Once authorized, TVO will gradually increase the power of the reactor from 60% to its full thermal power of 4300 megawatts. During this increase, the plant provider and TVO will ensure that the plant functions as planned also at these power levels. STUK monitors the power increase on site.

According to Essi Vanhanen, Project Manager responsible for regulatory control of OL3 at STUK, the commissioning tests carried thus far and related reports have shown that Finland's newest nuclear plant unit has operated safely and the reactor power can be increased further according to commissioning testing plans.

The commissioning tests were delayed when detached parts of the steam guide plates were found in the turbine reheater in May. After repairs and inspections, TVO submitted a report to STUK, stating that the incident did not compromise nuclear safety and that commissioning of the plant can be safely continued.

When the reactor power was increased after the repair shutdown, TVO and the plant supplier discovered that the plant's operational automation software still needed to be updated. TVO submitted a report on the matter to STUK and after the update, TVO and the plant supplier continued the commissioning as planned.

More detailed information on STUK’s surveillance observations can be found from the “Surveillance news” section of the stuk.fi website.