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Journal Articles

Modelling and simulation of source term for sodium-cooled fast reactor under hypothetical severe accident; Primary system/containment system interface source term estimation

Onoda, Yuichi; John Arul, A.*; Klimonov, I.*; Danting, S.*

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Sustainable Clean Energy for the Future (FR22) (Internet), 13 Pages, 2022/04

Journal Articles

Development of effectiveness evaluations technology of the measures for improving resilience of nuclear structures against excessive earthquake

Nishino, Hiroyuki; Onoda, Yuichi; Kurisaka, Kenichi; Yamano, Hidemasa

Proceedings of Asian Symposium on Risk Assessment and Management 2021 (ASRAM 2021) (Internet), 10 Pages, 2021/10

The objective of this study is to develop an effectiveness evaluations technology of the measures for improving resilience of nuclear structures against excessive earthquake by introducing the fracture control concept. After analyzing event tree in previous studies of PRA against earthquake, this study identified sequences of protected loss of heat sink and loss of reactor level induced from excessive earthquake as accident sequences in which improving resilience of nuclear structures become effective. This study focused on important components for safety (e.g., reactor vessel, air coolers, pipes of primary loops in decay heat removal systems, etc.) to be used as countermeasures for improving the resilience. Core damage frequency is selected as an index in evaluating effectiveness of the measures for improving the resilience. Seismic safety margin of the components is assumed to be enlarged when the measures for improving the resilience with the fracture control concept are implemented. Through the trial calculation, reduction effect of the core damage frequency was quantified. The result showed that the measures for improving the resilience are significantly effective for decreasing the core damage frequency in excessive earthquake twice higher than a design basis ground motion. The general concept for the effectiveness evaluations technology was formulated.

Journal Articles

Development of effectiveness evaluations technology of the measures for improving resilience of nuclear structures at ultra high temperature

Onoda, Yuichi; Nishino, Hiroyuki; Kurisaka, Kenichi; Yamano, Hidemasa

Proceedings of Asian Symposium on Risk Assessment and Management 2021 (ASRAM 2021) (Internet), 11 Pages, 2021/10

The effectiveness evaluations technology of the measures for improving resilience by applying a fracture control concept under ultra-high temperature conditions has developed for prototype sodium-cooled fast reactor Monju as a model plant, and the trial evaluation has conducted using this technology in this paper. The important accident sequences to which the fracture control concept is expected to be applied under ultra-high temperature condition are identified by investigating the results of the existing researches of level-2 probabilistic risk assessment for Monju. Accident sequences categorized in protected loss of heat sink and loss of reactor level are both identified as such important accident sequences which has the potential to prevent core damage. This study has developed the technology to evaluate the effectiveness of improving resilience, where the headings which stand for success or failure of the measures to improve resilience are introduced into the event tree, the branch probability of them is set, and the effectiveness of improving resilience is expressed as the reduction of core damage frequency. As a result of the trial evaluation of the effectiveness for the measures to improve resilience, it is confirmed that core damage frequency can be reduced by applying fracture control concept. The branch probability of the measures to improve resilience proposed in this study is tentatively assigned based on the assumption. This value is expected to be quantified by the forthcoming analyses of the integrity for the reactor vessel structure at ultra-high temperature. The technology developed in this study will be applied for the evaluation of improving resilience of the next generation sodium-cooled fast reactor.

Journal Articles

In-vessel thermal-hydraulics analyses of the ASTRID-600MWe reactor with STAR-CCM+ code to supply boundary conditions for mechanical evaluation

Onoda, Yuichi; Chikazawa, Yoshitaka; Nakamura, Hironori*; Barbier, D.*; Dirat, J.-F.*

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

no abstracts in English

Journal Articles

Electron-tracking Compton camera imaging of technetium-95m

Hatsukawa, Yuichi*; Hayakawa, Takehito*; Tsukada, Kazuaki; Hashimoto, Kazuyuki*; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

PLOS ONE (Internet), 13(12), p.e0208909_1 - e0208909_12, 2018/12

AA2018-0639.pdf:2.39MB

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

Imaging of $$^{95m}$$Tc radioisotope was conducted using an electron tracking-Compton camera (ETCC). $$^{95m}$$Tc emits 204, 582, and 835 keV $$gamma$$ rays, and was produced in the $$^{95}$$Mo(p,n)$$^{95m}$$Tc reaction with a $$^{95}$$Mo-enriched target. The recycling of the $$^{95}$$Mo-enriched molybdenum trioxide was investigated, and the recycled yield of $$^{95}$$Mo was achieved to be 70% - 90%. The images were obtained with each of the three $$gamma$$ rays. Results showed that the spatial resolution increases with increasing $$gamma$$-ray energy, and suggested that the ETCC with high-energy $$gamma$$-ray emitters such as $$^{95m}$$Tc is useful for the medical imaging of deep tissue and organs in the human body.

Journal Articles

Preliminary analysis of the post-disassembly expansion phase and structural response under unprotected loss of flow accident in prototype sodium cooled fast reactor

Onoda, Yuichi; Matsuba, Kenichi; Tobita, Yoshiharu; Suzuki, Toru

Mechanical Engineering Journal (Internet), 4(3), p.16-00597_1 - 16-00597_14, 2017/06

Journal Articles

Fundamental safety strategy against severe accidents on prototype sodium-cooled fast reactor

Onoda, Yuichi; Kurisaka, Kenichi; Sakai, Takaaki

Journal of Nuclear Science and Technology, 53(11), p.1774 - 1786, 2016/11

 Times Cited Count:1 Percentile:14.27(Nuclear Science & Technology)

Journal Articles

Preliminary analysis of the post-disassembly expansion phase and structural response under unprotected loss of flow accident in prototype sodium cooled fast reactor

Onoda, Yuichi; Matsuba, Kenichi; Tobita, Yoshiharu; Suzuki, Toru

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 10 Pages, 2016/06

Journal Articles

Production of $$^{rm 95m}$$Tc for Compton camera imaging

Hatsukawa, Yuichi; Hashimoto, Kazuyuki; Tsukada, Kazuaki; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Nagai, Yasuki; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1283 - 1285, 2015/02

 Times Cited Count:2 Percentile:22.25(Chemistry, Analytical)

Technetium-99m ($$^{rm 99m}$$Tc) is used in radioactive medical diagonostic tests, for example as a radioactive tracer that medical equipment can detect in the human body. It is well suited to the role because it emits readily detectable 141 keV $$gamma$$ rays, and its half-life is 6.01 hours (meaning that about 94% of it decays to technetium-99 in 24 hours). There are at least 31 commonly used radiopharmaceuticals based on technetium-99m for imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood, and tumors. Recent years, with the develop-ment of the Compton camera which can realize high position resolution, technetium isotopes emitting high energy $$gamma$$-rays are required. In this study, technetium-95m which emits some $$gamma$$ rays around 800 keV was produced by the $$^{95}$$Mo(p,n)$$^{rm 95m}$$Tc reaction.

Journal Articles

Identification of the accident sequences for the evaluation of the effectiveness of severe accident measures on prototype Sodium-cooled Fast Reactor

Onoda, Yuichi; Kurisaka, Kenichi; Sakai, Takaaki

Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 12 Pages, 2014/12

JAEA Reports

Development of microbeam formation and single-ion hit technologies at the TIARA cyclotron

Yokota, Wataru; Sato, Takahiro; Kamiya, Tomihiro; Okumura, Susumu; Kurashima, Satoshi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Yoshida, Kenichi; Funayama, Tomoo; Sakashita, Tetsuya; et al.

JAEA-Technology 2014-018, 103 Pages, 2014/09

JAEA-Technology-2014-018.pdf:123.66MB

The world's first microbeam focusing technology for heavy ions of hundreds MeV accelerated by a cyclotron has been developed at the TIARA facility in the Takasaki Advanced Radiation Research Institute of the Japan Atomic Energy Agency. The technology enables us to form a microbeam of less than 1 $$mu$$m in diameter and to shoot a specified point on a target by one ion (single-ion hit) with spatial accuracy of microbeam size. In the course of the development, a cyclotron technology to accelerate a small energy-spread beam of hundres MeV, which is necessary for focusing to 1 $$mu$$m, has been developed as well as a beam focusing apparatus, beam size measurement and so forth based on the several-MeV microbeam/single-ion hit system of the TIARA electrostatic accelerators. Applicability of the technologies was examined by actual use in irradiation experiment and the result were fed back to them. This paper reports the process and the results of the development over ten years.

Journal Articles

Generation of radioisotopes with accelerator neutrons by deuterons

Nagai, Yasuki; Hashimoto, Kazuyuki; Hatsukawa, Yuichi; Saeki, Hideya; Motoishi, Shoji; Sonoda, Nozomi; Kawabata, Masako; Harada, Hideo; Kin, Tadahiro*; Tsukada, Kazuaki; et al.

Journal of the Physical Society of Japan, 82(6), p.064201_1 - 064201_7, 2013/06

 Times Cited Count:38 Percentile:86.37(Physics, Multidisciplinary)

Journal Articles

Three-pin cluster CABRI tests simulating the unprotected loss-of-flow accident in sodium-cooled fast reactors

Onoda, Yuichi; Fukano, Yoshitaka; Sato, Ikken; Marquie, C.*; Duc, B.*

Journal of Nuclear Science and Technology, 48(2), p.188 - 204, 2011/02

 Times Cited Count:10 Percentile:65.84(Nuclear Science & Technology)

Two three-pin cluster tests simulating the Unprotected Loss-of-Flow (ULOF) accident of Sodium-cooled Fast Reactors (SFRs) were conducted focusing on fuel relocation and freezing behavior. Based on detailed data evaluation and theoretical interpretation for the three-pin cluster tests, it is concluded that axial fuel relocation and freezing are dominated by local fuel enthalpy, and the relation between fuel dispersal and fuel enthalpy observed in these CABRI tests is basically applicable to the pin-bundle condition. It is also clarified that a fuel/steel mixture tends to create tight blockages near the axial ends of the relocating fuel. Part of the fission gas released from the fuel is expected to be trapped within the bottled-up region between the upper and lower blockages and will keep this region pressurized for a relatively long period.

Journal Articles

Fuel pin behavior up to cladding failure under pulse-type transient overpower in the CABRI-FAST and CABRI-RAFT experiments

Fukano, Yoshitaka; Onoda, Yuichi; Sato, Ikken

Journal of Nuclear Science and Technology, 47(4), p.396 - 410, 2010/04

 Times Cited Count:6 Percentile:43.83(Nuclear Science & Technology)

Journal Articles

Fuel pin behavior under slow-ramp-type transient-overpower conditions in the CABRI-FAST experiments

Fukano, Yoshitaka; Onoda, Yuichi; Sato, Ikken; Charpenel, J.*

Journal of Nuclear Science and Technology, 46(11), p.1049 - 1058, 2009/11

 Times Cited Count:13 Percentile:65.67(Nuclear Science & Technology)

Journal Articles

Fuel pin behavior under slow ramp-type transient-overpower conditions in the CABRI-FAST experiments

Fukano, Yoshitaka; Onoda, Yuichi; Sato, Ikken; Charpenel, J.*

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13) (CD-ROM), 13 Pages, 2009/10

Journal Articles

CABRI-RAFT TP2 and TP-A1 tests simulating the unprotected loss-of-flow accident in sodium-cooled fast reactors

Onoda, Yuichi; Fukano, Yoshitaka; Sato, Ikken; Marquie, C.*; Duc, B.*

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13) (CD-ROM), 15 Pages, 2009/09

Journal Articles

Transient heat transfer characteristics between molten fuel and steel with steel boiling in the CABRI-TPA2 test

Yamano, Hidemasa; Onoda, Yuichi; Tobita, Yoshiharu; Sato, Ikken

Nuclear Technology, 165(2), p.145 - 165, 2009/02

 Times Cited Count:24 Percentile:85.38(Nuclear Science & Technology)

In the TPA2 test of the CABRI-RAFT program which is part of a fast reactor safety study, fuel-to-steel heat transfer characteristics within a molten fuel/steel mixture system were investigated. This test was performed in the French CABRI reactor and used a test capsule containing fresh 12.3% enriched UO$$_{2}$$ pellets with embedded stainless steel balls. Following a pre-heating phase, the capsule was subjected to a transient overpower resulting in fuel melting and steel vaporization. The observed steel vapor pressure build-up was quite low suggesting presence of a mechanism significantly limiting the fuel-to-steel heat transfer. A detailed experimental data evaluation by SIMMER-III led to one possible interpretation that the steel vaporization at the surface of the steel ball blanketed the steel from the molten fuel.

Journal Articles

Celebration of 30th anniversary of the experimental fast reactor Joyo

Nakai, Satoru; Aoyama, Takafumi; Ito, Chikara; Yamamoto, Masaya; Iijima, Minoru; Nagaoki, Yoshihiro; Kobayashi, Atsuko; Onoda, Yuichi; Ohgama, Kazuya; Uwaba, Tomoyuki; et al.

Kosoku Jikkenro "Joyo" Rinkai 30-Shunen Kinen Hokokukai Oyobi Gijutsu Koenkai, 154 Pages, 2008/06

no abstracts in English

JAEA Reports

Interpretation of the CABRI-RAFT TPA2 Test

Yamano, Hidemasa; Onoda, Yuichi; Tobita, Yoshiharu; Sato, Ikkenn

JNC TN9400 2005-045, 123 Pages, 2005/06

JNC-TN9400-2005-045.pdf:18.37MB

During the course of core disruptive accidents in liquid-metal fast reactors, a boiling pool of molten fuel/steel mixture could be formed. The stability of this boiling-pool, for which in-pile experimental data with real reactor materials are very limited, plays an important role in the determination of the accident scenarios. In the TPA2 test of the CABRI-RAFT program (from 1996 to 2002), the fuel-to-steel heat transfer characteristic governing the pool behavior was investigated as a joint study with the French 'Institut de Radioprotection et de Surete Nucleaire' (IRSN). This test was performed in the CABRI reactor in 2001 using a test capsule that contains fresh 12.3% enriched UO$$_{2}$$ pellets with embedded stainless steel balls. Following a pre-heating phase, the capsule was submitted to a transient overpower resulting in fuel melting and steel vaporization. The steel vapor-pressure build-up observed during the transient was quite weak, suggesting the presence of a strong mechanism to limit the fuel-to-steel heat transfer. The detailed experimental data evaluation suggested a phenomenon that the steel vaporization at the surface of steel ball blanketed the steel from molten fuel. This vapor blanketing seems to be a mechanism reducing the fuel-to-steel heat transfer. An analysis with the SIMMER-III code, a multi-component multi-phase thermal-hydraulics code, was performed in this study. This code simulation could well reproduce the pressure buildup and boiling pool behavior which occurred in the test by applying specifically reduced heat transfer coefficients.

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