for uranium age-dating. Act to perform the isotope analysis after the addition a known quantity of the isotope (spike) to the sample, after spiking, analytical sample is assumed to be in the state of isotopic equilibrium. However, the samples which have complex speciation of uranium and thorium are analyzed, may not sufficiently reach to the state of isotopic equilibrium has been suggested from the experimental results. In this study, without the addition of a spike, from the measurement results of the uranium isotope ratios and thorium isotope ratio in the sample, it was investigated a method for calculating the $$^{230}$$Th / $$^{234}$$U isotope ratio. The state of radioactive equilibrium between $$^{238}$$U and $$^{234}$$Th in the sample was utilized in the $$^{234}$$Th / $$^{230}$$Th method. The $$^{230}$$Th / $$^{234}$$U ratio was calculated using measured $$^{234}$$Th / $$^{230}$$Th isotope ratio, $$^{234}$$U / $$^{238}$$U isotope ratio and $$^{234}$$Th / $$^{238}$$U ratio in the radioactive equilibrium.

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