Study on the applicability of the fiber-optic crack detection sensor as a safety technology (FY2015-FY2018) (Joint research)

Kono, Masaru*; Hayama, Kazunori*; Matsui, Hiroya; Ozaki, Yusuke

JAEA-Technology 2019-011, 35 Pages, 2019/07

JAEA-Technology-2019-011.pdf:2.65MB

To verify long-term safety performance of the sensor for decades, we decided the extension of the collaborative research and the evaluation test of long-term durability of fiber-optic crack detection sensor developed by Tokyo Measuring Instruments Laboratory Co., Ltd. at the Mizunami Underground Research Laboratory were continued from FY 2015 to FY 2018. As a result, the measurement system using of the fiber-optic crack detection sensor is applicable for long-term measurement in deep underground area and find the future subject.

Transient ionization of the mesosphere during auroral breakup; Arase satellite and ground-based conjugate observations at Syowa Station

Kataoka, Ryuho*; Nishiyama, Takanori*; Tanaka, Yoshimasa*; Kadokura, Akira*; Uchida, Herbert Akihito*; Ebihara, Yusuke*; Ejiri, Mitsumu*; Tomikawa, Yoshihiro*; Tsutsumi, Masaki*; Sato, Kaoru*; et al.

Earth, Planets and Space (Internet), 71, p.9_1 - 9_10, 2019/01

https://doi.org/10.1186/s40623-019-0989-7

Transient ionization of the mesosphere was detected at around 65 km altitude during the isolated auroral expansion occurred at 2221-2226 UT on June 30, 2017. A general-purpose Monte Carlo particle transport code PHITS suggested that significant ionization is possible in the middle atmosphere due to auroral X-rays from the auroral electrons of 10 keV.

Transition of near surface resistivity of tunnel wall during drift closure test

Ozaki, Yusuke; Ishibashi, Masayuki; Matsushita, Tomoaki*; Masumoto, Kazuhiko*; Imasato, Takehiko*

Proceedings of 13th SEGJ International Symposium (USB Flash Drive), 4 Pages, 2018/11

In the Mizunami Underground Research Laboratory, Groundwater REcoverty Experiment in Tunnel (GREET) is performed to understanding the recovery process of geological environment after the closure of drift. In this experiment, we performed 2D electrical resistivity surveys three times. First survey was performed before the closure of test drift. Second and third surveys were performed after the closure test. The first survey detected two layers conformation that consists of conductive and resistive zones at shallower and deeper part from the drift surface, respectively. These layers correspond to the shotcrete and host rock, respectively. Second and third measurements show that the conductive zone expanded to deeper resistive part while the shallower conductive part did not change. We concluded that we captured the saturation process of dried fractures near the drift wall by closure of drift as an electrical resistivity response.

Investigations of fluid flow in fractured crystalline rocks at the Mizunami Underground Research Laboratory

Hadgu, T.*; Kalinina, E.*; Wang, Y.*; Ozaki, Yusuke; Iwatsuki, Teruki

Proceedings of 2nd International Discrete Fracture Network Engineering Conference (DFNE 2018) (Internet), 5 Pages, 2018/06

Experimental hydrology data from the Mizunami Underground Research Laboratory in Central Japan have been used to develop a site-scale fracture model and a flow model for the study area. The discrete fracture network model was upscaled to a continuum model to be used in flow simulations. A flow model was developed centered on the research tunnel, and using a highly refined regular mesh. In this study development and utilization of the model is presented. The modeling analysis used permeability and porosity fields from the discrete fracture network model as well as a homogenous model using fixed values of permeability and porosity. The simulations were designed to reproduce hydrology of the modeling area and to predict inflow of water into the research tunnel during excavation. Modeling results were compared with the project hydrology data. Successful matching of the experimental data was obtained for simulations based on the discrete fracture network model.

NIRS3; The Near Infrared Spectrometer on Hayabusa2

Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Otake, Makiko*; Arai, Takehiko*; Arai, Tomoko*; Hirata, Naru*; Hiroi, Takahiro*; Honda, Chikatoshi*; Imae, Naoya*; et al.

Space Science Reviews, 208(1-4), p.317 - 337, 2017/07

https://doi.org/10.1007/s11214-017-0341-0

NIRS3: The Near Infrared Spectrometer is installed on the Hayabusa2 spacecraft to observe the target C-type asteroid 162173 Ryugu at near infrared wavelengths of 1.8 to 3.2 micrometer. It aims to obtain reflectance spectra in order to detect absorption bands of hydrated and hydroxide minerals in the 3 micrometer-band. We adopted a linear-image sensor with indium arsenide (InAs) photo diodes and a cooling system with a passive radiator to achieve an optics temperature of 188 K, which enables to retaining sufficient sensitivity and noise level in the 3 micrometer wavelength region. We conducted ground performance tests for the NIRS3 flight model (FM) to confirm its baseline specifications. The results imply that the properties such as the signal-to-noise ratio (SNR) conform to scientific requirements to determine the degree of aqueous alteration, such as CM or CI chondrite, and the stage of thermal metamorphism on the asteroid surface.

Study on effects of coupled phenomenon on long-term behavior for crystalline rock; FY2015 (Contract research)

Ichikawa, Yasuaki*; Kimoto, Kazushi*; Matsui, Hiroya; Kuwabara, Kazumichi; Ozaki, Yusuke

JAEA-Research 2016-018, 23 Pages, 2016/12

JAEA-Research-2016-018.pdf:4.41MB

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. On the other hand, it was revealed that the chemical reaction of groundwater in a rock had an influence on the long-term behavior. An evaluation of the microcracks to have an influence on this mechanical and chemical coupled phenomena should be worked on chiefly. In fiscal year 2015, using a laser Doppler vibrometer that extends a frequency band up to 20 MHz, and measuring the surface wave transmitted through the granite specimens were estimated group velocity. As a result, group velocity until 100 kHz 500 kHz, revealed that tends to decrease while vibrating. The group speed estimate from a group delay was shown to be easier than the estimate by wave number - frequency spectrum. This is because in order to improve reliability, the estimated frequency band is by using a spatially averaged waveform. As a result obtained, in the case of the modeling by the viscoelastic theory of the granite and a microcrack nondestructiveness evaluation, it is thought that it is useful information in the future. In order to use the knowledge of this study, there is a need to clarify the correspondence between the microscopic properties of the medium such as a crack and crystal grain and the change of the group velocity.

Encapsulating mobile proton carriers into structural defects in coordination polymer crystals; High anhydrous proton conduction and fuel cell application

Inukai, Munehiro*; Horike, Satoshi*; Itakura, Tomoya*; Shinozaki, Ryota*; Ogiwara, Naoki*; Umeyama, Daiki*; Nagarker, S.*; Nishiyama, Yusuke*; Malon, M.*; Hayashi, Akari*; et al.

Journal of the American Chemical Society, 138(27), p.8505 - 8511, 2016/07

https://doi.org/10.1021/jacs.6b03625

Improvement of exchanging method of neutron startup source of high temperature engineering test reactor

Sawahata, Hiroaki; Shimazaki, Yosuke; Ishitsuka, Etsuo; Yamazaki, Kazunori; Yanagida, Yoshinori; Fujiwara, Yusuke; Takada, Shoji; Shinozaki, Masayuki; Hamamoto, Shimpei; Tochio, Daisuke

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 8 Pages, 2016/06

https://doi.org/10.1115/ICONE24-60842

In the HTTR, Cf is loaded in the reactor core as a neutron startup source and changed at frequency. In this exchange work, there were two technical issues; slightly higher radiation exposure of workers by neutron leakage and reliability of neutron source transportation container in handling. To reduce the radiation dose by neutron leakage, detail numerical evaluations using PHITS code were carried out, the effective shielding method for fuel handling machine was proposed. Easily removable polyethylene blocks and particles were used as the neutron shielding, and installed in the cooling paths of the fuel handling machine. As a result, the collective effective dose by neutron was reduced from about 700 man-microSv to about 300 man-microSv. As to the neutron source transportation container, the handling performance was improved and the handling work was safety accomplished by downsizing.

Manufacturing and development of JT-60SA vacuum vessel and divertor

Sakasai, Akira; Masaki, Kei; Shibama, Yusuke; Sakurai, Shinji; Hayashi, Takao; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Yokoyama, Kenji; Seki, Yohji; Shibanuma, Kiyoshi; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/51_FTPP720.pdf

The JT-60SA vacuum vessel (VV) and divertor are key components for the performance requirements. Therefore the manufacturing and development of VV and divertor are in progress, inclusive of the superconducting magnets. The vacuum vessel has a double wall structure in high rigidity to withstand electromagnetic force at disruption and to keep high toroidal one-turn resistance. In addition, the double wall structure fulfills originally two functions. (1) The remarkable reduction of the nuclear heating in the superconducting magnets is made by boric-acid water circulated in the double wall. (2) The effective baking is enabled by nitrogen gas flow of 200C in the double wall after draining of water. Three welding types were chosen for the manufacturing of the double wall structure VV to minimize deformation by welding. Divertor cassettes with fully water cooled plasma facing components were designed to realize the JT-60SA lower single null closed divertor. The divertor cassettes in the radio-active VV have been developed to ensure compatibility with remote handling (RH) maintenance in order to allow long pulse high performance discharges with high neutron yield. The manufacturing of divertor cassettes with typical accuracy of *1 mm has been successfully completed. Brazed CFC (carbon fiber composite) monoblock targets for a divertor target have been manufactured by precise control of tolerances inside CFC blocks. The infrared thermography test of monoblock targets has been developed as new acceptance inspection.

Characterization of homoionic Fe-type montmorillonite; Potential chemical species of iron contaminant

Kozai, Naofumi; Inada, Koichi*; Adachi, Yoshifusa*; Kawamura, Sachi*; Kashimoto, Yusuke*; Kozaki, Tamotsu*; Sato, Seichi*; Onuki, Toshihiko; Sakai, Takuro; Sato, Takahiro; et al.

Journal of Solid State Chemistry, 180(8), p.2279 - 2289, 2007/08

https://doi.org/10.1016/j.jssc.2007.06.002

Fe-montmorillonite with Fe ions occupying cation exchange sites is an ideal transformation product in bentonite buffer material. We previously prepared a Fe-montmorillonite sample using a FeCl solution under an inert gas condition. This study attempted to determine the potential contaminant iron chemical species in the sample. It was found that a small amount of Cl ions remained dispersed throughout the sample. The Cl ion retention may be due to the adsorption of FeCl in the initial FeCl solution and the subsequent containment of the Cl ions that are dissociated from the FeCl during excess salt removal treatment. The latter may be explained by the slow release of the remaining Cl ions from the collapsed interlayer of the montmorillonite or the transformation of a minor fraction of the remaining FeCl to iron (III) hydroxide chloride complexes having low solubility.