Nuclear fission is generated by splitting atoms of Uranium. Uranium undergoes radioactive decay in a chain reaction. The rate of this reaction depends completely on the presence of a moderator ( How a Nuclear Reactor Makes Electricity 1). Whether the moderator is present, and how much moderator is present controls the rate of the reaction, and therefore the rate of energy output. As Uranium splits into several smaller elements, a small amount of mass is turned into a massive amount of energy. Albert Einstein was able to explain the phenomenon through the famous equation: E=mc2(Woodford 1). This is the energy that heats water and forms radiation.