The back end of the nuclear fuel cycle covers everything that happens after the fuel has been used in the reactor:
- At-reactor storage — Spent fuel is stored in the spent fuel pool (a deep pool of water) at the reactor site to allow it to cool and its radioactivity to decrease.
- Transport off site — After a period of cooling, spent fuel is transported in heavily shielded transport flasks (casks) to a storage or reprocessing facility.
- Interim storage — Spent fuel may be stored for an extended period in either wet storage (pools) or dry storage (sealed casks or vaults) at a dedicated facility.
- Reprocessing (optional) — In a closed fuel cycle, spent fuel is chemically processed to recover usable uranium and plutonium for recycling into new fuel. This is carried out at sites such as Sellafield (UK) and La Hague (France).
- Waste conditioning and disposal — High-level waste (from reprocessing) is vitrified (incorporated into glass blocks). Spent fuel or vitrified waste is intended for geological disposal — placement deep underground in a stable geological formation.