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Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei; Miyara, Nobukatsu*
Journal of Rock Mechanics and Geotechnical Engineering, 16(2), p.365 - 378, 2024/02
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.
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2022-065, 111 Pages, 2023/03
JAEA-Review-2022-065.pdf:6.8MB
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 FY2021. 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 from FY2018 to FY2021. Since the final year of this proposal was FY2021, the results for four fiscal years were summarized. 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 with a position resolution of less than 10 
m, and the measurement test for the energy spectra was operated using several alpha-ray sources with an unfolding method.
Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*
JAEA-Review 2022-033, 80 Pages, 2022/12
JAEA-Review-2022-033.pdf:4.08MB
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 FY2021. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), 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 FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. The present study aims to develop an optical fiber type radiation sensor that can measure the radiation distribution one-dimensionally along the fiber under a high radiation field for the decommissioning of 1F. Based on the conventional time-of-flight method, we found several promising sensor candidates for the radiation distribution measurement under high dose rate and many scattered gamma-rays.
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.
Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*
JAEA-Review 2021-033, 55 Pages, 2021/12
JAEA-Review-2021-033.pdf:2.9MB
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 FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted in FY2020. We are developing a one-dimensional optical fiber radiation sensor that can estimate the radioactive source distribution "along lines" instead of "at points". To improve the conventional time-of-flight optical fiber radiation sensor for the application under high dose rate environment, basic evaluation tests were conducted using various optical fibers with different diameters and materials.
Sakai, Kenji; Oku, Takayuki; Okudaira, Takuya; Kai, Tetsuya; Harada, Masahide; Hiroi, Kosuke; Hayashida, Hirotoshi*; Kakurai, Kazuhisa*; Shimizu, Hirohiko*; Hirota, Katsuya*; et al.
JPS Conference Proceedings (Internet), 33, p.011116_1 - 011116_6, 2021/03
In neutron fundamental physics, study of correlation term 
of a neutron spin 
and a target nuclear spin 
is important because term interferes to parity non-conserving (PNC) and time reversal non-conserving terms. For this study, a xenon (Xe) is an interesting nucleus because it has been observed an enhancement of PNC effect around neutron resonance peaks, and polarizes up to 
by using a spin exchange optical pumping (SEOP) method. We would plan to develop a polarized Xe gas target with a compact in-situ SEOP system, and to study term by utilizing epithermal neutron beams supplied from a high intense pulsed spallation neutron source. As the first step, we attempted to measure neutron polarizing ability caused by term at a 9.6 eV s-wave resonance peak of 
Xe at BL10 in MLF, by detecting change 
of ratio between neutron transmissions with the polarized and unpolarized Xe target. After demonstrating that our apparatus could detect small change (
) of neutron transmissions caused by Doppler broadening effect, a signified value of has been obtained as preliminary results. For analyzing the obtained in detail, we are improving our nuclear magnetic resonance and electron paramagnetic resonance systems for evaluating Xe polarization independently of neutron beams.
Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*
JAEA-Review 2020-063, 44 Pages, 2021/01
JAEA-Review-2020-063.pdf:2.55MB
JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted in FY2019.
Hata, Koji*; Niunoya, Sumio*; Uyama, Masao*; Nakaoka, Kenichi*; Fukaya, Masaaki*; Aoyagi, Kazuhei; Sakurai, Akitaka; Tanai, Kenji
JAEA-Research 2020-010, 142 Pages, 2020/11
JAEA-Research-2020-010.pdf:13.74MB
JAEA-Research-2020-010-appendix(DVD-ROM).zip:149.9MB
In the geological disposal study of high-level radioactive waste, it is suggested that the excavation damaged zone (EDZ) which is created around a tunnel by the excavation will be possible to be one of the critical path of radionuclides. Especially, the progress of cracks in and around the EDZ with time affects the safety assessment of geological disposal and it is important to understand the hydraulic change due to the progress of cracks in and around EDZ. In this collaborative research, monitoring tools made by Obayashi Corporation were installed at a total of 9 locations in the three boreholes near the depth of 370 m of East Shaft at the Horonobe Underground Research Laboratory constructed in the Neogene sedimentary rock. The monitoring tool consists of one set of "optical AE sensor" for measuring of the mechanical rock mass behavior and "optical pore water pressure sensor and optical temperature sensor" for measuring of groundwater behavior. This tool was made for the purpose of selecting and analyzing of AE signal waveforms due to rock fracture during and after excavation of the target deep shaft. As a result of analyzing various measurement data including AE signal waveforms, it is able to understand the information on short-term or long-term progress of cracks in and around EDZ during and after excavation in the deep shaft. In the future, it will be possible to carry out a study that contributes to the long-term stability evaluation of EDZ in sedimentary rocks in the deep part of the Horonobe Underground Research Laboratory by evaluation based on these analytical data.
Aoyagi, Kazuhei; Sakurai, Akitaka; Miyara, Nobukatsu; Sugita, Yutaka
JAEA-Research 2020-004, 68 Pages, 2020/06
JAEA-Research-2020-004.pdf:6.4MBJAEA-Research-2020-004-appendix1(DVD-ROM).zip:636.84MBJAEA-Research-2020-004-appendix2(DVD-ROM).zip:457.72MBJAEA-Research-2020-004-appendix3(DVD-ROM).zip:595.19MB
In construction and operational phase of a high-level radioactive waste disposal project, it is necessary to monitor on mechanical stability of underground facility for long term. In this research, we measured the displacement of the rock around the gallery and the stress acting on support materials. Furthermore, we investigated the durability of measurement sensor installed in the rock mass and the support material such as concreate lining and steel support. As a result, optical fiber sensor is appropriate for measurement of the displacement of rock mass around the gallery, while it is enough to apply the conventional electric sensor for the measurement of stress acting on the support material in the geological environment (soft rock and low inflow). The result of the measurement in the fault zone in 350 m gallery, show that the stresses acting on both shotcrete and steel arch lib exceeded the value which will cause the instability of the gallery. However, as, we found no crack on the surface of the shotcrete. By observation on the surface of shotcrete, thus, it was concluded that careful observation of shotcrete around that section in addition to the monitoring the measured stress was necessary to continue. In other measurement sections, there was no risk for the instability of the gallery as a result of the investigation of the measurement result.
Aoki, Tomoyuki*; Tani, Takuya*; Sakai, Kazuo*; Koga, Yoshihisa*; Aoyagi, Kazuhei; Ishii, Eiichi
JAEA-Research 2020-002, 83 Pages, 2020/06
JAEA-Research-2020-002.pdf:8.25MBJAEA-Research-2020-002-appendix(CD-ROM).zip:6.63MB
The Japan Atomic Energy Agency (JAEA) has conducted with the Horonobe Underground Research Project in Horonobe, Teshio-gun, Hokkaido for the purpose of research and development related to geological disposal technology for high-level radioactive wastes in sedimentary soft rocks. The geology around the Horonobe Underground Research Laboratory (HURL) is composed of the Koetoi diatomaceous mudstone layer and the Wakkanai siliceous layer, both of which contain a large amount of diatom fossils. Since these rocks exhibit relatively high porosity but low permeability, it is important to investigate the poro-elastic characteristics of the rock mass. For this objective, it is necessary to measure parameters based on the poro-elastic theory. However, there are few measurement results of the poro-elastic parameters for the geology around HURL, and the characteristics such as dependence on confining pressure are not clearly understood. One of the reasons is that the rocks show low permeability and the pressure control during testing is difficult. Therefore, a poro-elastic parameter measurement test was conducted on the siliceous mudstone of the Wakkanai formation to accumulate measurement results on the poro-elastic parameters and to examine the dependence of the parameters on confining pressure. As a result, some dependency of the poro-elastic parameters on confining pressure was observed. Among the measured or calculated poro-elastic parameters, the drained bulk modulus increased, while the Skempton's pressure coefficient, and the Biot-Wills coefficient in the elastic region decreased with the increase in confining pressure. The measurement results also inferred that the foliation observed in the rock specimens might impact a degree of dependency of those parameters on confining pressure.
Collaborative Laboratories for Advanced Decommissioning Science; Ibaraki University*
JAEA-Review 2019-041, 71 Pages, 2020/03
JAEA-Review-2019-041.pdf:3.38MB
JAEA/CLADS, has been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") since FY2018. The Project aims at 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 has been collected from all over the world, and basic research and human resource development have been 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 "Contribution to Risk Reduction in Decommissioning Works by the Elucidation of Basic Property of Radioactive Microparticles". In order to establish the decommissioning procedures (recovery of the melted fuels, decontamination inside the reactors, ensuring the safety of the workers, etc.) of the Fukushima Daiichi Nuclear Power Station, radioactive microparticles released by the accident are an important information source for clarifying what had happened inside the reactors in the course of the accident. The purpose of the present study is to obtain detailed knowledge on the basic properties (particle size, composition, electrical/optical properties, etc.) of the radioactive microparticles, as well as to further elucidate the various properties of the radioactive microparticles including the quantitative evaluation of alpha-ray-emitters, through the Japan-UK synergetic research. Thus, we are conducting research and development that will contribute to the comprehensive works towards the risk reduction in the "decommissioning" plan.
Niunoya, Sumio*; Hata, Koji*; Uyama, Masao*; Aoyagi, Kazuhei; Tanai, Kenji
Dai-47-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (Internet), p.92 - 97, 2020/01
Since underground water at the Horonobe Underground Research Laboratory site includes the dissolved gas, it is important to understand the quantitative behavior of AE signal waveform clearly and to develop the criteria of sorting technique. In this report, we tried to perform two types of laboratory tests (Small pipe test and Flat-plate test) in order to obtain detail data of AE signal wave form under two-phase flow. As the result, we could understand that there exists the relationship between the pressure breathing and AE generation, and that the diameter of pipe did not affect the AE behavior.
6 rod bundleHan, X.*; Shen, X.*; Yamamoto, Toshihiro*; Nakajima, Ken*; Sun, Haomin; Hibiki, Takashi*
International Journal of Heat and Mass Transfer, 144, p.118696_1 - 118696_19, 2019/12
Times Cited Count：15 Percentile：64.13(Thermodynamics)Ito, Chikara; Naito, Hiroyuki; Ishikawa, Takashi; Ito, Keisuke; Wakaida, Ikuo
JPS Conference Proceedings (Internet), 24, p.011038_1 - 011038_6, 2019/01
A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels at the Fukushima Daiichi Nuclear Power Station. The tentative dose rate in the reactor pressure vessels is assumed to be up to 1 kGy/h. We developed a radiation resistant optical fiber consisting of a 1000 ppm hydroxyl doped pure silica core and 4 % fluorine doped pure silica cladding. We attempted to apply the optical fiber to remote imaging technique by means of fiberscope. The number of core image fibers was increased from 2000 to 22000 for practical use. The transmissive rate of infrared images was not affected after irradiation of 1 MGy. No change in the spatial resolution of the view scope by means of image fiber was noted between pre- and post-irradiation. We confirmed the applicability of the probing system, which consists of a view scope using radiation-resistant optical fibers.
Wakaida, Ikuo; Oba, Hironori; Miyabe, Masabumi; Akaoka, Katsuaki; Oba, Masaki; Tamura, Koji; Saeki, Morihisa
Kogaku, 48(1), p.13 - 20, 2019/01
By Laser Induced Breakdown Spectroscopy and by related resonance spectroscopy, elemental and isotope analysis of Uranium and Plutonium for nuclear fuel materials and in-situ remote analysis under strong radiation condition for melt downed nuclear fuel debris at damaged core in "Fukushima Daiichi Nuclear Power Station", are introduced and performed as one of the application in atomic energy research field.
Do, V. K.; Yamamoto, Masahiko; Taguchi, Shigeo; Takamura, Yuzuru*; Surugaya, Naoki; Kuno, Takehiko
Talanta, 183, p.283 - 289, 2018/06
Times Cited Count：10 Percentile：39.09(Chemistry, Analytical)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.
Niunoya, Sumio*; Hata, Koji*; Uyama, Masao*; Aoyagi, Kazuhei; Wakasugi, Keiichiro
Dai-45-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.226 - 231, 2018/01
The objective of this research is to investigate the long-term hydro-mechanical behavior of rock mass around the shaft in the Horonobe Underground Research Laboratory (URL). The long-term monitoring has been carried out by optical AE sensors, optical water pressure sensors, and optical temperature sensors below 350m depth of the shaft in the Horonobe URL. From the first analytical results, it was too hard to discriminate the uncleared AE wave by using the resonant characteristic. Thus, at this time, we tried to reanalysis by using the half width of spectrum, we could discriminate it correctly as AE from the breaking of rock.
Gu, B.; Takahashi, Saburo*; Maekawa, Sadamichi
Physical Review B, 96(21), p.214423_1 - 214423_6, 2017/12
Times Cited Count：9 Percentile：42.46(Materials Science, Multidisciplinary)Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei
Dai-14-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2017/01
The objective of this research is to investigate the long-term hydro-mechanical behavior of rock mass around the shaft in the Horonobe Underground Research Laboratory (URL). The long-term monitoring has been carried out by optical AE sensors, optical water pressure sensors, and optical temperature sensors below 350m depth of the shaft in the Horonobe URL. From the measurement results, the extent of an excavation damaged zone was 1.5m within the shaft wall. After the excavation, it was observed that the unsaturated zone of the groundwater was spread more than 1.5m within the shaft wall.
Tokuyasu, Kayoko; Furuta, Sadaaki*; Kokubu, Yoko; Umeda, Koji
Nihon Hoshasen Anzen Kanri Gakkai-Shi, 15(1), p.80 - 87, 2016/07
An optically stimulated luminescence reader (Riso TL/OSL DA-20) was installed in Toki Research Institute of Isotope Geology and Geochronology (Toki-shi, Gifu Prefecture), Japan Atomic Energy Agency (JAEA) for dating the geological sample. An accumulated dose of the sample is obtained using the reader. Sealed beta source of strontium-90 is required to be mounted on the reader because repeated artificial irradiation is necessary for the accumulated dose estimation. However, there are not many introduction examples for the reader domestically, and the information as to radiation control of the reader is limited. We therefore report here the process of source loading on the reader and radiation control associated with the use of the source.
