Abstract
Bentonite buffer is an essential component planned in the
KBS-3 concept for safe disposal of spent nuclear fuel. It
limits mass flow to and from the copper canister to
prevent corrosion, and in the case of canister failure,
it retards transport of radionuclides to bedrock, and it
protects the canister in the case of large dislocations
of bedrock caused by e.g. tectonic movement. Bentonite
consists of montmorillonite which is the clay's main and
functional component, some dissolved salts and accessory
mine als. Montmorillonite is a swelling clay mineral that
consists of 1 nm thick and approximately 200-400 nm wide
negatively charged layers and charge compensating cations
near the mineral surfaces. It has the ability to absorb
water molecules into the inter layer space, resulting in
swelling of the mineral, and the ability to change its
cationic composition. Bentonite's beneficial properties
are based on nano level reactions and structures, and
therefore molecular level studies are needed regarding
long term performance studies of spent fuel disposal.
The aim of this work is to study the effect of layer
charge on montmorillonite's swelling properties. Three
different layer charges are applied to four
montmorillonites (Na, Ca, K and Cs) with 16 different
water contents (from 1-16 molecules per unit cell), which
means about 1-3 water layers in the interlayer space.
Larger basal spacings are observed with lower layer
charges of Na- and Ca- montmorillonites, and swelling is
greater with lower charges. Results for K- and
Cs-montmorillonites will be reported later. Molecular
dynamics calculations are performed on an onelayered
montmorillonite particle in a periodic simulation box.
The objective is to determine the interlayer thickness at
equilibrium state in each case. Calculations are done
using the molecular dynamics software LAMMPS with the
CLAYFF interaction potential. As a result, swelling
curves with respect to the number of water molecules per
unit cell are determined. Comparisons to the sample
system density (contribution only f om mineral layer and
interlayer) and the number of interlayer water layers are
made.
Original language | English |
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Title of host publication | IMA 2014 Abstract Volume |
Publisher | Geological Society of South Africa/Geologiese Vereniging van Suid-Afrika |
Pages | 12 |
Number of pages | 1 |
ISBN (Print) | 978-0-620-60082-8 |
Publication status | Published - 2014 |
MoE publication type | Not Eligible |
Event | 21st General Meeting of the International Mineralogical Association, IMA 2014 - Johannesburg, South Africa Duration: 1 Sep 2014 → 5 Sep 2014 |
Conference
Conference | 21st General Meeting of the International Mineralogical Association, IMA 2014 |
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Abbreviated title | IMA |
Country/Territory | South Africa |
City | Johannesburg |
Period | 1/09/14 → 5/09/14 |