NMR study of C-A-S-H structures

Walker, C.*

NIMS Bisai Kozo Kaiseki Purattofuomu Riyo Hokokusho (Internet), 2 Pages, 2021/09

High content fly ash silica fume cement (HFSC) has been considering a candidate low alkali cements for the geological disposal of radioactive waste in Japan. JAEA has been currently performing many experiments and modeling studies relevant to validation for the long-term stability of the C-A-S-H gel which is a dominant component of the HFSC. For developing the C-A-S-H model of hydration and degradation, it is necessary to determine the composition of C-A-S-H gel and accompanied minerals when it reacts with water. In the present subject, the synthesized sample of C-A-S-H gels were analyzed by using the NMR spectra of Al and Si to determine the coordination of these element in the C-A-S-H gel.

Development of molecular simulation technology for elucidating radiation concentration mechanism in fungi and lichens; Quantitative evaluation of complexation selectivity of secondary metabolites using quantum chemical calculations

Suno, Hiroya; Machida, Masahiko

RIST News, (66), p.3 - 16, 2020/10

no abstracts in English

Evaluation of hydrogeochemical processes provoked by tunnel excavation and closure based on simulated experiment in a mock-up test drift

Hayashida, Kazuki; Kato, Toshihiro*; Kubota, Mitsuru*; Murakami, Hiroaki; Amano, Yuki; Iwatsuki, Teruki

Chikyu Kagaku, 52(1), p.55 - 71, 2018/03

https://doi.org/10.14934/chikyukagaku.52.55

In this study, the simulated experimental drift was constructed in the granite of 500 m depth at Mizunami Underground Research Laboratory, and the hydrochemical process after the drift closure was observed. The groundwater chemistry around the drift changed with the change of the groundwater flow in the fractures when the gallery was constructed. The redox potential increased due to the infiltration of oxygen from the drift into the rock. After closing the drift, the redox potential of the groundwater plunged due to microbial activity, while the groundwater became alkalized conditon due to the influence of cement material such as shotcrete. The amount of cement material consumed for this alkalization was small, and it was considered that its influence would last long in accordance with the amount of cement used.

Chemical state analysis of trace-level alkali metals sorbed in micaceous oxide by total reflection X-ray photoelectron spectroscopy

Baba, Yuji; Shimoyama, Iwao; Hirao, Norie*

Applied Surface Science, 384, p.511 - 516, 2016/10

AA2016-0127.pdf:0.71MB

https://doi.org/10.1016/j.apsusc.2016.05.067

Chemical states of cesium as well as the other alkali metals (sodium and rubidium) sorbed in micaceous oxides have been investigated by total reflection X-ray photoelectron spectroscopy (TR-XPS). For cesium, it was shown that ultra-trace amount of cesium down to about 100 pg/cm can be detected by TR-XPS. This amount corresponds to about 200 Bq of Cs (t = 30.2y). It was demonstrated that ultra-trace amount of cesium corresponding to radioactive cesium level can be measured by TR-XPS. As to the chemical states, it was found that core-level binding energy in TR-XPS for trace-level cesium shifted to lower-energy side compared with that for thicker layer. A reverse tendency is observed in sodium. Based on charge transfer within a simple point-charge model, it is concluded that chemical bond between alkali metal and micaceous oxide for ultra-thin layer is more polarized that for thick layer.

Quantum control based on dynamic Stark effect

Kurosaki, Yuzuru

Shototsu, 12(4), p.114 - 125, 2015/07

http://www.atomiccollision.jp/collision/syoutotsu/15_1204s.pdf#page=19

no abstracts in English

Recovery of alkali salt by supercritical fluid leaching method using carbon dioxide

Watanabe, Takeshi*; Tsushima, Satoru*; Yamamoto, Ichiro*; Tomioka, Osamu; Meguro, Yoshihiro; Nakashima, Mikio; Wada, Ryutaro*; Nagase, Yoshiyuki*; Fukuzato, Ryuichi*

Proceedings of 2nd International Symposium on Supercritical Fluid Technology for Energy and Environment Applications (Super Green 2003), p.363 - 366, 2004/00

Recovery of salts by supercritical fluid leaching (SFL) method using carbon dioxide was experimentally studied. It was confirmed that LiCl was recovered with a mixed fluid of carbon dioxide and methanol, and KCl and SrCl were recovered with a mixed fluid of carbon dioxide, methanol and crown ether. The influence of crown ether for KCl and SrCl extraction were found to increase in the order of 15-crown-5 (15C5) 18-crown-6 (18C6) dicychlohexyl-18-crown-6 (DC18C6). It is expected that other salts can be recovered selectively with a mixed fluid of carbon dioxide, methanol and suitable crown ether.

Fine fibrous amidoxime adsorbent synthesized by grafting and uranium adsorption-elution cyclic test with seawater

Seko, Noriaki; Katakai, Akio; Tamada, Masao; Sugo, Takanobu*; Yoshii, Fumio

Separation Science and Technology, 39(16), p.3753 - 3767, 2004/00

https://doi.org/10.1081/SS-200042997

Fibrous amidoxime adsorbents were prepared by radiation-induced co-grafting of acrylonitrile (AN) and methacrylic acid (MAA) and subsequent amidoximation. Adsorption of uranium in seawater was evaluated by pumping seawater into the adsorbent column. The best monomer ratio of AN and MAA was 7:3 for continual usage of uranium adsorption. Though hydrochloric acid is an effective eluting agent for the metals adsorbed on the adsorbent, amidoxime groups were simultaneously damaged after five cycles of adsorption-desorption. This deterioration was reduced by an alkaline treatment of the adsorbents after each elution. Furthermore, various organic acids were examined as elution agents. It was found that the 80% of adsorption activity was still maintained after five cycles of adsorption-desorption when tartaric acid was used for eluting agent.

Evidence for a difference in the dissociation mechanisms of acetylene (HCCH) and vinylidene (HC=C:) from charge inversion mass spectrometry

Hayakawa, Shigeo*; Tomozawa, Koji*; takeuchi, takae*; Arakawa, Kazuo; Morishita, Norio

Physical Chemistry Chemical Physics, 5(11), p.2386 - 2390, 2003/05

https://doi.org/10.1039/B212834A

The process of formation of the negative ions in charge inversion mass spectrometry is via near-resonant neutralization followed by spontaneous dissociation, and then endothermic negative ion formation. The intensity of the C peak relative to the CH peak in these spectra increased with decreasing ionization potential of the targets for both of the isomeric CH cations. The formation of the C anion is proposed to result from the dissociation of excited CH neutrals into C and H. The dependence on target species of the intensities of C peak relative to the CH peak for HCCH and HC=C: cannot be rationalized by the internal energy of the excited CH neutrals. The differences indicate that the isomeric CH neutrals dissociate into CH and H prior to 1,2-hydrogen atom migration.

A study on long term stability of bentonite; The preliminary study on the bentonite stability in the groundwater influenced by cementitious material

*; Mihara, Morihiro;

JNC TN8430 2001-007, 56 Pages, 2002/01

JNC-TN8430-2001-007.pdf:13.13MB

In the geological disposal concept of radioactive wastes, a kind of clay with sorption ability and low permeability, called bentonite, is envisaged as an engineered barrier system in the geological repository. Also, the cemetitious material is envisaged as the backfill material in the vaults and the structure material of the vaults. The groundwater in contact with the cementitious material will promote hyperalkaline conditions in the repository environment and these conditions will affect the performance of the bentonite. Therefore, it is necessary to investigate the interaction between the cementitious material and the bentonite for the evaluation of long term stability of the disposal system. In this study, for the identification and the investigation of the secondary minerals, the batch immersion experiments of the powder bentonite were carried out using synthetic cement leachates (pH=7, 12.5, 14) at 200C. As the results, it was confirmed that Na as exchangeable cations in the bentonite can exchange relatively easily with Ca in the solution from the experiment results. And the ratio of cation exchange was estimated to be about 25% based on the amount of exchangeable cations Ca between layers. Furthermore, it was concretely shown that the generation of analcime might be affected by the Na concentration from results of the solution analyses and a stability analysis of analcime using the chemical equilibrium model, in addition to the pH in the solution.

Alkali hydrolysis experiment of organic materials such as cement additives

Fukumoto, Masahiro; Nishikawa, Yoshiaki*

JNC TN8400 2001-017, 355 Pages, 2001/03

JNC-TN8400-2001-017.pdf:6.43MB

The alkali hydrolysis experiments which seem to be important from the view point of the alteration mechanism using the following seven organic materials was performed as a part of the evaluation of the influence on the disposal of the organic materials contained in the TRU wastes. As a result of the alkali hydrolysis experiments (90C and 91d), each organic materials became those of lower molecular weight. The degradation products were able to be detected in the solution. The organic materials seem to be degraded to the organic matters which were confirmed in this study in a long term of disposal. The degradation products were shown below. Therefore, the evaluation of the influence on the migration of radionuclides by degradation products becomes important in the future. (1)Cement additives of Naphthalenesulfonic acid and Ligninsulfonic acid ( Naphthalenedisulfonic acid etc.) (2)Cement additives of polycarboxylic acid ( Oligomer of distal methoxypoly ethylene glycol.) (3)Ethylenediamine-N,N,N',N'-tetraacetic acid disodium salt ( Acetic acid desorped and cyclized organic matters from EDTA.) (4)Tributyl phosphate ( Dibutyl phthalate, n-butanol) (5)Poly vinyl acetate ( Acetic acid) (6)Nylon66 ( Adipic acid, Hexamethylenediamine) (7)Cured epoxy resin ( Glycerol poly glycidyl ether, Carboxylic acid)