Fire atthe power generator of a power plant

A nuclear power lant experienced a generator hydrogen fire.
The event started with a short circuit inside the main transformer, which damaged the hydrogen coolant system of the generator, followed by multiple hydrogen fires in the turbine hall.
The steam supply system of the reactor detected the failure of the transformer and was separated from the turbine-generator unit. The reactor was successfully shut down. There was no radiation emission.

The damage was limited to the plant's main transformer, electrical conductors and wires leading from the generator to the transformer.
The fire was extinguished by onsite personnel.
The outage lasted one month.

The INITIATING CAUSE was an electrical failure of the main transformer, responsible for the supply of the electrical power generated in the reactor to the electrical national grid.
The power plant operator stated that "... there is no way of guaranteeing that transformer will not fail". The ROOT CAUSE can then by identified as unspecified material failure.

Main generator

Damage was limited to the transformer itself and to a part of the hyrogen supply system.

The reactor was successfully isolated from the power generation unit and shut down.
According to a NRC note, fighting of the emergency put a strain on the resource available.
Although a senior reactor operator and auxiliary operators from another shift were available immediately, the need to provide personnel for the fire brigade and at the same time to perform the many actions required by the event caused a heavy workload for the control room staff.
This workload contributed to the licensee's failure to notify some key emergency response personnel as specified in the licensee's procedure.

The US.NRC issued a note to alert addressees to problems that could result from inadequate controls to ensure that shift staffing is sufficient to accomplish all necessary functions required by an event. It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.

In this plant, the breaker was installed between the transformer and the offsite electrical grid. The transformer was placed outside the turbine-generator hall and is separated from it by a hall wall.
The operator investigated how to further minimise the effects of transformer failures.