The owner of the plant, nuclear power utility TVO, on Sunday said the Olkiluoto 2 (OL2) would reconnect to the grid at the end of next week, after previously estimating the reactor would start running again between Sunday night and Monday morning.
TVO has said the Radiation and Nuclear Safety Authority (STUK) still needs to sign off on restarting the reactor. The unit is set to undergo a battery of checks, maintenance and repairs.
OL2 has been in a cold shutdown state since Thursday after warmer-than-usual water entered the cleaning system of the reactor, causing a momentary peak in the steam line's radiation measurement which triggered the safety systems, according to TVO.
On Friday, STUK issued a statement saying, "no radioactivity was released that would have had any impact on people or environment."
The emergency shutdown momentarily raised the price of electricity in Finland to a record level, spiking to 3,500 euros at 1pm on Thursday. The price was 139 euros per megawatt-hour at the same time the day before.
The Olkiluoto plant, located between Rauma and Pori on Finland's west coast, has two reactors and a long-delayed third one still under construction.