Mohamed Bakkali is a suspect in the Paris attacks. And Bakkali apparently tried to find out more about the comings and goings of the director of Belgium's nuclear research program by conducting a little video surveillance operation.

"The Paris attackers are casting an eye on our nuclear sites," the Belgian paper "DH" reported when the story broke in November.

So it didn't come as a surprise when a network of German newspapers on Thursday reported that Salah Abdeslam, a major suspect in the Paris attacks, who had been living in the Brussels district of Molenbeek, had apparently been gathering information about a nuclear research facility in Germany.

Belgium's jihadi connection

"The threat of nuclear terrorism is one of the greatest challenges to international security," said US President Barack Obama at a recent summit on nuclear safety.

The danger that such a threat would be coming from Belgium appears particularly high. According to the International Center for the Study of Radicalization at King's College in London, an estimated 500 Belgian nationals have traveled to Syria or Iraq to become fighters for the so-called "Islamic State" - the highest number per capita in Europe.

One Belgian jihadi spent three years working at the Doel nuclear site, home to Belgium's oldest reactor. As a security engineer employed by a contractor, Ilyass Boughalab had access to the high-security zone, before he left to fight for the so-called "Islamic State" in Syria at the end of 2012. Two years later, Boughalab was tried in absentia for being a member of the terrorist organization Sharia4Belgium. During the trial, news emerged he had already died in Syria.

At around the same time, Belgian utility company Electrabel had to shut down a reactor at Doel for a few months, following an oil leak that was the result of sabotage. All circumstantial evidence suggested that one of the 800 workers employed at the site must have perpetrated the attack.

It thus seemed logical that Electrabel would send home most of the employees at the Tihange site in eastern Belgium following the March 22 terrorist attacks in Brussels out of concerns about its staff trustworthiness, though that was something Electrabel denied vis-à-vis the German news site "Spiegel Online."

Long history of nuclear research

Belgium is home to seven nuclear reactors. Though a date has been set for an exit from nuclear energy by the end of 2025, few steps have actually been taken to prepare for this transition.

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The country has a long history of doing nuclear research for civil purposes only and helped supply the United States with uranium from its colony in Congo during World War II.

"By way of saying 'thank you,' the US authorities then invited Belgian scientists to join US scientists in doing civil nuclear research," said Philippe Massart, a sociologist with the French-speaking Free University Brussels. "And when the Belgian researchers returned, the first European nuclear research reactor was built in the Belgian community of Mol."

Later, Belgium was also the first European country to build an industrial reactor in Europe.

Other security concerns

Belgium's nuclear sites have repeatedly sparked concern long before any terrorist attacks.

The oldest reactor, Doel 1, was supposed to be shut down for good last year. But instead, 2015 saw the extension of the reactor's operating time until 2025. Since then, Doel 1 has been in an on-again-off-again mode of operation and was turned off for repairs earlier this week.

Currently, Doel 1 - shown as an active reactor on this map - is down for repairs.

Other reactors at the sites in Doel and Tihange were restarted last December despite the fact that cracks had been found in the reactors' pressure vessels. Various lawsuits, including one by the German city and region of Aachen, have since been filed to stop the operation of these reactors.

Extent of nuclear terrorism threat anybody's guess

But terrorism expert Pieter Van Ostaeyen says nobody knows how big the nuclear terrorism threat emanating from Belgium really is. "Nobody has any idea what the terrorists were planning to do with the video taken of the director of Belgium's nuclear research facility, " he said.

The head of the International Atomic Energy Agency (IAEA), Yukiya Amano, recently warned that with the rise in amount of nuclear material, more incidents could occur in which nuclear material goes missing. "That material could be combined with conventional explosives to create a dirty bomb," Amano said.

If anything, that would be what IS terrorists are after, said Van Ostaeyen. "They're not capable of making a real nuclear bomb, and they also can't simply blow up a reactor," he says. "If they were capable of putting together a dirty bomb, they might try to do that."

He adds that the easiest way for IS terrorists to get their hands on this material would be to infiltrate the nuclear industry.

But asked how worried Belgians still reeling from the March 22 attacks now are about something like this happening, the sociologist Philippe Massart only shrugs his shoulders.

"We are aware of the dangers of the situation, but we are also a very pragmatic people. And while we do take certain precautions, we also want the nuclear power plants to just continue their operations, so that we can have our electricity at affordable prices."