In addition to the three-stage approach, two alternative strategies exist:
Safestore (Safe Enclosure / Deferred Dismantling)
This approach involves placing the facility into a passively safe condition after Stage 1, deferring dismantling for an extended period (potentially 85—100 years). This allows radioactive decay to reduce activity levels significantly, thereby reducing worker dose during eventual dismantling. EDF Energy adopted this strategy for its Magnox fleet. The advantages include:
- Reduced worker doses due to radioactive decay
- Lower dismantling costs
- Potential for improved technologies to become available
The disadvantages include:
- Extended period of institutional control required
- Ongoing maintenance costs
- Risk of loss of records/knowledge over time
Entombment (In Situ Decommissioning)
This approach involves encasing the radioactive structures in a durable material such as concrete, effectively isolating them on-site indefinitely. This approach is generally considered only for:
- Accident situations (e.g. Chernobyl sarcophagus)
- Facilities where removal of radioactive material would cause greater risk than leaving it in place
- Small, low-activity facilities
Note: Entombment is not generally favoured in the UK as regulatory policy requires demonstration that the site can ultimately be released from regulatory control.