Project : Pelletized Clay Mixtures with Enhanced Thermal Conductivity for Engineered Barriers in a Geologic Repository for High-Level Nuclear Waste and Spent Nuclear Fuel.
Clay-pellets presents a number of advantage, e.g., they are very suitable for filling (small) technological voids (as shown in (a)), there is no need for additional in-situ compaction when they are used as a buffer/backfill material ( as shown in (b)), and it is relatively easy to manufacture them.
(a) Filling technological voids
(b) As main buffer/backfill materials (Liu et al., 2019).
(c) Scheme for the emplacement of granular bentonite by gravity fall from the auger (Alonso and Hoffmann, 2007).
Manufacturing High density Pellets
Compacted bentonite sample after extruded from the stainless-steel ring.
Hydraulic press machine (50-ton capacity)
Jaw crusher machine, crushing compacted bentonite to make pellets
Crushed Pellets
The nine size classes of crushed pellets with sizes ranging from 10 mm to 0.075 mm.
For the preparation of pellets, MX-80 bentonite powder with an initial water content of 5.5% was weighed to achieve a target dry density of 2.10 Mg/m3. Then, the clay powder was poured into a cylindrical mold, 50 mm diameter and 100 mm height. Afterwards, the material was statically compacted in a hydraulic press machine (50-ton capacity) until reaching the desired dry density in a clay sample of dimensions 50 mm diameter and 27 mm height. The maximum load was kept for one hour for homogenization of the specimen. The compacted bentonite specimen was then extruded from the mold and crushed into small and irregular pellets using a jaw crusher for producing particles of different sizes, from P10 (10 mm) until P0.075 (0.075 mm), as shown in Fig. 3. Particles coarser than 0.3 mm were regarded as coarse size classes, whereas the others were considered as fine size classes.
