Unit 4 of the Doel nuclear power plant in Belgium will "definitely not" return to operations before 31 December 2014 after damage to its steam turbine, said operator Electrabel.

The unit, a 1090 MW pressurized water reactor, was shut down automatically on Tuesday 5 August, following a loss of lubricating oil in the steam turbine.

Belgium’s Federal Agency for Nuclear Control (FANC), which sent an expert team to make assessments at the site, concluded that the oil leak "probably resulted from a voluntary manual intervention."

FANC said that further investigation should reveal the precise circumstances behind this event. Meanwhile, the regulator says it has taken ‘additional action’ to ensure the safety and security of the nuclear installations.

Electrabel immediately launched a thorough investigation into the damage caused to the Doel 4 steam turbine.

Initial results, reported 14 August, after opening of the high-pressure part of the turbogenerator, suggest that "significant damage" has been caused to the HP turbine.

Electrabel says that once the low-pressure parts of the turbogenerator have been opened and investigated, a more in-depth assessment of the time needed for repair will be made.

Photo: Doel nuclear plant in Belgium