Olkiluoto 3 unit operating at low power level due to a disturbance

Olkiluoto 3 was in normal production when one of the reactor's control rods unexpectedly dropped into the reactor. The drop was caused by a failure in the control rod drive mechanism. Normally, the drive mechanism keeps the control rods outside the reactor, and in a disturbance, the safety automation system drops the control rods into the reactor.

As a result of the incident, the plant's production power automatically decreased to approximately 1220 MW. To investigate the cause of the disturbance and to repair the fault, the unit is being operated at a low power level.

The purpose of the control rods is to regulate the reactor's power and, if necessary, shut down the reactor. The OL3 reactor has 89 control rods.

This event has no impact on nuclear safety.

Edit, October 9, 2024, at 14:20:
OL3 is operating at a low power level during the disturbance investigation. You can follow more detailed information about the power level and schedule on the Nordpool electricity market here.

Edit2, October 9, 2024, at 15:35: Text has been corrected due to a clarified information.

Edit3, October 9, 2024, at 18:00: The cause of the disturbance related to the unexpected drop of the control rod in the OL3 reactor has been identified and the issue has been resolved. The plant unit will begin power increase and return to normal production.