Belgium Clears Two Reactors for Restart

Written by Martin Lynch, European News Editor for Industrial Info (Galway, Ireland)--Belgium's nuclear regulator has approved the restart of two nuclear power reactors that have been offline since last year due to numerous technical issues.

The Federal Agency for Nuclear Control (FANC) has informed owner and operator Electrabel SA (Brussels, Belgium), which is part of ENGIE (EPA:ENGI) (Paris, France), that it can restart the Doel 3 and Tihange 2 nuclear power plant units.

This is the second time in recent years that the plants have been cleared for restart. In May 2013, the regulator approved the restarting of both units, after they were shut in 2012, when ultrasonic inspections discovered tiny cracks in the reactor pressure vessels. For additional information, see May 22, 2013, article - Belgium 'OKs' Restart of Two Nuclear Reactors. However, in 2014, Electrabel shut down the two power plants for routine, scheduled maintenance and then kept them closed to perform additional testing.

"The Federal Agency for Nuclear Control (FANC) has given permission to restart the reactors at Doel 3 and Tihange 2," FANC stated. "Both reactors were already shut for some time because there was some uncertainty about their safety. This uncertainty was caused by the discovery of thousands of error indications in the steel walls of their reactor vessel during the maintenance shutdown in the summer of 2012. Further research showed that it was hydrogen bubbles that were left in the material in the manufacture of the rings of the reactor vessel and then were flat-rolled into hydrogen flakes having an average length of 12 to 16 millimetres and the thickness of a cigarette paper. This hydrogen flakes are laminar, which means that they run parallel to the wall of the reactor vessel and, thus, are not "punctures."".

Electrabel spent 18 months preparing a series of safety reports, alongside those from independent testing authorities. The final reports were submitted last month.

Electrabel said: "The conclusions reached after inspections, tens of thousands of hours of investigative work and more than 1,500 material tests are as follows:

• The flaws detected in the reactor vessels are hydrogen flakes that were produced during the forging process. In other words, they have been there from the outset.
• The hydrogen flakes are quasi-laminar, lying parallel to the interior wall of the reactor vessel. As a result, they are marginally subjected to mechanical stresses and have no negative impact on the reactor vessel's structural integrity.
• The qualification of the ultrasonic inspection method showed that the method is perfectly capable of detecting, locating and sizing each hydrogen flakes."

Belgium has seven nuclear reactors split between the Doel and Tihange plants, supplying about half of the country's power. In February, the oldest reactor, Doel 1, was permanently disconnected from the electricity grid, despite being cleared for 10 more years of operation. For additional information, see February 18, 2015, article - Belgium Shuts First Nuclear Reactor.

The country's fleet has experienced a number of problems in recent years. Last summer, an act of sabotage forced the automatic closure of Doel 4. For additional information, see August 14, 2014, article - Sabotage Shuts Belgian Nuclear Plant.

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