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Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri. A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:9 Percentile:88.96(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2018

Nakano, Masanao; Fujii, Tomoko; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yamada, Ryohei; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; Kikuchi, Masaaki*; et al.

JAEA-Review 2019-045, 120 Pages, 2020/03

JAEA-Review-2019-045.pdf:2.54MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2018. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2017

Nakano, Masanao; Fujita, Hiroki; Mizutani, Tomoko; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yamada, Ryohei; Yoshii, Hideki*; Hiyama, Yoshinori*; Otani, Kazunori*; et al.

JAEA-Review 2018-028, 120 Pages, 2019/02

JAEA-Review-2018-028.pdf:2.69MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2017. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2016

Nakano, Masanao; Fujita, Hiroki; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yoshii, Hideki*; Hiyama, Yoshinori*; Otani, Kazunori*; Kikuchi, Masaaki*; Sakauchi, Nobuyuki*; et al.

JAEA-Review 2017-037, 119 Pages, 2018/03

JAEA-Review-2017-037.pdf:2.58MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and bylaw of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2016. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2015

Nakano, Masanao; Fujita, Hiroki; Kono, Takahiko; Nagaoka, Mika; Inoue, Kazumi; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; Kikuchi, Masaaki*; Sakauchi, Nobuyuki*; et al.

JAEA-Review 2017-001, 115 Pages, 2017/03

JAEA-Review-2017-001.pdf:3.57MB

Based on the regulations (the safety regulation of Tokai reprocessing plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and bylaw of Ibaraki prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2015. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2014

Watanabe, Hitoshi; Nakano, Masanao; Fujita, Hiroki; Kono, Takahiko; Inoue, Kazumi; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; Kikuchi, Masaaki*; Sakauchi, Nobuyuki*; et al.

JAEA-Review 2015-030, 115 Pages, 2015/12

JAEA-Review-2015-030.pdf:25.28MB

Based on the regulations (the safety regulation of Tokai reprocessing plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and bylaw of Ibaraki prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2014. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

Journal Articles

The Change of water treatment reagent for boiler operation

Ishiyama, Toru; Kawasaki, Ichio; Asano, Naoki

Boira Kenkyu, (366), p.9 - 15, 2011/04

The Hydrazine has been used for water treatment of the boiler in general industry scene. It has been used in NCL from 1995, too. Ministry of Health, Labour and Welfare do announcement about using hydrazine in 2006, and NCL began to try operation without hydrazine. Hydrazine was replaced to the other reagent that was selected based on the result of a research and an evaluation. Therefore safeguard of environment and labour was carried on by new operation method of water treatment from 2010. This report was described about the result of research and development.

Journal Articles

Propagation behaviour of general and localised corrosion of carbon steel in simulated groundwater under aerobic conditions

Taniguchi, Naoki; Suzuki, Hiroyuki; Kawasaki, Manabu; Naito, Morimasa; Kobayashi, Masato*; Takahashi, Rieko*; Asano, Hidekazu*

Corrosion Engineering, Science and Technology, 46(2), p.117 - 123, 2011/04

 Times Cited Count:9 Percentile:51.86(Materials Science, Multidisciplinary)

Carbon steel has been selected as one of the candidate materials for overpack for geological disposal of high-level radioactive waste in Japan. Corrosion of carbon steel is divided into two types; general corrosion and localized corrosion. In this study, propagation behaviors of general and localized corrosions (pitting corrosion and crevice corrosion) were investigated by immersion tests of carbon steel under aerobic condition. The results of the immersion tests showed that the growth rate of corrosion was strongly dependent on the environmental condition and steel type, but the upper limit of pitting factor (the ratio of the maximum corrosion depth and the average corrosion depth) was approximately determined by only average corrosion depth. Based on these experimental data and literature data, an empirical model that predicts the maximum corrosion depth of an overpack from average corrosion depth was developed by applying the extreme value statistical analysis using the Gumbel distribution function.

Journal Articles

Long term integrity of overpack closure weld for HLW geological disposal, 2; Corrosion properties under anaerobic conditions

Kobayashi, Masato*; Yokoyama, Yutaka*; Takahashi, Rieko*; Asano, Hidekazu*; Taniguchi, Naoki; Naito, Morimasa

Corrosion Engineering, Science and Technology, 46(2), p.212 - 216, 2011/04

 Times Cited Count:4 Percentile:32.74(Materials Science, Multidisciplinary)

The corrosion behaviour of a carbon steel weld joint under anaerobic conditions was investigated to estimate the long-term integrity of the carbon steel overpack. The weld specimens in this study were produced using three welding methods: GTAW, GMAW and EBW. General corrosion was observed for each immersion specimen and the weld joint corrosion rate was the same as or less than that of the base metal. The hydrogen concentration absorbed during immersion testing was less than 2.48$$times$$10$$^{-5}$$ mol kg[Fe]$$^{-1}$$(0.05 ppm) after three years, a value regarded as having little influence on hydrogen embrittlement. The susceptibility to hydrogen embrittlement was highest in the base metal, suggesting that there was little adverse effect on the weld joint from welding. The welded carbon steel overpack is assumed to maintain its resistance to corrosion as a disposal container for the expected lifetime under anaerobic underground conditions.

Journal Articles

The Development of boiler operation method; Investigation of deoxidizer for hydrazine

Ishiyama, Toru; Kawasaki, Ichio; Asano, Naoki

Boira, Nyusu, (735), P. 6, 2010/09

The Hydrazine has been used for water treatment of the boiler in general industry scene. It has been used in NCL from 1995, too. Ministry of Health, Labour and Welfare do announcement about using hydrazine in 2006, and NCL began to try operation without hydrazine. Hydrazine was replaced to the other reagent that was selected based on the result of a research and an evaluation. Therefore safeguard of environment and labour was carried on by new operation method of water treatment from 2010. This report was described about the result of research and development.

JAEA Reports

Management of energy-save and environment on the boiler system

Ishiyama, Toru; Asano, Naoki; Kawasaki, Ichio

JAEA-Technology 2009-066, 79 Pages, 2010/02

JAEA-Technology-2009-066.pdf:15.64MB

Tokai Utility Center (TUC) is the facility that products and feeds steam for Tokai Reprocessing Plant (TRP), Plutonium Fuel Production Facility (PFPF), etc. The boiler system needs the management based on the law of "Industrial safety and Health Act" and "Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors". In this situation, activity of preservation of environment and energy-save are carried out by means of the improvement of steam generation process and the change of additive to water. Quality assurance procedure has been applied in order to improve the boiler operation continuously. This report describes about various activities of the management, the environment, the energy-saving, and a future action.

JAEA Reports

Study on the corrosion assessment of overpack welds, 4 (Joint research)

Yokoyama, Yutaka*; Mitsui, Hiroyuki*; Takahashi, Rieko; Taniguchi, Naoki; Asano, Hidekazu*; Naito, Morimasa; Yui, Mikazu

JAEA-Research 2008-072, 232 Pages, 2008/10

JAEA-Research-2008-072.pdf:45.2MB

It is possible that the corrosion resistance at the overpack welds is different from that at base metal due to the differences of material properties. In this study, corrosion behavior of welded joint for carbon steel was compared with base metal using the specimens taken from welded joint model fabricated by TIG (Tungsten Arc Welding, GTAW), MAG (Gas Metal Arc Welding, GMAW) and EBW (Electron Beam Welding) respectively. The results of these corrosion tests indicated that the corrosion resistance to general corrosion, pitting corrosion and crevice corrosion at welded metal of TIG and MAG was inferior to base metal. No deterioration of corrosion resistance was observed in any corrosion modes for EBW, which does not need filler material. Neither the base metals nor the welds is not susceptible to SCC under the carbonate concentration near that of the disposal environment.

JAEA Reports

Study on the corrosion assessment of overpack welds, 3 (Joint research)

Mitsui, Hiroyuki*; Takahashi, Rieko*; Taniguchi, Naoki; Otsuki, Akiyoshi*; Asano, Hidekazu*; Yui, Mikazu

JAEA-Research 2006-080, 322 Pages, 2006/12

JAEA-Research-2006-080.pdf:90.52MB

There is some possibility that the corrosion resistance of overpack welds is different from that of base metal due to the differences of material properties. In this study, corrosion behavior of welded joint for carbon steel was compared with base metal using the specimens taken from welded joint model fabricated by TIG, MAG and EBW respectively. The corrosion tests were performed for following four items. (1) Passivation behavior and corrosion type, (2) Propagation of general corrosion, pitting corrosion and crevice corrosion under aerobic condition, (3) Stress corrosion cracking susceptibility, (4) Propagation of general corrosion and hydrogen embrittlement under anaerobic condition. The results of these corrosion tests indicated that the corrosion resistance of welded metal by TIG and MAG was inferior to base metal for general corrosion, pitting corrosion and crevice corrosion. It was implied that the filler materials used for welding affected the corrosion resistance. No deterioration of corrosion resistance was observed in any corrosion modes for EBW, which does not need filler material. The susceptibility to stress corrosion cracking of welded metal and heat affected zone was lower than that of base metal.

JAEA Reports

Study on the corrosion assessment of overpack welds, 2 (Joint research)

Mitsui, Hiroyuki*; Taniguchi, Naoki; Otsuki, Akiyoshi*; Kawakami, Susumu; Asano, Hidekazu*; Yui, Mikazu

JAEA-Research 2006-031, 88 Pages, 2006/06

JAEA-Research-2006-031.pdf:4.72MB

The corrosion experiments for welded carbon steel were planed to contribute to an assessment of long-term integrity of carbon steel overpack welds considering corrosion damage specific to overpack welds. Based on this plan, electrochemical tests for welded carbon steel using the samples welded by EBW and TIG were carried out, and the corrosion behavior of welded zone was compared with that of base metal. The results of anodic polarization tests in 0.01M and 0.1M carbonate aqueous solutions for base metal, heat affected zone and welded metal indicated that; -As for EBW, the anodic polarization curves were not affected by welding although the metallurgical structures vary with base metal, heat affected zone and welded metal. -As for TIG, the current density of welded metal was larger than that of base metal and of heat affected zone, and local dissolution with immediate increase in current density was observed in 0.01M-pH10 carbonate aqueous solution.

Journal Articles

Research activities for development of CTBT-related technologies in JAERI

Shinohara, Nobuo; Asano, Yoshie; Hirota, Naoki*; Hokida, Takanori; Inoue, Yoji; Kumata, Masahiro; Nakahara, Yoshinori*; Oda, Tetsuzo*; Uchikoshi, Takako*; Yamamoto, Yoichi

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 3 Pages, 2005/10

Research activities of JAERI related to the CTBT verification regime are presented in the International Conference. The subjects of this presentation are (1) an overview of the CTBT verification regime, (2) construction and operation of the radionuclide monitoring stations of Okinawa (RN37) and Takasaki (RN38) and the certified radionuclide laboratory (RL11), and (3) preparation of the National Data Center at Tokai (JAERI NDC) for radionuclide data. The RN38 station has been certified by the CTBTO/PrepCom and sending the measured data every day. The infrastructures and operational manuals for RN37 and RL11 are now preparing for their operations. The JAERI NDC has experimentally analyzed and evaluated the radionuclide data from all over the world through International Data Center (IDC). As an example of the JAERI NDC works, atmospheric dispersion backtracking system has been developing by using WSPEEDI (Worldwide Version of System for Prediction of Environmental Emergency Dose Information) code to estimate a source location of radionuclide release by nuclear explosion/accident.

JAEA Reports

Study on the corrosion assessment of overpack welds (Joint research)

Asano, Hidekazu*; Taniguchi, Naoki; Kawakami, Susumu; Yui, Mikazu

JNC TY8400 2004-008, 30 Pages, 2004/04

JNC-TY8400-2004-008.pdf:2.6MB

It is necessary to understand the corrosion behavior of welds in overpack for ensuring the quality of welding, and improving the long term reliability of overpack. In this study, the method for evaluation of corrosion of welded joint was planned by Radioactive Waste Management Funding and Research Center (RWMC) and Japan Nuclear Cycle Development Institute (JNC). RWMC has been developed the overpack welding techniques and the inspection techniques of welded joint. In this study, RWMC provided the information on current status of welding techniques for applying the overpacks. Electron Beam Welding (EBW) and Tungsten Inert Gas Welding (TIG) were prospected to be available for overpack and the results of the examinations to find adequate conditions for overpack welding were presented. JNC has been studying the corrosion behavior and lifetime of overpack, and provided the information on corrosion of welded carbon steel under repository conditions. According to immersion tests by JNC, it was shown that corrosion rates of carbon steel welded by EBW were almost equal to those of base metal under anaerobic condition, which is representative condition in repository environment. Based on the information provided by RWMC and JNC, the research subjects on the corrosion of welds were extracted and the concept of corrosion tests for overpack welds was given.

Oral presentation

Development of the technology for the melter dismantling, 2

Kozaka, Tetsuo; Asano, Naoki; Ito, Yoshiyuki; Komori, Masanori

no journal, , 

no abstracts in English

Oral presentation

Study on stress corrosion cracking susceptibility of welded joint of carbon steel overpack

Mitsui, Hiroyuki*; Takahashi, Rieko*; Otsuki, Akiyoshi*; Asano, Hidekazu*; Taniguchi, Naoki; Yui, Mikazu

no journal, , 

The slow strain rate tests(SSRT) of carbon steel were performed in sodium carbonate-sodium-bicarbonate aqueous solution to acquire knowlwdges regarding susceptibility to stress corrosion cracking of welded joint of carbon steel overpack for high-level radioiactive waste disposal. The specimens were taken from thick cylindrical sample welded by TIG and EBW, and then SSRT tests were applied to the each of specimens of base metal, heat affected zone and welded metal. Based on the results, the susceptibility to stress corrosion cracking of welded joint of carbon steel overpack was evaluated.

Oral presentation

Corrosion behavior of the weld zone of carbon steel overpack for HLW final disposal

Yokoyama, Yutaka*; Mitsui, Hiroyuki*; Takahashi, Rieko*; Otsuki, Akiyoshi*; Asano, Hidekazu*; Taniguchi, Naoki; Yui, Mikazu

no journal, , 

In Japan, carbon steel is one of the candidate materials for the disposal container (overpack) for high-level radioactive waste (HLW). Overpack seals vitrified waste and is required to isolate it from contact with groundwater for 1,000 years in Japan's waste management program. After overpack is placed in a deep underground repository, it is presumed that it will be exposed to environmental conditions which include lithospheric pressure from bedrock, hydrostatic pressure from groundwater and swelling pressure of the buffer material as mechanical forces and contact with groundwater as chemical conditions that may induce corrosion. Therefore, the wall thickness of overpack is designed with consideration for mechanical strength and corrosion property so that it can maintain its integrity for 1000 years. On the other hand, the overpack is enclosed by welding. With regard to the assessment of the applicability of welding techniques to the overpack, it is important to confirm the long-term integrity of the weld joint from the aspects of mechanical strength and corrosion property, too. In this study, the corrosion behavior of weld joints, which were provided by TIG (GTAW), MAG (GMAW) and EBW (Electron Beam Welding), was investigated by immersion tests under the aerobic conditions considering environment at the early stage of the repository.

Oral presentation

Assessment of corrosion behavior of carbon steel overpack weld in oxidizing environment

Yokoyama, Yutaka*; Takahashi, Rieko*; Asano, Hidekazu*; Taniguchi, Naoki; Naito, Morimasa

no journal, , 

In order to clarify the corrosion behavior of overpack weld at the initial stage of repository, immersion tests were carried out in oxidizing environment and following results were obtained;(1) Selective corrosion was prone to occur at welded metal of TIG and MAG welding. It is possible that the welded metal has affected by the composition in filler material used in welding and by the change of microstructure at welded zone. (2) According to the results of extreme value statistical analysis, estimated corrosion depths by the selective corrosion at welded metal did not exceed the maximum corrosion depth evaluated in the past lifetime assessment of overpack.

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