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Journal Articles

3D-microstructure analysis of compacted Na- and Cs-montmorillonites with nanofocus X-ray computed tomography and correlation with macroscopic transport properties

Takahashi, Hiroaki*; Tachi, Yukio

Applied Clay Science, 168, p.211 - 222, 2019/02

Microstructural and mass transport properties of compacted Na- and Cs-montmorillonites with different swelling properties were investigated by combining 3D microstructure analysis using nanofocus X-ray CT and diffusion measurement of HDO. The X-ray CT observations indicated that macropores in the dry state of compacted Na-montmorillonite are filled with gel phases, and the grain sizes of clay particles shifted toward smaller values through the saturation and swelling processes. By contrast, no gel phase and no decrease in the grain and pore volumes were observed for saturated Cs-montmorillonite. The geometrical factors of the macropores including tortuosity and geometric constrictivity of saturated Cs-montmorillonite determined by the X-ray CT was consistent with the corresponding values derived in the HDO diffusion test. In the case of Na-montmorillonite, the larger differences between the geometric factors evaluated by the X-ray CT and the diffusion tests can be explained by the electrostatic constrictivity factor and the additional geometrical factors in gel phase and interlayer that are smaller than the detection limit of the X-ray CT.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste; Scientific Program for fiscal year 2018

Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Akiomi; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Saiga, Atsushi; Sueoka, Shigeru; Komatsu, Tetsuya; et al.

JAEA-Review 2018-020, 46 Pages, 2019/01

JAEA-Review-2018-020.pdf:1.25MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency, in fiscal year 2018. The objectives and contents in fiscal year 2018 are described in detail based on the outline of 7 years plan (fiscal years 2015-2021). Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. In addition, the plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.

Journal Articles

Position-by-position cooling paths within the Toki granite, central Japan; Constraints and the relation with fracture population in a pluton

Yuguchi, Takashi*; Sueoka, Shigeru; Iwano, Hideki*; Izumino, Yuya*; Ishibashi, Masayuki; Danhara, Toru*; Sasao, Eiji; Hirata, Takafumi*; Nishiyama, Tadao*

Journal of Asian Earth Sciences, 169, p.47 - 66, 2019/01

This study presents position-by-position t-T paths within a granitic pluton based on thermochronological data, and describes their constraints and their relationship with fracture frequency, as an example from the Toki granite, central Japan. The cooling paths have position-specific characteristics; a single t-T path does not represent the cooling behavior of the entire pluton. Such position-specific t-T paths enable us to evaluate three-dimensional thermal evolution within the granitic pluton, and thus can clarify the detailed formation history of the entire pluton after the incipient intrusion of the granitic magma into the shallow crust. This study reveals the relationship between position-specific t-T paths and fracture frequency, and thus provides a criterion for evaluating the fracture population in terms of thermal stress.

JAEA Reports

Mizunami Underground Research Laboratory Project, Plan for fiscal year 2018

Takeuchi, Ryuji; Iwatsuki, Teruki; Matsui, Hiroya; Ikeda, Koki; Mikake, Shinichiro; Hama, Katsuhiro; Iyatomi, Yosuke; Sasao, Eiji

JAEA-Review 2018-019, 29 Pages, 2018/12

JAEA-Review-2018-019.pdf:6.16MB

The Mizunami Underground Research Laboratory (MIU) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of geological disposal technologies through investigations of the deep geological environment in the crystalline host rock (granite) at Mizunami, Gifu Prefecture, central Japan. On the occasion of the reform of the entire JAEA organization in 2014, JAEA identified three important issues on the geoscientific research program: "Development of countermeasure technologies for reducing groundwater inflow", "Development of modelling technologies for mass transport" and "Development of drift backfilling technology", based on the latest results of the synthesizing research and development (R&D). The R&D on three remaining important issues have been carrying out on the MIU Project. This report summarizes the R&D activities planned for fiscal year 2018 on the basis of the MIU Master Plan updated in 2015 and Investigation Plan for the Third Medium to Long-term Research Phase.

JAEA Reports

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*; Monma, 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".

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2016

Ishimaru, Tsuneari; Yasue, Kenichi*; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Yokoyama, Tatsunori; Fujita, Natsuko; Saiga, Atsushi; Shimizu, Mayuko; et al.

JAEA-Research 2018-008, 83 Pages, 2018/12

JAEA-Research-2018-008.pdf:11.43MB

This annual report documents the progress of research and development (R&D) in the 2nd fiscal year during the JAEA 3rd Mid- and Long-term Plan (fiscal years 2015-2021) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. The planned framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. In this paper, the current status of R&D activities with previous scientific and technological progress is summarized.

Journal Articles

Present status of development of isobar separation using ion channeling

Matsubara, Akihiro*; Fujita, Natsuko; Miyake, Masayasu; Isozaki, Nobuhiro*

Dai-31-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.108 - 111, 2018/12

加速器質量分析(AMS)では測定目的核種とこの安定同重体の分別(以下、同重体分別)をより小型の加速器で可能にする技術が望まれている。現在の主流はディグレーダー膜法と呼ばれる方法である。これはイオンを薄膜に通した際の阻止能の原子番号依存性により目的核種と同重体の間でエネルギーの差を作り両者を分別する方法である。われわれはディグレーダー膜法にイオンチャネリングを取入れた方法を開発している。本研究ではイオンチャネリングが同重体分別の性能向上に効果があることを示したので報告する。

Journal Articles

Present status of the accelerator facility at the JAEA-AMS-TONO; 2017

Fujita, Natsuko; Miyake, Masayasu; Watanabe, Takahiro; Kokubu, Yoko; Matsubara, Akihiro*; Kato, Motohisa*; Okabe, Nobuaki; Isozaki, Nobuhiro*; Ishizaka, Chika*; Torazawa, Hitoshi*; et al.

Dai-31-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.92 - 95, 2018/12

日本原子力研究開発機構東濃地科学センターではJAEA-AMS-TONOを平成9年に導入し、当機構で進める深地層の科学的研究の基盤となる年代測定等を行っている。本発表では平成29年度のJAEA-AMS-TONOの状況について報告する。平成29年度は、タンク内の定期メンテナンスに加え、不具合の生じていたペレットチェーン用インバータ及びストリッパーガス圧計の交換を実施した。装置に関する不具合としては、4月にダブルスリットの動作の不具合が生じた。調査の結果、原因は制御基板のコンデンサーの老朽化による破損にあることが判明した。また、平成30年2月にはイオン源のリークが発生した。調査の結果、原因はセシウム輸送管の溶接部の亀裂にあることが分かった。このため、アイオナイザーハウジング一式の更新を行った。

Journal Articles

Development of evaluation technique for long-term mechanical behavior of near-field

Takayama, Yusuke

Genshiryoku Bakkuendo Kenkyu (Internet), 25(2), p.103 - 106, 2018/12

At the 34th Back-end Summer Seminar, I introduce the evaluation technique for long-term mechanical behavior of near field. This report summarizes the presentation at the seminar.

Journal Articles

New insights into the Cs adsorption on montmorillonite clay from $$^{133}$$Cs solid-state NMR and density functional theory calculations

Okubo, Takahiro*; Okamoto, Takuya*; Kawamura, Katsuyuki*; Gu$'e$gan, R.*; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*; Tachi, Yukio; Iwadate, Yasuhiko*

Journal of Physical Chemistry A, 122(48), p.9326 - 9337, 2018/12

The structures of Cs adsorption on montmorillonite were investigated by the nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Cs adsorbed on montmorillonite samples were measured under different Cs contents and relative humidity levels. NMR parameters were evaluated by the first principle calculations in order to identify the relationship between adsorbed Cs structures and NMR parameters. The comparisons between experimental and theoretical NMR spectra revealed that Cs is preferentially adsorbed at sites near Al for low Cs substituted montmorillonites, and that non-hydrated Cs present in partially Cs substituted samples, even after being hydrated under high relative humidity.

JAEA Reports

Investigation of simulated waste glass samples prepared from borosilicate glass frit including vanadium

Nagai, Takayuki; Okamoto, Yoshihiro; Shiwaku, Hideaki; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*; Hirono, Kazuya*; Homma, Masanobu*; Kobayashi, Hiromi*; Takahashi, Tomoe*; et al.

JAEA-Research 2018-007, 87 Pages, 2018/11

JAEA-Research-2018-007.pdf:61.21MB

To select the chemical composition of a glass frit which can increase the waste content, the simulated waste glass samples prepared from a borosilicate glass frit including vanadium (V) were investigated by using Laser Ablation (LA) ICP-AES analysis, Raman spectrometry, and synchrotron XAFS measurement in this study on foundation business of the Agency for Natural Resources and Energy.

Journal Articles

Safe and rapid development of capillary electrophoresis for ultratrace uranyl ions in radioactive samples by way of fluorescent probe selection for actinide ions from a chemical library

Haraga, Tomoko; Ouchi, Kazuki; Sato, Yoshiyuki; Hoshino, Hitoshi*; Tanana, Rei*; Fujihara, Takashi*; Kurokawa, Hideki*; Shibukawa, Masami*; Ishimori, Kenichiro; Kameo, Yutaka; et al.

Analytica Chimica Acta, 1032, p.188 - 196, 2018/11

The development of safe, rapid and highly sensitive analytical methods for radioactive samples, especially actinide (An) ions, represents an important challenge. Here we propose a methodology for selecting appropriate emissive probes for An ions with very low consumption and emission of radioactivity by capillary electrophoresis-laser-induced fluorescence detection (CE-LIF), using a small chemical library of probes with eight different chelating moieties. It was found that the emissive probe, which possesses the tetradentate chelating moiety, was suitable for detecting uranyl ions. The detection limit for the uranyl-probe complex using CE-LIF combined with dynamic ternary complexation and on-capillary concentration techniques was determined to be 0.7 ppt. This method was successfully applied to real radioactive liquid samples collected from nuclear facilities.

Journal Articles

Effect of surface conditions of the filament used in thermal ionization mass spectrometry on an uranium isotopic measurement

Taguchi, Shigeo; Miyauchi, Hironari*; Horigome, Kazushi; Yamamoto, Masahiko; Kuno, Takehiko

Bunseki Kagaku, 67(11), p.681 - 686, 2018/11

In thermal ionization mass spectrometry, de-gassing is one of the important treatments to release impurities of filaments and to minimize the influence of background. In this work, the effect of the surface change in the tungsten filament induced by the conductively heating treatment on uranium isotopic ($$^{235}$$U/$$^{238}$$U) measurement has been investigated. It was found that the conductively heating treatment of the filament has the effect of smoothing the surface of the filament and also has the effect of improving the deposition of the sample on the filament surface. As a result of either these effects, the precision of uranium isotopic ($$^{235}$$U/$$^{238}$$U) measurement was improved.

Journal Articles

Investigation for dust behavior of cutting in air and cutting underwater by thermal cutting methods

Soejima, Goro; Iwai, Hiroki; Nakamura, Yasuyuki; Tsuzuki, Satoshi*; Yasunaga, Kazushi*; Kume, Kyo*

Heisei-29-Nendo Koeki Zaidan Hojin Wakasawan Enerugi Kenkyu Senta kenkyu Nempo, 20, P. 80, 2018/11

We investigated the behavior of the dust generated by Laser and Plasma-arc cutting underwater and in air aimed at the simulant material of reactor components (SUS304) and the pressure and calandria tube (Zr-2.5%Nb, Zry-2) of the prototype reactor "FUGEN".

Journal Articles

Simulation of fluidity, dispersion and mass transfer in an annular centrifugal contactor

Sano, Yuichi; Sakamoto, Atsushi; Takeuchi, Masayuki; Misumi, Ryuta*; Kunii, Kanako*; Todoroki, Kei*; Nishi, Kazuhiko*; Kaminoyama, Meguru*

Kagaku Kogaku Rombunshu, 44(6), p.335 - 340, 2018/11

Concerning an annular centrifugal contactor which has high throughput and separation performance, the effect of operational condition on fluidic and dispersion behavior, which are important to improve the contactor performance, was investigated by computational fluid dynamics (CFD) analysis based on the turbulence model, and the calculated results were validated by experimental data. The liquid phase in the annular zone was gradually divided into two regions vertically with increasing the rotor speed and decreasing the flowrate, and the liquid flow moved toward the center of the housing bottom was generated in the lower annular zone under any operational condition. The droplet size of the dispersed phase in the annular zone decreased with increasing the rotor speed and decreasing the flowrate. These calculation results showed a good agreement with experimental data. The CFD analysis considering mass transfer between aqueous and organic phases was also attempted, and it was confirmed that the change of extraction performance with the rotor speed showed the same tendency as the experimental result.

Journal Articles

Evolution of the excavation damaged zone around a modelled disposal pit; Case study at the Horonobe Underground Research Laboratory, Japan

Aoyagi, Kazuhei; Miyara, Nobukatsu; Ishii, Eiichi; Nakayama, Masashi; Kimura, Shun

Proceedings of 13th SEGJ International Symposium (USB Flash Drive), 5 Pages, 2018/11

The construction of underground facilities induces fractures in the rock mass around the underground voids due to the resultant stress redistribution. This has particular implications for high-level radioactive waste (HLW) disposal projects, where fracture development creates an excavation damaged zone (EDZ) that increases the hydraulic conductivity of the surrounding rock mass and can provide a pathway for the migration of radionuclides from the storage facilities. It is therefore important to understand the long-term evolution of the EDZ and perform a comprehensive HLW disposal risk assessment. An in situ engineered barrier system experiment was conducted in the 350 m gallery at the Horonobe Underground Research Laboratory, Japan, to observe the near-field coupled thermo-hydro-mechanical-chemical (THMC) process in situ and validate coupled THMC models. Here we investigate the evolution of the EDZ around the gallery and model a test pit that was excavated below the floor of the gallery using a series of seismic tomography surveys. There was a significant decrease in the seismic velocity field around the test pit due to its excavation, which became slightly more pronounced over time after the excavation. These seismic results, coupled with hydraulic tests and pore pressure measurements around the pit, indicate that fracture development and the decrease in saturation around the test pit resulted in a decrease in the seismic velocity field after the excavation of the test pit. Furthermore, the increase in saturation around the test pit is a key reason for the increase in the seismic velocity field after the heater test.

Journal Articles

Thermodynamic data development; Solubility method and future research needs (PLENARY)

Rai, D.*; Yui, Mikazu; Kitamura, Akira

Progress in Nuclear Science and Technology (Internet), 5, p.19 - 26, 2018/11

The objectives of this presentation are (1) to describe the solubility method, (2) to list desirable criteria of the solubility method so that the reader can recognize which studies have been done in a way that yields quality information, (3) to present an example of how to use the evaluation criteria, and (4) to provide a few examples of future research needs where the solubility method is ideally suited and the other methods are unsuitable for these investigations.

Journal Articles

Effects of fine-scale surface alterations on tracer retention in a fractured crystalline rock from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi*; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

Water Resources Research, 54(11), p.9287 - 9305, 2018/11

Effects of fine-scale surface alterations on radionuclide migration in fractured crystalline rocks were investigated by a comprehensive approach coupling a series of laboratory tests, microscopic observations and modelling, using a single fractured granodiorite sample from the Grimsel Test Site, Switzerland. Laboratory tests including through-diffusion, batch sorption and flow-through tests using five tracers indicated that tracer retention was consistently in the sequence of HDO, Se, Cs, Ni, Eu, and as well as showing the existence of a diffusion-resistance layer near the fracture surface, cation excess and anion exclusion effects for diffusion. Microscale heterogeneities in structural properties around the fracture were clarified quantitatively by coupling X-ray CT and EPMA. A three layer model including weathered vermiculite, foliated mica and undisturbed matrix layers, and their properties such as porosity, sorption and diffusion parameters, could provide a reasonable interpretation for breakthrough curves and concentration distributions near fracture surface of all tracers, measured in flow-through tests.

JAEA Reports

Study on crystalline rock aiming at evaluation method of long-term behavior of rock mass, 2 (Joint research)

Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya

JAEA-Research 2018-006, 57 Pages, 2018/10

JAEA-Research-2018-006.pdf:2.99MB

It is important to evaluate the stability of a repository for high-level radioactive waste not only during the design, construction and operation phases, but also during the post-closure period, for time frames likely exceeding several millennia or longer. The rock mass around the tunnels could be deformed through time in response to time dependent behavior. In view of above points, this study has been started as a collaboration study with the University of Tokyo from FY2016. In the FY2017, the creep test of Tage tuff was continuously conducted and reached its twentieth year. The overview of the test was described, and the phenomenological aspects and the mechanisms of the creep of tuff were discussed with comparing the long- and short-term creep tests. The effects of loading rate and water content on rock strength were examined under various water conditions. The variable-compliance-type constitutive model was modified to reproduce those under uniaxial tension.

JAEA Reports

Data of long term hydro-pressure monitoring on Mizunami Underground Research Laboratory Project for fiscal year 2013-2014

Keya, Hiromichi; Beppu, Shinji*; Takeuchi, Ryuji

JAEA-Data/Code 2018-011, 112 Pages, 2018/10

JAEA-Data-Code-2018-011.pdf:10.11MB
JAEA-Data-Code-2018-011-appendix1(DVD-ROM).zip:388.14MB
JAEA-Data-Code-2018-011-appendix2(DVD-ROM).zip:467.11MB
JAEA-Data-Code-2018-011-appendix3(DVD-ROM).zip:325.24MB

Mizunami Underground Research Laboratory (MIU) Project has three overlapping phases: Surface-based investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III), with a total duration of 20 years. Currently, the project is being carried out under the Phase II and the Phase III. One of the Phase II goals of Project is set to develop and revise models of the geological environment using the investigation results obtained during excavation, and determine and assess the changes in the geological environment in response to excavation. The long term hydro-pressure monitoring has been continued to achieve the Phase II goals. This paper describes the results of the long term hydro-pressure monitoring from April 2013 to March 2015.

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