What is Loss of coolant accident in a Nuclear Reactor?

A loss of coolant accident (LOCA) is a mode of failure for a nuclear reactor ; if not managed effectively, the results of a LOCA could result in reactor core damage.

Every Nuclear power plant's Emergency Core Cooling System(ECCS) exists specifically to deal with LOCA.

When coolant flow is reduced, or lost altogether, the nuclear reactor's emergency shutdown is designed to stop fission chain reaction. However due to radioactive decay the nuclear fuel will continue generate a significant amount of heat.

The decay heat produced by reactor shutdown from full power is initially equal to about 5% to 6% of thermal rating of reactor.

If all independent cooling trains of ECCS fail to operate as designed, this heat can increase the fuel temperature to the point of damaging the reactor.  

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