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Journal Articles

Eutectic melting of metals

Sumita, Takehiro; Ikeda, Atsushi

Isotope News, (783), p.28 - 32, 2022/10

no abstracts in English

Journal Articles

Potential bacterial alteration of nuclear fuel debris; A Preliminary study using simulants in powder and pellet forms

Liu, J.; Dotsuta, Yuma; Sumita, Takehiro; Kitagaki, Toru; Onuki, Toshihiko; Kozai, Naofumi

Journal of Radioanalytical and Nuclear Chemistry, 331(6), p.2785 - 2794, 2022/06

 Times Cited Count:3 Percentile:71.05(Chemistry, Analytical)

Remnant nuclear fuel debris in the damaged nuclear reactors at the Fukushima Daiichi Nuclear Power Plant (FDNPP) has contacted the groundwater containing microorganisms for over ten years. Herein, we report the possibility of bacterial alteration of fuel debris. We investigated the physical and chemical changes of fuel debris simulants (FDS) in the powder and pellet forms via exposure to two ubiquitous bacteria, Pseudomonas fluorescens and Bacillus subtilis. In the experiments using FDS composed of the powders of Fe(0), solid solution of CeO$$_{2}$$ and ZrO$$_{2}$$, and SiO$$_{2}$$, Ce, Zr, and Si were hardly dissolved, while Fe was dissolved, a fraction of the dissolved Fe was present in the liquid phase as Fe(II) and Fe(III), and the rest was precipitated as the nano-sized particles of iron (hydr)oxides. In the experiment using P. fluorescens and FDS pellet pieces prepared by melting the Fe(0) particles and solid solution of CeO$$_{2}$$ and ZrO$$_{2}$$, the bacteria selectively gathered on the Fe(0) particle surface and made corrosion pits. These results suggest that bacteria in groundwater corrode the iron in fuel debris at FDNPP, change fuel debris into porous one, releasing the nano-sized iron (hydr)oxide particles into the water.

Journal Articles

Direct ${it in-situ}$ temperature measurement for lamp-based heating device

Sumita, Takehiro; Sudo, Ayako; Takano, Masahide; Ikeda, Atsushi

Science and Technology of Advanced Materials; Methods (Internet), 2(1), p.50 - 54, 2022/02

Journal Articles

High temperature reaction of multiple eutectic-component system; The Case of solid metallic Zr and molten stainless steel-B$$_{4}$$C

Sumita, Takehiro; Kobata, Masaaki; Takano, Masahide; Ikeda, Atsushi

Materialia, 20, p.101197_1 - 101197_11, 2021/12

Journal Articles

Solidification and re-melting mechanisms of SUS-B$$_{4}$$C eutectic mixture

Sumita, Takehiro; Kitagaki, Toru; Takano, Masahide; Ikeda, Atsushi

Journal of Nuclear Materials, 543, p.152527_1 - 152527_15, 2021/01

 Times Cited Count:10 Percentile:88(Materials Science, Multidisciplinary)

Oral presentation

Cs Adsorption behavior evaluation on the surface of nuclear reactor structure materials under high temperature and high pressure steam

Sumita, Takehiro*; Yonekawa, Kazuo*; Sekio, Yoshihiro; Sato, Isamu*; Kobayashi, Yoshinao*; Osaka, Masahiko; Maeda, Koji; Akasaka, Naoaki

no journal, , 

During Fukushima Daiichi Nuclear Power Plant (1F) accident, high radionuclides such as $$^{137}$$Cs and $$^{133}$$I were mainly released as fission products (FPs) due to fuel melting in units 1 to 3, and it increased radiation dose in reactor buildings. With the aim of 1F decommissioning, it is necessary to establish methods to retrieve fuel and an adequate access route, which requires knowledge of Cs adsorption behavior on the surface of structural materials during Severe Accidents (SA). However, there are no Cs adsorption behavior evaluations under the simulated SA condition with high pressure in the previous studies. In this study, CsI adsorption behavior on SUS304L under the condition was evaluated using newly designed apparatus which can control temperature, pressure, moisture and gas atmosphere. The findings from microstructural observation and elemental analysis after the adsorption test suggested that the adsorption of CsI was influenced by especially pressure.

Oral presentation

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