Terrorists in Belgium – What Can Terrorists Do to a Nuclear Reactor?

Plant Doel; seen from the north. Doel, Beveren, East Flanders, Belgium

Plant Doel; seen from the north. Doel, Beveren, East Flanders, Belgium

Dear Dr. Zoomie – I read in the news that those terrorists in Belgium were trying to get into a nuclear reactor. What can terrorists do to a nuclear reactor? Can they melt it down? Or make a dirty bomb? How worried should we be?

This is a fairly complicated question and there are a few things to think about:

  • Can terrorists gain access to a nuclear reactor?
  • Can they cause a meltdown or a release of radioactivity to the environment?
  • Can they gain access to radioactive materials to make a dirty bomb?

Let’s take these one at a time.

First – can terrorists gain access to a nuclear reactor? Well – the best answer to this is maybe. Nuclear reactors are guarded by some pretty well-trained security forces. In addition, every nuclear reactor is located within some law enforcement jurisdiction – a sheriff’s office, police department, state police, and so forth – in addition to whatever federal assets (FBI, military, etc.) might be available. A terrorist group can certainly attack a nuclear reactor plant – either head-on or by cutting through the security fence – but there will be a fight that will slow them down. I have to admit that I’m not a security expert (and the exact security arrangements are classified) so I can’t predict which side would prevail. But even if the reactor security staff are overcome, the other assets will be on their way as soon as they’re notified – even just delaying the terrorists a bit makes it more likely that law enforcement or other forces can arrive in time to lend a hand.

Let’s assume that a terrorist group is able to get past the security force and/or the security perimeter – the next question is whether or not they can gain access to the reactor control room or to areas where radioactive materials are stored.

Both of these are certainly possible but, unless they know exactly how the power station is laid out, it could take them awhile to figure out where to head. Most of these sites are fairly large and they have a dozen or more buildings, some of which are fairly large. Eventually it might be possible for a terrorist group to gain access to the control room or to radioactive materials storage areas, but it will likely take some time.

Second – can terrorists cause a reactor meltdown? The answer to this one is “probably not,” and almost certainly not without some sort of insider help. First, every reactor plant has a number of automatic safety systems that are designed to keep it from melting down. It’s not necessarily hard to make a reactor plant shut down – they’re designed to do so automatically in order to keep the reactor safe – but it IS hard to damage the plant; causing damage requires not only a fairly detailed understanding of how nuclear reactors work, but also some very detailed knowledge of how a particular reactor plant works. For example, a terrorist would have to know the reactor plant well enough to know how to override or thwart all of the various safety systems because it only takes a single operating one to keep a meltdown from occurring. And to put this in perspective, I spent 8 years operating Naval nuclear reactors and I’d be hard-pressed to cause a meltdown in one of the reactors that I actually operated – I can’t picture walking into the control room of an unknown reactor plant and being able to do much of anything, let alone finding the right controls to operate in the correct sequence to override a dozen or so safety features to cause a meltdown. I’m not saying it’s impossible – but it certainly isn’t a simple matter.

And forget entering the reactor compartment itself and, say, setting explosive charges to damage the reactor directly – there are locked doors, entry controls, and other security features to defeat, not to mention knowing enough to understand exactly where to set the charges to cause damage that would lead to a reactor meltdown. The reactor compartment itself will be have very high radiation levels, but not high enough to really have an impact – the biggest obstacle would be not knowing which components are vitally important. Even someone with schematics of the reactor compartment might not be able to figure out what to do – I can tell you from personal experience that there’s a huge difference between looking at a schematic and the actual welter of pipes and cables, just as there’s a huge difference between looking at a schematic of your car’s engine and the engine itself. Again – I’m not saying that it’s impossible, but it’s highly unlikely.

What about a release of radioactivity to the environment? OK – so let’s say that a terrorist group manages to cause a meltdown. Can they turn this into a Chernobyl- or Fukushima-style environmental disaster? Believe it or not, this is also more difficult than it seems, mainly because the reactor plant is surrounded by a robust containment (that’s the dome or cylinder that we associate with reactor plants). This is a shell of reinforced concrete that’s about three to six feet thick and even the reactor melts down, the radioactivity has to find a way into the environment. This means finding a way to breach the containment. There are openings in the containment as well as pipes, drains, ducts, and so forth to let air and fluids in and out. But all of these openings are designed to slam shut (and stay shut) in the event of any emergency. The whole plant is designed to keep radioactivity from reaching the environment and it does it quite well. At Three Mile Island, for example, the reactor melted down but the containment worked as designed. Some radioactivity was released – but it was released deliberately when the operators vented hydrogen (and some of the gaseous radionuclides) to the environment to prevent a hydrogen explosion. And as we all know, the Fukushima accident released a lot of radioactivity, but the containment here was damaged by the earthquake as well as by the hydrogen explosions. As above – it’s not impossible to conceive of a terrorist group first causing a meltdown and then finding a way to cause an environmental release – but it’s very unlikely.

OK – so what about the last concern? Can terrorists get their hands on the makings of a dirty bomb? Here, the odds might be a bit higher since making a dirty bomb only requires radioactive material, and nuclear reactor sites are full of these – there’s radioactive waste, the reactor itself, the spent fuel, and maybe some radioactive sources as well. Let’s think about each of these.

The greatest amount of radioactivity is in the reactor core, but this is pretty much impossible to remove since it’s locked up inside the reactor. So we can rule this out. Spent fuel is also pretty hard to make off with – the spent fuel rods are fairly long and unwieldy (a few tens of feet in length) and they’re stored in either a huge spent fuel pool or they’ll be inside a spent fuel casks that are at least ten feet tall, several feet in diameter, and weigh many tons. Either way, it’s not plausible that a terrorist group is going to make off with spent reactor fuel. And even if they do, they’d still have to find a way to break into the cask (or the fuel rods) to release the radioactivity – another difficult task.

There is a bunch of radioactive waste at a reactor site – mostly low-level stuff like contaminated paper towels, gloves worn by radiation workers, and so forth. This low-level stuff has to be controlled as radioactive materials, but it’s hardly the sort of thing to inspire fear – I know, because I ran a radioactive waste program at a few universities in addition to keeping track of the waste on the submarine I was assigned to. There are some higher-level wastes – reactor components removed for repair or replacement, the filters used to purify the water, and so forth. But high-level waste have to be kept in secure locations – at the very least, finding and getting at them will cause further delay. They also have to be kept heavily shielded for safety purposes – this makes them hard to sneak off with or to breach…even more delay for potential thieves.

Finally, every reactor plant will have radioactive sources that it uses for a number of purposes. Most of these sources are going to be fairly low-activity but a few will be stronger – these might be able to cause a fair amount of contamination if strapped to an explosive. These will also be secured according to regulation and the highest-activity ones will also be shielded. Again – none of this will prevent a theft, but it all adds to the difficulty of making off with these sources and using them for nefarious purposes.


So let’s put this all together. First, a terrorist group can always attack a nuclear reactor plant but they’ll be going up against a trained security force as well as the local, state, and maybe even federal response that’s sure to follow. If they manage to get into the reactor site, they’ve got to figure out which building contains their target, not to mention figuring out which room (or rooms) they need to enter. If they’re trying to cause a meltdown they have to understand the reactor and its controls well enough to override all of the safety systems that are designed to prevent exactly that. And if they’re trying to cause a release of radioactivity to the environment, they have to go even further and create a hole of some sort in a thick shell of reinforced concrete. Finally, if they’re after stealing radioactive materials to make a dirty bomb, they have to find some of the high-activity radioactive waste or high-activity sources – and they then have to spirit them away.

Is all of this possible? Well…it’s not impossible, but it’s pretty unlikely unless there’s an insider involved. As I mentioned earlier – I’m not sure I could do it, and I think it’s safe to say that my level of knowledge is higher than that of most.


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