Shearon Harris (USA)

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900 MW PWR unit; constructed by Westinghouse; grid connection in 1987.

Facilities in Shearon Harris

plantreactor typconstruction startoperation startshut down
Shearon HarrisPWR19741987

Reactor trip breaker did not open following an automatic trip signal because of a failed undervoltage driver card.


On 3 April 1991 workers at the Shearon Harris pressurized water reactor in New Hill, North Carolina discovered damaged piping and valves within the alternate minimum flow system provided for the pumps in the emergency core cooling system.
Most of these pumps are in standby mode during normal operation and start when needed to supply makeup water for cooling the reactor core. Because some of these emergency pumps deliver water at low pressure, they cannot supply water to the reactor vessel until pressure drops low enough. The alternate minimum flow system at
Shearon Harris provided a place for the pump output to go until pressure dropped low enough for the water to be sent to the reactor vessel.

The piping and valve damage was serious because had an accident occurred, water needed to cool the reactor core would have instead poured out onto the floor through the ends of broken components. The NRC calculated the severe core damage risk from this event to be 6 x 10-3 or 0.6% per reactor year. The event was not rated on the INES scale.

(source: Residual risk,


Short in main transformer traveled over electrical leads to the turbine generator, caused a leak in hydrogen piping and a hydrogen-explosion -> turbine trip and scram. It took 90 min. to bring the fire under control. The fire was confined to the non-nuclear side of the plant.