Evaluation of excavation damaged zones (EDZs) in Horonobe Underground Research Laboratory (URL)

Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei; Miyara, Nobukatsu*

Journal of Rock Mechanics and Geotechnical Engineering, 16(2), p.365 - 378, 2024/02

https://doi.org/10.1016/j.jrmge.2023.05.010

Excavation of underground caverns, such as mountain tunnels and energy-storage caverns, may cause the damages to the surrounding rock as a result of the stress redistribution. In this influenced zone, new cracks and discontinuities are created or propagate in the rock mass. Therefore, it is effective to measure and evaluate the acoustic emission (AE) events generated by the rocks, which is a small elastic vibration, and permeability change. The authors have developed a long-term measurement device that incorporates an optical AE (O-AE) sensor, an optical pore pressure sensor, and an optical temperature sensor in a single multi-optical measurement probe (MOP). Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high-level radioactive waste (HLW) deep geological disposal technology. In a high-level radioactive disposal project, one of the challenges is the development of methods for long-term monitoring of rock mass behavior. Therefore, in January 2014, the long-term measurements of the hydro-mechanical behavior of the rock mass were launched using the developed MOP in the vicinity of 350 m below the surface at the Horonobe Underground Research Center. The measurement results show that AEs occur frequently up to 1.5 m from the wall during excavation. In addition, hydraulic conductivity increased by 2 to 4 orders of magnitude. Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures. Based on this, a conceptual model is developed to represent the excavation damaged zone (EDZ), which contributes to the safe geological disposal of radioactive waste.

Analysis of gadolinium oxide using microwave-enhanced fiber-coupled micro-laser-induced breakdown spectroscopy

Ikeda, Yuji*; Soriano, J. K.*; Oba, Hironori; Wakaida, Ikuo

Scientific Reports (Internet), 13, p.4828_1 - 4828_9, 2023/03

https://doi.org/10.1038/s41598-023-32146-x

Development of high-resolution imaging camera for alpha dust (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2021-044, 58 Pages, 2022/01

JAEA-Review-2021-044.pdf:3.53MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of high-resolution imaging camera for alpha dust" conducted in FY2020. The present study aims to develop a novel alpha-ray camera consisting of imaging and an energy spectrometer to find the alpha dust to reduce the risk of health damage in Decommissioning. We have developed the camera in FY2020, and the measurement test for the energy spectra. Moreover, the imaging test has been operated. In addition, we have also developed a high-dose-rate monitor system using novel scintillators with red/infra-red emission.

Development of imaging system with ultra-high spatial resolution aiming to detect alpha-dust (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2019-038, 57 Pages, 2020/03

JAEA-Review-2019-038.pdf:4.6MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Imaging System with Ultra-high Spatial Resolution Aiming to Detect Alpha-dust". In the present study, we have developed a prototype of a system aiming to elucidate the behavior of alpha-dust generated at the time of debris retrieval. In this system, alpha-ray is first converted to visible light by novel scintillator. Then, imaging with ultra-high resolution will be possible using a lens and an Si-semiconductor camera (CMOS camera). Also, it will be possible to identify the species of alpha-ray emitting nuclides by unfolding of the spectra. The demonstration tests of the system will be conducted for dust samplers at the Plutonium Fuel Development Center, JAEA. In the development of the present system, it is important to use scintillator whose emission wavelength is sensitive to the CMOS camera as well as high emission scintillator. Considering these conditions, the key technology will be the improvement of the purity of crystals and optimization of the shapes of the materials including powers.

Spectrochemistry of technetium by liquid electrode plasma optical emission spectrometry and its applicability of quantification for highly active liquid waste

Yamamoto, Masahiko; Do, V. K.; Taguchi, Shigeo; Kuno, Takehiko; Takamura, Yuzuru*

Spectrochimica Acta, Part B, 155, p.134 - 140, 2019/05

https://doi.org/10.1016/j.sab.2019.03.014

The emission spectra of technetium (Tc) by liquid electrode plasma optical emission spectrometry have been investigated in this study. From the spectra, 52 emission peaks of Tc were observed in the 250-500 nm wavelength range. All peaks were assigned to the neutral state or singly ionized state. The relative intensities of these peaks were similar to those excited by an electric spark. The strongest intensity peaks were found at 254.3 nm, 261.0 nm, and 264.7 nm. Spectral interferences of coexisting elements in highly active liquid waste of reprocessing stream on those three strongest peaks were investigated using simulated sample. No spectral interferences were observed around the 264.7 nm Tc peak. Therefore, analytical performance using 264.7 nm peak was evaluated. The detection limit, estimated on standard and blank samples in 0.4 M nitric acid, was 1.9 mg/L. The relative standard deviation of Tc standard sample (12.0 mg/L) was 3.8% (N = 5, 1).

Quantitative determination of total cesium in highly active liquid waste by using liquid electrode plasma optical emission spectrometry

Do, V. K.; Yamamoto, Masahiko; Taguchi, Shigeo; Takamura, Yuzuru*; Surugaya, Naoki; Kuno, Takehiko

Talanta, 183, p.283 - 289, 2018/06

https://doi.org/10.1016/j.talanta.2018.02.023

We develop a novel analytical method employing liquid electrode plasma optical emission spectrometry for measurement of total cesium in highly active liquid wastes. Limit of detection and limit of quantification are 0.005 mg/L and 0.02 mg/L, respectively. The method is validated and applied to the real samples.

Study of HTGR contribution to Japan's CO emission reduction goal in 2050

Kamiji, Yu; Suzuki, Koichi*; Yan, X.

JAEA-Technology 2016-010, 24 Pages, 2016/07

JAEA-Technology-2016-010.pdf:1.05MB

Japanese government has set the goal of reducing CO emission by 26% in 2030 below the 2013 level, in longer term, by 80% below the 1990 level. To achieve the goals, various measures should be taken. The GTHTR300, a commercial High Temperature Gas-cooled Reactor (HTGR) design being developed by JAEA offers spectrum of heat applications by using its high temperature heat up to 950C. The potential contribution of CO emission reduction by HTGR is estimated considering domestic and overseas deployment of the GTHTR300. The best estimate for domestic CO reduction is 2.0710 ton- CO/yr and that from oversea is 2.2510 ton- CO/yr. The sum of these is about 47% of 9.1310 ton- CO/yr which is CO reduction target in 2050, for which deployment of 52 plants in Japan and 113 plants abroad, with each plant containing four 600 MWt reactor units, is required.

Secondary electron emission yields from the J-PARC RCS vacuum components

Yamamoto, Kazami; Shibata, Takeo*; Ogiwara, Norio; Kinsho, Michikazu

Vacuum, 81(6), p.788 - 792, 2007/02

https://doi.org/10.1016/j.vacuum.2005.11.052

The J-PARC 3GeV Rapid-Cycling Synchrotron (RCS) is required to provide 1MW pulsed protons to the spallation neutron target and the 50 GeV main ring. Since the acceleration period is set at a repetition rate of 25Hz, the eddy current effect due to such rapid repetition magnetic field is a big issue (i.e. the perturbation of the magnetic field and the heating owing to the ohmic loss) in the metal duct. Therefore, we choose the ceramics duct in the magnets in order to avoid the eddy current effect. But the total secondary electron emission yield (SEY) from the ceramics surface is larger than the metal one. In order to reduce these undesirable electron emitted from the chamber surface, Titanium Nitride (TiN) is coated on the inside surface of the chambers. We measured SEY from TiN coating surface with various conditions. We further investigated Diamond Like Carbon coating to search the possibility of another coating. The results of these measurements are shown.

Synchrotron radiation photoelectron emission study of SiO film formed by a hyperthermal O-atom beam at room temperature

Tagawa, Masahito*; Sogo, Chie*; Yokota, Kumiko*; Hachiue, Shunsuke; Yoshigoe, Akitaka; Teraoka, Yuden

Japanese Journal of Applied Physics, 44(12), p.8300 - 8304, 2005/12

https://doi.org/10.1143/JJAP.44.8300

Si oxide layers formed on Si(001) substrates by irradiation of hyperthermal oxygen atomic beams at room temperature were analysed at the JAERI soft X-ray beamline by photoemission spectroscopy. It was found that sub-oxide components were scarcely observed in the Si oxide layers formed by the atomic oxygen beam.

Synchrotron radiation photoabsorption and photoemission spectroscopy for thermal-induced reoriented Si polymer

Nath, K. G.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.323 - 326, 2005/06

https://doi.org/10.1016/j.elspec.2005.01.185

The effect of laser annealing on electronic atructures and molecular orientation for poly(dimethylsilane), {PDMS, [Si(CH)]} has been studied by synchrotron radiation photoemission and photoabsorption spectroscopy. Prior to annealing, PDMS powder was mounted on the basal plane of highly oriented pyrolytic graphite. Both Si 1s X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at Si 1s edge show that electronic structures have been modified due to annealing. Furthermore, the angle-dependent NEXAFS spectra clearly indicate that the annealed products maintain a specific orientation. Interestingly, no such kind of orientation is present in as-received PDMS powder as no angle-dependency is observed before annealing.