Unit 3 at Finland’s Olkiluoto NPP was shut down on 26 April as part of a test programme, plant owner-operator Teollisuuden Voima Oyj (TVO) said. However, the boron pumps started unexpectedly. TVO said the plant “is in a safe state” and “the reason for starting the boron pumps regulating the chain reaction is being determined”. A subsequent announcement said the boron pumps (safety system) had started unexpectedly “due to an incorrectly triggered signal from the automation system”. The fault has been rectified and the plant's test operation programme is continuing “in accordance with the production forecast”.