Investigation of the electronic structure of the MgZnY alloy using X-ray photoelectron spectroscopy

Miyazaki, Hidetoshi*; Akatsuka, Tatsuyoshi*; Kimura, Koji*; Egusa, Daisuke*; Sato, Yohei*; Itakura, Mitsuhiro; Takagi, Yasumasa*; Yasui, Akira*; Ozawa, Kenichi*; Mase, Kazuhiko*; et al.

Materials Transactions, 64(6), p.1194 - 1198, 2023/06

https://doi.org/10.2320/matertrans.MT-MD2022019

We investigated the electronic structure of the MgZnY alloy using hard and soft X-ray photoemission spectroscopy and electronic band structure calculations to understand the mechanism of the phase stability of this material. Electronic structure of the MgZnY alloy showed a semi-metallic electronic structure with a pseudo-gap at the Fermi level. The observed electronic structure of the MgZnY alloy suggests that the presence of a pseudogap structure is responsible for phase stability.

A New critical assembly: STACY

Araki, Shohei; Gunji, Satoshi; Tonoike, Kotaro; Kobayashi, Fuyumi; Izawa, Kazuhiko; Ogawa, Kazuhiko

Proceedings of European Research Reactor Conference 2020 (RRFM 2020) (Internet), 7 Pages, 2020/10

Critical experiments of thermal neutron system are still expected to be playing an important role for wide technical issues. The Japan Atomic Energy Agency (JAEA) is renovating the Static Experimental Critical Facility (STACY) to maintain the experimental capability. The new STACY is designed as a general-purpose criticality facility. Its core mainly consists of low enriched UO fuel rods, grid plates, and light water moderator. The first experiment campaign in the new STACY aims to obtain criticality characteristics of fuel debris, which will be used in validation of criticality analysis methods. The designs of the experimental core configurations are in progress.

Real-time X-ray diffraction of metastable phases during solidification from the undercooled LuFeO melt by two-dimensional detector at 1 kHz

Kumar, M. V.*; Kuribayashi, Kazuhiko*; Nagashio, Kosuke*; Ishikawa, Takehiko*; Okada, Jumpei*; Yu, J.*; Yoda, Shinichi*; Katayama, Yoshinori

Applied Physics Letters, 100(19), p.191905_1 - 191905_4, 2012/05

https://doi.org/10.1063/1.4712124

identification of metastable phases formed from the undercooled LuFeO melt under controlled oxygen partial pressure o was studied by X-ray diffraction measurements at a synchrotron radiation source. Real-time observation of the formation and growth of individual phases during the single recalescence of LuFeO and LuFeO phases at o of 110 Pa has been revealed by a high speed imaging system at 1 kHz. The obtained diffraction pattern of the metastable phase in the LuFeO system was consistent with that of the metastable and stable phases reported in the Lu-Fe-O system.

Assessment of heterogeneous geological environment at Tono -Japanese fiscal year 2004- (Contract research)

Toida, Masaru*; Suyama, Yasuhiro*; Mori, Takayuki*; Inaba, Takeshi*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Masumoto, Kazuhiko*; Kobayashi, Ichizo*; Iwano, Keita*; Furuichi, Mitsuaki*; et al.

JAEA-Research 2007-065, 210 Pages, 2007/09

JAEA-Research-2007-065-1.pdf:28.82MB
JAEA-Research-2007-065-2.pdf:42.37MB
JAEA-Research-2007-065-3.pdf:24.46MB
JAEA-Research-2007-065-4.pdf:48.78MB

"Geoscientific research" at the Tono Area is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important goals are to establish a methodology for analyzing uncertainties in heterogeneous geological environment and to develop investigation techniques for efficiently reducing the uncertainties. The current study proposes a new approach where all the possible options in the models and data-sets, which cannot be excluded in the light of the evidences available, are identified. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicitly using an uncertainty analysis technique based on Fuzzy geostatistics. This approach supports the design of the following investigation stage and reduces the uncertainties efficiently. In FY H16 the technique has been tested through geological modelling and groundwater analyses with Tono Area case based on current knowledge, to demonstrate its applicability and to compile the knowledge / information required to describe the H17 report. This report can be summarized as follows: (1) The knowledge / information required to describe the heterogeneous characteristics was compiled and connected to uncertainties associated with the characterization of a geological environment using a synthesis diagram. (2) Methodologies for assignment and screening of parameters were developed by using Evidential Support Logic (ESL). (3) Applicability of the techniques could be confirmed with Tono Area case. (4) This report proposed a new methodology that integrates the technique into JAEA ordinary technique to good advantage in the geoscientific research project.

Introduction to plasma fusion energy

Takamura, Shuichi*; Kado, Shinichiro*; Fujii, Takashi*; Fujiyama, Hiroshi*; Takabe, Hideaki*; Adachi, Kazuo*; Morimiya, Osamu*; Fujimori, Naoji*; Watanabe, Takayuki*; Hayashi, Yasuaki*; et al.

Kara Zukai, Purazuma Enerugi No Subete, P. 164, 2007/03

no abstracts in English

Real-time X-ray observation of solidification from undercooled Si melt

Nagashio, Kosuke*; Adachi, Masayoshi*; Higuchi, Kensuke*; Mizuno, Akitoshi*; Watanabe, Masahito*; Kuribayashi, Kazuhiko*; Katayama, Yoshinori

Journal of Applied Physics, 100(3), p.033524_1 - 033524_6, 2006/08

https://doi.org/10.1063/1.2210267

Grain refined microstructure is often obtained spontaneously in the solidification of metals and semiconductors from the undercooled melt without any external forces. Although it has been reported that the grain refinement is mainly caused by the fragmentation of the dendrites, the dynamic process of the fragmentation of dendrites has not been fully understood because the microstructure after the solidification has been analyzed. Here, we present a time-resolved 2- dimensional X-ray diffraction experiment on the solidification of Si from the undercooled melt. The number of diffraction spots observed at low undercoolings (100K) did not increase at the plateau stage, while the diffraction pattern at medium undercoolings (100K200K) changed from the spots with the tail to rings with the lapse of time. Both this result and high speed video imaging suggested that the high-order arms of the dendrites mostly detached from the main stems because nucleation could not be expected at the melting point after recalescence. The several spots observed at low undercoolings drastically changed to rings at high undercoolings (200K), which indicated the complete fragmentation of dendrite main stem as well as high-order arms. This complete fragmentation resulted in the grain refined microstructure.

Precise Measurement of density and structure of undercooled molten silicon by using synchrotron radiation combined with electromagnetic levitation technique

Higuchi, Kensuke*; Kimura, Kakuryo*; Mizuno, Akitoshi*; Watanabe, Masahito*; Katayama, Yoshinori; Kuribayashi, Kazuhiko*

Measurement Science and Technology, 16(2), p.381 - 385, 2005/02

https://doi.org/10.1088/0957-0233/16/2/008

X-ray diffraction and density measurements have been simultaneously performed to investigate the atomic structure of molten silicon in wide temperature range including undercooling region by using the electromagnetic levitation technique. The density was obtained from the mass and the shape of levitated sample by non-contact method based on the image analysis technique. X-ray diffraction experiments were performed by using the synchrotron radiation at SPring8, Japan. From structural analysis of undercooled molten silicon, first nearest neighbour coordination numbers and interatomic distances were about 5 and 2.48 with no dependence on temperature in the range of 1900-1550 K. We conclude as a result that the short-range order based on tetrahedral bonds of undercooled molten silicon does not change with the degree of undercoolings but medium-range order changes by the degree of undercoolings.

Study on construction technology for repository

Tanai, Kenji; Iwasa, Kengo; Hasegawa, Hiroshi; Miura, K.*; Okutsu, Kazuo*; Kobayashi, Masaaki*

JNC TN8400 99-046, 177 Pages, 1999/11

JNC-TN8400-99-046.pdf:6.03MB

For the construction of underground facilities comprising access tunnels, connecting tunnels, main tunnels and disposal tunnels, a large number of tunnels will be excavated in deep rock formations. These excavations will extend hundreds kilometers in total length. Therefore, special attention must be paid, to transporting large volume of debris, ventilation, emergency escape routes in case of accident, and other factors. In addition, special attention must also paid to potential accidents which might in underground excavations, including unstable facing phenomena (such as collapse and swelling of facing at weak layer sections), spring water flow resulting collapse of rock, gas eruption, and rock burst. While considering these factors to be emphasized during the construction of geological disposal facilities, the investigation reviewed the existing working methods on individual construction technologies of access tunnels, main tunnels, connecting tunnels, disposal tunnels, and disposal pit, based on the recognition that the present state deals with a wide range of geological environments, and conducted investigation about the construction methods for each tunnel on the basis current technologies, and described the outline of these methods. Furthermore, for the items to be particulaly emphasized on site characterization koko and siting data such as ground pressure and spring water, the investigation reviewed the current countermeasure works, and made survey on the phenomena appeared during actual tunnel construction works and their countermeasres, and carried out a study on effectiveness of these countermeasures. This constructing of disposal site in deep geological formations is basically possible by applying, or confirming, current excavation technologies for tunnels and underground facilities, A systematic construction system combines separate technologies relating to construction, (excavation technology, tunnel support work method, etc.). Such systems ...

Out-of-pile demonstration test program of hydrogen production system coupling with HTTR

Inagaki, Yoshiyuki; Takeda, Tetsuaki; Nishihara, Tetsuo; Hada, Kazuhiko; Hayashi, Koji

Nihon Genshiryoku Gakkai-Shi, 41(3), p.250 - 257, 1999/00

https://doi.org/10.3327/jaesj.41.250

no abstracts in English

Design of High Temperature Engineering Test Reactor (HTTR)

Saito, Shinzo; Tanaka, Toshiyuki; Sudo, Yukio; Baba, Osamu; Shindo, Masami; Shiozawa, Shusaku; Mogi, Haruyoshi; Okubo, Minoru; Ito, Noboru; Shindo, Ryuichi; et al.

JAERI 1332, 247 Pages, 1994/09

JAERI-1332.pdf:11.53MB

no abstracts in English