Influence of surface condition on deuterium release from LiTiO pebble

Tsuchiya, Akihito*; Yamauchi, Yuji*; Nobuta, Yuji*; Hino, Tomoaki*; Akiba, Masato; Enoeda, Mikio

Fusion Engineering and Design, 89(7-8), p.1280 - 1283, 2014/10

https://doi.org/10.1016/j.fusengdes.2014.03.054

Lithium titanate (LiTiO) pebbles were irradiated with D3+ ions with energy of 5.0 keV, and the amounts of retained deuterium in the pebbles were measured by thermal desorption spectroscopy. Cycles of irradiation and heating were carried out repeatedly in order to investigate the influence of surface condition on deuterium release from LiTiO. The composition of Li decreased with the increase in the number of the irradiation and heating cycle. The desorption peaks of the gases contained deuterium atoms were shifted to higher temperature region. Total amount of desorbed deuterium showed the tendancy to increase. These results suggest that the tritium recovery efficiency would deteriorate with the increase in the damages and the defects especially at the lower temperature region during the use of blanket.

Enhancement of critical current densities by high-pressure sintering in (Sr,K)FeAs PIT wires

Pyon, S.*; Tsuchiya, Yuji*; Inoue, Hiroshi*; Kajitani, Hideki; Koizumi, Norikiyo; Awaji, Satoshi*; Watanabe, Kazuo*; Tamegai, Tsuyoshi*

Superconductor Science and Technology, 27(9), p.095002_1 - 095002_7, 2014/09

https://doi.org/10.1088/0953-2048/27/9/095002

Many scientists have been trying to improve the superconductor performance of ferrous strand "((Sr,K)FeAs" with improvement of the dope materials and fabricating process. Especially, it is expected that heat treatment under high pressure for the strand is good for improvement of the critical current performance because it makes intercrystalline bond power in the material stronger. In past study, using some kinds of tape strand, the improvement of critical current performance could be experimentally achieved with this method. In this paper, it is shown that the author newly fabricated rounded strand and HIP (700 degrees, 4 hours, 120 MPa) was applied for it and then the critical performance was measured. The result could be achieved as 1[kA/mm]. This high value is meaningful in terms of the application for the magnet and some apparatuses.

Study to improve recriticality evaluation methodology after severe accident (Joint research)

Kugo, Teruhiko; Ishikawa, Makoto; Nagaya, Yasunobu; Yokoyama, Kenji; Fukaya, Yuji; Maruyama, Hiromi*; Ishii, Yoshihiko*; Fujimura, Koji*; Kondo, Takao*; Minato, Hirokazu*; et al.

JAEA-Research 2013-046, 53 Pages, 2014/03

JAEA-Research-2013-046.pdf:4.42MB

The present report summarizes the results of a 2-year cooperative study between JAEA and Hitachi-GE in order to contribute to the settlement of the Fukushima-Daiichi Nuclear Power Plants which suffered from the severe accident on March 2011. In the present study, the possible scenarios to reach the recriticality events in Fukushima-Daiichi were investigated first. Then, the analytical methodology to evaluate the time-dependent recriticality events has been developed by modelling the reactivity insertion rate and the possible feedback according to the recriticality scenarios identified in the first step. The methodology developed here has been equipped as a transient simulation tool, PORCAS, which is operated on a multi-purpose platform for reactor analysis, MARBLE. Finally, the radiation exposure rates by the postulated recriticality events in Fukushima-Daiichi were approximately evaluated to estimate the impact to the public environment.

Effects of hydrogen mixture into helium gas on deuterium removal from lithium titanate

Tsuchiya, Akihito*; Hino, Tomoaki*; Yamauchi, Yuji*; Nobuta, Yuji*; Akiba, Masato; Enoeda, Mikio

Fusion Engineering and Design, 88(9-10), p.2298 - 2301, 2013/10

https://doi.org/10.1016/j.fusengdes.2013.05.028

Lithium titanate (LiTiO) pebbles were irradiated with deuterium ions with energy of 1.7 keV and then exposed to helium or helium and hydrogen mixed gas at various temperatures, in order to evaluate the effects of gas exposure on deuterium removal from the pebbles. The amounts of residual deuterium in the pebbles were measured by thermal desorption spectroscopy. The mixing of hydrogen gas into helium gas enhanced the removal amount of deuterium. In addition, we also evaluated the pebbles exposed to the helium gas with different hydrogen mixture ratio from 0% to 1%, at 573 K. Although the amount of residual deuteriumin the pebbles after the exposure decreased with increasing the hydrogen mixture ratio, the implanted deuterium partly remained after the exposure. These results suggest that the tritium inventory may occur at low temperature region in the blanket during the operation.

Basic study on surface chemical combination between beryllium metal and hydrogen isotope gas, 2

Ito, Masayasu; Kitagishi, Shigeru; Hanawa, Yoshio; Tsuchiya, Kunihiko; Hatano, Yuji*; Matsuyama, Masao*; Nagasaka, Takuya*; Hishinuma, Yoshimitsu*

Annual Report of National Institute for Fusion Science; April 2011 - March 2012, P. 535, 2012/12

http://www.nifs.ac.jp/report/annrep12/pdf/535.pdf

Beryllium has been utilized as a moderator and/or reflector in a number of material testing reactors. Beryllium is also supposed to be widely used in fusion reactors as neutron multiplier and protective walls of plasma facing components. It is important to perform the characterization of the different grade beryllium such as the productivity, mechanical and chemical properties and the interaction under water and/or gas environment. In this study, three kinds of beryllium (S-200F, S-65H, I-220H) were prepared, and corrosion test and surface analysis of these beryllium samples were carried out for life time expansion under pure water. As a result, the surface change of each Be sample was observed by the corrosion test and influenced by the content of BeO and the grain size.

Effects of particle irradiations on vortex states in iron-based superconductors

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Yagyuda, Hidenori*; Tsuchiya, Yuji*; Mohan, S.*; Taniguchi, Tomotaka*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; et al.

Superconductor Science and Technology, 25(8), p.084008_1 - 084008_14, 2012/08

https://doi.org/10.1088/0953-2048/25/8/084008

Various kinds of energetic particles are irradiated into iron-based superconductors, and their effects on the critical current density and vortex dynamics have been systematically studied. It is found that is enhanced and vortex dynamics is strongly suppressed by energetic particles having a sufficient energy deposition rate, similar to the case of high temperature cuprate superconductors. The enhancement of , in general, persists up to much higher irradiation doses than in cuprates. However, details of the effect of irradiation depend on the kind of ion species and their energies. Even with the same ions and energies, the effect is not universal for different kinds of iron-based superconductors. The correlated nature of defects created by heavy-ion irradiation is confirmed by the angular dependence of irreversible magnetization.

Basic study on surface chemical combination between beryllium metal and hydrogen isotope gas

Tsuchiya, Kunihiko; Kitagishi, Shigeru; Ito, Masayasu; Hanawa, Yoshio; Hatano, Yuji*; Matsuyama, Masao*; Nagasaka, Takuya*; Hishinuma, Yoshimitsu*

Annual Report of National Institute for Fusion Science; April 2010 - March 2011, P. 545, 2011/11

http://www.nifs.ac.jp/report/annrep11/index.html

no abstracts in English

Surface analysis for chemical combination of beryllium metals

Tsuchiya, Kunihiko; Hanawa, Yoshio; Kitagishi, Shigeru; Ito, Masayasu; Hatano, Yuji*; Matsuyama, Masao*

Heisei-21-Nendo Toyama Daigaku Kyodo Riyo, Kyodo Kenkyu Seika Hokokusho, p.9 - 10, 2010/12

no abstracts in English

Dismantlement technique of irradiation facilities in JMTR

Onuma, Yuichi; Okada, Yuji; Hanawa, Hiroshi; Tsuchiya, Kunihiko; Kanno, Masaru

JAEA-Review 2010-047, 27 Pages, 2010/11

JAEA-Review-2010-047.pdf:3.0MB

The Japan Materials Testing Reactor (JMTR) has been refurbished to re-operate from 2011. As a part of the establishment of new irradiation facilities, technology development for the dismantling and removing of irradiation facilities such as OWL-1 (Oarai Water Loop No.1), OWL-2 (Oarai Water Loop No.2) and IASCC (Irradiation Assisted Stress Corrosion Cracking) facility installed in the JMTR loop cubicles has been performed. By using developed methods, techniques for the dismantling and removing of the irradiation facilities were established.

Critical current densities and vortex dynamics in Ba(FeCo)As single crystals

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Tsuchiya, Yuji*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*

Journal of Superconductivity and Novel Magnetism, 23(5), p.605 - 608, 2010/07

https://doi.org/10.1007/s10948-009-0606-2

Superconducting properties are evaluated for high-quality single crystals of Ba(FeCo)As in a wide range of doping levels. The critical current density, , in an optimally-doped crystal (Tc 24 K) shows a fishtail effect with its value over 10 A/cm even at 5 T below 10 K. Magneto-optical imaging has clarified rather homogeneous supercurrent flow in the crystal, in spite of a large amount of impurities. In the heavy-ion irradiated sample, the presence of columnar defects are confirmed and has been enhanced by a factor of five at low temperatures, reaching 6 10 A/cm at 2 K under zero field. Flux creep rate in the heavy-ion irradiated sample has been reduced in accordance with the enhancement of .