Finnish nuclear operator plans Dec 17 restart after reactor trip

[OSLO] Finnish nuclear operator Teollisuuden Voima Oyj (TVO) late on Sunday said it had established the cause of last week's reactor trip at its Olkiluoto 2 plant and is seeking regulatory permission to restart power production on Dec 17.

"The progression of events has become clearer, and it has now been confirmed that the situation was caused due to hot water moving into the filters of the reactor water clean-up system," TVO said in a statement.

The hot water had dissolved filter particles, which were activated as they passed through the reactor core. This raised radiation levels inside the main steam lines briefly to about three to four times their normal levels, triggering the shutdown, it added.

"The plant and all of the safety systems worked as planned during the situation," TVO said.

The preliminary rating of the event on the international nuclear event scale (INES) was zero, which means the event has not affected nuclear safety. The event also did not impact radiation doses of employees and no increased radiation levels were detected in outdoor areas, TVO said.

"Restarting the plant requires careful inspection and testing," it added.

TVO will carry out a detailed investigation on the progression of events, as well as the necessary immediate measures to avoid a similar disturbance, it said.

According to data provided via energy exchange Nord Pool, the reactor is currently scheduled to reconnect to the grid on Thursday, Dec 17.

Any restart is subject to permission from Finnish Radiation and Nuclear Safety Authority STUK, and TVO is currently preparing the application, it said.

REUTERS