01 How It Works
AGRs use carbon dioxide gas as coolant, flowing over stainless-steel-clad uranium oxide fuel elements embedded in a graphite moderator. The high operating temperature (~650°C outlet) allows direct steam generation at temperatures comparable to a conventional coal plant, giving better thermal efficiency. Reactors are built inside a prestressed concrete pressure vessel. The graphite moderator - like in the RBMK - has led to cracking issues as reactors aged.
02 Pros & Cons
✓ Advantages
- Higher operating temperature → better thermal efficiency
- Graphite moderated → good neutron economy
- Robust prestressed concrete containment
- Proved reliable over decades of operation
✗ Disadvantages
- Graphite bricks crack with age - major end-of-life issue
- CO₂ coolant causes corrosion at high temperatures
- Very expensive to decommission
- Unique UK design - no international supply chain
03 Specifications
THERMAL EFFICIENCY~41%
OPERATING TEMP~650°C outlet
PRESSURE~40 bar (CO₂)
FUELEnriched UO₂ in stainless steel
FUELEnriched UO₂ in stainless steel
COUNTRIESUnited Kingdom only
04 Did You Know?
All UK AGRs are now in the process of closing. The graphite brick cracking problem was discovered to be worse than predicted. Decommissioning the Sellafield site alone (home of the related Magnox reactors) is expected to cost £121 billion.