OL3 faces potential safety affecting events

A potential sequence of events affecting safety, beginning with a grid disturbance, was identified in the safety analyses of the Olkiluoto 3 (OL3) nuclear plant unit, said the owner of the plant Teollisuuden Voima Oyj (TVO) in a press release on Monday.

The authority, however, took immediate corrective actions to ensure the continuation of electricity production without interruption.

A network disturbance could have led to the inoperability of certain equipment related to reactor cooling.

TVO has submitted a preliminary operational event report regarding the matter to the Radiation and Nuclear Safety Authority (STUK).

TVO has initially assessed the severity of the event as level 1 on the international INES scale.

STUK will confirm the final INES rating in connection with its review of the special report.

The severity level of incidents at nuclear facilities is classified according to the international rating system.

The INES scale has seven different severity levels, of which levels 4-7 are classified as accidents, levels 1-3 as safety-significant events, and level 0 as an exceptional event with no safety significance.