Hazards

Pumps turned off: The contamination of the instrument air line caused the feedwater pumps, condensate booster pumps, and condensate pumps to turn off.
Turbine trip: With the steam generators no longer receiving feedwater, heat and pressure increased in the reactor coolant system, causing the reactor to perform an emergency shutdown (SCRAM).
Decay heat: Within eight seconds, control rods were inserted into the core to halt the nuclear chain reaction. The reactor continued to generate decay heat and, because steam was no longer being used by the turbine, heat was no longer being removed from the reactor's primary water loop

Blockage in a condensate polisher: Blockages are common with these resin filters and are usually fixed easily, but in this case the usual method of forcing the stuck resin out with compressed air did not succeed.
Contamination of the instrument air line: The operators decided to blow the compressed air into the water and let the force of the water clear the resin. When they forced the resin out, a small amount of water forced its way past a stuck-open check valve and found its way into an instrument air line.
Fault: Valve of the instrument air line stuck open
Fault: PORV stuck open

The guide warns about the risks of latent hazards.

Updated on 18 May 2016.