Regulator approves Olkiluoto 3 vessel report

The steel of the reactor pressure vessel for the EPR under construction at Finland's Olkiluoto nuclear power plant site does not have any anomalies similar to those found in that for the EPR being built at France's Flamanville site, Finland's radiation and nuclear safety authority has concluded.

The steel of the reactor pressure vessel for the EPR under construction at Finland's Olkiluoto nuclear power plant site does not have any anomalies similar to those found in that for the EPR being built at France's Flamanville site, Finland's radiation and nuclear safety authority (STUK) has concluded.

The reactor vessel of Olkiluoto 3 was installed in June 2010 (Image: Areva)

In early April, Areva informed the French nuclear regulator that anomalies had been identified in the composition of the steel in certain parts of the reactor vessel of the EPR under construction at Flamanville. Chemical and mechanical tests, it said, had "revealed the presence of a zone in which there was a high carbon concentration, leading to lower than expected mechanical toughness values".

In response, STUK requested utility Teollisuuden Voima Oyj (TVO) compile a report on the quality of the steel used in the reactor pressure vessel for the EPR under construction at the Olkiluoto site.

TVO submitted that report to STUK in late June. The report - prepared in cooperation with Areva - concluded that the Olkiluoto unit 3 vessel material does not have any such anomalies and meets all the requirements for safe operation.

TVO noted that the steel forgings for the vessel of Olkiluoto 3 were manufactured in Japan and was made using a different manufacturing process to the vessel forgings for Flamanville 3, which were produced in France.

The material properties of the pressurizer forgings for the Olkiluoto EPR were also assessed in TVO's report. These were manufactured in France at the same factory as the reactor pressure vessel forgings of the Flamanville EPR. However, TVO concluded these too meet safety requirements. Further tests in October confirmed no anomalies in the carbon content of the pressurizer steel.

Since submitting its report to STUK, TVO has also looked at the material properties of other components of the primary circuit of Olkiluoto 3. In early November, TVO submitted a complementary report to STUK on these components.

In an 8 December letter, STUK informed TVO that it had approved the conclusions of its report.

Olkiluoto 3 has been under construction since 2005 and has seen several revisions to its start-up date, which is now expected by 2018. Taishan 1 in China, which has been under construction since 2009, is expected to start up in 2016, while Taishan 2 is scheduled to begin operating a year later. The Flamanville EPR, construction of which began in 2007, is now expected to start up in late 2018.

Researched and written
by World Nuclear News