Part one of term paper
I think that right now, fission is the only way that we can get more energy out of a nuclear reaction than we put in. First, the energy per fission is very large. In practical units, the fission of 1 kg (2.2 lb) of uranium-235 releases 18.7 million kilowatt-hours as heat. Second, the fission process initiated by the absorption of one neutron ...

Part two of term paper
... of nuclear energy. Naturally occurring uranium contains only 0.71 percent uranium-235; the remainder is the non-fissile isotope uranium-238. A mass of natural uranium by itself, no matter how large, cannot sustain a chain reaction because only the uranium-235 is easily fissionable. The probability that a fission neutron with an initial energy of about 1 MeV will induce fission is rather low, but can be increased by a factor of hundreds when the neutron is slowed down through a series of elastic c ...