Emergency core cooling systems are the high-pressure and low-pressure injection pumps, passive accumulators, core spray and depressurisation features that replace lost reactor coolant and remove decay heat. They start automatically on low pressure, low level or high containment pressure signals, first injecting from a storage tank and later recirculating water collected in the containment sump. Their performance is judged against limits on peak cladding temperature and oxidation.
ECCS actuated on low pressurizer pressure, high head is injecting, start the sump recirc checklist.
A small break can leave pressure too high for low-pressure injection, which is why operators train to depressurise the plant deliberately.
Also heard as
- emergency core cooling system
- emergency core cooling
Related terms
LOCA
Loss of coolant accident: a break or leak in the reactor coolant system that lets coolant escape faster than it can be replaced.
Decay heat
Heat produced by radioactive decay of fission products after a reactor shuts down, which must be removed.
Redundancy
Providing more components or trains than needed, so a safety function survives if one fails.
Design basis accident
A postulated accident that a nuclear plant is explicitly designed to withstand without exceeding set safety limits.