OL3 nuke plant resumes test production after October glitch

The electricity test production of Olkiluoto 3 resumed on Tuesday, according to the owner of the plant Teollisuuden Voima Oyj (TVO).

During test production, about 1.3 terawatt hours of electricity will be produced. The plant will go through around ten significant tests before regular electricity production scheduled to start on March 8.

The investigation into the damage in Olkiluoto 3’s feedwater pumps took place in October has mainly been completed.

The cracks in the impellers of the feedwater pumps have most likely been caused by the test production, where the pumps are used in abnormal circumstances.

The feedwater pumps have been operated outside the range of normal use during production tests, which has led to a higher-than-normal strain on the pumps.

The recurrence of similar damage can be avoided by the optimal operation of the pumps as well as using impellers with more robust measurements.

“It is of course extremely unfortunate that Olkiluoto 3’s test production was interrupted during late autumn when the feedwater pumps’ damage was discovered. This caused a long period of uncertainty relating to our production during the winter period. The investigations, which turned out to be especially challenging, have now been completed so that based on them, we can return to completing the last tests in the test production programme and proceed towards regular electricity production,” said President and CEO of TVO Jarmo Tanhua.

Based on comprehensive investigations and the planned inspection programme for the pumps, the plant unit’s test production can be continued temporarily by using intact pumps of the current model together with cracked feedwater pumps.

Test production will be continued with two feedwater pumps which are using a spare impeller and two feedwater pumps with a cracked impeller. One of the pumps with a cracked impeller is used as a reserve. The feedwater pumps are located in the turbine island, and they are not significant in terms of nuclear safety. However, their role in electricity production is central.

Test production will continue for about 11 days, during which power levels vary significantly. After tests at full power, electricity production will be interrupted for around four weeks in order to inspect the feedwater pumps and restart the plant unit.

Before the start of regular electricity production, an approximately month-long production phase will still follow in the test production, where Olkiluoto 3 will produce electricity at mostly full power 24/7.

Impellers reinforced with a new design are being produced and are estimated to arrive at the end of February or beginning of March 2023.