STUK called a halt to welding work in France pending reports from the power utility TVU and French builder Areva.
It now says the cracks on pipes for the Olkiluoto 3 reactor can be rendered harmless by re-welding them.
Areva and Germany's Siemens are building the world's first pressurised water nuclear reactor for TVO on the south-west coast near Pori.
The project has been plagued by massive cost overruns, delays and legal disputes.
In late May, The New York Times called the Olkiluoto project a "cautionary tale" about next generation reactors, noting that "the reactor's 3 billion euro price tag has climbed at least 50 percent" and that Areva and TVO "are no longer willing to make certain predictions on when it will go online".