Morphology evolution of -phase in Al-Mg-Si alloys during aging treatment

Ahmed, A.*; Uttarasak, K.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Journal of Alloys and Compounds, 988, p.174234_1 - 174234_9, 2024/06

https://doi.org/10.1016/j.jallcom.2024.174234

This study aims to clarify the growth process of the-phase in Al-Mg-Si alloys from the point of view of morphology evolution. For this research, the -phase orientation relationship, shape, growth process, misfit value, and interfacial condition between the -phase and Al matrix were investigated using high-resolution transmission electron microscopy (HR-TEM), focus ion beam (FIB), and optical microscope (OM). Results include the identification of {111} facets at the edges of the -phase, as well as the proposal of two new three-dimensional shapes for the -phase. We purposed the morphology evolution during the growth process of MgSi crystal and calculated the misfit to understand the unstable (111) facet has a higher misfit value as compared to the (001) and (011) facets. Our observations provide how they influence the behavior of MgSi crystals.

Identification of hydrogen trapping in aluminum alloys muon spin relaxation method and first-principles calculations

Tsuru, Tomohito; Nishimura, Katsuhiko*; Matsuda, Kenji*; Nunomura, Norio*; Namiki, Takahiro*; Lee, S.*; Higemoto, Wataru; Matsuzaki, Teiichiro*; Yamaguchi, Masatake; Ebihara, Kenichi; et al.

Metallurgical and Materials Transactions A, 54(6), p.2374 - 2383, 2023/06

https://doi.org/10.1007/s11661-023-07024-w

Although hydrogen embrittlement susceptibility of high-strength Al alloys is recognized as a critical issue in the practical use of Al alloys, identifying the hydrogen trapping or distribution has been challenging. In the present study, an effective approach based on experiment and simulation is proposed to explore the potential trap sites in Al alloys. Zero-field muon spin relaxation experiments were carried out for Al-0.5%Mg, Al-0.2%Cu, Al-0.15%Ti, Al-0.011%Ti, Al-0.28%V, and Al-0.015%V (at.%) in the temperature range from 5 to 300 K. The temperature variations of the dipole field widths have revealed three peaks for Al-0.5%Mg, four peaks for Al-0.2%Cu, three peaks for Al-0.011%Ti and Al-0.015%V. Atomic configurations of the muon trapping sites corresponding to the observed peaks are well assigned using the first-principles calculations for the trap energies of hydrogen around a solute and solute-vacancy pair. The extracted linear relationship between the muon peak temperature and the trap energy enables us to explore the potential alloying elements and their complex that have strong binding energies with hydrogen in Al alloys.

Introduction of a new framework of safety, maintenance and quality management activities in Japan Atomic Energy Agency under the new nuclear regulatory inspection system since FY 2020

Sono, Hiroki; Sukegawa, Kazuhiro; Nomura, Norio; Okuda, Eiichi; Study Team on Safety and Maintenance; Study Team on Quality Management; Task Force on New Nuclear Regulatory Inspection Systems

JAEA-Technology 2020-013, 460 Pages, 2020/11

JAEA-Technology-2020-013.pdf:13.46MB

Japan Atomic Energy Agency (JAEA) has completed the introduction of a new frame work of safety, maintenance and quality management activities under the new acts on the Regulation of nuclear source material, nuclear fuel material and reactors since April 2020, in consideration of variety, specialty and similarity of nuclear facilities of JAEA (Power reactor in the research and development stage, Reprocessing facility, Fabrication facility, Waste treatment facility, Waste burial facility, Research reactor and Nuclear fuel material usage facility). The JAEA task forces on new nuclear regulatory inspection systems prepared new guidelines on (1) Safety and maintenance, (2) Independent inspection, (3) Welding inspection, (4) Free-access response, (5) Performance indicators and (6) Corrective action program for the JAEA's nuclear facilities. New Quality management systems and new Safety regulations were also prepared as a typical pattern of these facilities. JAEA will steadily improve these guidelines, quality management systems and safety regulations, reviewing the official activities under the new regulatory inspection system together with the Nuclear Regulation Authority and other nuclear operators.

An Unreported precipitate orientation relationship in Al-Zn-Mg based alloys

Bendo, A.*; Matsuda, Kenji*; Lervik, A.*; Tsuru, Tomohito; Nishimura, Katsuhiko*; Nunomura, Norio*; Holmestad, R.*; Marioara, C. D.*; Shimizu, Kazuyuki*; Toda, Hiroyuki*; et al.

Materials Characterization, 158, p.109958_1 - 109958_7, 2019/12

https://doi.org/10.1016/j.matchar.2019.109958

Characterization of precipitates in Al-Zn-Mg alloys, using a combination of electron diffraction, bright field transmission electron microscopy and atomic scale scanning transmission electron microscopy imaging revealed the presence of an unreported orientation relationship between the -MgZn phase and the Al lattice with the following orientation relationship (0001) (120) and () (001), plate on (120). The precipitate interfaces were observed and analyzed along two projections 90 to one-another. The precipitate coarsening was through the common thickening ledge mechanism. The ledges were significantly stepped along one lateral direction. An interface relaxation model using density functional theory was carried out to explain the precipitate behavior.

Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; Maeda, Tomoyoshi*; Matsuda, Kenji*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

https://doi.org/10.1080/14786435.2019.1637032

Optimization of mechanical properties in aluminum alloys hydrogen partitioning control

Toda, Hiroyuki*; Yamaguchi, Masatake; Matsuda, Kenji*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Su, H.*; Fujihara, Hiro*; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito; et al.

Tetsu To Hagane, 105(2), p.240 - 253, 2019/02

https://doi.org/10.2355/tetsutohagane.TETSU-2018-083

no abstracts in English

Study on the method of safety assessment for in-service nuclear fuel facilities

Nomura, Norio; Kashimura, Yoshinori

JNC TN9410 2003-009, 53 Pages, 2004/03

JNC-TN9410-2003-009.pdf:0.57MB

On regulatory concern, the nuclear reactor and the nuclear fue1 facility shall form various safety assessments for the plant safety at the design phase prior to the construction and operation. And the regulatory authority intends to establish the law required the various safety assessments for the equipments of in-service reactors. Consequently, the author made investigation of the status of the various safety assessment in the chemical plants. And, the author study the standard method of safety assessment for nuclear fuel facility to use the chemical plants safety assessment for the alleged company based the method of the Health, Labor and Welfare Ministry. In the result, It was designed to the standard method of safety assessment for nuclear fuel facility, and it is able to apply an approach to this standard method in the existing these facility. It is necessary to review their attitude of that risk point and technical intricacy.

A Study of nuclear energy supply system in extremely severe surroundings mainly using radioisotope

Nomura, Norio; Haga, Kazuo; Otsubo, Akira

PNC TN9410 93-169, 71 Pages, 1993/10

PNC-TN9410-93-169.pdf:2.87MB

Within a framework of transportable reactor study, a conceptual design study of power source has been performed for lunar base or space stations. Energy supply systems using Radioisotope fueled Thermoelectric Generators(RTGs) for extremely severe surroundings are introduced in this paper. At first, potential of RTGs for small-scale energy supply unit was researched from the point of theory, system structure, and performance. Also the manufacturing processes of radioisotopes to be used in RTGs were investigated. Secondly in order to make the nuclear energy system on the moon independent of the earth as much as possible, we proposed concepts of an investigation and mining method for uranium ore and continuous operation for nuclear fuel cycle which uses laser technology to reprocessing and group separation of elements as well as enrichment of uranium. Thirdly a Rankine cycle system sourced solar energy (Solar Ray System) was introduced. The power generating equipments of the system is the same as those of transportable reactor. Lastly we showed a concept of electrostatic power system sourced cosmic rays and a shielding method from cosmic rays.

A Conceptual design study of lunar nuclear power plants

Nomura, Norio; Haga, Kazuo; ; Seino, Hiroshi; Otsubo, Akira

PNC TN9410 93-154, 218 Pages, 1993/08

PNC-TN9410-93-154.pdf:7.31MB

Within a framework of transportable reactor study, a conceptual design of power source to lunar base or space station has been performed. In this paper, structure and capability of compornents for a lunar base power plant are described. It is shown that SPECTRA-L is applicable to it. This is a 300kWe reactor, which needs no refueling during ten years operation. It is found that total weight is less than ten tons and the decay heat can be removed by natural circulation. The optimum construction method on lunar base is also proposed. A concept of a 3000kWe LUnar Base Activities Reactor (LUBAR) is also introduced. LUBAR is composed of one reactor unit and two generation units. The reactor section has three reactors. This plant can be operated for thirty years by changing the reactors. The optimized construction method is also proposed for this plant. The key technologies to realize these plants are described with the tentative R&D schedule.

None

Haga, Kazuo; Otsubo, Akira; ; ; Seino, Hiroshi; ; Nomura, Norio

PNC TN9420 91-007, 152 Pages, 1991/04

PNC-TN9420-91-007.pdf:12.18MB

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