A Study of the evaluation of the excavation damaged zone in the Horonobe Underground Research Laboratory, 1; Investigation in the 140 m gallery (Joint research)

Sugita, Yutaka; Aoyagi, Kazuhei; Kubota, Kenji*; Nakata, Eiji*; Oyama, Takahiro*

JAEA-Research 2018-002, 72 Pages, 2018/06

JAEA-Research-2018-002.pdf:6.16MB

In a excavation of shafts and galleries in the deep underground for disposing radioactive waste, an excavation damaged zone (EDZ) is developed around the galleries and shafts owing to the stress redistribution. Since the characteristic changes of the rock mass in the EDZ affects the radionuclides migration behavior, it is important to understand the long-term behavior of the EDZ. Thus, we performed the in situ experiment to investigate the long-term behavior of EDZ as part of the collaborative research between Japan Atomic Energy Agency and Central Research Institute of Electric Power Industry in the 140m gallery in the Horonobe Underground Research Laboratory. In this research, we investigated the extent, mechanism of the change of hydro-mechanical characteristic, and long-term behavior of the EDZ on the basis of the comprehensive estimation of the results of the observation of the drift wall and the various investigations using boreholes such as geological investigation, the seismic and resistivity tomography, hydraulic test, water content monitoring, borehole loading test, convergence measurement, and so on. In addition, we clarified applicability and future tasks of the testing method used in this research for the investigation of the long-term behavior of the EDZ.

Roles of argon seeding in energy confinement and pedestal structure in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Hayashi, Nobuhiko; Yoshida, Maiko; Kamada, Yutaka; JT-60 Team

Nuclear Fusion, 55(3), p.033010_1 - 033010_9, 2015/03

https://doi.org/10.1088/0029-5515/55/3/033010

Physics picture of improving energy confinement with argon seeding at high density has been investigated in JT-60U. Better confinement is sustained at high density by argon seeding accompanied by higher core and pedestal temperatures. Peaked density profiles are kept with argon seeding. Density peaking and dilution effects lower the pedestal density at a given averaged density. The pedestal density in the argon seeded plasmas which is relatively lower than that in a single deuterium puff enables the pedestal temperature to be higher. The density peaking is a key factor of sustaining better confinement in argon seeded H-mode plasmas.

Temporal and spatial responses of temperature, density and rotation to electron cyclotron heating in JT-60U

Yoshida, Maiko; Ide, Shunsuke; Takenaga, Hidenobu; Honda, Mitsuru; Urano, Hajime; Kobayashi, Takayuki; Nakata, Motoki; Miyato, Naoaki; Kamada, Yutaka

Nuclear Fusion, 53(8), p.083022_1 - 083022_10, 2013/07

https://doi.org/10.1088/0029-5515/53/8/083022

Time and special responses of electron channels and ion channels with central electron cyclotron heating (ECH) have been investigated in JT-60U positive shear H-mode and internal transport barrier (ITB) plasmas. The ion temperature reduces with ECH after the increase in the electron temperature where an increase in the ion heat transport with ECH accompanies an increase in the electron thermal transport. The core electron density decreases with ECH when the density profile is peaked before ECH injection. The counter intrinsic rotation with ECH is identified using H-mode plasmas with small torque input (BAL-NBI). The counter intrinsic rotation is generated after the increase in the electron temperature and correlates with the change in the electron temperature with ECH around the EC deposition. Time scale of the change in the toroidal rotation velocity is about 90-200 ms around the ECH deposition and the time scale is longer compared to those in and .

Tensile property evaluation by stress and strain analyses of small punch test specimen using finite element method

Nakata, Toshiya; Komazaki, Shinichi*; Kono, Yutaka*; Tanigawa, Hiroyasu

Metallurgical Journal, LXIII(Sp.), p.146 - 150, 2010/08

http://www.hutnickelisty.cz/en/images/dokumenty/conference-abstracts_en.pdf

The small punch (SP) test is one method of small specimen test technology. We constructed a model for finite element analysis (FEA) using the Ramberg-Osgood equation to try to estimate tensile properties from the SP test. The results showed that the SP curve obtained from previous experiments could be reproduced by FEA to the point where the necking behavior of SP specimens became prominent. It was found that the relationship between the Mises equivalent stress at the point giving the largest equivalent plastic strain, and the total strain based on the Ramberg-Osgood equation, in the SP specimens, agreed well with the true stress-true strain curve plotted from tensile test measurements, and could thus be used to evaluate the 0.2% proof stress, tensile strength and uniform elongation.

Evaluation of creep properties of reduced activation ferritic steels

Nakata, Toshiya; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Komazaki, Shinichi*; Fujiwara, Mikio*; Kono, Yutaka*; Koyama, Akira*

Nihon Kinzoku Gakkai-Shi, 71(2), p.239 - 243, 2007/02

https://doi.org/10.2320/jinstmet.71.239

no abstracts in English

A Consideration about major business control system for independent administrative institution

Abe, Shinya*; Nakata, Yutaka; Iitsuka, Tomoaki; Yamagishi, Kojiro*

JAERI-Tech 2003-077, 233 Pages, 2003/10

JAERI-Tech-2003-077.pdf:15.07MB

Japanese government is carrying out the administrative reform aiming to promote decentralization of authority, to magnify the field of private sectors, etc. in order to correspond appropriately to matured economy, internationalized market, etc. As one of the reforms, Japanese government decided that JAERI and JNC would unite into an independent administrative agency. The aims of the independent administrative agency institution include realization of effective and transparent system and management. The aim of the present investigation is to be useful for the new agency to develop a major business control system, which manages financial affairs and accounts not only efficiently but also in correspondence with open information to the public and promoting research activities effectively.

Effect of doped amounts of N on creep properties of reduced avtivation ferritic steels

Nakata, Toshiya; Tanigawa, Hiroyasu; Komazaki, Shinichi*; Kono, Yutaka*

no journal, , 

no abstracts in English

Microstructure evolution in pressurized creep tube specimens of neutron-irradiated ferritic/martensitic steels

Ando, Masami; Tanigawa, Hiroyasu; Li, M.*; Nakata, Toshiya; Stoller, R.*; Kono, Yutaka*

no journal, , 

Irradiation creep of RAF/M steels has been recognized as one of the most important properties for engineering data due to the ITER test blanket structural design. The objective of this work is to examine an irradiation creep mechanism by using a microstructural observation in pressurized tubes of irradiated F82H and JLF-1. Irradiation was performed in the HFIR up to 5 dpa at 573 and 773 K. A small piece was cut from the center of each irradiated tube after diametral measurement. The microstructural examination with FIBed samples and replica films was carried out using a TEM. The creep strain for all steels at 573 and 773 K shows linear dependence on the applied hoop stress up to 250 MPa and 100 MPa, respectively. As results of extraction replica samples irradiated at 573 K, finer spherical precipitations were observed in highest hoop stress level. The detailed discussion will be presented along with the results of microstructure observation for irradiated specimens.

Evaluation of mechanical properties of weldments for reduced activation ferritic/martensitic steel

Nakata, Toshiya; Tanigawa, Hiroyasu; Ando, Masami; Komazaki, Shinichi*; Kono, Yutaka*

no journal, , 

Reduced activation ferritic/martensitic steels are the first candidate material for fusion reactor, and will be used as the structural materials of ITER test blanket modules (TBM). TBM will be assembled by welding various parts, it is important to be clearly mechanical properties of weldments to qualify TBM structure. In this paper, unirradiated mechanical properties of weldments, which is consisted of weld metal, heat affected zone (HAZ) and base metal region, obtained from TIG and EB welded F82H IEA-heat were evaluated by charpy impact and creep test. The creep tests were carried out at temperatures of 773-873 K and at stress levels of 150-260 MPa, with the specimens which include weld metal and HAZ region in the gage section. In these conditions, rupture time of weldments yield to about 100-1000 hours. The mechanism of these properties deterioration will be discussed based on the detailed analyses on microstructure changes.

Investigation of excavation disturbed zone (EdZ) in the 140m Gallery off the East-shaft, Horonobe Underground Research Laboratory

Nakata, Eiji*; Sugita, Yutaka

no journal, , 

no abstracts in English