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.

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.

Angle-resolved photoemission study of the -chain compound [Ni(chxn)Br]Br; Spin-charge separation in hybridized - chains

Fujimori, Shinichi; Ino, Akihiro; Okane, Tetsuo; Fujimori, Atsushi; Okada, Kozo*; Manabe, Toshio*; Yamashita, Masahiro*; Kishida, Hideo*; Okamoto, Hiroshi*

Physical Review Letters, 88(24), p.247601_1 - 247601_4, 2002/06

https://doi.org/10.1103/PhysRevLett.88.247601

We report on the results of angle-resolved photoemission experiments on a quasi-one-dimensional -chain compound [Ni(chxn)Br]Br (chxn = 1,2-cyclohexanediamine), a one-dimensional Heisenberg system with and K, which shows a gigantic non-linear optical effect. A "band" having about 500meV energy dispersion is found in the first half of the Brillouin zone , but disappears at . Two dispersive features, expected from the spin-charge separation, as have been observed in other quasi-one-dimensional systems like SrCuO, are not detected. These characteristic features are well reproduced by the - chain model calculations with a small charge-transfer energy compared with that of one-dimensional Cu-O based compounds. We propose that this smaller is the origin of the absence of clear spin- and charge-seperation in the photoemission spectra and strong non-linear optical effect in [Ni(chxn)Br]Br.

Optical emission behavior and radiationresistance of epoxy resins

Kawanishi, Shunichi; Udagawa, Akira; Hagiwara, Miyuki

JAERI-M 87-185, 21 Pages, 1987/11

JAERI-M-87-185.pdf:0.7MB

no abstracts in English

Effect of aromatic additives on the radiation resistance of ethylene-propylene-diene-terpolymer studied by optical emission spectroscopy of both steady-state and picosecond pulse radiolysis

Kawanishi, Shuichi; Hagiwara, Miyuki; *; *; *

Radiation Physics and Chemistry, 26(6), p.705 - 713, 1985/00

no abstracts in English