Influence of sample preparation on MX-80 bentonite microstructure

M Matusewicz,V.-M Pulkkanen,M Olin

doi:10.1180/claymin.2015.051.2.06

M Matusewicz, V.-M Pulkkanen + Show 1 more

Open Access

https://doi.org/10.1180/claymin.2015.051.2.06

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Journal: Clay Minerals	Publication Date: May 1, 2016
Citations: 6	License type: CC BY 4.0

Affiliation: VTT Technical Research Centre of Finland

Abstract

AbstractCompacted bentonite is to be used as a buffer material between waste canisters and the bedrock in the deep geological disposal of high-level nuclear waste in several countries. In spite of the fact that such large bentonite systems have long equilibration times, estimation of the material properties and performance in repository conditions is often based on short-term, laboratory-scale experiments. Sample-preparation procedures in these experiments may differ from the natural evolution of the bentonite in the repository, however, affecting the bentonite properties. The present study reports the influence on the structure of clay tactoids of four different preparation procedures of water-saturated, compacted MX-80 bentonite samples using four target dry bulk densities. Small-angle X-ray scattering was used to illustrate the differences between the samples. The different treatments of the bentonite samples may lead to different structural features. Clear differences between low-density samples prepared using different procedures were observed. The influence of the preparation methods was less, but still noticeable, for the high-density samples.

Highlights

ABSTR AC T : Compacted bentonite is to be used as a buffer material between waste canisters and the bedrock in the deep geological disposal of high-level nuclear waste in several countries
The MX-80 bentonite is considered as a possible material for clay buffers to be used in repositories for spent nuclear fuel, in countries such as Finland (Posiva, 2012; SKB, 2011)
Due to the uncontrollable conditions in real repository systems and to the long times needed for large bentonite systems to equilibrate, many properties of the MX-80 clay are estimated in small-scale laboratory experiments (Van Loon et al, 2003; Schatz et al, 2013)

Summary

Introduction

ABSTR AC T : Compacted bentonite is to be used as a buffer material between waste canisters and the bedrock in the deep geological disposal of high-level nuclear waste in several countries. In spite of the fact that such large bentonite systems have long equilibration times, estimation of the material properties and performance in repository conditions is often based on short-term, laboratory-scale experiments. The present study reports the influence on the structure of clay tactoids of four different preparation procedures of water-saturated, compacted MX-80 bentonite samples using four target dry bulk densities. Due to the uncontrollable conditions in real repository systems and to the long times needed for large bentonite systems to equilibrate, many properties of the MX-80 clay are estimated in small-scale laboratory experiments (Van Loon et al, 2003; Schatz et al, 2013). One possible problem in making the predictions needed for performance analysis of full-scale models (including both size and time) based on laboratory experiments, lies in sample preparation, which may bias the experimental results in numerous ways.

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Conclusion