How This Rare Natural Fission Reactor Could Solve Our Nuclear Waste Problem

How This Rare Natural Fission Reactor Could Solve Our Nuclear Waste Problem


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–again, totally naturally–for millions
of years since. Surely we can learn from this, right? And also this DEFINITELY sounds like the origin
story for an awesome comic book hero, I’m just saying. Before we dive into how the heck 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. So when humans make a nuclear reactor we have
to work pretty hard to get fission to occur. First, we’ve gotta have that heavy element
to split, which for us is usually uranium. There are three main kinds–or isotopes–of
uranium. The most common isotope is U-238, and it’s
found all over the earth and in our oceans–But it’s not fissionable by itself because it’s
just not unstable enough, so we can’t break it apart to release that energy we need. Isotope U-235, however, is unstable enough
to be fissionable…but it makes up less than 1% of the naturally occurring uranium in the
world. So when we mine uranium, we have to manually
enrich it to contain about 3% U-235 before we can use it in a nuclear reactor. But fissionable fuel is just step one–for
your power-producing nuclear reactor to be safe you also need some kind of moderator
that will slow down the neutrons enough so that they don’t cause an uncontrollable
reaction. In most nuclear reactors, we use water for
this. There are also control rods made out of other
neutron-absorbing materials like silver, and water is also be used as a coolant so the
whole operation doesn’t overheat and go into meltdown. So how is it that something we’ve spent
decades trying to perfect just magically happened all by itself in nature? Well, two billion years ago there was a lot
more U-235 than there is now, since it decays more quickly than U-238. And in a place called Oklo, Gabon, there was
a high enough concentration of U-235 to induce spontaneous nuclear fission. Wow. Presumably there was also enough of a moderator,
probably water, to keep the whole thing from exploding. AND there weren’t enough neutron absorbing
materials around to prevent the fission from sustaining itself. This is the only natural nuclear reactor in
the world that we know of so far. But that’s not to say there aren’t others–they
may have been subducted or eroded, or maybe we just haven’t found them! But this one natural nuclear reactor has been
completely mined by humans. It’s gone now. That’s how we even know about it in the
first place, we went down into the ground looking for uranium to enrich and came back
up and said, ‘Uhhhhh, either someone’s stolen almost 200 kilograms of uranium-235
or this is a natural nuclear reactor that’s burned it all off already’. It’s the latter, in case you haven’t been
following along. But we can learn a lot from Oklo today. Because again, it operated safely for MILLIONS
of years and NONE of its nuclear waste has leaked or adversely affected ANYTHING! This is remarkable because uranium fission
byproducts can be highly hazardous, and we struggle to know what to do with that waste. Cesium is one particularly nasty fission byproduct,
and is one of a suite of compounds that could cause symptoms of radiation poisoning. Cesium is one of the elements that makes the
Chernobyl and Fukushima sites so dangerous. Researchers recently studying the Oklo mines
discovered that the cesium byproducts from the natural reactor were most likely absorbed
and contained by another element that occurred naturally there called ruthenium. Ruthenium’s structure allows it to bind
to these radioactive elements, kinda like an atomic hug, making the elements like cesium
less radioactive. Ruthenium itself is too rare for us to use
on an industrial scale in taking care of commercial nuclear power waste. But this new insight into the world’s natural
fission reactor gives researchers hope that they can find or make something similar to
safeguard our modern nuclear waste. Check out this video here to learn more about
radioactive material, and subscribe to Seeker to keep Seeker to keep up worth all the amazing
natural phenomena around the world. And fun fact, the Oklo reactors isn’t just
one reactor-it’s SIX.TEEN. different reactors. PLUS one nearby. Mother nature’s an overachiever. Thanks for watching!

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