2 Billion year old nuclear reactors. Oklo, Nigeria
May 16, 2015 14:43:40 GMT
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Post by Hill on May 16, 2015 14:43:40 GMT
This post is a redo of an old oGEC post which can not now be edited or repaired. LINK
From Science News, Volume 167, No. 11, March 12, 2005, p. 170.
Around 2 billion years ago, something happened naturally at the site of the present-day, but now closed, Oklo uranium mine in the west African Republic of Gabon. And it kept happening for for hundreds of thousands of years.
"Scientists explain the formation of what has turned out to be 18 reactors in and near Oklo without invoking exotic physics or visitations by space aliens. The sites were fortuitous accumulations of uranium that went critical for a while. Still, many researchers are awed that nature could achieve this result, something that people accomplished only after centuries of scientific and technological advancements.
Using sophisticated micro-analysis techniques, the St. Louis scientists have extracted major new findings about how the natural reactors might have operated. As a practical bonus, Meshik notes, the results might also point toward better ways to immobilize radioactive waste from nuclear-power plants.
Over many millennia of operation, every cycle would have generated the same mix of xenon isotopes. The researchers have used the known rates of all of those xenon-producing processes and the isotope concentrations that they have measured in their sample to calculate that the reactor turned on for about half an hour and then shut down for some two-and-a-half hours before turning on again.
Since the earliest Oklo studies, scientists have proposed a role for water in the creation of the natural reactors. According to the leading theory, deposits of the radioactive metal formed when water running off vegetation-free landmasses carried uranium compounds to the delta of an ancient African river. The theory holds that early biological processes produced oxygen that accumulated in the planet's atmosphere and oxidized the uranium, making it soluble."
"Once those compounds had settled in the delta, geological processes such as uplifting of earth layers and erosion eventually positioned the deposits of concentrated uranium underground, where they were bathed in enough water to start the chain reactions. Under those circumstances, the scientists propose that in each 30-minute active phase, the reactor became so hot that the water boiled away and the reactor stopped working. Then, as the reactor cooled, inflowing water no longer evaporated and so could again slow down neutrons, restarting the cycle.
The reactors eventually shut down because the fissionable uranium isotope decayed radioactively, its half-life left too little of the fissionable isotope."
From APOD 2002 October 16 Credit & Copyright: Robert D. Loss (Curtin U.)
Caption: 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 fissile 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 and distance scales and to develop more effective means for disposing of human-manufactured nuclear waste.
Wikipedia LINK
Map Location SOURCE
From Science News, Volume 167, No. 11, March 12, 2005, p. 170.
Around 2 billion years ago, something happened naturally at the site of the present-day, but now closed, Oklo uranium mine in the west African Republic of Gabon. And it kept happening for for hundreds of thousands of years.
"Scientists explain the formation of what has turned out to be 18 reactors in and near Oklo without invoking exotic physics or visitations by space aliens. The sites were fortuitous accumulations of uranium that went critical for a while. Still, many researchers are awed that nature could achieve this result, something that people accomplished only after centuries of scientific and technological advancements.
Using sophisticated micro-analysis techniques, the St. Louis scientists have extracted major new findings about how the natural reactors might have operated. As a practical bonus, Meshik notes, the results might also point toward better ways to immobilize radioactive waste from nuclear-power plants.
Over many millennia of operation, every cycle would have generated the same mix of xenon isotopes. The researchers have used the known rates of all of those xenon-producing processes and the isotope concentrations that they have measured in their sample to calculate that the reactor turned on for about half an hour and then shut down for some two-and-a-half hours before turning on again.
Since the earliest Oklo studies, scientists have proposed a role for water in the creation of the natural reactors. According to the leading theory, deposits of the radioactive metal formed when water running off vegetation-free landmasses carried uranium compounds to the delta of an ancient African river. The theory holds that early biological processes produced oxygen that accumulated in the planet's atmosphere and oxidized the uranium, making it soluble."
"Once those compounds had settled in the delta, geological processes such as uplifting of earth layers and erosion eventually positioned the deposits of concentrated uranium underground, where they were bathed in enough water to start the chain reactions. Under those circumstances, the scientists propose that in each 30-minute active phase, the reactor became so hot that the water boiled away and the reactor stopped working. Then, as the reactor cooled, inflowing water no longer evaporated and so could again slow down neutrons, restarting the cycle.
The reactors eventually shut down because the fissionable uranium isotope decayed radioactively, its half-life left too little of the fissionable isotope."
Caption: 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 fissile 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 and distance scales and to develop more effective means for disposing of human-manufactured nuclear waste.
Wikipedia LINK
Map Location SOURCE
Once more unto the breach, dear friends, once more, Or close the wall up with our English dead! In peace there's nothing so becomes a man As modest stillness and humility, But when the blast of war blows in our ears, Then imitate the action of the tiger: Stiffen the sinews, summon up the blood, Disguise fair nature with hard-favored rage; Then lend the eye a terrible aspect: FUAS! :/