Finland's long-delayed Olkiluoto 3 (OL3) nuclear reactor was hit by another setback after the nation's safety watchdog reported valve problems in a component involved in the cooling process.
The reactor, located on the west coast of Finland, between the cities of Rauma and Pori, was built by a consortium of France's Areva and Germany's Siemens and had been due to start producing electricity in November this year.
"A leak was observed in the mechanical control valve of one of the pressuriser safety valves," nuclear watchdog STUK said in a statement on Monday, adding that a full investigation is required before it can issue a nuclear fuel loading permit.
"This is very serious," STUK's head of inspection, Iiro Paajanen, told, adding that the leak was in part of the reactor's primary circuit and involved in its cooling.
However, Areva said the issue is unlikely to cause further delay for the reactor, which was originally due to be completed in 2009.
"One component had indeed been damaged, but we are 90% sure this will not cause a further delay for the planned start-up," Areva Chief Executive Philippe Soulie told.
Reactor operator Teollisuuden Voima (TVO) applied for fuel loading on April 8, saying it expected a permit to be issued in a couple of months.
However, it warned that the coronavirus pandemic would delay fuel loading from a planned June schedule, possibly pushing back the November start-up.
Impact of Covid-19
Areva's Soulie said the French supplier is still in the process of updating its schedule because of the coronavirus outbreak.
"It is difficult to judge the Covid-19 impact, but without it we would be loading fuel this summer as planned," Soulie said.
Standard & Poor's downgraded TVO's long-term credit rating after the operator's announcement in April.
"A few technical issues have appeared during the test runs and they will be solved before the fuel is loaded," TVO said in a statement.
Although Finland's government issued an operating permit for the 1.6 gigawatt reactor in March 2019, OL3 needs final approval from STUK to load fuel and start production.
"At present, the plant unit still has several outstanding issues before a loading permit can be issued," STUK wrote in its January-April safety report.