Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 41

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Magnetic Bragg peak enhancement under ultrasound injection

Shamoto, Shinichi*; Akatsu, Mitsuhiro*; Matsuura, Masato*; Kawamura, Seiko; Harii, Kazuya*; Ono, Masao*; Chang, L.-J.*; Ito, Takashi; Nemoto, Yuichi*; Ieda, Junichi

Physical Review Research (Internet), 4(1), p.013245_1 - 013245_7, 2022/03

Ultrasound injection effect on a magnetic Bragg peak of yttrium iron garnet has been studied by quasielastic neutron scattering. The magnetic Bragg peak is vastly enhanced with decreasing temperature. The energy width increases proportionally to the square root of the sample temperature increase induced by the ultrasound injection. Because the magnetic Bragg peak is enhanced by the lattice vibration, the enhancement is expected to relate to the spin-lattice coupling closely. An observed sharp drop above 100 K in the longitudinal mode suggests the degradation of the spin-lattice coupling. It is consistent with the decline of spin Seebeck effect with increasing temperature above 100 K, proving the degradation mechanism by the spin-lattice coupling.

Journal Articles

Development of an integrated computer code system for analyzing irradiation behaviors of a fast reactor fuel

Uwaba, Tomoyuki; Nemoto, Junichi*; Ito, Masahiro*; Ishitani, Ikuo*; Doda, Norihiro; Tanaka, Masaaki; Otsuka, Satoshi

Nuclear Technology, 207(8), p.1280 - 1289, 2021/08

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Computer codes for irradiation behavior analysis of a fuel pin and a fuel pin bundle and for coolant thermal hydraulics analysis were coupled into an integrated code system. In the system, each code provides data required by other codes and the analyzed results are shared among them. The system allows for the synthesizing of analyses of thermal, chemical and mechanical behaviors in a fuel subassembly under irradiation. A test analysis was made for a fuel subassembly containing a mixed oxide fuel pin bundle irradiated in a fast reactor. The results of the analysis were presented with transverse cross-sectional images of the fuel subassembly and three-dimensional images of a fuel pin and fuel pin bundle models. For detailed evaluation, various irradiation behaviors of all fuel pins in the subassembly were analyzed and correlated with irradiation conditions.

Journal Articles

Ultralow-energy magnon anomaly in yttrium iron garnet

Shamoto, Shinichi; Yasui, Yukio*; Matsuura, Masato*; Akatsu, Mitsuhiro*; Kobayashi, Yoshiaki*; Nemoto, Yuichi*; Ieda, Junichi

Physical Review Research (Internet), 2(3), p.033235_1 - 033235_6, 2020/08

Ultralow energy magnon in yttrium iron garnet crystal has been studied by inelastic neutron scattering in an energy range from 10 to 45 $$mu$$eV. When a magnetic field of about 0.1 T is applied along [111], ultralow energy magnon anomaly is found at 10 K.

Journal Articles

Computer code analysis of irradiation performance of axially heterogeneous mixed oxide fuel elements attaining high burnup in a fast reactor

Uwaba, Tomoyuki; Yokoyama, Keisuke; Nemoto, Junichi*; Ishitani, Ikuo*; Ito, Masahiro*; Pelletier, M.*

Nuclear Engineering and Design, 359, p.110448_1 - 110448_7, 2020/04

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Coupled computer code analyses of irradiation performance of axially heterogeneous mixed oxide (MOX) fuel elements with high burnup in a fast reactor were conducted. Post-irradiation experiments revealed local concentration of Cs near the interfaces between MOX fuel and blanket columns including the internal blanket of the fuel elements as well as an increase in their cladding diameters. The analyses indicated that the local Cs concentration occurred as a result of Cs axial migration from the MOX fuels toward the blanket pellets near the interfaces. Swelling of the blanket pellets induced by the formation of low-density Cs-U-O compound was not sufficient to cause pellet-to-cladding mechanical interaction (PCMI). The PCMI analyzed in the MOX fuel column regions was insignificant, and the cladding diameter increases were caused mainly by void swelling in cladding and irradiation creep due to fission gas pressure.

Journal Articles

Neutron scattering studies on short- and long-range layer structures and related dynamics in imidazolium-based ionic liquids

Nemoto, Fumiya*; Kofu, Maiko; Nagao, Michihiro*; Oishi, Kazuki*; Takata, Shinichi; Suzuki, Junichi*; Yamada, Takeshi*; Shibata, Kaoru; Ueki, Takeshi*; Kitazawa, Yuzo*; et al.

Journal of Chemical Physics, 149(5), p.054502_1 - 054502_11, 2018/08

 Times Cited Count:12 Percentile:72.95(Chemistry, Physical)

Journal Articles

Coupled computer code study on irradiation performance of a fast reactor mixed oxide fuel element with an emphasis on the fission product cesium behavior

Uwaba, Tomoyuki; Nemoto, Junichi*; Ishitani, Ikuo*; Ito, Masahiro*

Nuclear Engineering and Design, 331, p.186 - 193, 2018/05

 Times Cited Count:3 Percentile:45.99(Nuclear Science & Technology)

A computer code for the analysis of the overall irradiation performance of a fast reactor mixed-oxide (MOX) fuel element was coupled with a specialized code for the analysis of fission product cesium behaviors in a MOX fuel element. The coupled code system allowed for the analysis of the radial and axial Cs migrations, the generation of Cs chemical compounds and fuel swelling due to Cs-fuel-reactions in association with the thermal and mechanical behaviors of the fuel element. The coupled code analysis was applied to the irradiation performance of a fast reactor MOX fuel element attaining high burnup for discussion on the axial distribution of Cs, fuel-to-cladding mechanical interaction owing to the Cs-fuel-reactions by comparing the calculated results with post irradiation examinations.

Journal Articles

Development of a new detector system to evaluate position and activity of plutonium particles in nasal cavities

Morishita, Yuki; Yamamoto, Seiichi*; Momose, Takumaro; Kaneko, Junichi*; Nemoto, Norio

Radiation Protection Dosimetry, 178(4), p.414 - 421, 2018/03

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

Plutonium dioxide (PuO$$_{2}$$) is used to fabricate a mixed oxide fuel for fast breeder reactors. When a glove box containing PuO$$_{2}$$ fails, such as by rupture of a glove or a vinyl bag, airborne contamination of plutonium (Pu) can occur. If the worker inhale PuO$$_{2}$$ particles, they deposit in the lung and cause lung cancer. The nasal smear and nose blow methods are useful for checking workers for PuO$$_{2}$$ intake in the field. However, neither method can evaluate the quantitative activity of Pu. No alpha-particle detector that can be used for direct measurements in the nasal cavity has been developed. Therefore, we developed a nasal monitor capable of directly measuring the activity of Pu in the nasal cavity to precisely evaluate the internal exposure dose of a worker. Prismatic-shaped 2$$times$$2 acrylic light guides were used to compose a detector block, and a ZnS(Ag) scintillator was adhered to the surface of these light guides. Silicon photomultiplier (SiPM) arrays with 8$$times$$8 channels were used as a photodetector. Actual PuO$$_{2}$$ particles were measured using the nasal monitor. The nasal monitor could be directly inserted in the nasal cavities. The activity distribution of Pu was obtained by the nasal monitor. The average efficiencies in 4$$pi$$ were 11.43% and 11.58% for the left and right nasal cavities, respectively. The effect of $$gamma$$ and $$beta$$ rays on the detection of the alpha particles of Pu was negligible. The difference in the measured Pu activity between the ZnS(Ag) scintillation counter and the nasal monitor was within 4.0%. The developed nasal monitor can solve the uncertainty problem encountered with the nasal smear and the nose blow methods. We expect this monitor to be useful for accurately estimating the internal exposure dose of workers.

Journal Articles

Flexible alpha camera for detecting plutonium contamination

Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Nemoto, Norio

Radiation Measurements, 103, p.33 - 38, 2017/08

 Times Cited Count:8 Percentile:75.2(Nuclear Science & Technology)

Nuclear fuel materials, such as uranium and plutonium (Pu), are handled at nuclear fuel facilities. There are a contamination source of Pu in tight spaces that cannot be directly measured by a ZnS(Ag) scintillation detector, such as interspace between a glovebox window and a platform, pipe flange, port cover of vinyl bag, and filter interspaces. Therefore, we developed a new imaging detector called a flexible alpha camera that enables to identify the Pu contamination for tight spaces at work sites. The thickness of the flexible alpha camera was only $$sim$$1/5 of the ZnS(Ag) scintillation detector, and its efficiency for 4-pi direction was 42.7% for 5.5-MeV alpha particles. Minimal detectable activity (MDA) was 0.014 Bq. Four types of PuO$$_{2}$$ sample, removed from a duct, Bag-In/Bag-Out port, glovebox glove, and vinyl sheet, were measured by the flexible alpha camera and the PuO$$_{2}$$ particle was automatically identified. Using the flexible alpha camera, the Pu contamination source can be quickly detected, preventing the spread of contamination.

Journal Articles

Development of a mixed oxide fuel pin performance analysis code "CEDAR"; Models and analyses of fuel pin irradiation behavior

Uwaba, Tomoyuki; Mizuno, Tomoyasu; Nemoto, Junichi*; Ishitani, Ikuo*; Ito, Masahiro*

Nuclear Engineering and Design, 280, p.27 - 36, 2014/12

 Times Cited Count:8 Percentile:60.89(Nuclear Science & Technology)

A deterministic computer code CEDAR has been developed to analyze irradiation behaviors of a mixed-oxide fuel pellet pin in a FBR. The FEM was incorporated into the mechanical calculation part of the code for properly analyzing stress-strain status in the fuel pellet and cladding, and mechanical interaction between the fuel pellet and cladding. The code features mechanistic analyses of irradiation behaviors of a fuel pin by integrating a lot of models to analyze major irradiation phenomena, thus expressing actual fuel pin irradiation behaviors. Analysis capabilities of the code were validated by calculations of fuel pellet temperatures, fractional fission gas releases of fuel pins and fuel pin cladding diametral strain profiles. The mechanisms of the fuel pin irradiation behaviors such as redistribution of Americium, PCMI and JOG formation were interpreted from the code analyses for the actual irradiation test fuel pins.

Journal Articles

Verification of the FBR fuel bundle-duct interaction analysis code BAMBOO by the out-of-pile bundle compression test with large diameter pins

Uwaba, Tomoyuki; Ito, Masahiro*; Nemoto, Junichi*; Ichikawa, Shoichi; Katsuyama, Kozo

Journal of Nuclear Materials, 452(1-3), p.552 - 556, 2014/09

 Times Cited Count:1 Percentile:10.7(Materials Science, Multidisciplinary)

The BAMBOO code was verified by results for the out-of-pile bundle compression test with large diameter pin bundle deformation under the bundle-duct interaction (BDI) condition. The pin diameters of were 8.5 mm and 10.4 mm, which are targeted as preliminary fuel pin diameters for the upgraded core of the prototype FBR and for demonstration and commercial FBRs studied in the FaCT project. In the bundle compression test, bundle cross-sectional views were obtained from X-ray computer tomography (CT)images and local parameters of bundle deformation were measured by CT image analyses. In the verification, calculation results of bundle deformation obtained by the BAMBOO code analyses were compared with the experimental results from the CT image analyses. The comparison showed that the BAMBOO code reasonably predicts deformation of large diameter pin bundles under the BDI condition by assuming that pin bowing and cladding oval distortion are the major deformation mechanisms.

JAEA Reports

Evaluating techniques and phenomena of Stress Corrosion Cracking (SCC) in Light Water Reactors (LWRs); SCC evaluating techniques for predicting core internal and pipe aging of LWRs, technical data collection (Contract research)

Yamamoto, Masahiro; Kato, Chiaki; Sato, Tomonori; Nakano, Junichi; Ugachi, Hirokazu; Tsukada, Takashi; Kaji, Yoshiyuki; Tsujikawa, Shigeo*; Hattori, Shigeo*; Yoshii, Tsuguyasu*; et al.

JAEA-Review 2012-007, 404 Pages, 2012/03

JAEA-Review-2012-007.pdf:36.72MB

There are many LWRs which have been operated for more than 20 years in Japan and it is expected that technique corresponding to aging plants are necessary established for safety operation in LWRs. A lot of troubles related to SCC are reported and many investigations are concerned with SCC mechanism and technical evaluation. In this paper, those research data were collected as possible widely and reviewed systematically. Current circumstances concerned with SCC in LWRs were reviewed specifically as follows: SCC incidents, SCC evaluation methods for crack initiation and propagation, the investigations concerned with SCC mechanism and monitoring technique for corrosive environment. Influences with reactor types (BWR, PWR), materials (stainless steels, Ni alloys) and SCC evaluating methods (laboratories and actual plants) were summarized as graphs and tables easy to understand in common/difference points concerned with SCC. From these arranged results, future themes were considered and remarked SCC phenomenon was summarized in actual plants. As for SCC evaluations under the accelerate conditions in the laboratory test, it was suggested that a computational prediction and modeling including statistical technique and microscopic analysis in crack initiation were important. Furthermore it was suggested that monitoring techniques predicting SCC initiation and grasping plant circumstance in operation and feasibility in actual plants were important.

Journal Articles

SCC susceptibility of cold-worked stainless steel with minor element additions

Nakano, Junichi; Nemoto, Yoshiyuki; Tsukada, Takashi; Uchimoto, Tetsuya*

Journal of Nuclear Materials, 417(1-3), p.883 - 886, 2011/10

 Times Cited Count:1 Percentile:11.72(Materials Science, Multidisciplinary)

To examine the effects of minor elements on stress corrosion cracking (SCC) susceptibility of low carbon stainless steels with work hardened layer, a high purity type 304 stainless steel was fabricated and minor elements, Si, S, P, C or Ti, were added. Work hardened layer was introduced by shaving on the surface of stainless steels. The specimens were exposed to a boiling 42% MgCl$$_{2}$$ solution for 20 hours and the number and the length of initiated cracks were examined. SCC susceptibility of the specimen with P was the highest and that of the specimen with C was the lowest in all specimens. By magnetic force microscope examination, magnetic phase expected to be martensitic phase was detected near surface. Since corrosion resistance of martensite is lower than that of austenite, the minor elements additions would affect SCC susceptibility through the amount of the transformed martensite, i.e. austenite stability.

Journal Articles

Examination of relation between IASCC susceptibility and magnetic property

Takaya, Shigeru; Nagae, Yuji; Yoshitake, Tsunemitsu; Nemoto, Yoshiyuki; Nakano, Junichi; Ueno, Fumiyoshi; Aoto, Kazumi; Tsukada, Takashi

E-Journal of Advanced Maintenance (Internet), 1(1), p.44 - 51, 2009/05

As the result of comparing the magnetic flux density and the IASCC susceptibility evaluated by SSRT test on neutron irradiated model alloys, it was shown that there is the relation without depending on dose level and chemical compositions as long as the contribution of neutron irradiation to SCC was seen. Furthermore, measuring the magnetic flux density of unirradiated simulated degraded materials indicates that not only change in chemical compositions but also some defects are needed for the magnetic flux density to increase. These results show the possibility of non-destructive estimation of susceptibility to IASCC by measuring magnetic flux density.

Journal Articles

In-situ SCC observation of thermally-sensitized and cold-worked type 304 stainless steel irradiated to a neutron fluence of 1$$times$$10$$^{25}$$n/m$$^{2}$$

Nakano, Junichi; Nemoto, Yoshiyuki; Miwa, Yukio; Usami, Koji; Tsukada, Takashi; Hide, Koichiro*

Journal of Nuclear Materials, 386-388, p.281 - 285, 2009/04

 Times Cited Count:3 Percentile:26.15(Materials Science, Multidisciplinary)

Crack initiation and crack growth processes of irradiation assisted stress corrosion cracking on stainless steels were studied by slow strain rate testing in oxygenated high temperature water at 561 K. In-situ observation was carried out during SSRT. Specimens of type 304 stainless steel were subjected to a solution annealing (SA), a thermally sensitization (TS), or a cold working (CW) and irradiated to 1.0$$times$$10$$^{25}$$ n/m$$^{2}$$ (E $$>$$ 1 MeV) at 323 K in the Japan Material Testing Reactor (JMTR). Crack initiations were observed before the maximum stress would be reached for the CW material in in-situ observation. In fracture surface examination, the TS material exhibited almost intergranular stress corrosion cracking while mixtures of transgranular stress corrosion cracking and ductile dimple fracture were observed for the SA and the CW materials.

Journal Articles

Development of a performance analysis code for vibro-packed MOX fuels

Ishii, Tetsuya; Nemoto, Junichi*; Asaka, Takeo; Sato, Seichi*; Mayorshin, A.*; Shishalov, O.*; Kryukov, F.*

Journal of Nuclear Science and Technology, 45(4), p.263 - 273, 2008/04

 Times Cited Count:1 Percentile:10.92(Nuclear Science & Technology)

In order to develop a vibro-packed MOX fuel performance analysis code, thermochemical and mechanical properties of the vibro-packed fuels were incorporated into a pellet type fuel performance analysis code CEDAR. Calculations were made by the developed code on a vibro-packed MOX fuel pin irradiated at BN-600 in Russia. Since the calculated results agreed well with the behaviors obtained from the experimental data, it can be concluded that the code was well modeled and qualitatively validated.

Journal Articles

PIE technologies for the study of stress corrosion cracking of reactor structural materials

Ugachi, Hirokazu; Nakano, Junichi; Nemoto, Yoshiyuki; Kondo, Keietsu; Miwa, Yukio; Kaji, Yoshiyuki; Tsukada, Takashi; Kizaki, Minoru; Omi, Masao; Shimizu, Michio

JAEA-Conf 2006-003, p.253 - 265, 2006/05

Irradiation assisted stress corrosion cracking (IASCC) is one of the critical concerns when stainless steel components have been in service in the light water reactors (LWRs) for a long period. In general, IASCC can be reproduced on the materials irradiated over a certain threshold fluence level of fast neutron by the post-irradiation examinations (PIEs) at hot laboratories. On the other hand, recently in the Japanese boiling water reactor (BWR) power plants, many incidents of stress corrosion cracking (SCC) of structural material such as the reactor core shrouds and primary loop recirculation (PLR) system piping were reported. In order to investigate the cause of SCC, PIEs at hot laboratories were carried out on the sample material extracted from BWR power plants. SCC studies require various kind of PIE techniques, because the SCC is caused by a complicated synergistic effects of stress and chemical environment on material that suffered degradations by irradiation and/or thermal aging. In this paper, we describe the PIE techniques adopted recently for our SCC studies, especially the crack growth measurement, uniaxial constant load (UCL) tensile test method, in-situ observation during slow strain rate test (SSRT) and several metallurgical test techniques using the FEtype transmission electron microscopy (FE-TEM), focused ion beam (FIB) processing technique, three Dimensional Atom Probe (3DAP) analysis and atomic force microscopy (AFM).

JAEA Reports

JNC-JAERI united research report; A Study on degradation of structural materials under irradiation environment in nuclear reactors (Joint research)

Hoshiya, Taiji; Ueno, Fumiyoshi*; Takaya, Shigeru; Nagae, Yuji; Nemoto, Yoshiyuki*; Miwa, Yukio*; Aoto, Kazumi; Tsukada, Takashi*; Abe, Yasuhiro; Nakamura, Yasuo; et al.

JNC TY9400 2004-026, 53 Pages, 2004/10

JNC-TY9400-2004-026.pdf:22.07MB

Japan Nuclear Cycle Development Institute (JNC) and Japan Atomic Energy Research Institute (JAERI) have started a JNC-JAERI united research program cooperatively in 2003, which has been aimed for efficient progress and synergistic effect on the research activities of both Institutes in order to lead the facing task of unification between JNC and JAERI. This study has been chosen one of the united research themes, and the purpose of it is to clarify damage mechanism of structural materials under irradiation, and then to develop the methods for damage evaluation and detection in earlier stage of progressing process of damage. In fiscal year 2003, magnetic flux density distribution (JNC) and micro-corrosion (JAERI) measurement apparatus were newly developed and equipped in Hot Facilities in two Institutes, respectively. These apparatus were designed and produced in consideration of radiation resistance and remote-controlled operation to equip in hot cells. We will start the study on neutron irradiation damage by employing the two apparatus as the next step.

JAEA Reports

JNC-JAERI united research report; A Study on degradation of structural materials under irradiation environment in nuclear reactors (Joint research)

Hoshiya, Taiji*; Ueno, Fumiyoshi; Takaya, Shigeru*; Nagae, Yuji*; Nemoto, Yoshiyuki; Miwa, Yukio; Aoto, Kazumi*; Tsukada, Takashi; Abe, Yasuhiro*; Nakamura, Yasuo*; et al.

JAERI-Research 2004-016, 53 Pages, 2004/10

JAERI-Research-2004-016.pdf:22.07MB

Japan Nuclear Cycle Development Institute (JNC) and Japan Atomic Energy Research Institute (JAERI) have started a JNC-JAERI united research program cooperatively in 2003, which has been aimed for efficient progress and synergistic effect on the research activities of both Institutes in order to lead the facing task of unification between JNC and JAERI. This study has been chosen one of the united research themes, and the purpose of it is to clarify damage mechanism of structural materials under irradiation, and then to develop the methods for damage evaluation and detection in earlier stage of progressing process of damage. In fiscal year 2003, magnetic flux density distribution (JNC) and micro-corrosion (JAERI) measurement apparatus were newly developed and equipped in Hot Facilities in two Institutes, respectively. These apparatus were designed and produced in consideration of radiation resistance and remote-controlled operation to equip in hot cells. We will start the study on neutron irradiation damage by employing the two apparatus as the next step.

Journal Articles

Characterization of 316L(N)-IG SS joint produced by hot isostatic pressing technique

Nakano, Junichi; Miwa, Yukio; Tsukada, Takashi; Kikuchi, Masahiko; Kita, Satoshi; Nemoto, Yoshiyuki; Tsuji, Hirokazu; Jitsukawa, Shiro

Journal of Nuclear Materials, 307-311(Part2), p.1568 - 1572, 2002/12

 Times Cited Count:12 Percentile:62.82(Materials Science, Multidisciplinary)

Type 316LN stainless steel of the international thermonuclear experimental reactor (ITER) Grade (316LN-IG SS) is being considered for the first wall/ blanket component. Hot isostatic pressing (HIP) technique is expected for the fabrication of module. To evaluate the integrity and susceptibility to stress corrosion cracking (SCC) of HIPed 316LN-IG SS, tensile tests in vacuum and slow strain rate tests (SSRT) in high temperature water were performed. Specimen with the HIPed joint shows no deterioration of the tensile strength and susceptibility to SCC in oxygenated water. Thermally sensitized specimen with the HIPed joint was low susceptible to SCC in creviced environment. It is concluded that the strength at joint location is as high as that at the base alloy and the joint interface appears integrity.

JAEA Reports

Absolute calibration of the neutron yield measurement on JT-60 Upgrade

Nishitani, Takeo; Takeuchi, Hiroshi; Barnes, C. W.*; Iguchi, Tetsuo*; Nagashima, Akira; Kondoh, Takashi; Sakasai, Akira; Itami, Kiyoshi; Tobita, Kenji; Nagashima, Keisuke; et al.

JAERI-M 91-176, 23 Pages, 1991/10

JAERI-M-91-176.pdf:1.08MB

no abstracts in English

41 (Records 1-20 displayed on this page)