Belgium’s nuclear safety agency (Fanc) says 40-year-old unit 2 at Tihange NPP and unit 3 at Doel NPP meet the "strictest possible safety requirements".

Belgium on 20 April rejected a request by neighbouring Germany to shut down the two reactors, located near their shared border. German Environment Minister Barbara Hendricks had requested that they should be closed "until the resolution of outstanding security issues", according to a statement from the German federal ministry for the environment, nature conservation, building and nuclear safety (BMUB).

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. The oldest Doel and Tihange units have been in service since 1974-1975, and were scheduled to be shut down in 2015. However, the Belgian government in December decided to extend their lives to 2025.

The reactor pressure vessels (RPVs) at the two units, both pressurised water reactors (PWRs), have shown signs of metal degradation, raising fears about their safety. The two units were shut down in 2012 after the RPV flaws were discovered. They were restarted in June 2013, but shut down again in March 2014 after unexpected results from additional tests. In May 2015, operator Electrabel postponed the 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 found in the RPVs.

Fanc said it had submitted the RPV test results to "numerous national and international experts", including Oak Ridge National Laboratory in the US and had analysed the reports and opinions to consolidate its own conclusions. In November 2015, Fanc authorised the restart of both Tihange 2 and Doel 3 based on satisfactory results from structural assessments. The units restarted in December.

"I believe it is right to temporarily take the plants off-line, at least until further investigations have been completed," Hendricks said in a statement. This would be "a strong precautionary measure" and "would show that Belgium takes the concerns of its German neighbours seriously," she added.

The German request came after the German Reactor Safety Commission (Reaktorsicherheitskommission (RSK), an independent expert group of the BMUB, said it could not confirm that the two PWRs are safe. RSK said this was the result of discussions with Belgian nuclear safety experts. A newly formed Belgian-German bilateral expert group met on 5 and 6 April to discuss the issue of hydrogen flakes found in the wall material of the Tihange 2 and Doel 3 RPVs, BMUB said.

As a result of the April bilateral meeting, BMUB said initial proposals for further testing of the two reactors have already been drawn up by the Belgian side. BMUB said the German ministry welcomed this initiative and was willing to support the inspection programme. However, Fanc said the points raised by the German side during the April bilateral meeting "did not compromise" Belgium’s point of view and Fanc "remains convinced" that the two reactors comply with international safety standards, making a shutdown unnecessary.

Based on a collection of "objective data", test results, reports and opinions from various international experts and laboratories, Fanc said it is "convinced" that the two reactors are safe for operation despite the presence of hydrogen flakes in the RPV walls. Fanc said it "is always willing to collaborate with their German counterparts… but only as long as a shared willingness to cooperate in a constructive fashion is demonstrated".