The objective of conditioning is to convert the waste to a solid form with decreased solubility and improved mechanical stability.
| Process | Waste Type | Description | Advantages | Disadvantages |
|---|---|---|---|---|
| Vitrification | HLW | Liquid HLW mixed with borosilicate glass at ~1100 degrees C; may be one-step (direct injection into molten glass) or two-step (evaporation/calcination then incorporation into glass melt); carried out at Sellafield using the AVM process | Very stable waste form; high waste loading; good radiation resistance; low leachability | High-temperature process; requires specialised facility |
| Encapsulation | Spent fuel (once-through cycle) | Fuel pins rearranged (optimised) then enveloped in multi-component barrier of metals (copper, lead etc.) and packaging canister | Proven technology; robust multi-barrier system | Large canister volumes; expensive metals |
| Cementation | ILW / LLW | Waste incorporated into cement matrices | Radiation resistant; compatible with many environmental conditions; established technology | Increases waste volume; consequent increase in disposal cost |
| Bituminisation | LLW / ILW (chemical precipitates from treatment of effluents) | Waste mixed with bitumen | Very low permeability and solubility in water; compatible with most environmental conditions | Uncertain long-term stability; not suitable for high alpha-bearing materials, biodegradable materials or soluble salts (which increase leach rate); not for heat-generating waste |
| Polymerisation | LLW / ILW (resins, sludges, evaporator bottoms, ashes) | Waste immobilised in organic polymers (urea formaldehyde, polyethylene, styrene di-vinyl benzene, epoxy, polyester, PVC, polyurethane) | Versatile; various polymer types available for different waste forms | Requires knowledge of waste chemical composition; adequate understanding of chemical reactions needed |