Alumino-silicate structural formation during alkali-activation of metakaolin; In-situ and ex-situ ATR-FTIR studies

Onutai, S.; Osugi, Takeshi; Sone, Tomoyuki

Materials, 16(3), p.985_1 - 985_14, 2023/02

https://doi.org/10.3390/ma16030985

Emulsification of low viscosity oil in alkali-activated materials

Reeb, C.*; Davy, C. A.*; Pierlot, C.*; Bertin, M.*; Cantarel, V.; Lambertin, D.*

Cement and Concrete Research, 162, p.106963_1 - 106963_16, 2022/12

https://doi.org/10.1016/j.cemconres.2022.106963

Kinetic and Fourier transform infrared studies on the thermal decomposition of sodium hydride

Kawaguchi, Munemichi

Journal of Physical Chemistry C, 125(22), p.11813 - 11819, 2021/06

https://doi.org/10.1021/acs.jpcc.1c00538

Isothermal and constant heating thermogravimetry-differential thermal analysis (TG-DTA) and Fourier transform infrared spectrometer (FTIR) measurements have been performed for pre- and post-fired sodium hydride (NaH) in the temperature range of 500-700 K, respectively. Temperature dependence of NaH thermal decomposition rates obtained by the isothermal TGs showed an inflection point at around 620 K, which was caused by two kinds of hydrogen states (rapid diffusing and immobile hydrogen). In the FTIR spectra for the NaH and sodium (Na), the specific signals were observed at around 873.4, 1010.4, 1049.5 and 1125.7 cm, and the integrated values of FTIR signals for post-fired NaH at below 550K and at above 698 K were comparable to those for pre-fired NaH and Na, respectively. Those for post-fired NaH at 602-667 K were the intermediate values of the pre-fired NaH and Na, which denoted that the Na-Na bonds haven't grown sufficiently and the hydrogen coexisted in metallic Na. In order to predict the practical kinetics of NaH thermal decomposition reaction, we suggested the simple kinetics model which assumed two kinds of rapidly diffusing and immobile hydrogen states. The simulation results revealed the inflection point in temperature dependence of the thermal decomposition rates accordingly because the transition from immobile hydrogen to rapid diffusing hydrogen crosses over at around 620 K.

Safe, efficient cementation of challenging radioactive wastes using alkali activated materials with high-flowability and high-anion retention capacity (Contract research); FY2019 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*

JAEA-Review 2020-054, 72 Pages, 2021/01

JAEA-Review-2020-054.pdf:5.62MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Safe, efficient cementation of challenging radioactive wastes using alkali activated materials with high-flowability and high-anion retention capacity". The purpose of this study is to find safe, efficient cementation of challenging radioactive wastes using alkali activated materials with high-flowability and high-anion retention capacity, and to propose the concept of a manufacturing apparatus that is established as an actual plant. As a result of study in this year, it was revealed that the K-based alkali activated material has high-flowability and quick curing, and that high-iodine retention capacity is achieved by incorporating silver ions during manufacturing of solidified waste.

Phase-field model for crystallization in alkali disilicate glasses; LiO-2SiO, NaO-2SiO and KO-2SiO

Kawaguchi, Munemichi; Uno, Masayoshi*

Journal of the Ceramic Society of Japan, 128(10), p.832 - 838, 2020/10

https://doi.org/10.2109/jcersj2.20145

This study developed phase-field method (PFM) technique in oxide melt system by using a new mobility coefficient (). The crystal growth rates () obtained by the PFM calculation with the constant were comparable to the thermodynamic driving force in normal growth model. The temperature dependence of the was determined from the experimental crystal growth rates and the . Using the determined , the crystal growth rates () in alkali disilicate glasses, LiO-2SiO, NaO-2SiO and KO-2SiO were simulated. The temperature dependence of the was qualitatively and quantitatively so similar that the PFM calculation results demonstrated the validity of the . Especially, the obtained by the PFM calculation appeared the rapid increase just below the thermodynamic melting point () and the steep peak at around -100 K. Additionally, as the temperature decreased, the apparently approached zero ms, which is limited by the representing the interface jump process. Furthermore, we implemented the PFM calculation for the variation of the parameter in the . As the increased from zero to two, the peak of the became steeper and the peak temperature of the shifted to the high temperature side. The parameters and in the increased exponentially and decreased linearly as the atomic number of the alkali metal increased due to the ionic potential, respectively. This calculation revealed that the and in the were close and reasonable for each other.

Stabilization of lead with amorphous solids synthesized from aluminosilicate gel

Sato, Junya; Shiota, Kenji*; Takaoka, Masaki*

Journal of Hazardous Materials, 385, p.121109_1 - 121109_9, 2020/03

https://doi.org/10.1016/j.jhazmat.2019.121109

Lead is a hazardous heavy metal that can be stabilized by incorporation into the matrix of aluminosilicate bearing phases as they solidify. The actual mechanism by which lead is stabilized, however, continues to be unclear because the individual mechanisms of Pb incorporation into crystalline and amorphous aluminosilicate phases have not yet been studied separately. A detailed investigation of the incorporation of Pb into the amorphous phase of aluminosilicate solids was therefore performed. Amorphous aluminosilicate solids were synthesized with 0.7, 1.5, and 3.7 wt% of Pb from aluminosilicate gel produced from chemical reagents. Based on Raman spectroscopy, the Si-O stretching vibration bond shifted to lower wavenumbers with increasing Pb concentration. This shift suggested that covalent bonding between Pb and O in the matrix of the aluminosilicate solids increased. In addition, sequential extraction revealed that most of the Pb (75-90%) in the aluminosilicate solids was in a poorly soluble form (i.e. reducible, oxidizable, and residual fractions). These findings indicate that most of Pb is bonded covalently to the amorphous phase in aluminosilicate solids.

Confirmation of the applicability of low alkaline cement-based material in the Horonobe Underground Research Laboratory

Nakayama, Masashi; Niunoya, Sumio*; Minamide, Masashi*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.25 - 30, 2016/06

https://doi.org/10.3327/jnuce.23.1_25

In Japan, any high-level radioactive waste repository is to be constructed at over 300m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly fly-ash contained silicafume cement), containing over 60wt% of silica-fume (SF) and coal ash (FA). JAEA is presently constructing an underground research laboratory (URL) at Horonobe for research and development in the geosciences and repository engineering technology. HFSC was used experimentally as the shotcrete material in construction of part of the 350m deep gallery in Horonobe URL in 2013. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel constructed using HFSC shotcrete is about 112m at 350m deep drift. The workability of HFSC shotcrete was confirmed by this experimental construction. In this report, we present detailed results of the in-situ construction test.

Mineralogical changes and associated decrease in tritiated water diffusivity after alteration of cement-bentonite interfaces

Yamaguchi, Tetsuji; Sawaguchi, Takuma; Tsukada, Manabu; Hoshino, Seiichi*; Tanaka, Tadao

Clay Minerals, 51(2), p.279 - 287, 2016/02

https://doi.org/10.1180/claymin.2016.051.2.13

Alteration of bentonite-cement interfaces and accompanying changes in diffusivity of tritiated water was experimentally investigated using intact hardened cement specimens. The alteration by carbonate solution was accompanied by mineralogical changes at the interface and a decrease in the diffusivity to 70% of the initial value after 180-day period. Another alteration under silicate system contacting hardened cement and compacted bentonite was accompanied by mineralogical changes at the interface and a decrease in the diffusivity to 71% of the initial value after 600-day period. The changes in the diffusivity were much less than those observed for mixed specimens of granulated hardened cement and bentonite where the diffusivity decreased down to 20% of the initial value over 180 days. The results were extrapolated to 15 years under simple assumptions and showed good agreement with those observed in the cement-argillite interface at Tournemire URL. Such an explanation enhances our confidence in our assessment of alteration of cement-bentonite systems and can be a base for using our data and models in long term assessment of radioactive waste disposal.

Interaction between ultra-trace amount of cesium and oxides studied by total-reflection X-ray photoelectron spectroscopy

Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Izumi, Toshinori

e-Journal of Surface Science and Nanotechnology (Internet), 13, p.417 - 421, 2015/09

https://doi.org/10.1380/ejssnt.2015.417

The interaction between alkali metals and oxides has attracted much attention as heterogeneous catalysis, chemical reaction promoters, and high intensity electron emitter. Also the interaction of cesium and oxides has become important subject, because radioactive cesium trapped in minerals such as clay and soil may cause health risks. In the present study, we analyzed chemical states of ultra-trace amount of cesium on oxide surfaces by total reflection X-ray photoelectron spectroscopy (TR-XPS) exited by synchrotron radiation. For the adsorbed cesium thicker than 0.01 layer, cesium is weakly bound with oxide through Van-der-Waals force. On the other hand, for ultra-thin layer about 0.002 layer, the chemical bond changes to covalent bond. It is suggested that this change in the chemical bonding state is one of the reasons why radioactive cesium is hard to be released from minerals.

Draft genome sequence of potassium-dependent alkaliphilic sp. strain TS-2, isolated from a jumping spider

Fujinami, Shun*; Takeda, Kiyoko*; Onodera, Takefumi*; Sato, Katsuya; Sano, Motohiko*; Narumi, Issey*; Ito, Masahiro*

Genome Announcements (Internet), 2(3), p.e00458-14_1 - e00458-14_2, 2014/05

https://doi.org/10.1128/genomeA.00458-14