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Journal Articles

Hydration and degradation of High content Fly ash Silica fume Cement (HFSC)

Anraku, Sohtaro; Walker, C.*; Oda, Chie; Mihara, Morihiro; Honda, Akira

Proceedings of 15th International Congress on the Chemistry of Cement (ICCC 2019) (Internet), 11 Pages, 2019/09

Journal Articles

Formation of metal ion complexes in cementitious porewaters and leachates

Walker, C.*; Anraku, Sohtaro; Oda, Chie; Mihara, Morihiro; Honda, Akira

Proceedings of 15th International Congress on the Chemistry of Cement (ICCC 2019) (Internet), 11 Pages, 2019/09

Journal Articles

Report on the weekend basic course for Division of Nuclear Fuel Cycle and Environment in fiscal year 2016

Anraku, Sohtaro

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.65 - 68, 2017/06

no abstracts in English

Journal Articles

Geochemical factors for secondary mineral formation at naturally-occurring hyperalkaline spring in Oman ophiolite

Anraku, Sohtaro; Matsubara, Isamu*; Morimoto, Kazuya*; Sato, Tsutomu*

Nendo Kagaku, 55(2), p.17 - 30, 2017/00

Anionic radionuclides are important for the long-term safety assessment of Japanese transuranic (TRU) waste disposal facilities. Degradation of cementitious materials used to construct the TRU waste disposal facilities, however, can produce a hyperalkaline leachate and so it is necessary to understand the reaction mechanisms that will control the behavior and fate of anionic radionuclides under these hyperalkaline conditions. An excellent natural analogue site to study relevant reaction mechanisms is provided in Oman where hyperalkaline spring waters (pH $$>$$ 11) from serpentinized peridotites discharge into moderately alkaline rivers. Aragonite was found in all secondary mineral samples, with accessory minerals of calcite, layered double hydroxide (LDH) and brucite. LDH was observed at the high Al concentration springs and brucite at the low Al concentration springs. Calcite was only found close to the springs. Distal calcite formation was inhibited due to high Mg concentrations in the river water. The spatial distribution of minerals therefore implicates the importance of the mixing ratio of spring to river water and the relative chemical compositions of the spring and river waters. Supporting mixing model calculations could successfully reproduce the precipitation of aragonite and LDH. The observed decrease in Ca concentration could be explained by aragonite precipitation. pH exerted a strong control on the precipitation of LDH and so too, therefore, on Al concentration. In the mixing water experiments containing up to 40% river water, LDH and brucite were both oversaturated, but brucite was not always identified by XRD. The possible inhibition of brucite by LDH precipitation was an unexpected result.

Oral presentation

Expansion and alteration behavior of NH$$_4$$-montmorillonite

Kawakita, Ryohei*; Saito, Akito*; Sakuma, Hiroshi*; Anraku, Sohtaro; Oda, Chie; Mihara, Morihiro; Sato, Tsutomu*

no journal, , 

no abstracts in English

Oral presentation

Effect of ammonium ion on expandability of montmorillonite

Kawakita, Ryohei*; Saito, Akito*; Sakuma, Hiroshi*; Anraku, Sohtaro; Oda, Chie; Mihara, Morihiro; Sato, Tsutomu*

no journal, , 

no abstracts in English

Oral presentation

C-S-H gel solubility modelling at high temperatures

Walker, C.; Anraku, Sohtaro; Mitsui, Seiichiro; Oda, Chie; Mihara, Morihiro; Honda, Akira

no journal, , 

Oral presentation

Thermodynamic properties of hydrotalcite

Anraku, Sohtaro

no journal, , 

no abstracts in English

Oral presentation

Thermodynamic properties of SiO$$_{2(aq)}$$, HSiO$$_{3}$$$$^{-}$$ and SiO$$_{3}$$$$^{2-}$$

Walker, C.*; Anraku, Sohtaro; Oda, Chie; Mitsui, Seiichiro; Mihara, Morihiro

no journal, , 

Equilibrium constants (${it K}$) describing the formation reactions of SiO$$_{2(aq)}$$, HSiO$$_{3}$$$$^{-}$$ and SiO$$_{3}$$$$^{2-}$$ can be used to derive their thermodynamic properties. However, SiO$$_{2(aq)}$$ was derived from inaccurate quartz solubility data, HSiO$$_{3}$$$$^{-}$$ was not extrapolated to zero ionic strength and SiO$$_{3}$$$$^{2-}$$ is routinely ignored because of its restricted dominance to very high pH $$>$$ 13 solutions. Using quartz and water data as well known "anchor" points, ${it K}$ values describing the formation reactions of SiO$$_{2(aq)}$$, HSiO$$_{3}$$$$^{-}$$ and SiO$$_{3}$$$$^{2-}$$ were revised to derive new thermodynamic properties and revised Helgeson-Kirkham-Flowers equation of state (r-H-K-F EoS) parameters. These properties and parameters can be used in the derivation of the thermodynamic properties of other Si bearing aqueous species/complexes and the thermodynamic properties of cementitious, clay, zeolite, and rock forming minerals, and in calculating groundwater compositions relevant to the geological disposal of radioactive wastes.

Oral presentation

In situ interactions of concretes with mudstones from Horonobe URL

Anraku, Sohtaro; Sato, Hisao*; Walker, C.*; Amano, Yuki; Sakurai, Akitaka; Nakayama, Masashi; Tachi, Yukio

no journal, , 

Oral presentation

C(-A)-S-H gel solubility model development and its application to high content fly ash silica fume cement

Walker, C.*; Anraku, Sohtaro; Sasamoto, Hiroshi; Mihara, Morihiro

no journal, , 

A thermodynamically credible calcium(-aluminate)-silicate-hydrate (C(-A)-S-H) gel solubility model has to consider a variety of features, including structure, composition, phase boundaries, measured/estimated thermodynamic properties, molar volumes, and, of course, solubility behavior in terms of pH values and Ca, Al and Si concentrations expressed as a function of C(-A)-S-H gel composition, temperature and ionic strength. This study provides an account of the rapidly growing body of data that are concerned with these features and of the more promising approaches that can be used to develop a C(-A)-S-H gel solubility model. JAEA research on the degradation of high content fly ash silica fume cement (HFSC) provides a good working example that highlights the need to develop a C(-A)-S-H gel solubility model.

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