17 Nov (NucNet): Belgium’s nuclear regulator has announced that it has authorised operator Electrabel to restart the Doel-3 and Tihange-2 nuclear units, both of which have been offline because of uncertainties over the structural integrity of their reactor pressure vessels (RPVs).
The Federal Agency for Nuclear Control (Fanc) said Electrabel had shown that hydrogen flakes, or “microbubbles”, in the walls of the RPVs have no “unacceptable impact” on reactor safety.
Fanc said Electrabel can restart the reactors and operate them until their planned final shutdown dates – 1 October 2022 for Doel-3 and 1 February 2023 for Tihange-2.
Doel-3 and Tihange-2 were shut down in 2012 after the RPV flaws were discovered. In June 2013 the units were restarted, but were shut down again in March 2014 after unexpected results from additional tests.
Fanc said the reactors could not be restarted before Electrabel was able to prove convincingly that reactor safety was not compromised
The problems date to a 2012 outage at Doel-3 when ultrasonic in-service inspections were performed to check for underclad cracking in the RPV. No underclad defects were found, but a large number of “quasilaminar indications” were detected in the lower and upper core shells of the Doel-3 RPV.
Similar issues were discovered following inspections of the Tihange-2 RPV. No other reactor units were affected.
In May Electrabel postponed the restart of the units following an announcement by Fanc that it would take “several months” to analyse the safety case put forward by Electrabel related to hydrogen flakes on the two units’ RPVs.
Fanc said today it had submitted the results of tests on the RPVs to “numerous national and international experts”, including Oak Ridge National Laboratory in the US. It said it had “centralised and analysed” the reports and opinions to consolidate its own conclusions.
There are seven reactor units in commercial operation in Belgium, four at Doel and three at Tihange. Together, they generate about 55 percent of the country’s electricity.
