Change in dislocation density via ausforming in Fe-5%Mn-C alloy with lath martensitic structure

Takanashi, Misa*; Hidaka, Ryota*; Okubo, Kota*; Masumura, Takuro*; Tsuchiyama, Satoshi*; Morooka, Satoshi; Maeda, Takuya*; Nakamura, Shuichi*; Uemori, Ryuji*

Tetsu To Hagane, 111(9), p.503 - 513, 2025/06

https://doi.org/10.2355/tetsutohagane.TETSU-2024-092

Neutronic design of basic cores of the new STACY

Izawa, Kazuhiko; Ishii, Junichi; Okubo, Takuya; Ogawa, Kazuhiko; Tonoike, Kotaro

Proceedings of 11th International Conference on Nuclear Criticality Safety (ICNC 2019) (Internet), 9 Pages, 2019/09

Japan Atomic Energy Agency, JAEA, is conducting the renewal program of the heterogeneous water moderated critical assembly STACY (Static Experiment Critical Facility) in order to verify the criticality calculation considering fuel debris which have been produced in the accident of Fukushima Daiichi Nuclear Power Station. The first criticality of the new STACY is scheduled at the beginning of 2021. After the first criticality, it is necessary to perform a series of critical experiments with a series of basic experimental core in order to gain a proficiency of operators and grasp the uncertainty that accompanies the result of critical experiments in STACY. Prior to the construction of the new STACY, a series of neutronic calculation was carried out for licensing and planning first series of critical experiment. In this paper, possible core configuration of the basic experimental core and their limitations are discussed and presented.

Radioactivity evaluation of the secondary sodium in DRACS of the Japan Sodium-cooled Fast Reactor

Sasaki, Kenji*; Naito, Katsuaki*; Oki, Shigeo; Okubo, Tsutomu; Kotake, Shoji*

Progress in Nuclear Science and Technology (Internet), 4, p.94 - 98, 2014/04

https://doi.org/10.15669/pnst.4.94

This paper evaluates the amount of activation of the secondary sodium in Direct Heat Exchanger (DHX) by neutrons leaked from the core, the radioactivity density, and the dose rate around the secondary sodium pipes in Direct Reactor Auxiliary Cooling System (DRACS) and confirms that the requirements in radioactivity free areas are satisfied by improving the exactness of calculation model with Monte Carlo Methodology.

Operation of the electrostatic accelerators

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

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 173, 2012/01

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2011-043.pdf

Three electrostatic accelerators of TIARA were operated smoothly in FY 2010, and all the planned experiments were carried out except those canceled by users or the impact of Great East Japan Earthquake on March 11, 2011. On the other hand, Saturday operation for experiments was carried out after October on the Global Nuclear-Human Resource Development Initiative. The yearly operation time of the tandem accelerator, the single-ended accelerator and the ion implanter amounted to 2116, 2367 and 1800 hours, respectively, which were similar to those of usual years. Regarding the single-ended accelerator, the generator in the high-voltage terminal failed and was replaced with new one. A switching magnet was installed for a new branch beam line of the ion implanter. As to the tandem accelerator, In ion was generated and accelerated at intensity of 500 nA.

Conceptual design for a large-scale Japan sodium-cooled fast reactor, 3; Core design in JSFR

Okubo, Tsutomu; Oki, Shigeo; Ogura, Masashi*; Okubo, Yoshiyuki*; Kotake, Shoji*

Proceedings of 2011 International Congress on Advances in Nuclear Power Plants (ICAPP '11) (CD-ROM), p.479 - 486, 2011/05

http://www.icapp.ans.org/icapp11/program/abstracts/11345.pdf

A conceptual design study and related R&D on a commercial-base large-scale Japan Sodium-cooled Fast Reactor (JSFR) have been carried out in the framework of the Fast Reactor Cycle Technology development (FaCT) project. As a next generation plant, JSFR adopts a number of innovative technologies in order to achieve economic competitiveness, enhanced reliability and safety. This paper describes the current results of the ongoing conceptual design study on the JSFR core. The most important point in the core design is to achieve a high core average burn-up around 150 GWd/t, assuming the ODS steel utilization as the cladding material. Another design target for the breeding ratio is intended to have some flexibility and is set at from around 1.0 to 1.2 under the design philosophy of the compatible fuel assembly among them. Also, the fuel composition is considered to have some variation range based on the wide variety of the spent fuel composition expected to be treated during the LWR to FBR transition period. The core design study performed in the FaCT project has clarified the feasibility of the JSFR core concept, which is based on the high internal conversion ratio type core using a large fuel rod diameter around 10 mm and satisfies a number of design targets and requirements including ones mentioned above.

Current status of electrostatic accelerators at TIARA

Chiba, Atsuya; Uno, Sadanori; Yamada, Keisuke; Yokoyama, Akihito; Agematsu, Takashi; Yokota, Wataru; Kitano, Toshihiko*; Takayama, Terumitsu*; Kanai, Shinji*; Orimo, Takao*; et al.

Dai-23-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.119 - 122, 2010/11

Operation times of each accelerator are keeping the same level as in recent 10 years, Tandem accelerator, Single-ended and Ion implanter amounted to about 2,000, 2,500 and 1,900 hours, respectively. In the last fiscal year, we succeeded in maintaining the terminal voltage of the tandem accelerator to high stability for long periods by exchanging the material of a corona-probe needle to the tungsten (NPS Co.). In the ion-implanter, the oven control system equipped with the Freeman ion source was renewed. There was no trouble to affect on the machine-time in the last fiscal year, so the all planned experiments were carried out.

Operation of the electrostatic accelerators

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

JAEA-Review 2009-041, JAEA Takasaki Annual Report 2008, P. 175, 2009/12

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2009-041.pdf

Three electrostatic accelerators of TIARA were operated smoothly in FY 2008, 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 2009, 2426 and 1882 hours, respectively. Regarding the tandem accelerator, the control system was renewed, and the unstable acceleration voltage caused by mechanical vibration reduced by adjusting the driving mechanism of the pellet chains. The SF gas for the single-ended accelerator was purified, and its storage tank was repainted. As to the ion implanter, Bi ion, which was requested by users, was successfully generated and accelerated with intensity of 0.5A.

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

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2008-055.pdf

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 is leaking from the SF 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 A.

Reactivity effect measurement of neutron interaction between two slab cores containing 10% enriched uranyl nitrate solution without neutron isolater

Tonoike, Kotaro; Miyoshi, Yoshinori; Okubo, Kiyoshi

Journal of Nuclear Science and Technology, 40(4), p.238 - 245, 2003/04

https://doi.org/10.3327/jnst.40.238

The reactivity effect of neutron interaction between two identical units containing low enriched (10% enrichment) uranyl nitrate solution was measured in the STACY. The unit has 350mm of thickness and 690mm of width and distance between those two units was adjustable from 0mm to 1450mm. Condition of the solution was about 290gU/L in uranium concentration, about 0.8N in free nitric acid molarity, 2427C in temperature and about 1.4g/cm in solution density. The reactivity effect was estimated from variation of critical solution level from 495mm to 763mm depending on the core distance. The reactivity effect was also evaluated by the solid angle method and a computational method using the continuous energy Monte Carlo code MCNP-4C and the nuclear data library JENDL3.2. Comparison of those estimations is presented.

Conceptual design toward the commercial reactor of JSFR, 3; Fast reactor core and fuel concepts for high burnup

Kaito, Takeji; Otsuka, Satoshi; Inoue, Masaki; Asayama, Tai; Okubo, Tsutomu; Mizuno, Tomoyasu; Okubo, Yoshiyuki*; Kotake, Shoji*

no journal, , 

An innovative core and fuel concept of Japan Sodium-cooled Fast Reactor (JSFR) is aiming at achieving as high burn-up as 150 GWd/t of average discharge burn-up to improve its economical competitiveness. A candidate of innovative technology to achieve such high burn-up is oxide-dispersion-strengthened (ODS) ferritic cladding material with both excellent irradiation resistance and high strength at elevated temperature. This paper reports the result of applicability study of the innovative technologies for the JSFR core.