11–16 May 2014
Casino Conference Centre
Europe/Prague timezone

First Shrinkage Parameters of Slovak Bentonites Considered for Engineered Barriers in the Geological Repository for Radioactive Waste and Spent Nuclear Fuel

13 May 2014, 17:15
1h 30m
Gallery (Casino Conference Centre)

Gallery

Casino Conference Centre

Reitenbergerova 4/95, Mari&#225;nsk&#233; L&#225;zn&#283;, Czech Republic <font color=white>
Poster Radionuclides in the Environment, Radioecology Poster Session - Radionuclides in the Environment, Radioecology

Speaker

Mr Adrian Krajnak (Comenius University in Bratislava, Faculty of Natural Sciences)

Description

In a previous research for the deep geological repository of radioactive waste and spent nuclear fuel, the swelling potential of bentonites from Slovak deposits was evaluated by indicative parameters (Atterberg liquid limit) and by swelling pressure tests (Adamcova et al., 2009). The noticed absence of data on shrinkage behaviour initiated a pilot research of bentonite shrinkage parameters in Slovakia (within the project VEGA 1/0828/13 granted by the Slovak Ministry of Education). Comparison of Slovak, Austrian, German and British Standards for shrinkage test methods showed that Slovak Technical Standards (STN) pertain to undisturbed soil samples, where shrinkage depends not only on the current moisture, but also on the grain size distribution and porosity. Shrinkage limit ws (%) and relative linear shrinkage Ls (%) determined according to the foreign technical standards are independent from those properties, because sample preparation brings all soils to equal starting conditions: sieved to grain size below 0.5 mm, water added to reach moisture w near the liquid limit wL, suspension smeared without bubbles into standard moulds. Applied Austrian ONORM B 4411: 2009 offers three test procedures for ws. First, ws was determined by manifold measuring of the sample weight and volume during drying. Calculation followed from the moisture vs. relative volume plot with a linear trend line. Results were compared to data from the other two methods. Highest Ls (up to 32.5% of the initial length) was observed in bentonite J250 from the Jelsovy Potok deposit, the best Slovak bentonite because of its swelling potential and excellent sorption properties for radionuclides (Galambos et al., 2009; Galambos et al, 2010a; Galambos et al, 2010b; Galambos et al., 2011). Reaching of the shrinkage limit (ws = 11%) was indicated also by a color change from light brownish grey (2,5Y 6/2) to light grey (2,5Y 7/1 - Munsell Soil-Color Charts, 2009). Because ws is lower than the equilibrium moisture of the bentonite J250 under room conditions, which is 14%, bentonite blocks might shrink and gaps between them open due to high temperature around the containers with radioactive waste and spent nuclear fuel in the geological repository, until water from the host rock mass intrudes and bentonite swells. Results indicated the necessity of further shrinkage tests, this time on bentonite powder compacted to high-density segments. Methods described in STN 72 1019 were recommended as relevant for the assessment of their total shrinkage. REFERENCES: Adamcova R., Frankovska J., Durmekova T. 2009. Engineering geological clay research for a radioactive waste repository in Slovakia. AGEOS, 1, 2, 2009, 71-82. Galambos M., Kufcakova J., Rajec P. 2009. Sorption of strontium on Slovak bentonites. Journal of Radioanalytical and Nuclear Chemistry, 281, 3, 347-357. Galambos M., Kufcakova J., Rosskopfova O., Rajec P. 2010a. Adsorption of cesium and strontium on natrified bentonites. Journal of Radioanalytical and Nuclear Chemistry, 283, 3, 803-813. Galambos M., Paucova V., Kufcakova J., Rosskopfova O., Rajec P., Adamcova R. 2010b. Cesium sorption on bentonites and montmorillonite K10. Journal of Radioanalytical and Nuclear Chemistry, 284, 1, 55-64. Galambos M., Rosskopfova O., Kufcakova J., Rajec P. 2011. Utilization of Slovak bentonites in deposition of high-level radioactive waste and spent nuclear fuel. Journal of Radioanalytical and Nuclear Chemistry, 288, 3, 765-777.

Primary author

Mr Adrian Krajnak (Comenius University in Bratislava, Faculty of Natural Sciences)

Co-authors

Mr Michal Galambos (Comenius University in Bratislava, Faculty of Natural Sciences) Mr Vladimir Suraba (Comenius University in Bratislava, Faculty of Natural Sciences)

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