Neutrons are central to nuclear chain reactions involving enriched U-235 reactors. A ‘slow’ neutron strikes a U-235 atom, thus breaking it down into two major fragments and releasing three more neutrons in the process. This initiates a chain reaction if all the projectiles get targets at their warhead. This is the number one fate of a neutron in a nuclear fission power reactor. Also in the core are control rods. These rods have pellets inside that are made of very efficient neutron capturers, like cadmium. These control rods are connected to machines that can raise or lower them in the core. When they are fully lowered into the core, fission can not occur because these Cd-rods absorb free neutrons. This is another fate of neutrons in a nuclear fission power reactor. Lastly, if a neutron is moving too fast, and thus is at a high-energy state, it passes right through the U-235 nucleus and releasing into the atmosphere, out of the reactor core.