Gennady Negrivoda, the plant's technical director, said that the fire prevention system was triggered off on Aug. 22 by a heavy downpour in Visaginas where the Lithuanian nuclear plant is situated.
Firemen said that the turbine was switched off automatically when fire sprinklers started spraying foam.
The Ignalina NPP said the radiation level had not changed because of the incident.
As a result of the faulty shutdown, the capacity of the plant went down from 1,200 MW to 750 MW.
Currently there is only one turbine in operation at the second power unit, as the first power unit has been out of operation since May, when it was shut down for routine maintenance. The Lithuanian NPP, equipped with two Soviet-made RBMK reactors, generates about 70 percent of the country's energy.