Nuclear terrorism is the mother of all nightmare scenarios for national security experts.  It's been the topic of numerous global summits, worldwide international cooperation initiatives, and old George Clooney movies.  It is also very unlikely to occur in any conventional sense. Still, it is a threat whose implications are too horrendous to comprehend. And so, last week, world leaders gathered at the White House for a global Nuclear Security Summit.  Among the topics at this event were nuclear proliferation by non-state actors (groups without a recognized country such as ISIS), the state of security at nuclear power plants, and the safe transport and disposal of nuclear materials to prevent them from falling into the wrong hands.  This week, we'll take a good look at these possibilities and decide if we should all be heading to the nearest fallout shelter anytime soon.

1) Terrorists Acquiring Nuclear Weapons: Worst Outcome, Least Likely

When people think of nuclear terrorism, they tend to jump to the worst case scenario.  Let's be real here, if (and that is a huge if) a terrorist faction were to gain control of a nuclear weapon, it would create an unprecedented disaster.  They could detonate the weapon, bringing untold death and destruction upon whichever city happened to be within their targeting range.  Or, they could keep it, and hold the world hostage to their demands while also making it very difficult to attack them back.  Fortunately, as Iran has been finding out for a long time, getting your hands on a nuclear weapon is really, really hard.

For one thing, they are nearly impossible to make without the right knowledge and equipment.  Like your new dresser from IKEA, a nuclear weapon requires insanely advanced knowledge to produce, and its fuel (either plutonium or uranium in a fission bomb) is even harder to create.  No terrorist organization even comes close to having either the technical knowledge or the industrial ability to produce something like that.  Ok, so building one is probably out.  Could they buy one on the black market or steal one from a current nuclear power?  Perhaps, but even that isn't as easy as it sounds.  Most nations have very strict security measures around the protection of their nuclear devices (and the engineering secrets that go with them).  The one thing nuclear powers hate more than losing their nuclear weapons is seeing other organizations gain them, so most aren't in much of a mood to sell their weapons either. 

2) Attacks On Nuclear Power Plants: Plausible

Everyone can remember the handful of major accidents which have occurred at the world's nuclear power plants.  Chernobyl, Three Mile Island, and Fukushima have all become synonymous with the anti-nuclear movement.  Despite the risks, nuclear power remains one of the safest and most highly regulated (not to mention efficient) power sources in the world.  But one drawback is that these stations could potentially serve as a target of terrorist attack.  Allegedly, the Brussels attackers were following a nuclear scientist around for quite a while, potentially signaling a desire to attack a power plant.  If we assume that terrorists aren't trying to harness nuclear power to become radioactive jihadi supervillians, what would this attack actually look like? 

Most likely, they would try to disable the power plant (slightly disruptive) or force a meltdown (super disruptive).  It's possible this could be achieved through just sabotage alone, but nuclear plants tend to have dozens of countermeasures and fail-safes in place to prevent a meltdown from occurring.  Again, it would probably take a fair amount of specialized knowledge of nuclear engineering and power plant operations to cause any major damage.  Since this sort of thing would tend to be a pretty high profile event, there likely wouldn't be enough time to pull off a full meltdown. 

Still, the effects would be terrible.  We should probably point out here that nuclear meltdowns aren't Hiroshima-like explosions where everything (except for lead-lined refrigerators according to Indiana Jones) is complete destroyed.  Instead, nuclear meltdowns are usually dangerous because of the large amounts of harmful radioactive materials which can be dispersed throughout the area.  In small cases like Three Mile Island, no major damage occurred.  But more severe meltdowns can cause radioactive damage dozens of miles from the original accident site. 

3) "Dirty Bomb" Attack: Possible, but only In Some Locations

One of the main focuses of the nuclear security summit was the monitoring and safe transport of nuclear materials.  Raw uranium and plutonium are super dangerous on their own.  When added to an explosive device, they can disperse radioactive material over a small area, making a so-called dirty bomb (as opposed to a clean bomb that just blows stuff up?).  Obtaining this material still isn't easy, but it is probably the most likely scenario out of anything on this list. 

Governments and multi-national organizations have kept a close watch on this nuclear material for a long time.  Additionally, any would-be terrorist organization would need a way to deliver this material to the intended target.  All of this basically means that creating a dirty bomb would (hopefully) raise a lot of red flags to the Intelligence Community, so getting one all the way into the United States or Europe would be super hard.   But attacks on targets in places like the Middle East or Africa are much more plausible.  ISIS has shown particular interest in this type of attack, either against opposing military targets or their own people. 

In all, today's nuclear threat is fundamentally different than that of twenty years ago.  Gone are the days when people were taught in school to "duck and cover" and all the cool kids had bomb shelters in their basements.  The threat of impending nuclear annihilation has now been replaced by the creeping perceived threat of nuclear terrorism.  The Russians had nukes during the Cold War, but were almost certainly never going to use them.  Terrorists may use them, but will almost certainly never have them.  In short, the threat is there, but the true chances of nuclear terrorism remain remote.