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Journal Articles

Criticality characteristics of fuel debris mixed by fuels with different burnups based on fuel loading pattern

Watanabe, Tomoaki; Okubo, Kiyoshi*; Araki, Shohei; Tonoike, Kotaro

Proceedings of 11th International Conference on Nuclear Criticality Safety (ICNC 2019) (Internet), 8 Pages, 2019/09

Journal Articles

Structure of nitride layer formed on titanium alloy surface by N$$_{2}$$-gas exposure at high temperatures

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

JPS Conference Proceedings (Internet), 25, p.011023_1 - 011023_3, 2019/03

In this study, we prepared samples under two different conditions, (1) 810$$^{circ}$$C, for 600 min, and (2) 850$$^{circ}$$C, for 720 min. A depth-profile analysis of the surfaces of the samples is conducted through Doppler broadening (DB) measurements of positron annihilation $$gamma$$ rays using a slow positron beam. It was indicated that many of positrons annihilated in defects near the surface. According to the TEM image, there are nano-crystal grains near the surface and then positrons can diffuse in the grains and annihilate in defects at the grain boundaries. Furthermore, DB measurements indicated that there is a depth dependence on the chemical composition where positrons annihilate. EDS spectroscopy measurements also indicated that there is a depth dependence of impurities such as Vanadium. These results indicated change of the chemical composition at the grain boundaries.

Journal Articles

Structure of nitride layer formed on titanium alloy surface by N$$_{2}$$-gas exposure at high temperatures

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

Journal of Physics; Conference Series, 791(1), p.012022_1 - 012022_4, 2017/02

 Times Cited Count:1 Percentile:49.45

Titanium alloy is widely used for applications such as golf club heads and structural materials for aircrafts. The surface can be exceedingly hardened by nitriding treatment that initiates defects, but there are some difficulties on use of titanium nitride because the layer can be exfoliated by stress. Therefore, we prepared samples in two different treatment conditions, (1) 810$$^{circ}$$C 600 min and (2) 850$$^{circ}$$C 720 min and performed depth profile analysis of Doppler broadening of positron annihilation $$gamma$$-rays (DB) for these samples. According to a calculation of nitrogen diffusion depth, the nitride layer should be only about 0.05-0.1$$mu$$m. However, the depth profile analysis of the DB measurement indicated that the defects introduced by nitriding treatment extended to a depth of 0.5$$mu$$m.

Journal Articles

Criticality characteristics of MCCI products possibly produced in reactors of Fukushima Daiichi Nuclear Power Station

Tonoike, Kotaro; Okubo, Kiyoshi; Takada, Tomoyuki*

Proceedings of International Conference on Nuclear Criticality Safety (ICNC 2015) (DVD-ROM), p.292 - 300, 2015/09

The damaged Unit 1-3 reactors of the Fukushima Daiichi Nuclear Power Station may contain fuel debris of a significant amount that is in a form of molten-core-concrete-interaction (MCCI) product with porous structure. Such low density MCCI product including fissile material is a great concern for its criticality control, especially under submerged condition, due to its fairly good neutron moderation. This report shows computation results of basic criticality characteristics of the MCCI product, which will facilitate criticality risk assessments during decommissioning of the reactors. The results imply that water bound in concrete may raise the risk from the viewpoints of possibility of criticality events and of effectiveness of mitigation measures such as neutron poison injection into coolant water.

JAEA Reports

Examination of measurement method of isotopic composition of fission products in spent fuel

Fukaya, Hiroyuki; Suyama, Kenya; Sonoda, Takashi; Okubo, Kiyoshi; Umeda, Miki; Uchiyama, Gunzo

JAEA-Research 2013-020, 81 Pages, 2013/10

JAEA-Research-2013-020.pdf:3.81MB

Japan Atomic Energy Agency conducted a project "Isotopic Composition measurement of Fission Products in Spent Fuel from FY2008 to FY2011" by the entrustment of Japan Nuclear Energy Safety Organization. In that project, we measured the isotopic composition of neodymium isotopes which are important to evaluate the burnup value of spent nuclear fuel by using two different methods and obtained different results. So that we carried out the follow-up measurement in order to investigate the reason of the difference between two neodymium measurements. It was found that we needed correction to the measurement results of neodymium for two samples and a part of other fission products for all samples in total five samples. This report summarizes the all works carried out in this follow-up measurement and obtained results.

Journal Articles

Mach-Zehnder polymer waveguides fabricated using proton beam writing

Miura, Kenta*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; Kiryu, Hiromu*; Ozawa, Yusuke*; Takano, Katsuyoshi*; Okubo, Takeru; Yamazaki, Akiyoshi; Kada, Wataru; et al.

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 126, 2013/01

Journal Articles

Fabrication of Mach-Zehnder polimer waveguides by a direct-drawing technique using a focused proton beam

Miura, Kenta*; Sato, Takahiro; Ishii, Yasuyuki; Kiryu, Hiromu*; Ozawa, Yusuke*; Koka, Masashi; Takano, Katsuyoshi*; Okubo, Takeru; Yamazaki, Akiyoshi; Kada, Wataru; et al.

Key Engineering Materials, 534, p.158 - 161, 2013/00

 Times Cited Count:5 Percentile:92.66

Journal Articles

Infinite multiplication factor of low-enriched UO$$_2$$-concrete system

Izawa, Kazuhiko; Uchida, Yuriko; Okubo, Kiyoshi; Totsuka, Masayoshi; Sono, Hiroki; Tonoike, Kotaro

Journal of Nuclear Science and Technology, 49(11), p.1043 - 1047, 2012/11

AA2012-0375.pdf:0.63MB

 Times Cited Count:11 Percentile:69.17(Nuclear Science & Technology)

Possibility of criticality of fuel debris in a form of UO$$_2$$-concrete mixture is evaluated by calculating infinite multiplication factor ($$k_infty$$) for a study of criticality control on the fuel debris generated through the molten core concrete interaction (MCCI) in a severe accident of a light water reactor (LWR). The infinite multiplication factor can be greater than unity, which means that handling of the mixture is subject to criticality control. This paper shows that concrete have efficient slowing-down capability of neutron and points out the necessity of further investigations on the criticality of low-enriched UO$$_2$$-concrete system for actual handling of fuel debris.

Journal Articles

Fabrication of Y-junction waveguides using proton beam writing

Miura, Kenta*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; Uehara, Masato*; Kiryu, Hiromu*; Takano, Katsuyoshi*; Okubo, Takeru; Yamazaki, Akiyoshi; Kada, Wataru; et al.

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 126, 2012/01

Journal Articles

Improvement of spatial resolution of PIXE-CT using ML-EM algorithm in TIARA

Sato, Takahiro; Koka, Masashi; Kada, Wataru; Yokoyama, Akihito; Okubo, Takeru; Yamazaki, Akiyoshi; Ishii, Yasuyuki; Kamiya, Tomihiro

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 83, 2012/01

Journal Articles

The Analysis of boron micro-distribution in 9L gliosarmoma cells and HUVEC cells using PIXE and PIGE

Endo, Kiyoshi*; Shibata, Yasushi*; Yamamoto, Tetsuya*; Nakai, Kei*; Matsumura, Akira*; Sato, Takahiro; Yokoyama, Akihito; Koka, Masashi; Okubo, Takeru; Yamazaki, Akiyoshi; et al.

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 86, 2012/01

Journal Articles

Fabrication of polymer optical waveguides for the 1.5-$$mu$$m band using focused proton beam

Miura, Kenta*; Machida, Yuki*; Uehara, Masato*; Kiryu, Hiromu*; Ozawa, Yusuke*; Sasaki, Tomoyuki*; Hanaizumi, Osamu*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; et al.

Key Engineering Materials, 497, p.147 - 150, 2012/00

 Times Cited Count:7 Percentile:96.61

Journal Articles

Fabrication of polymer optical waveguides for the 1.5-$$mu$$m band using focused proton beam

Miura, Kenta*; Machida, Yuki*; Uehara, Masato*; Kiryu, Hiromu*; Ozawa, Yusuke*; Sasaki, Tomoyuki*; Hanaizumi, Osamu*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; et al.

Key Engineering Materials, 497, p.147 - 150, 2011/12

 Times Cited Count:6 Percentile:2.48

Journal Articles

Study on reactivity effect of fission products for introducing burnup credit into the criticality safety evaluation of spent nuclear fuel

Okubo, Kiyoshi*; Suyama, Kenya; Uchiyama, Gunzo

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 6 Pages, 2011/12

The amount of the spent nuclear fuel (SNF) stored at the nuclear reactor sites is increasing continuously in Japan. To correspond to such a situation, it is considered to take into account the decrease in the reactivity of SNF according to the burnup for the criticality safety control of SNF. This idea is called as burnup credit. If the negative reactivity effect of the fission product nuclides accumulated during the burnup is adopted into the burnup credit which considers only uranium and plutonium, the amount of fuel assembly that can be treated in the same facility is increased. This study reveals the reactivity effect of fission products has almost linear correlation with the increase of burnup SNF for both solution and heterogeneous systems. The negative reactivity effect of the selected fission product is equal to the increase of the burnup of approximately 20-25% for the solution system and 30-35% for the heterogeneous system respectively. It also implies that the estimation error of burnup value of 20% could be acceptable if we take the burnup credit adopting only uranium and plutonium isotopes, considering the fission products as the safety margin.

Journal Articles

Re-evaluation of assay data of spent nuclear fuel obtained at Japan Atomic Energy Research Institute for validation of burnup calculation code systems

Suyama, Kenya; Murazaki, Minoru*; Okubo, Kiyoshi; Nakahara, Yoshinori*; Uchiyama, Gunzo

Annals of Nuclear Energy, 38(5), p.930 - 941, 2011/05

 Times Cited Count:13 Percentile:74.14(Nuclear Science & Technology)

The isotopic composition of spent nuclear fuels is vital data for studies on the nuclear fuel cycle and reactor physics. The Japan Atomic Energy Agency (JAEA) has been active in obtaining such data for pressurized water reactor (PWR) and boiling water reactor (BWR) fuels, and some data has already been published. These data have been registered with the international Spent Fuel Isotopic Composition Database (SFCOMPO) and widely used as international benchmarks for burnup calculation codes and libraries. In this paper, postirradiation examination (PIE) data from two fuel assemblies irradiated in the Ohi-1 and Ohi-2 PWRs in Japan are shown. The PIE data from Ohi-2 has already been published. However, these data were not suitable for the benchmarking of calculation codes and libraries because several important specifications and data were not included. This paper summarizes the details of PIE data from Ohi-1 and Ohi-2 and shows in detail the data and specifications required for analyses of isotopic composition. For precise burnup analyses, the burnup values of PIE samples were re-evaluated in this study. These PIE data were analyzed using the SWAT2.1 code, and the calculation results showed good agreement with experimental results. This indicates that the quality of PIE data from Ohi-1 and Ohi-2 PWRs is high, and that these PIE data are suitable for the benchmarking of burnup calculation code systems.

JAEA Reports

SWAT3.1; The Integrated burnup code system driving continuous energy Monte Carlo codes MVP and MCNP

Suyama, Kenya; Mochizuki, Hiroki*; Takada, Tomoyuki*; Ryufuku, Susumu*; Okuno, Hiroshi; Murazaki, Minoru; Okubo, Kiyoshi

JAEA-Data/Code 2009-002, 124 Pages, 2009/05

JAEA-Data-Code-2009-002.pdf:14.09MB

Integrated burnup calculation code system SWAT is a system that combines neutronics calculation code SRAC widely used in Japan and point burnup calculation code ORIGEN2. It has been used to evaluate the composition of the uranium, plutonium, minor actinide and the fission products in the spent nuclear fuel. Because of the ability to treat the arbitrary fuel geometry and no requirement of generating the effective cross section data, there is a great advantage to introduce continuous energy Monte Carlo Code into the burnup calculation code. Based on this idea, the integrated burnup calculation code system SWAT3.1 was developed by combining the continuous energy Monte Carlo code MVP and MCNP and ORIGEN2. This report describes the outline, input data instruction and several example of the calculation.

Journal Articles

Current status of electrostatic accelerators at TIARA

Uno, Sadanori; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Agematsu, Takashi; Mizuhashi, Kiyoshi; Kitano, Toshihiko*; Takayama, Terumitsu*; Orimo, Takao*; Koka, Masashi*; et al.

JAEA-Conf 2008-012, p.44 - 47, 2009/03

no abstracts in English

Journal Articles

Evaluation method of thermal deformation for Fast Spectrum Light Water Reactor (FLWR)

Ishijima, Yasuhiro; Ioka, Ikuo; Kiuchi, Kiyoshi; Kaneko, Tetsuji*; Okubo, Tsutomu; Yamamoto, Masahiro

Atsuryoku Gijutsu, 47(1), p.12 - 17, 2009/01

We investigate one of these innovative water reactors; Fast Spectrum Light Water Reactor (FLWR). It has unique construction for the reactor core but the fuel cladding material will be exposed in high internal pressure and axial load and complex temperature distribution. Therefore, we conducted a specially designed fatigue-creep test that were simulated several parameters (thermal distribution, temperature variation, internal pressure variation and binding stress) to evaluate an applicability of fuel cladding material for FLWR. Zircalloy-2, which is common cladding material, was used for the test. Test result was confirmed to compare the deformation value between tested and calculated. The result showed the evaluation method could be controlled several parameters simultaneously and the deformation value after the test coincided to the calculated value. This method is sufficient to evaluate thermal deformation characteristics for FLWR.

Journal Articles

Development of beam generation and irradiation technology for electrostatic accelerator

Yamada, Keisuke; Uno, Sadanori; Chiba, Atsuya; Yokoyama, Akihito; Saito, Yuichi; Ishii, Yasuyuki; Sato, Takahiro; Okubo, Takeru; Agematsu, Takashi; Mizuhashi, Kiyoshi

JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 185, 2008/11

no abstracts in English

Journal Articles

Operation of the electrostatic accelerators

Agematsu, Takashi; Uno, Sadanori; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Saito, Yuichi; Ishii, Yasuyuki; Sato, Takahiro; Okubo, Takeru; Mizuhashi, Kiyoshi; et al.

JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 191, 2008/11

Three electrostatic accelerators were operated smoothly in FY 2007, and all the planned experiments were carried out except those canceled by users. The yearly operation time of the tandem accelerator, the single-ended accelerator and the ion implanter amounted to 1949, 2437 and 1900 hours. The high-pressure residual gas of SF$$_{6}$$ is leaking from the SF$$_{6}$$ gas handling system of the tandem accelerator. The most amount of the leak comes out when the accelerator tank pressure is high. Therefore, in order to reduce the leak by lowering the residual gas pressure, a pipe was installed to carry the gas in the high-pressure part of the system for the accelerator to the low-pressure storage tank. As to the ion implanter, Pb ion, which was requested by users, was successfully generated using oven method and accelerated with intensity of 1.5 $$mu$$A.

53 (Records 1-20 displayed on this page)