Are Plutonium and Uranium found in the ground?
Sun, 9th Dec 2007
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from the show Naked Science Q&A Show
Les, Cambridge asked:
Are Plutonium and Uranium found in the ground, and if so could you accidentally trigger a nuclear explosion?
Plutonium is not found in the ground. All the Plutonium we use is artificially made in a nuclear reactor. Uranium is found in the ground. Today it would be very difficult to accidentally create a nuclear explosion, or a nuclear reactor, because thereís very little of the active form, Uranium-235, left. Itís slowly decaying away, and the longer we leave it the less there is.
A couple of billion years ago, there was a case where some bacteria concentrated Uranium underground in Africa, and we have since discovered that it did form a nuclear reactor. The reaction caused the area to get so hot that it killed off the bacteria, and so stopped them from concentrating more Uranium.
A lot of the heat locked away in the core of the Earth is thought to be the result of radioactive decay of things like Thorium and radioactive Potassium, but this doesnít have the chain reaction that a nuclear reactor does have.