Spent nuclear fuel pools Spent nuclear fuel (SNF) refers to fuel
after it has fueled a reactor. This fuel looks like new fuel in
the sense that it is made of solid pellets contained in fuel
rods. The only difference is that SNF contains fission products
and actinides, such as plutonium, which are radioactive, meaning
it needs to be shielded. Just as with the fuel rods in a
shutdown reactor, the SNF produces decay heat because most of
the decay radioactivity from the fission products and actinides
is deposited in the fuel and converted into thermal energy (aka
heat). As a result, the SNF also needs to be cooled, but at a
much lower level than fuel in a recently (<12 hours) shutdown
reactor as it produces only a fraction of the heat. In summary,
the SNF is stored for a certain time to: 1) allow the fuel to
cool as its decay heat decreases; and 2) shield the emitted
radiation. To accomplish these goals, SNF is stored in water
pools and large casks that use air to cool the fuel rods. The
pools are often located n