Bentonite buffer blocks manufactured by isostatic compression

Isostatic compression is a technically highly specialised technology for manufacturing solid components from powder. There are only few reported experiences for isostatic compression of bentonite clay, which forms the basis of the engineered barrier system in the geological disposal concept KBS-3V, currently under investigation in Sweden and Finland. An isostatically compressed middle-scale MX-80 bentonite ring block (approximately 2/3 of full-scale diameter) was examined with regard to its dimensions, shape and surface texture. The physical and mechanical characteristics of the middle-scale ring block were analysed. The measured results were compared to previously obtained data from other isostatically compacted disc and ring blocks of similar scale, as well as to a full-scale ring block also manufactured by isostatic compression. Irrespective of the different manufacturing conditions, a consistent homogeneity among the middle-scale blocks and between the middle and full-scale blocks was determined. Results show that isostatic compression is a feasible manufacturing method that meets the high technical standards demanded in nuclear waste management.