Below we give a sample essay, written by Katie Krotz on the last midterm, which earned full 20 points of credit. This can serve as an example of what we are looking for. (Congratulations, Katie!)
Nuclear terrorism. How real is the threat that an organization such as
al Qaeda could develop a nuclear weapon? What difficulties do they
face to get the different kinds of nuclear weapons? What approach would
be most likely to work for them?
The type of nuclear bomb most likely to be used by a terrorist group would
be a uranium bomb. While it is hard to get weapons-grade uranium (which
needs to be about 80% U-235) since natural uranium is only 0.7% U-235, it is
still possible, either by using a calutron which separates U-238 from U-235
using a magnetic field or by acquiring some of the unaccounted for soviet
weapons (this being the most likely way for a terrorist organization to
get the necessary uranium because of their limited means -- financially and
scientifically). Once they had the necessary 15 pounds U-235 rich Uranium,
building the actual bomb would be relatively easy as the design is a simple
cannon that pushes two uranium pieces together so that they have critical
mass and start a chain reaction.
It is highly unlikely that a terrorist group would be able to make a plutonium
or hydrogen bomb. While the necessary 6 pounds plutonium is easy to get
(a "waste" product of nuclear reactors), it is highly radioactive because
of Pu-240 (which makes up a small percentage of the plutonium), and can
make the bomb go off early. This requires a special bomb design where the
plutonium is imploded by expolsives. To make this type of bomb requires
the sort of resources that a small country like North Korea, might have,
but that a terrorist group wouldn't.
Because of these difficulties in acquiring and making nuclear weapons,
it is much more likely a terrorist group would use gasoline and TNT to do
damage in an easier and cheaper way.