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JAEA Reports

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.

Journal Articles

The Possible transition mechanism for the meta-stable phase in the 7xxx aluminium

Bendo, A.*; Matsuda, Kenji*; Nishimura, Katsuhiko*; Nunomura, Norio*; Tsuchiya, Taiki*; Lee, S.*; Marioara, C. D.*; Tsuru, Tomohito; Yamaguchi, Masatake; Shimizu, Kazuyuki*; et al.

Materials Science and Technology, 36(15), p.1621 - 1627, 2020/09

 Times Cited Count:1 Percentile:0(Materials Science, Multidisciplinary)

Metastable phases in aluminum alloys are the primary nano-scale precipitates which have the biggest contribution to the increase in the tangible mechanical properties. The continuous increase in hardness in the 7xxx aluminum alloys is associated with the phase transformation from clusters or GP-zones to the metastable $$eta'$$ phase. The transformation which is structural and compositional should occur following the path of the lowest activation energy. This work is an attempt to gain insight into how the structural transformation may occur based on the shortest route of diffusion for the eventual structure to result in that of $$eta'$$ phase. However, for the compositional transformation to occur, the proposed mechanism may not stand, since it is a prerequisite for the atoms to be at very precise positions in the aluminum lattice, at the very beginning of structural transformation, which may completely differ from that of the GP-zones atomic arrangements.

Journal Articles

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

 Times Cited Count:9 Percentile:78.99(Materials Science, Multidisciplinary)

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 $$eta$$$$_{13}$$ orientation relationship between the $$eta$$-MgZn$$_2$$ phase and the Al lattice with the following orientation relationship (0001)$$eta$$ $$||$$ (120)$$_{rm Al}$$ and ($$2bar{1}bar{1}0$$)$$eta$$ $$||$$ (001)$$_{rm Al}$$, plate on (120)$$_{rm Al}$$. The precipitate interfaces were observed and analyzed along two projections 90$$^{circ}$$ 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.

Journal Articles

Effect of copper addition on precipitation behavior near grain boundary in Al-Zn-Mg alloy

Matsuda, Kenji*; Yasumoto, Toru*; Bendo, A.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Marioara, C. D.*; Lervik, A.*; Holmestad, R.*; et al.

Materials Transactions, 60(8), p.1688 - 1696, 2019/08

 Times Cited Count:5 Percentile:46.2(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

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

 Times Cited Count:13 Percentile:83.11(Materials Science, Multidisciplinary)

Journal Articles

Abnormally enhanced diamagnetism in Al-Zn-Mg alloys

Nishimura, Katsuhiko*; Matsuda, Kenji*; Lee, S.*; Nunomura, Norio*; Shimano, Tomoki*; Bendo, A.*; Watanabe, Katsumi*; Tsuchiya, Taiki*; Namiki, Takahiro*; Toda, Hiroyuki*; et al.

Journal of Alloys and Compounds, 774, p.405 - 409, 2019/02

 Times Cited Count:3 Percentile:37.05(Chemistry, Physical)

Journal Articles

Optimization of mechanical properties in aluminum alloys $$via$$ hydrogen partitioning control

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

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

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

Simulation studies and measurements of beam instabilities caused by the kicker impedance at high intensities in the 3-GeV RCS of J-PARC

Saha, P. K.; Shobuda, Yoshihiro; Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kinsho, Michikazu; Nomura, Masahiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.

Proceedings of 7th International Particle Accelerator Conference (IPAC '16) (Internet), p.589 - 591, 2016/06

JAEA Reports

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.

Journal Articles

None

; Nomura, Norio; ; Koyama, Shinichi;

Donen Giho, (92), 0 Pages, 1994/12

None

JAEA Reports

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

Nomura, Norio; ;

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.

Journal Articles

Natural circulation analysis of a 300kwe lunar base reactor under decay power level

Haga, Kazuo; Nomura, Norio; Otsubo, A.

7th International Conference on Emerging Nuclear Energy Systems (ICENES '93), 0 Pages, 1993/09

None

JAEA Reports

A Conceptual design study of lunar nuclear power plants

Nomura, Norio; ; ; Seino, Hiroshi;

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.

JAEA Reports

Study of Co-generation system in sever environment

Nomura, Norio; ;

PNC TN9410 91-298, 74 Pages, 1991/08

PNC-TN9410-91-298.pdf:2.0MB

High-temperature transpotable liquid-metal-cooled fast reactors are also expected as an energy source in sever environments such as lunar base. Only electricity has been considered as the energy supply system to the lunar base, however, both use of electricity and heat power (co-generation system) may offer better effective use of energy than only the electrification system is considered. In this report, the advantage of co-generation system based on a transpotable reactor examined to a usage in a lunar base. Two energy system diagrams on heat and electricity flows have been compared from the view point of total weight. One is the case of all electrification. The other (co-generation system) is the case in which the exhaust heat from the nuclear reactor is actively utilized to reduce the demand of electricity. A heat transport technique using a chemical process as the heat media is adapted for the latter. In the chemical system, hydrogen and carbon monoxide are formed from methane and steam by adding nuclear heat. Then the gases are transported through a pipe and changes to the original materials generating heat at the consuming spot. As the result of present study, it is clarified that the co-generation system has a possibility to have an advantage over the case of all electrification in total weight of system when the energy demand increase to MWe level. Finally, future R&D items ware mentioned to reduce the weight of this co-generation system and to increase the effectively.

JAEA Reports

None

; ; ; ; Seino, Hiroshi; ; Nomura, Norio

PNC TN9420 91-007, 152 Pages, 1991/04

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

None

JAEA Reports

A Conceptual design study of space nuclear power plant SECTRA (II); Investigation of shielding structure

Nomura, Norio; ;

PNC TN9410 91-125, 75 Pages, 1991/04

PNC-TN9410-91-125.pdf:1.87MB

Within a framework of transportable reactor study, a conceptual design of power source to lunar base or space station is being performed. In the lunar base power plant SPECTRA-L, dose equivalent at the area around the reactor can be reduced till the natural back ground level by the shield of regolish. But, it is not easy to reduce the dose equivalent to an acceptable level the limit of dose equivalent from the reactor. Because shields abobe the reactor are only thin regolish whose thickness are 2m, and plant equipments such as boiler, condenser, alternator, and turbine. In case of SPECTRA for the space station, shield must be furnished from the beginning. In this report, shielding structure of SPECTRA is analyzed seeking for an optimum one. The analytical condition are as follows. (1)Thickness of shield is less than 1 m. (2)Weight is as light as possible. The finally obtained shielding structure is a layer by Beryllium, tungsten, lithium-hydrogen, and SUS304. These total thickness is 90cm. Using this shield, the dose equivalent rate at 25m apart point from the reactor, where life module will be located, is estimated to be 14.4$$mu$$Sv/h. This value is more than a proposed limit of dose equivalent from the reactor (40mSv/y : 4.6$$mu$$ Sv/h). But it is expected that the actual dose equivalent is less than the limit value owing to the plant equipment in the direction and the life module shield of cosmic ray.

JAEA Reports

OHP Sheets in the FY 1990 internal meeting on advanced nuclear-energy system research

; Nomura, Norio; Seino, Hiroshi; *

PNC TN9430 91-005, 112 Pages, 1991/03

PNC-TN9430-91-005.pdf:3.49MB

This paper complies OHP sheets used in the FY 1990 internal meeting on advanced nuclear-energy system research at O-arai Engineering Center, PNC on January 17, 1991. The frontier research which seeks innovative fast reactor and its new field of application includes [1]research submersible reactor, [2]hydrogen production reactor, [3]transportable reactor, and [4]lunar base reactor. Followings are the main topics presented in the meeting. ([1]Research submersible reactor) This type of a reactor might be used for deep sea development. The reactor will be built on the deep sea floor or will be set as a power source in a research submersible. A reactor vessel and a heat exchanger are set at the bottom region in a pressure hull. A radiation shield and a secondary system containing coolant gas are arranged above them. A closed Brayton cycle is used for electric power generation. For a nuclear reactor used for the submersible, one of the key issues is how to exhaust heat unused for clectric power generation. Here, it is proposed to exhaust the heat by using a cooling system set inside the pressure hull. Heat is transferred from the outer surface of the hull to sea water by thermal convection. The sea water is moved by a fan under the hull and flows upward over the surface of the hull. A preliminary heat transfer calculation has been performed assuming that the shape of the hull is a pipe of 3 m in inner diameter and 6 m in height. The cooling system is set inside its inner surface area of 63.6 m$$^{2}$$. The thickness of the hull wall is 7.64$$times$$10$$^{-2}$$ m for the 6,500 m research submersible. The material of the hull is high tension steel, or titanium alloy. Width of a coolant gas passage is 8$$times$$10$$^{-2}$$ m in the cooling system. The electric power of the reactor is 100 to 300 kWe. The power conversion efficiency of the reactor and the closed Brayton cycle is 17%. A heat transfer coefficient is assumed to be increased about 40 % by setting fins over ...

JAEA Reports

Conceptual design study of transportable reactor SPECTRA-L for lunar base (II); Study on the dose-bquivalent limit in space

Nomura, Norio; ;

PNC TN9410 91-107, 40 Pages, 1991/03

PNC-TN9410-91-107.pdf:0.88MB

Conceptual design of the SPECTRA-L power plant for lunar base is being performed as one of the transportable reactor study. It is necessary to establish an acceptable limit of dose equivalent in space as well as that on the earth so as to design the shield to the reactor. Because the natural radiation dose in space is higher than that on the earth, terrestrial dose equivalent limit can not be directly applied. In this report, we examined the dose equivalent limit on the moon based on the terrestrial one, then analyzed the shielding effect of lunar soil (regolish) which is expected as shielding material in this plant. The study led us to propose some limits on the acceptable radiation in the human activity in space, that is 2.0 Sv in life and 0.4 Sv/year, consequently 0.04 Sv/month. The yearly limit is less than 0.5 Sv which is admitted in the ICRP Publication 60 to emergency situation. A limit of 40 mSv/year is suggested to the radiation from nuclear reactor at the place where stuffs of lunar base is easily accessible. The suggested value is 10% of the proposed yearly limit to the natural radiation in space. A one-dimensional analysis on the shielding effect of the regolish covering SPECTRA-L showed that the neutron dose equivalent rate of the reactor is attenuated to the background level of space at a point about 10 m apart from the reactor center and to that on the earth at about 12 m. Lastly, it is emphasized that the exposure to radiation should be reduced by the following methods. (1)Automatic operating system of the plant. (2)Development of materials for easy-working protection clothes and radiation shield using magnetism ln the living area. (3)Minimum exposure to radiation, especially in the living area, following the spirit of ALARA. (4)Underground base and underground transport routes to other facilities.

JAEA Reports

Conceptual design study of transportable reactor SPECTRA-L for lunar base (I); Safety evaluation of launch fallure accldent

Nomura, Norio; ;

PNC TN9410 91-100, 73 Pages, 1991/03

PNC-TN9410-91-100.pdf:1.73MB

Liquid Metal cooled Fast Reactor is a good candidate of a large-scale energy supply system to a manned lunar base because of the compact structure and being free of refueling. A 300 kWe transportable reactor SPECTRA-L is being studied as the power source on the moon. Because the reactor system is launched by a launch vehicle, safety evaluation is necessary to the launch failure accident. We examined (i) the possibility of recriticality, and (ii) the influence of nuclear fuel leakage to the environment in the case of reactor damage. The followings are the main findings of this preliminary study. (1)Under-criticality is maintained even the reactor falls into water or crashes against the earth. (2)The external exposure dose by a radiation cloud of released fuel is less than the natural radiation. (3)The internal exposure dose by inhaling the cloud is less than 1 mSv/year which is a reco㎜ended dose limit to the public. (4)The surface radioactive density increased of land by the accident is be less than 0.4 Bq/square centimeter, which is a limit for things contaminated by alpha radiation to be transported from a controlled area, regardless the whether. This estimation is based on a leakage of five percent fuel, but the exposure dose would be far less than the estimated from the following reasons. (1)Nuclear fuel is in a ceramic form called pellets, and they are inserted in fuel cladding, and contained in the coolant material (metal) and the reactor vessel. (2)The nuclear fuel does not break into fragment as aerosol by the accident.

JAEA Reports

None

; Ishida, Junichiro; ; ; ; Nomura, Norio

PNC TN9080 91-002, 31 Pages, 1990/12

PNC-TN9080-91-002.pdf:0.6MB

None

27 (Records 1-20 displayed on this page)