Fire at a generator of a power plant

During a turbine testing at 100 percent power, a problem developed in the auto-stop trip system, which led to a turbine and reactor trip.
The turbine stop valves closed as expected, but after closure they re-opened due to the fact that some solenoid-operated valves of the turbine protection system failed to open. Steam flow to the turbine led to an over-speed of about 160 percent of rated speed. The low-pressure turbine blades broke and penetrated the turbine shroud.
A hydrogen explosion and fires and turbine lubricating oil fires resulted. The damage in turbine generator systems was extensive, for instance the turbine, the generator and the main condenser were damaged.

INITIATING CAUSES
The failure of the turbine was caused by its accidental re-start despite the fact that a reactor shut down was ongoing.
ROOT CAUSE
The fact that a series of malfunctioning led to the restart of the turbine indicates the safety systems were not properly designed, or at least not well integrated in an overall risk assessment considering also the emergency procedures.

turbine, collant system, cables, control room

The release of hydrogen was preceded by the failure of the turbine.

DESCRIPTION OF THE FACILITY
The nuclear power plant was a pressurised water reactor, consisting of two units of approximately 1160 MW each.

A hydrogen explosion and fires and turbine lubricating oil fires resulted. The damage in turbine generator systems was extensive, for instance the turbine, the generator and the main condenser were damaged. Being the reactor shutdown, it is assumed that no radiation was lost to the environment.

The operator shut down the compressors and the circulation pumps, and alerted the fire brigade of a neighbouring company. Internal firefighters and external emergency services extinguished the fire within 45 minutes by injecting pressurised nitrogen. After which they focussed on the insulations, which was till burning.

For a generic , see HIAD ID = 042