When was the first nuclear reactor created? You probably think it was Enrico Fermi’s CP-1 pile built under the bleachers at the University of Chicago in 1942. However, you’d be off by — oh — about 2 billion years.
The first reactors formed naturally about 2 billion years ago in what is now Gabon in West Africa. This required several things coming together: natural uranium deposits, just the right geology in the area, and a certain time in the life of the uranium. This happened 17 different times, and the average output of these natural reactors is estimated at about 100 kilowatts — a far cry from a modern human-created reactor that can reach hundreds or thousands of megawatts.
The reactors operated for about a million years before they spent their fuel. Nuclear waste? Yep, but it is safely contained underground and has been for 2 billion years.
The Basics of Fission Reactors
Any fission reactor basically works the same. An unstable atom like uranium or plutonium breaks apart, creating fast neutrons. There’s a chance some of those neutrons will strike nearby unstable atoms, causing them to break apart too. However, because these neutrons are fast, statistically this won’t happen very often. However, if a moderating substance like water or graphite slows down the neutrons, they have more time to interact with other unstable atoms, so more atoms break down.
If you balance it right, the atoms breaking apart will cause a chain reaction that sustains itself. That is, neutrons hit atoms, releasing more neutrons, which hit more atoms. The heat released is substantial and we usually use it to make steam to drive an electric generator.
