Dry storage is less common than wet storage but is particularly relevant for fuels with cladding vulnerable to corrosion (e.g. Magnox fuel). Dry storage facilities must satisfy five requirements:
- Containment --- prevent release of radioactivity
- Shielding --- adequate radiation protection
- Cooling --- remove decay heat
- Criticality safety --- prevent any critical configuration
- Security --- protect fuel from damage or theft
Typical Dry Storage Design
- Fuel container: Close-fitting cast iron cask surrounded by a stainless steel jacket
- Cooling method: Passive air cooling (preferred) --- no pumps or active systems needed
- Heat transfer: Cooling fins on the cask to increase surface area
- Outer containment: Concrete silo providing shielding and security
- Gas monitoring: Air removed from store is monitored and filtered before discharge
- Hydrogen exclusion: Explosive gases (e.g. ) must be excluded from the store
Additional design considerations:
- The store must withstand seismic and mechanical shocks
- The design must account for water ingress (e.g. from fire-fighting) as this could introduce a moderator and affect criticality safety
- Careful attention to shine paths and gamma scattering when fuel is being moved or inspected
- Dose meters and alarms around the perimeter of the store
- The stored fuel must remain accessible for later removal or transport