It could happen: sabotage. It may be that the Brussels terrorists who spied on the nuclear official were aiming for option three, wreaking havoc by damaging a nuclear power plant. It’s hard to say how close they might have come. Belgium experienced a major incident of sabotage at its Doel-4 nuclear power reactor in 2014, when someone opened a valve and allowed lubricant to escape so that the turbine overheated and destroyed itself. No radioactive material was released, but the cost of the damage was estimated at between $100 and $200 million. As authorities investigated, they also happened to discover that a former contractor at the plant had left to fight for terrorists in Syria . (The jihadi contractor wasn’t responsible for the valve incident.) Needless to say, Belgium has since tightened security at its nuclear power plants, but at least as of March 2016, security elsewhere remained lax. “Some countries have no armed guards at all at nuclear facilities, relying on offsite response forces some distance away; others have no background checks before allowing employees access to reactor vital areas or nuclear security systems,” the Belfer Center report says.