Modelling concrete degradation by coupled non-linear processes

Oda, Chie; Kawama, Daisuke*; Shimizu, Hiroyuki*; Benbow, S. J.*; Hirano, Fumio; Takayama, Yusuke; Takase, Hiroyasu*; Mihara, Morihiro; Honda, Akira

Journal of Advanced Concrete Technology, 19(10), p.1075 - 1087, 2021/10

https://doi.org/10.3151/jact.19.1075

Concrete in a transuranic (TRU) waste repository is considered a suitable material to ensure safety, provide structural integrity and retard radionuclide migration after the waste containers fail. In the current study, coupling between chemical, mass-transport and mechanical, so-called non-linear processes that control concrete degradation and crack development were investigated by coupled numerical models. Application of such coupled numerical models allows identification of the dominant non-linear processes that will control long-term concrete degradation and crack development in a TRU waste repository.

A Coupled modeling simulator for near-field processes in cement engineered barrier systems for radioactive waste disposal

Benbow, S. J.*; Kawama, Daisuke*; Takase, Hiroyasu*; Shimizu, Hiroyuki*; Oda, Chie; Hirano, Fumio; Takayama, Yusuke; Mihara, Morihiro; Honda, Akira

Crystals (Internet), 10(9), p.767_1 - 767_33, 2020/09

https://doi.org/10.3390/cryst10090767

Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.

Natural systems evidence for the effects of temperature and the activity of aqueous silica upon montmorillonite stability in clay barriers for the disposal of radioactive wastes

Savage, D.*; Wilson, J.*; Benbow, S.*; Sasamoto, Hiroshi; Oda, Chie; Walker, C.*; Kawama, Daisuke*; Tachi, Yukio

Applied Clay Science, 179, p.105146_1 - 105146_10, 2019/10

https://doi.org/10.1016/j.clay.2019.105146

Natural systems evidence for the effects of temperature and the activity of aqueous silica upon montmorillonite stability was evaluated. Thermodynamic modeling using three different TDBs shows that stability fields for montmorillonite exist from 0 to 140C, but at low values of silica activity, a stability field for illite replaces that for montmorillonite. Pore fluid chemical and mineralogical data for sediments from ODP sites from offshore Japan show a trend from montmorillonite + amorphous silica stability at temperatures up to 60C to that for illite + quartz at higher temperatures. However, even over very long timescales ( 1 Ma), smectite does not transform to illite under thermodynamically-favourable conditions at temperatures less than 80C.

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

Evaluation of the intake of radon through skin from thermal water

Sakoda, Akihiro; Ishimori, Yuu; Tschiersch, J.*

Journal of Radiation Research, 57(4), p.336 - 342, 2016/07

https://doi.org/10.1093/jrr/rrw024

In general, the deposition of inhaled radon progeny on lung gives the largest dose when the dose evaluation is made for the so-called radon exposure. In this case, the dose from inhalation of radon itself is much lower than that from its progeny. Also, very little studies of the absorption of radon via skin have not been done so far. However, specific environments such as radon hot springs have the characteristics that radon concentration in water is significantly higher by a few orders than that in air. In the present study, a biokinetic model of radon into which its skin-absorption process was incorporated was developed to discuss the change in radon concentrations in tissues during and after bathing in thermal water. This derived dose was compared with other exposure routes from radon and its progeny.

Calcium silicate hydrate (C-S-H) gel solubility data and a discrete solid phase model at 25C based on two binary non-ideal solid solutions

Walker, C.; Suto, Shunkichi; Oda, Chie; Mihara, Morihiro; Honda, Akira

Cement and Concrete Research, 79, p.1 - 30, 2016/01

https://doi.org/10.1016/j.cemconres.2015.07.006

Modeling the solubility behavior of calcium silicate hydrate (C-S-H) gel is important to make quantitative predictions of the degradation of hydrated ordinary Portland cement (OPC) based materials. Experimental C-S-H gel solubility data have been compiled from the literature, critically evaluated and supplemented with new data from the current study for molar Ca/Si ratios = 0.2-0.83. All these data have been used to derive a discrete solid phase (DSP) type C-S-H gel solubility model based on two binary non-ideal solid solutions in aqueous solution(SSAS). Features of the DSP type C-S-H gel solubility model include satisfactory predictions of pH values and Ca and Si concentrations for all molar Ca/Si ratios = 2.7 0 in the C-S-H system, portlandite (CH) for Ca/Si ratios 1.65, congruent dissolution at Ca/Si ratios = 0.85, and amorphous silica (SiO) for Ca/Si ratios 0.55 as identified in the current study by IR spectroscopy.

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

Molecular orbital analysis on dissolution of smectite under strong alkaline condition with high Ca concentration

Matsue, Naoto*; Abidin, Z.*; Fujii, Naoki*; Oda, Chie; Honda, Akira

Nendo Kagaku, 52(2), p.62 - 70, 2014/00

https://doi.org/10.11362/jcssjnendokagaku.52.2_62

Bentonite is expected to be used along with cement as engineered barrier components of TRU waste geological disposal system. There is a concern that the bentonite dissolved or altered owing to the contact with strong alkaline and high Ca concentration water derived from the reaction of the cement and groundwater. The first-principles quantum chemical calculations using the cluster model of montmorillonite, the main component of bentonite, were performed, and it was indicated that octahedral Al has higher solubility than octahedral Mg under strong alkaline condition and unsaturated Si-O-Al bond connecting tetrahedral and octahedral sheets at the edge of 110 and 010 planes cleaves easily. The adsorption of OH on tetrahedral Si atom caused dissolution of adjacent Si and Al atoms in addition to the Si atom. While, the dissociation of Si-OH and Al-OH groups and the difference in exchangeable cation species were shown to be less likely to affect the dissolution behavior of montmorillonite.

Reactive-transport model analyses of bentonite alteration behavior at alkaline condition generated by cement-water interaction in a TRU wastes repository

Oda, Chie; Honda, Akira; Takase, Hiroyasu*; Ozone, Kenji*; Sasaki, Ryoichi*; Yamaguchi, Kohei*; Sato, Tsutomu*

Nendo Kagaku, 51(2), p.34 - 49, 2013/02

http://ci.nii.ac.jp/naid/110009594110

Proposed TRU repository designs for geological disposal envisage the use of a bentonite buffer to limit the migration of radionuclides by impeding groundwater flow. Under highly alkaline conditions due to cementitious materials could cause a complex series of coupled changes in the porewater chemistry, mineralogy and, ultimately, the mass transport properties of the bentonite buffer. To elucidate the consequences of these coupled changes, reactive-transport model analyses have been conducted for eight bentonite alteration test cases using different combinations of secondary minerals that could form in the bentonite buffer. It was found that after 100,000 years the amount of dissolved bentonite was at a maximum when metastable secondary minerals precipitated. It was also found that the diffusion and hydraulic coefficients after 100,000 years in all test cases were on the same order of magnitude as the initial values.

Research and development for treatment and disposal technologies of TRU waste; JFY 2010 annual report

Kamei, Gento; Honda, Akira; Oda, Chie; Hirano, Fumio; Ichige, Satoru; Kurimoto, Yoshitaka; Hoshino, Seiichi; Akagi, Yosuke; Sato, Nobuyuki; Takahashi, Kuniaki; et al.

JAEA-Research 2012-010, 80 Pages, 2012/06

JAEA-Research-2012-010.pdf:7.45MB

Based on Japanese governmental policy and general scheme, research and development of geological disposal technology for TRU waste has been proceeding to improve reliability of the safety assessment of the co-locational disposal of TRU waste and of HLW, to expand the basement of generic safety assessment, and to develop the alternative technology to cope with the broad geologic environment of Japan. Japan Atomic Energy Agency is dealing with the assignments in the governmental generic scheme. We report here the progress of the studies at the end of H22 (2010) Japanese fiscal year and their products during the last 5 years. These include (1) evaluation of long-term mechanical stability in the near-field including development of a creep mode of rock and analyses of mechanical behavior of TRU waste repository, (2) performance assessment of the disposal system including cementitious material alteration, bentonite and hostrock alteration with alkaline solution and nitrate effect, and (3) alternative technology development including decomposition of nitrate.