Thread: Natural nuclear reactor

2 billion years ago there was a water-moderated nuclear reactor in Gabon:

At the time that the Gabon reactor went critical, the abundance of 235U was 3%, similar to that in current commercial nuclear reactors. The approximate shape of the reactor zones is that of a compact mass of uranium oxide surrounded by porous rocks, which were presumably hydraulically connected to surface or ground water, allowing moderation and reflection of the neutrons produced by spontaneous fission or cosmic ray induced fission.
The relatively large size and spherical shape of the uranium bearing region reduced buckling. When the surrounding porous rocks were saturated with water, the subsequent moderation and reflection allowed the reactor to achieve criticality. It is likely that criticality was not continuous.
As the reactor power increased, the water moderator would heat, reducing its density and its effectiveness as a moderator and reflector. This process, known as a negative temperature coefficient, helps to control power during transient conditions in manmade nuclear reactors.

http://physics.isu.edu/radinf/Files/Okloreactor.pdf

Always through it really interesting.

Wonder what it was like on the surface or if it had any effect on the development of multicellular life that was starts about that time. Don't think any life was on land yet.

Originally Posted by Lynx_Fox

Always through it really interesting.

Wonder what it was like on the surface or if it had any effect on the development of multicellular life that was starts about that time. Don't think any life was on land yet.

Hah. You mean like Blinky, the three-eyed fish? No, don't worry there are plenty of mutations besides the ones due to radiation, and there is plenty of radiation around without nuclear reactors.

I don't think it would have had much effect on the surface because the reaction was very slow, occurring intermittently for a million years or so. The amount of reaction at any one time would only be enough to boil the water off that had seeped in.

One interesting thing is that the plutonium produced hardly moved anywhere from where it was formed. That means underground storage like at Yucca Mtn would probably work pretty well.

More proof of the great age of the earth. Because the half life of U235 is lower than for U238 it must have been present at higher levels in the past. But to get it to high enough levels to achieve criticality would still require one to go back 100s of millions of years , in fact 1.7 billion in the case of the Gabon reactors. Much more than the 6000 years of the creationists. Also, the radioactive waste and by-products of the fission process have various half lives, some, like Pu & Am, with half lives of 100s of 1000s of years. That they have all gone from the Gabon reactors is further proof of their great age. We know they were formed because their stable daughters are still there, and it has even been possible to show that the plutonium only moved less than 10 feet from its source. But not a trace of Pu remains. Had it formed in the last 6000 years as the creationists think the Pu should still be there! For more info see www.ocrwm.doe.gov/factsheets/doeymp0010.shtml and the references therein. Now wait for Jollybear to find this thread and subject us to a rambling, dyslexic essay "rebutting" it.

well, if god was able to insert varves and tree rings just because he feels like it, he needn't have followed the normal laws of chemistry and physics, does he ?

mind you, in that case jollybear would still maintain that this wasn't deceitful, but somehow part of a higher order of understanding that poor science can never fathom

somehow i find it depressing that these type of people blissfully make assertions which would negate centuries of scientific advance in about every branch of science that matters these days