Mother Nature Does Nuclear Power

wjwlsn writes "Back in the day (2 billion years ago), even before the time of iron men and wooden reactors, Mother Nature had mastered nuclear power. She built a passively safe system at Oklo that had fully automatic control and built-in waste containment, and operated it safely for about 150 million years. Now researchers at Washington University in St. Louis have deduced the operational characteristics by examining the isotopic composition of xenon contained in rock samples taken from the reactor site. More details at Eurekalert."

Comments

Not just 2 billion years ago.

[noselasd]

Even today mother nature does nuclear power

Re:Not just 2 billion years ago.

[n6mod]

I've always wondered about this in the context of Berkeley and Santa Cruz's "Nuclear Free Zones".

'You! With the solar panel! Don't you know this is a Nuclear Free Zone!'

OPOD Link

[Trikenstein]

APOD: 2002 October 16 - Oklo: Ancient African Nuclear Reactors

Time spans

[Richard_at_work]

Humans really do not have an adequet grasp of timespans when it comes to geology or similiar such things. This happened over 150million years, didnt cause the end of the world, and life went on around it, whereas today we cant run powerstations without people declaring that they will bring about the end of hte human race, anything that comes within a hundred miles will die of radiation poisoning. This shows that the world can cope with nuclear waste, and it can cope pretty damn well. But then the world has always had to deal with bigger issues than anything humanity can throw at it anytime soon.

We have been around for 50,000 years, give or take. The earth has been around for 4billion years. Give nature some credit.

Re:Time spans

[Baron_Yam]

To quote George Carlin, "The world isn't going anywhere... we are!"

Just because it's unlikely we'll screw up the environment enough to sterilize the planet doesn't mean there isn't a significant chance we'll screw it up enough it kill off humanity.

Re:Time spans

[jfengel]

This is true. But the existence of a safe nuclear reactor doesn't mean that any particular power plant is safe. The plants currently in existence are run by people, are located within tens of miles of human homes, and are vastly complicated pieces of machinery. When they're done they leave radioactive bits lying around; even self-contained they're potentially dangerous for thousands of years.

You're right: if somebody were to mimic nature's design by building a totally safe and self-contained a bunch of know-nothing, knee-jerk environmentalists would protest against it anyway. But that doesn't imply that the same know-nothing, knee-jerk environmentalists are wrong to protest current designs.

The Oklo reactor has a number of design advantages (as it were) over ours. For one thing it doesn't actually have to generate any power, so it can run at an arbitrarily low level and far away from anybody who might care what it does. For another it didn't have to cope with the possibility of somebody attempting to steal its fuels or attempting to destroy it hoping to cause injury.

For a third, it didn't consider the possibility that its waste products would be a danger to anybody walking by. Our waste products must not only be sealed, but potentially people may even forget where they are, and warnings must be placed for thousands of years.

I don't think that these problems are insoluble. I believe safe reactors can be built, the risks reduced to acceptable levels. There will be those who don't understand, and I get frustrated at them, too. But neither will I pretend that nuclear power is totally safe, especially in its present implementation. Those opposed to nuclear power are not completely off base, and it's wise to listen to the smart ones. As for the stupid ones... well, there are stupid people on every side of every argument.

Re:cool, but not a practcal method

[turgid]

Recent tokamak reactors have been operated for around a fraction of a second to a second.

When I visited JET back in 2001 they said they were achieving sustained reactions over several tens of seconds (~30) before the plasma became unstable.

Fission reactors are easier to manage but still 30 minutes of reaction is pretty substantial.

Well, my old powerstation used to manage several months of continuous fission reactions on each reactor, before thunderstorms or welding operations or rod-drops would cause the reactors to come off. In theory, a reactor could be run continuously for 2 years i.e. between statutory (legal) biennial outages. These were reactors designed in the late 1950s.

Reactor design is not simple, there are many things to think about, how to moderate, how to cool down, how not to overheat (this is critical because the claddings around the elements usually get weaker when heated and crack. Once cracked, you cannot stop contaminating the water used for the reactor).

Here in the UK most of our reactors are gas-cooled (using carbon dioxide). We have one commercial PWR in Suffolk (Sizewell B). The Magnoxes were positive-feedback systems and could, in theory, overheat, but in practice the passive safety systems prevented this. The AGRs avoid this problem (caused by plutonium resonance with the thermal neutrons and graphite moderator) by holding the graphite temperature steady, by providing the graphite with it's own cooling loop (actually the first stage of core cooling, the gas then gets passed over the fuel). In effect the cold gas coming in cools the moderator, picking up some heat (being pre-heated) and then cooling the fuel, up to about 650 degrees C IIRC.

This all relies on active feedback systems as it is a chaotic system (in conjunction with the boilers).

If an AGR looses forced cooling, it's quite dangerous, as there is a maximum period of time in which you must get the automatic system back up and running. Otherwise you risk ruining your boilers. The "superheat" part of the boilers must under no circumstances get wet or else they are knackered forever, and your powerstation is useless. (AGRs and the two concrete pressure vessel Magnoxes, Oldbury and Wylfa, have "once-through boilers" which are a unique British design developed specifically for nuclear reactors and used nowhere else in the world).

AGRs are better than PWRs in another respect and that is the reactor pressure vessel is too strong to ever develop a significant breach that would result in a depressurisation and catastrophic release of radioactive substances.

Unfortunately, Margaret Thatcher chose a PWR for Sizewell B to improve Anglo-American relations. PWRs do not have concrete pressure vessels and are more "dosey" that AGRs (and the two concrete Magnoxes). They od have a sealed containment building, whic saved the day at Three Mile Island, but this is not required in an AGR or PBMR since the pressure vessel is much stronger and the failure modes are different. AGRs can not melt their fuel even with no forced convection, as long as you keep water in the boilers.

Somebody tell Bush

[eap]

We should invade, capture, or kill this "Mother Nature" immediately.