Belgian power company Electrabel has been authorised by the Federal Agency for Nuclear Control (Fanc) to restart Doel 3 and Tihange 2, both of which have been offline to undergo tests because of concerns over the structural integrity of their reactor pressure vessels (RPVs).

Fanc said Electrabel had shown that hydrogen flakes, or "microbubbles", in the walls of the RPVs have no "unacceptable impact" on reactor safety. 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.

The units were taken off line after the RPV flaws were discovered in 2012. During a 2012 outage at Doel 3, ultrasonic in-service inspections intended to check for underclad cracking in the RPV found a large number of "quasilaminar indications" in the lower and upper core shells of the RPV. Similar issues were discovered following inspections of the Tihange 2 RPV.

Both units restarted in June 2013, but were shut down again in March 2014 after unexpected results from additional tests. In May, Electrabel postponed restart of the units after Fanc said it would take "several months" to analyse the safety case put forward by Electrabel related to hydrogen flakes on the two units’ RPVs.

On 17 November, Fanc said it had submitted the results of RPV tests to "numerous national and international experts", including Oak Ridge National Laboratory in the USA, and had then "centralised and analysed" the reports and opinions to consolidate its own conclusions.

Belgium has seven nuclear units in commercial operation in, four at Doel and three at Tihange, which generate about 55% of total electricity.

Photo: Doel 3