The multi-barrier concept is adopted and applied for different types of radioactive waste. In principle, the multi-barrier consists of three successive barriers: waste packages, the engineered structure and the geological formation of the site that together provide physical and environmental levels of protection. The first barrier is the conditioned immobilized waste typically through cementation (ILW-LL) or vitrification (HLW-LL). The second one is the corrosion-resistant canisters (e.g., carbon steel for HLW-LL) that contain the immobilised waste. The last barrier is the host rock together with the disposal structure, which ensures isolation, stability and safety of the radioactive waste over a very long period of time. What does vitrification mean during the high-level radioactive waste (HLRW) disposal?
It literally means turning into glass. The waste is initially calcined (dried) to a granular powder. The product is then incorporated into molten glass, poured into a suitable container (such as a stainless steel vessel). when its cooled the vessel is sealed. So the waste is effectively contained within a very stable and impervious lump of glass.
