A loss of coolant accident ranges from a small-break LOCA, such as a stuck-open relief valve or failed instrument line, to a large-break LOCA, the double-ended rupture of the largest coolant pipe. The emergency core cooling system must refill and recover the core, then cool it for the long term from the containment sump. Small breaks can be the trickier ones, because pressure stays high and the event develops slowly.
Pressurizer level dropping, containment humidity rising, treat it as a small-break LOCA until proven otherwise.
Also heard as
- loss of coolant accident
Related terms
ECCS
Emergency core cooling system: the set of safety systems that inject water to keep the core covered after a loss of coolant.
Design basis accident
A postulated accident that a nuclear plant is explicitly designed to withstand without exceeding set safety limits.
Containment
The massive, leak-tight structure around a reactor that holds in radioactive material and steam if the coolant system fails.
Decay heat
Heat produced by radioactive decay of fission products after a reactor shuts down, which must be removed.