Posted on 10/16/2002 5:29:16 AM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
Explanation: The remnants of nuclear reactors nearly two billion years old were found in the 1970s in Africa. These reactors are thought to have occurred naturally. No natural reactors exist today, as the relative density of fissionable uranium has now decayed below that needed for a sustainable reaction. Pictured above is Fossil Reactor 15, located in Oklo, Gabon. Uranium oxide remains are visible as the yellowish rock. Oklo by-products are being used today to probe the stability of the fundamental constants over cosmological time-scales and to develop more effective means for disposing of human-manufactured nuclear waste.
Astronomy Fun Fact:
Actually it's not really off-topic. We know that very heavy elements such as uranium are probably only synthesized in supernovae. No scientific discipline stands alone.
Oklo was a BREEDER reactor - it made more fissionables than it consumed. Very odd; only its long "run" made this possible. Plutonium it had "bred" decayed back to U-235!
Did you recently hear news of a theory that says Earth's core itself may be a reactor? Interesting to say the least! And the Oklo natural reactor played a part in the concept! Here's a link: Giant Nuclear Reactor May Run Earth's Magnetic Field
A real treat for the physics/geology crowd today...
The missing ingredient here is critical mass. You have to put so much of a single radioactive isotope such as U235 into such and such a volume to set up a nuclear chain reaction. Careful measurement of both concentration of isotope and amount used are essential to success in controlling the reaction.
It's fun and educational to consider such possibilities. Yesterday the possibility was announced that the earth's core may have an inner core about 350 miles in diameter. This is apparently suggested by a discontinuity of seismic waves at the boundary.
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