NMR Study of Interlayer and Non-interlayer Porewater in Water-saturated Bentonite and Montmorillonite

Torbjörn Carlsson, Arto Muurinen, A. Root

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

Bentonite is planned to be used in many countries as an important barrier in high-level waste repositories. Assessment of the barrier with regard to, inter alia, its ability to hinder transport of dissolved radionuclides leaking from a damaged canister containing spent nuclear fuel, requires quantitative data about the pore structure inside bentonite. The present NMR study was made in order to determine the number of distinguishable porewater phases in compacted water-saturated samples of MX-80 bentonite and Na-montmorillonite. The samples were compacted to dry densities in the interval 0.7-1.6 g/cm3 and subsequently saturated with Milli-Q water or 0.1 M NaCl solution in equilibrium cells. The NMR measurements were performed with a high-field 270 MHz NMR spectrometer using a short inter-pulse CPMG method to study proton T1ρ relaxation. The measured relaxation curves were found to consist of one faster and one slower proton relaxation. Subsequent analysis of the data indicated that the faster relaxation was associated with interlayer (IL) water between montmorillonite unit layers, while the slower one was associated with non-interlayer (non-IL) water located outside the interlayer spaces. The results indicate for compacted samples with a dry density of ≥ 1.0 g/cm3, that Na montmorillonite contains a larger relative volume of non-IL water than the corresponding MX-80 bentonite. This in turn, suggests that the stacking number in Na-montmorillonite is smaller than in MX-80 bentonite. Changing the porewater chemistry seemed to have some effect on the non-IL water content in the Na montmorillonite but not in the MX-80 bentonite
Original languageEnglish
Title of host publicationMRS Proceedings
Subtitle of host publicationSymposium LL - Scientific Basis for Nuclear Waste Management XXXVI
EditorsN. Hyatt
PublisherMaterials Research Society MRS
Pages167-172
ISBN (Print)978-1-5108-4497-1
DOIs
Publication statusPublished - 2013
MoE publication typeNot Eligible
Event2012 MRS Fall Meeting & Exhibit - Boston, Massachusetts, United States
Duration: 25 Nov 201230 Nov 2012

Publication series

SeriesMaterials Research Society Symposia Proceedings
Volume1518

Conference

Conference2012 MRS Fall Meeting & Exhibit
CountryUnited States
CityBoston, Massachusetts
Period25/11/1230/11/12

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Keywords

  • microstructure
  • nuclear magnetic resonance (NMR)
  • waste management

Cite this

Carlsson, T., Muurinen, A., & Root, A. (2013). NMR Study of Interlayer and Non-interlayer Porewater in Water-saturated Bentonite and Montmorillonite. In N. Hyatt (Ed.), MRS Proceedings : Symposium LL - Scientific Basis for Nuclear Waste Management XXXVI (pp. 167-172). Materials Research Society MRS. Materials Research Society Symposia Proceedings, Vol.. 1518 https://doi.org/10.1557/opl.2013.93