Work has begun at unit 3 of Finland's Olkiluoto NPP to repair a previously reported problem that causes vibrations in its cooling unit, and which must be fixed before regulators sign off on its safety, operator TVO said on 23 May.
Start-up of the reactor, a 1600 MWe EPR and Finland's first new nuclear plant in 40 years, is a decade behind schedule and significantly over budget amid repeated setbacks in its construction. In March, the reactor received an operating permit from the Finnish government, the first one issued in 40 years, but it still requires a final approval from regulators before fuel is loaded and operation can start in 2020.
TVO said it is applying liquid absorbers that use bitumen as a material to fix the vibrations, a solution approved by the Finnish Radiation and Nuclear Authority (STUK). "Installation of absorbers has been started and will be completed during spring. STUK will audit the installed structures before the loading of nuclear fuel," it said. The use of bitumen as a damper has been studied in tests at Lappeenranta University of Technology, Lahti, in addition to which Areva, the reactor supplier, has made its own pilot plant tests. The installation of the dampers has started and STUK will the structures to be installed before refuelling.
Hot functional testing of the EPR began in December 2017 and was completed in May 2018, 50 days later than planned, because of vibrations in the pressuriser surge line. Based on the test results, TVO had said a comprehensive modification package would be implemented at OL3 to update the plant's electrical and instrumentation and control systems. The Areva-Siemens consortium began construction of Olkiluoto 3 in 2005 under a turnkey contract signed with TVO in late 2003. Completion of the reactor was originally scheduled for 2009. Fuel is now scheduled to be loaded into the reactor core in June, with grid connection in October, and the start of regular electricity generation scheduled for January 2020.