Evaluation of the dissolution behavior of zircon using high-resolution phase-shift interferometry microscope

Kitagaki, Toru

Journal of Nuclear Materials, 557, p.153254_1 - 153254_8, 2021/12

https://doi.org/10.1016/j.jnucmat.2021.153254

Material characterization of the VULCANO corium concrete interaction test with concrete representative of Fukushima Daiichi Nuclear Plants

Brissonneau, L.*; Ikeuchi, Hirotomo; Piluso, P.*; Gousseau, J.*; David, C.*; Testud, V.*; Roger, J.*; Bouyer, V.*; Kitagaki, Toru; Nakayoshi, Akira; et al.

Journal of Nuclear Materials, 528, p.151860_1 - 151860_18, 2020/01

https://doi.org/10.1016/j.jnucmat.2019.151860

First-principles calculation of mechanical properties of simulated debris ZrUO

Itakura, Mitsuhiro; Nakamura, Hiroki; Kitagaki, Toru; Hoshino, Takanori; Machida, Masahiko

Journal of Nuclear Science and Technology, 56(9-10), p.915 - 921, 2019/09

https://doi.org/10.1080/00223131.2019.1604271

To elucidate the mechanical properties of fuel debris inside the Fukushima Daiichi Nuclear Power Plant, we use first-principles calculations to evaluate mechanical properties of cubic ZrUO, which is a main component of the fuel debris. We focus on the dependence of mechanical properties on the fraction x of zirconium, compare our results with recent experiment of simulated debris, in which dependences of elastic moduli and fracture toughness on the ZrO content showed deviation from a simple linear relation. We show that elastic moduli drop at around x=0.25 and increase again for larger values of x, as has been observed in experiments. The reason of the drop is a softening owing to disordered atomistic structures induced by the solute zirconium atoms. We also find that stress-strain curves for the x=0.125 case show marked hysteresis owing to the existence of many meta-stable states. We show that this hysteresis leads to slightly increased fracture toughness, but it is not enough to account for the significant increase of fracture toughness observed in experiments.

A Laboratory investigation of microbial degradation of simulant fuel debris by oxidizing microorganisms

Liu, J.; Dotsuta, Yuma; Kitagaki, Toru; Kozai, Naofumi; Yamaji, Keiko*; Onuki, Toshihiko

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 2 Pages, 2019/05

To decommission the Fukushima Daiichi Nuclear Power Plant (FDNPP), it is necessary to estimate the current status of fuel debris and predicate the possible change under various condition. Some microorganisms may enter the plant due to the seawater injection after accident and future defueling activity. In this study, microbial influence on fuel debris under aerobic condition was experimentally investigated. By culturing some bacteria in the presence of simulant fuel debris in liquid medium, the microbial degradation of fuel debris was observed.

R&D strategy on mid- and long-term behavior of fuel debris

Yano, Kimihiko; Kitagaki, Toru; Washiya, Tadahiro; Miyamoto, Yasuaki; Ogawa, Toru

Progress in Nuclear Science and Technology (Internet), 5, p.225 - 228, 2018/11

https://doi.org/10.15669/pnst.5.225

According to the roadmap for decommissioning of Fukushima Daiichi NPS, fuel debris retrieval will start from 2021, after a decade from fuel debris generation. Fuel debris will stay in the reactors until the end of defueling. In addition, it is not hard to anticipate that storage is necessary for fuel debris removed from reactors. In order to consider such a post-accident operation for fuel debris, it is indispensable to discuss the states and characteristics of fuel debris during several decades. Therefore, JAEA directed R&D strategy on mid- and long-term behavior of fuel debris tentatively and is making a start of fundamental studies on this issue in corporation with the domestic universities and other research institutes.

Mechanical properties of cubic (U,Zr)O

Kitagaki, Toru; Hoshino, Takanori; Yano, Kimihiko; Okamura, Nobuo; Ohara, Hiroshi*; Fukasawa, Tetsuo*; Koizumi, Kenji

Journal of Nuclear Engineering and Radiation Science, 4(3), p.031011_1 - 031011_7, 2018/07

https://doi.org/10.1115/1.4039847

Mechanical properties of fuel debris for defueling toward decommissioning

Hoshino, Takanori; Kitagaki, Toru; Yano, Kimihiko; Okamura, Nobuo; Ohara, Hiroshi*; Fukasawa, Tetsuo*; Koizumi, Kenji

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

Fission product separation from seawater by electrocoagulation method

Kitagaki, Toru; Hoshino, Takanori; Sambommatsu, Yuji; Yano, Kimihiko; Takeuchi, Masayuki; Igarashi, Takeshi*; Suzuki, Tatsuya*

Journal of Radioanalytical and Nuclear Chemistry, 296(2), p.975 - 979, 2013/05

https://doi.org/10.1007/s10967-012-2120-4

Design and fabrication of the FBR fuel disassembly system

Kitagaki, Toru; Tasaka, Masayuki; Higuchi, Hidetoshi; Koizumi, Kenji; Hirano, Hiroyasu; Washiya, Tadahiro; Kobayashi, Tsuguyuki*

Proceedings of 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 5 Pages, 2009/06

JAEA has been developing a reliable disassembly system for FBR fuel reprocessing as a part of Fast Reactor Cycle Technology Development (FaCT). We fabricated the disassembly system testing machine. In this paper, we described design of it.

Development of disassembly technology for FBR fuel assembly

Kitagaki, Toru; Tasaka, Masayuki; Washiya, Tadahiro; Kobayashi, Tsuguyuki

no journal, , 

JAEA has been developing a reliable disassembly system for FBR fuel reprocessing as a part of Fast Reactor Cycle Technology Development (FaCT). We fabricated a testing machine of disassembly system. In this poster, we described design of this device.