Helsinki - Finland's long-delayed Olkiluoto 3(OL3) nuclear reactor resumed power trial production early on Wednesday after a two-month blackout, operator TVO said on its website, in line with a timetable published late on Tuesday.  

The OL3 outage was a blow to Finland's energy security this winter, with the operator saying in October that cracks had been found in four of the reactor's feed pumps after trial production, further delaying the start of the reactor, originally scheduled for 2009.  

TVO said that while the damaged pumps did not pose a safety risk, they were critical to the reactor's power output.  

The test output was scheduled to restart on December 27, but was later delayed by a day.  

TVO forecasts that the OL3 will reach full capacity on Wednesday, followed by tests at various output levels over the next week, followed by a month-long shutdown and additional testing ahead of the planned start of permanent production on March 8.  

Finland has told its citizens to prepare for possible power cuts this winter, as Europe struggles to curb energy use and cope with reduced supplies of Russian gas amid the Russia-Ukraine conflict.  

During tests in September, OL3's output reached its full capacity of 1,600 megawatts for the first time, making it the most powerful power production facility in Europe and the third most powerful globally, according to TVO.  

It is the first new nuclear power plant in Finland in more than 40 years and the first in Europe in nearly 15 years, with a capacity equivalent to about 14 per cent of Finland's total electricity consumption, TVO said.  

Electricity imports from Russia were halted in May after Russian utility Inter RAO said it had not been paid for the electricity it sold, increasing demand for OL3's exports.  

The OL3 project has been under construction since 2005, facing a number of technical glitches that have triggered costly delays and lengthy legal battles.