Two billion years ago, the earth’s geology came together to spontaneously and naturally form what was essentially a nuclear fission reactor. It operated stably for about a million years, and its radioactive waste has been safely contained, totally naturally, for millions of years since.
Before we dive into how this happened, let’s do a quick overview of fission. Nuclear fission happens when a heavy atomic nucleus splits into lighter elements and rogue particles and releases a large amount of energy. In addition to the energy, those smaller byproducts are usually lighter atomic nuclei that are unstable after the fission process and are therefore highly radioactive. This is where the bulk of nuclear power’s hazardous waste comes from.
Fission also releases stray neutrons, and these neutrons can excite other nearby heavy nuclei into the fission state, causing a chain reaction that when controlled in a nuclear power plant, can be harnessed to power our everyday life. But when left uncontrolled, it can be disastrously destructive.