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-ray analysisKinoshita, Norikazu*; Noto, Takuma*; Nakajima, Hitoshi*; Kosako, Kazuaki*; Kato, Takahiro*; Kuroiwa, Yoichi*; Kurabe, Misako*; Sasaki, Yuki*; Torii, Kazuyuki*; Maeda, Makoto; et al.
Journal of Radioanalytical and Nuclear Chemistry, 332(2), p.479 - 486, 2023/02
Mihara, Morihiro; Harasawa, Shuichi*; Torii, Kazuyuki*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(1), p.15 - 23, 2019/06
Hardened cement pastes (HCPs) of water/cement ratio (W/C) 50% and 30% using fly ash (FA), blast furnace slag (BFS) and silica fume (SF) for 28 days were prepared. Apparent diffusion coefficients (D
) of Cs and I in HCPs were obtained using electron probe microanalysis. For Cs, BFS and SF contributed to a reduction of D for W/C=50% and 30%, respectively. For I, BFS reduced D for W/C=50%, however a significant reduction in D for W/C=30% was not observed. Using SF enhanced sorption of Cs on HCP, and using BFS slightly improved sorption of Cs on HCP. It was also confirmed that the pore structures of HCP using SF and BFS were connected by fine pores. It was therefore considered that using SF and BFS contributes to the reduction of D in HCP.
Mihara, Morihiro; Torii, Kazuyuki*
JAEA-Research 2008-109, 46 Pages, 2009/03
JAEA-Research-2008-109.pdf:8.04MB
Low-alkaline cement using pozzolans is under consideration as a possible filling and structural material in geological disposal for long-lived radioactive waste. Silica fume and high-volume fly ash are used to develop the low-alkaline cement which is named as HFSC, High-volume Fly ash Cement. In this study, pore structure and diffusivity of chloride ion in HFSC pastes were investigated in order to understand the fundamental transport properties of ions.
Mihara, Morihiro; Iriya, Keishiro*; Torii, Kazuyuki*
Doboku Gakkai Rombunshu, F, 64(1), p.92 - 103, 2008/02
To reduce uncertainties in the safety assessment of a disposal system for long-lived radioactive waste, cement was developed which generates leachates with a lower pH than that of ordinary cement paste. This cement was termed "low-alkaline cement". Large amounts of pozzolans were used to produce the low-alkaline cement from ordinary Portland cement. To reduce the pH values, silica fume was found to be efficient, however large amounts of silica fume reduced the workability of fresh concrete. Therefore, we also used fly ash with silica fume, high-volume fly ash silica fume cement (HFSC). The low pH value and self-compacting HFSC was developed. Two types of HFSC showed high compressive strength, smaller drying shrinkage and lower temperature rise than those of ordinary cement concrete. They can therefore be applied to the structure and filling concrete in the disposal system.
Mihara, Morihiro; Torii, Kazuyuki*
Semento, Konkurito Rombunshu, (61), p.331 - 337, 2008/02
In order to evaluate a long-term behavior of hardened high-volume fly ash silica fume cement paste, HFSC, which is considered to be used as filling and structural materials in a repository for the radioactive waste disposal, apparent diffusion coefficients of chloride ion were obtained which might diffused from the surrounded groundwater into the cementitous material. The profiles of chloride concentration in hardened cement paste after the immersion of sodium chloride and calcium chloride solution were measured by electron probe microscopy analysis and apparent diffusion coefficients were calculated fitting these profiles. And, effects of mixture proportion of fly ash content, 40%, 30% and 20%, in HFSC and period of diffusion experiment, 28days and 91days, on the apparent diffusion coefficient were studied from the view point of the pore structure and immobilization ability of chloride ions in HFSC. It was found that the diffusion coefficient of HFSC using 40% of fly ash, HFSC424, was the smallest value in the cement pastes used and the apparent diffusion coefficient degreased as the experimental period. Although HFSC424 had a larger porosity and lower immobilization ability of chloride ion than ordinary Portland cement, it was concluded that the smallest diffusion coefficient was caused by the fine and discontinuous pore structure of HFSC424.
from EPMA and pore struacture of hardened cement pasteMihara, Morihiro; Matsumura, Masamitsu*; Nagasaka, Akiro*; Torii, Kazuyuki*
Konkurito Kogaku Nenji Rombunshu (DVD-ROM), 29(1), p.1023 - 1028, 2007/00
Apppearant diffusion coefficients of Cl in hardend cement pastes were obtained using EPMA.
Mihara, Morihiro; Matsumura, Masamitsu*; Nagasaka, Akiro*; Torii, Kazuyuki*
no journal, ,
no abstracts in English
Mihara, Morihiro; Osvaldo, C.*; Torii, Kazuyuki*; Ito, Yasufumi*
no journal, ,
no abstracts in English
Mihara, Morihiro; Camacho, A.*; Torii, Kazuyuki*
no journal, ,
Low-alkaline cements have been being developed to reduce high alkaline effects on the safety assessment for long-lived radioactive waste disposal by several countries. JAEA is developing High-volume Fly ash Silica fume Cement (HFSC) as low-alkaline cement in Japan. In order to apply to the repository construction, pore structure and diffusivity of chloride (Cl) in HFSC pastes were investigated.
Hayashi, Hirokazu; Nanri, Tomohiro; Hanzawa, Mamoru*; Sasaki, Yuki*; Torii, Kazuyuki*
no journal, ,
To prevent subsidence in a radioactive waste burial site, it is crucial to eliminate any harmful voids. To address this, a method utilizing a large shaking table to fill the voids in the container with sand has been developed. However, decommissioning facilities face constraints on installation space, making the use of a large shaking table challenging. Consequently, a portable sand filling device was developed, and both small-scale tests with a compact container and full-scale tests using a 200L drum were conducted. The test results confirmed a sand filling rate of 80% or more, indicating the feasibility of sand filling with the portable device.
