The physical layers between the radioactive inventory in the fuel and the outside world: the ceramic fuel pellet itself, the fuel cladding, the reactor coolant pressure boundary and the containment. Emergency classification schemes are built on the status of three of these barriers (cladding, coolant system and containment), so the loss or potential loss of each one drives the declared emergency level.
RCS leakage plus high coolant activity, that's potential loss on two fission product barriers, so we're at least a Site Area.
Also heard as
- FPB
- barrier
Related terms
Defence in depth
The safety strategy of stacking independent layers of protection so no single failure can lead to harm.
Containment
The massive, leak-tight structure around a reactor that holds in radioactive material and steam if the coolant system fails.
Emergency classification
The graded levels used to declare a nuclear plant emergency, each triggering a defined response.
LOCA
Loss of coolant accident: a break or leak in the reactor coolant system that lets coolant escape faster than it can be replaced.