Fluorescence emission behavior of Eu(III) sorbed on calcium silicate hydrates formed with no dried process

Yuichi Niibori, Masayuki Narita, Akira Kirishima, Taiji Chida, Hitoshi Mimura

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Calcium silicate hydrate (CSH) is a main component of cement-based material required for constructing the geological repository. As in many countries, since the repository in Japan is constructed below water table, we must consider the interaction of radionuclide with cement materials altered around the repository after the backfill. Using fluorescence emission spectra, so far, the authors have investigated the interaction of Eu(III) (as a chemical analog of Am(III)) with CSH gels formed with no dried process, considering a condition saturated with groundwater. However, in such fluorescence emission behaviors, a deexcitation process of OH vibrators of light water and a quenching effect caused by Eu-Eu energy transfer between Eu atoms incorporated in the CSH gel must be considered. This study examined the fluorescence emission behavior of Eu(III) sorbed on CSH gels formed with no dried process, by using La(III) (non-fluorescent ions) as a diluent of Eu(III). Furthermore, the CSH samples were synthesized with CaO, SiO2, and heavy water (D2O) as a solvent in order to avoid the obvious deexcitation process of OH vibrators of light water. This study prepared CSH samples with the Ca/Si ratio set to 1.6, 1.0, and 0.5. A 1 mM solution of a given combination of Eu(III) and La(III) (Eu(III) content: 100%, 67%, 50% or 33%) was added into CSH gel sample. The contact time-period of the CSH gel with the Eu(III)/La(III) solution was set to 60 days. In the results, the peak around 618 nm was split into two peaks of 613 nm and 622 nm in the cases of Ca/Si=1.0 and 1.6. Then, the peak of 613 nm decreased with increment of Eu(III)/La(III) ratio. This means that the relative intensity of 613 nm is useful to quantify the amount of Eu(III) incorporated in CSH gel. Besides, the intensity peak of 584 nm decayed with increment of Eu/La ratio, suggesting a quenching effect due to Eu-Eu energy transfer. However, the decay behavior of the fluorescence emission did not depend on the Eu/La concentration ratio. That is, such a quenching effect is neglectable. Additionally, the low Ca/Si ratio samples underwent slow attenuation of fluorescence and showed profiles similar to those of high Ca/Si ratio samples. Therefore, low Ca/Si ratio samples also include the reaction forming a complex on the surface of CSH gel with Eu(III). In other words, even if Ca/Si ratio is lower than 1.0, CSH gels would retard the migration of radionuclides released from the repository.

Original languageEnglish
Title of host publicationFuel Cycle, Radioactive Waste Management and Decommissioning; Reactor Physics and Transport Theory; Nuclear Education, Public Acceptance and Related Issues; Instrumentation and Controls; Fusion Eng.
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Print)9780791855829
DOIs
Publication statusPublished - 2013 Jan 1
Event2013 21st International Conference on Nuclear Engineering, ICONE 2013 - Chengdu, China
Duration: 2013 Jul 292013 Aug 2

Publication series

NameInternational Conference on Nuclear Engineering, Proceedings, ICONE
Volume5

Other

Other2013 21st International Conference on Nuclear Engineering, ICONE 2013
CountryChina
CityChengdu
Period13/7/2913/8/2

ASJC Scopus subject areas

  • Nuclear Energy and Engineering

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    Niibori, Y., Narita, M., Kirishima, A., Chida, T., & Mimura, H. (2013). Fluorescence emission behavior of Eu(III) sorbed on calcium silicate hydrates formed with no dried process. In Fuel Cycle, Radioactive Waste Management and Decommissioning; Reactor Physics and Transport Theory; Nuclear Education, Public Acceptance and Related Issues; Instrumentation and Controls; Fusion Eng. (International Conference on Nuclear Engineering, Proceedings, ICONE; Vol. 5). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/ICONE21-16524