This is one of a number of possible events. In a reactor for power generation, the KE of the moving fission products is converted into heat when passed through water in a very short time. Sometimes, we’re asked to find the average kinetic energy of the fragments knowing the temperature rise of a mass of coolant.
is the process by which the percentage of fissile uranium 235 is increased. Uranium 235 as mined is about 0.7% by mass and much of the rest is U 238 as oxides and other more complex salts. Enriching by isotope separation, gaseous or thermal diffusion and centrifuging boosts this percentage to between 3 and 4% for reactor grade uranium and if the process continues, high purity weapons grade uranium requires almost 90% purity. A crude, inefficient weapon can be manufactured with a source of 20% or more, however.
Control Rods and Moderators
The control rods absorb the neutrons which keeps the reaction rate relatively constant (rather than letting it grow exponentially). They create a situation where roughly one neutron per fission goes on to cause another fission event. Silver, indium, cadmium or boron are commonly used to make them.
Moderators slow down the neutrons without absorbing them. Fast neutrons are more inclined to bounce/deflect off of the surface of a nucleus so slower neutrons actually lead to a greater number of successful fissions i.e. moderators don’t slow the reaction down, they just help it to take place. Commonly-used moderators include regular (light) water (in 74.8% of the world’s reactors), solid graphite (20% of reactors) and deuterium oxide or heavy water (5% of reactors). Their job is to be introduced in controlled amounts into the nuclear pile (bundled fuel rods) to slow down neutrons and so increase the probability of a fission event.