Problems with seals found in OL3 connectors in Nov-Dec

Inspections carried out by Teollisuuden Voima Oyj (TVO) in November-December 2023 revealed defective seals in connectors used for level and pressure measurements of Olkiluoto 3 (OL3) nuclear power plant, said owner of the plant TVO in a press release on Tuesday.

The inspections were conducted as a result of the seal defects detected in the spring.

Defective seals were detected in seven of the eight inspected connectors, and in one connector the seal was missing completely. All the inspected connectors were provided with new seals.

Connectors with defective seals are fully operable in normal conditions but they will not necessarily fulfil requirements specified for accident conditions.

The failure of these measurements during a loss of coolant accident could impede operator actions, but would not be a risk to accident management, however. The probability that conditions in which these measurements are needed would occur is low.

TVO submitted the operating event report addressing this event to the Radiation and Nuclear Safety Authority of Finland (STUK) on 12 January and STUK provided TVO with a preliminary assessment of the INES rating on 17 January.

The preliminary rating of the degree of severity of the event is level 1 on the international INES scale. Although the basic rating of the event is 0, the rating of the event is upgraded by one taking the possibility of a common cause failure into account.