Finnish utility TVO has announced that containment pressure and leak tightness tests have been completed at its Olkiluoto 3 EPR nuclear power plant. It is the first time that such tests have been carried out on an Areva EPR reactor.

They were carried out over a two-week period to demonstrate that the inner containment, which protects the reactor primary circuit, is leak-tight and pressure-resistant. Large compressors were used to pressurise the containment to different levels, up to a maximum of 6 bar. The tests were supervised by the Finnish nuclear regulator, the Radiation and Nuclear Safety Authority (STUK).

"The sequenced measurement procedure verified that the structural behaviour of the containment is consistent with the design, also at the 4.9 bar pressure, which simulates a loss-of-coolant accident," said OL3 team manager Mika Hassinen.

TVO said it continues to analyse the findings and that the final test results will be available in the near future. The leak-tightness test will be repeated at the OL3 plant three times in every 15-year period.

The containment pressure and leak-tightness tests represent the first pre-operational test of a reactor containment in Europe since 2001, according to vendor Areva. It was also the first pressure and leak-tightness test conducted on an EPR unit.

The move brings the Olkiluoto 3 reactor closer to commissioning, however TVO has not provided an expected start-up date for the plant.

"Teollisuuden Voima (TVO) has not received the required updated overall schedule for Olkiluoto 3 project from the plant supplier Areva-Siemens Consortium. TVO therefore does not provide an estimate of the start-up time of OL3 nuclear power plant unit at the moment," it said on 12 February.

Photo: The Olkiluoto 3 nuclear power plant under construction (Source: TVO)