For 10 points, name this physical process where the nucleus of a large atom is split into two pieces by a neutron, releasing more neutrons and sometimes causing a chain reaction.
The four factor formula is used to gauge the sustainability of this process in an infinite medium, and this process occurred underground at Oklo, Gabon, around two billion years ago. In that case, water seeping through the ore slowed down neutrons, making them more likely to be absorbed, but now beryllium is often used as a neutron reflector in order to lower the necessary supercritical mass. For 10 points, name this physical process where the nucleus of a large atom is split into two pieces by a neutron, releasing more neutrons and sometimes causing a chain reaction.
The four factor formula is used to gauge the sustainability of this process in an infinite medium, and this process occurred underground at Oklo, Gabon, around two billion years ago.
nuclear {fission} 