With doubts about the safety of Belgium's nuclear reactors rife among neighboring countries, and the threat of attacks on its nuclear sites still a valid concern, the news that one of the country's disputed reactors had once again shut down unexpectedly on Thursday wasn't encouraging.

Late in the afternoon, utilities operator Engie Electrabel announced that the 34-year-old Doel 3 reactor near the city of Antwerp, close to the border with the Netherlands, had automatically shut down following a standard test - "normal procedure if there is an anomaly," according to a plant spokesperson. The Belga news agency said the outage was expected to last for 24 hours.

Earlier in the day, Engie also said the Doel 1 reactor - shut down since April 13 for maintenance work scheduled to last several days - would now remain offline until May 31 "for additional analyses" and "operational maintenance." Doel 1 and 2, in operation since the mid-1970s, were set to be taken out of service in 2015 after 40 years, until parliament decided to extend their lifespans by another decade.

The shutdowns are just the latest for Belgium's seven aging reactors, which in the last two years have gone offline around 10 times for various technical problems or minor emergencies like fires - four incidents this year alone.

On Wednesday, German Environment Minister Barbara Hendricks called on the Belgian government to shut down Doel 3 and Tihange 2, located near the eastern city of Liège, for an indefinite period to guarantee safety "until further research can be undertaken."

Her request came after a meeting between representatives of the German Environment Ministry, an independent German Reactor Safety Commission (RSK) and Belgium's Federal Agency for Nuclear Control (FANC) in early April, in which Germany expressed its concern over tiny cracks in the pressure vessels of the two reactors discovered in 2012.

Hendricks pointed out that RSK had failed to confirm that the reactors were safe, and called for further tests to show that Belgium "takes the concerns of its German neighbors seriously." The Tihange nuclear power station is located about 60 kilometers (37 miles) from the German border, and the decision to restart Tihange 2 in December sparked great concern in the nearby city of Aachen.

Belgium's Energy and Environment Minister Marie-Christine Marghem was unavailable for comment on Thursday.

'No need to shut down'

In its response to the German minister, FANC said that after stress tests at the two facilities and meetings with international experts and representatives of the EU, the Nuclear Energy Agency and the International Atomic Energy Agency, it believes both reactors "comply with international safety standards."

"Our German colleagues have asked lots of questions, but they did not raise any new issues that we had not taken into account during our review of the Doel 3 and Tihange 2 safety cases," said FANC Director-General Jan Bens in a press release. "Therefore, we are still convinced that there is no need to shut down these units from a nuclear safety point of view."

"That's false," said Jean-Marc Nollet, the head of the leftist Ecolo/Groen party. He said the concerns expressed by the German experts line up exactly with those of an expert appointed by the FANC and the European Green Party to study the case. "All three [representatives] said that the detailed studies needed in order to make a decision were lacking."

Nollet told DW that Doel 1 is unfit to continue for another 10 years, as "it's obvious that [the reactor] lacks the capability to deal with its operational problems."

He pointed out that Bens, the head of the federal nuclear regulator FANC, was head of the Doel plant from 2004 to 2008 - "an enormous conflict of interest."

In an internal newsletter from 2005, seen by DW, Bens said his goal was to convince politicians and the Belgian public that reactors Doel 1 and 2 - put into service in 1974 and 1975 - were ready for "another 30 years of service."

Nollet said Bens will have to decide whether to allow the continued operation of the Doel reactors, despite the fact that he himself "was responsible for maintenance and updates" during his time as head of the plant.

"It's a real problem, it's a serious problem," he said.

'Very strict conditions' on nuclear plants

When contacted by DW, a spokesperson for Bens said the agency did not want to give an interview on the subject, as the agency's work was "based on facts and figures, not opinions." The spokesperson pointed out that this wasn't the first time such an opinion had surfaced in the media, calling it part of a "long-running debate."

Els De Clercq, a spokewoman for the Doel nuclear plant, said despite Nollet's claim she was "convinced" Bens was taking his role as head of FANC "very seriously." She pointed out that in a small country like Belgium, it's not unusual for someone with nuclear expertise to work in several different roles in the sector.

De Clercq said FANC has put "very strict conditions" on the nuclear plants when it comes to investment and inspections, and if those conditions aren't fulfilled the agency has the right to shut them down, which isn't the case in all countries.

"I work here every day, my husband and my baby live [nearby]. Two thousand people work in this power plant, and we all have a responsibility toward ourselves and also to our environment and the local neighborhood," said De Clercq. "These power plants are safe to operate. If we had the smallest doubt about that, we would never have restarted them."

De Clercq told DW that in the event Doel 3 and Tihange 2 were forced be shut down it wouldn't necessarily be a problem in the short term, but it could lead to decreased energy capacity in the winter months.

With the current difficulties when it comes to investing in renewable energy, she added that energy shortages could become an issue over the next decade, especially as Belgium's reactors come offline and neighbors like Germany shut down their nuclear sectors altogether, making less electricity available for import.

"For now, we think that our nuclear power plants still have a role to play to give our federal government more time to develop a good strategy when it comes to investment in renewable energy," she said.

"That may be the case if the government reacts now [to plan for the future]," said Nollet. "But for the moment, the current government does not seem to be working toward that goal. That much is clear."