Smectite clay, especially montmorillonite, is proposed
for isolating canisters containing highly radioactive waste (HLW) like spent
reactor fuel placed in deep boreholes. It is used for minimizing groundwater
flow around and along waste packages (“Buffer Clay”) and for providing them
with ductile embedment for eliminating risk of canister damage caused by
displacements in the host rock. The clay has the form of heavily compacted
blocks of granules that swell in conjunction with water uptake until their full
hydration potential has been utilized. The dense clay blocks are fitted in
perforated supercontainers that are submerged in smectite mud. The long-term
chemical stability of the clay is sufficient for providing the required
waste-isolating capacity, which is primarily supplied by the heavyness of
stagnant, very salt groundwater at depth.
Smectite clay, montmorillonite, isolating canisters, highly
radioactive waste (HLW), supercontainers, dry density, settlement, creep
settlement, microstructure of smectite clay.