Natural nuclear reactor in Africa. Ancient nuclear reactor discovered in Africa

Natural nuclear reactors exist! At one time, the outstanding atomic physicist Enrico Fermi pathetically declared that only a person could create an atomic reactor ... However, as it turned out many decades later, he was wrong - he also produces nuclear reactors! They existed for many hundreds of millions of years ago, bubbling with nuclear chain reactions. The last of them, the natural nuclear reactor Oklo, went out 1.7 billion years ago, but still breathes radiation.

Why, where, how, and most importantly, what are the consequences of the emergence and activity of this natural phenomenon?

Natural nuclear reactors may well be created by Mother Nature herself - for this it will be enough for the necessary concentration of the uranium-235 isotope (235U) to accumulate in one "place". An isotope is a kind of chemical element that differs from others by a greater or lesser number of neutrons in the nucleus of an atom, while the number of protons and electrons remains constant.

For example, uranium always has 92 protons and 92 electrons, however, the number of neutrons varies: 238U has 146 neutrons, 235U has 143, 234U has 142, 233U has 141, etc. ... In natural minerals - on Earth, on other planets and in meteorites - the bulk is always 238U (99.2739%), and the isotopes 235U and 234U are represented only by traces - 0.720% and 0.0057%, respectively.

A nuclear chain reaction begins when the concentration of the uranium-235 isotope exceeds 1% and the more intense it is, the more it is. Precisely because the uranium-235 isotope is very scattered in nature, it was believed that natural nuclear reactors could not exist. By the way, in nuclear reactors of power plants, as fuel, and in atomic bombs, it is 235U that is used.

However, in 1972, in uranium mines near Oklo, in Gabon, Africa, scientists discovered 16 natural nuclear reactors that were actively operating almost 2 billion years ago ... Now they have already stopped, and the concentration of 235U in them is less than it had to be in "normal" natural conditions - 0.717%.

This, although meager, difference, compared with "normal" minerals, forced scientists to draw the only logical conclusion - natural atomic reactors really operated here. Moreover, the confirmation was the high concentration of decay products of uranium-235 nuclei, similar to what happens in artificial reactors. When an atom of uranium-235 decays, neutrons escape from its nucleus, hitting the nucleus of uranium-238, they turn it into uranium-239, which in turn loses 2 electrons, becoming plutonium-239...

It was this mechanism that generated more than two tons of plutonium-239 in Oklo. Scientists calculated that at the time of the "launch" of the natural nuclear reactor Oklo, about 2 billion years ago (the half-life of 235U is 6 times faster than 238U - 713 million years), the share of 235U was more than 3%, which is equivalent to industrial enriched uranium.

In order for the nuclear reaction to continue, a necessary factor was the slowing down of fast neutrons that flew out of the nuclei of uranium-235. This factor, as in man-made reactors, was ordinary water.

The reactor began to work at the time of flooding of porous rocks rich in uranium in Oklo with groundwater, and acted as some kind of neutron moderators. The heat released as a result of the reaction caused the water to boil and evaporate, slowing down and subsequently stopping the nuclear chain reaction.

And after the whole rock cooled and all short-lived isotopes decayed (these are the so-called neutron poisons, which are able to absorb neutrons and stop the reaction), water vapor condensed, flooding the rock, and the reaction resumed.

The scientists calculated that the reactor was “turned on” for 30 minutes until the water evaporated, and “turned off” for 2.5 hours until the steam condensed. This cyclical process resembled modern geysers and continued for several hundred thousand years. During the decay of the nuclei of the decay products of uranium, mainly radioactive isotopes of iodine, five isotopes of xenon were formed.

It was all 5 isotopes in various concentrations that were found in such rocks of a natural reactor. It was the concentration and ratio of the isotopes of this noble gas (xenon is a very heavy and radioactive gas) that made it possible to establish the frequency with which the Oklo reactor “worked”.

The decay of the nucleus of the uranium-235 atom (large atoms) causes the emission of fast neutrons, for a further nuclear reaction must be slowed down by water (small molecules)

It is known that high radiation is detrimental to living organisms. Therefore, in the places of existence of natural nuclear reactors, obviously, there were “dead spots”, where there was no life, because DNA is destroyed by radioactive ionizing radiation. But at the edge of the spot, where the radiation level was much lower, there were frequent mutations, which means that new species constantly arose.

Scientists still do not clearly know how life on Earth began. They only know that this required a strong energy impulse, which would have contributed to the formation of the first organic polymers. It is believed that such impulses could be lightning, volcanoes, meteorite and asteroid falls, however, in recent years it has been proposed to consider the hypothesis that such an impulse could be created by natural nuclear reactors as a starting point. Who knows …

Many people think that nuclear power is an invention of mankind, and some even believe that it violates the laws of nature. But nuclear power is actually a natural phenomenon, and life could not exist without it. This is because our Sun (and every other star) is itself a giant powerhouse, lighting up the solar system through a process known as nuclear fusion.

Humans, however, use a different process to generate this force called nuclear fission, in which energy is released by splitting atoms rather than by combining them, as in the process of welding. No matter how inventive humanity may seem, nature has already used this method as well. In a single but well-documented site, scientists have found evidence that natural fission reactors were created in three uranium deposits in the western African nation of Gabon.

Two billion years ago, uranium-rich mineral deposits began flooding with groundwater, causing a self-sustaining nuclear chain reaction. By looking at the levels of certain isotopes of xenon (a by-product of the fission process of uranium) in the surrounding rock, the scientists determined that the natural reaction took place over several hundred thousand years at intervals of about two and a half hours.

Thus, the natural nuclear reactor at Oklo operated for hundreds of thousands of years until most of the fissile uranium was exhausted. While most of the uranium in Oklo is the non-fissile isotope U238, only 3% of the fissile isotope U235 is needed to start a chain reaction. Today, the percentage of fissile uranium in the deposits is about 0.7%, which indicates that nuclear processes took place in them for a relatively long period of time. But it was precisely the exact characterization of the rocks from Oklo that first puzzled scientists.

Low levels of U235 were first observed in 1972 by employees at the Pierrelate uranium enrichment plant in France. During routine mass spectrometric analysis of samples from the Oklo mine, it was found that the concentration of the fissile uranium isotope differed by 0.003% from the expected value. This seemingly small difference was significant enough to alert authorities, who were concerned that the missing uranium could be used to build nuclear weapons. But later, in the same year, scientists found the answer to this riddle - it was the first natural nuclear reactor in the world.

Two billion years ago, in one place on our planet, geological conditions developed in an amazing way, accidentally and spontaneously forming a thermonuclear reactor. It worked steadily for a million years, and its radioactive waste, again in a natural way, without threatening anyone, was stored in nature all the time that had passed since its stop. It would be nice to understand how he did it, wouldn't it?

Nuclear fission reaction (quick reference)

Before we begin the story of how this happened, let's quickly recall what a fission reaction is. It occurs when a heavy nuclear nucleus breaks up into lighter elements and free fragments, releasing a huge amount of energy. The mentioned fragments are small and light atomic nuclei. They are unstable and therefore extremely radioactive. They make up the bulk of hazardous waste in the nuclear power industry.

In addition, scattered neutrons are released, which are able to excite neighboring heavy nuclei to the state of fission. So, in fact, a chain reaction takes place, which can be controlled at the same nuclear power plants, providing energy for the needs of the population and the economy. An uncontrolled reaction can be catastrophically destructive. Therefore, when people build a nuclear reactor, they have to work hard and take a lot of precautions to start a thermonuclear reaction.

First of all, you need to make the heavy element divide - usually uranium is used for this purpose. In nature, it is mainly found in the form of three isotopes. The most common of these is uranium-238. It can be found in many places on the planet - on land and even in the oceans. However, by itself, it is not capable of division, as it is quite stable. On the other hand, uranium-235 has the instability we need, but its share in nature is only about 1 percent. Therefore, after mining, uranium is enriched - the share of uranium-235 in the total mass is brought to 3%.

But that's not all - for safety reasons, a fusion reactor needs a moderator for neutrons so that they remain in check and do not cause an uncontrolled reaction. Most reactors use water for this purpose. In addition, the control rods of these structures are made of materials that also absorb neutrons, such as silver. Water, in addition to its main function, cools the reactor. This is a simplified description of the technology, but even from it it is clear how complex it is. The best minds of mankind have spent decades to bring it to mind. And then we found out that exactly the same thing was created by nature, and by accident. There is something incredible in this, isn't there?

Gabon is the birthplace of nuclear reactors

However, here we must remember that two billion years ago there was much more uranium-235. For the reason that it decays much faster than uranium-238. In Gabon, in an area called Oklo, its concentration was sufficient to start a spontaneous thermonuclear reaction. Presumably, in this place there was the right amount of moderator - most likely water, thanks to which the whole thing did not end with a huge explosion. Also in this environment there were no neutron-absorbing materials, as a result of which the fission reaction maintained itself for a long time.

It is the only natural nuclear reactor known to science. But this does not mean that he was always so unique. Others could have moved deep into the earth's crust as a result of the movement of tectonic plates or disappeared due to erosion. It's also possible that they just haven't been found yet. By the way, this natural Gabonese phenomenon also has not survived to this day - it is completely worked out by miners. It was thanks to this that they learned about him - they went deep into the earth in search of uranium for enrichment, and then returned to the surface, scratching their heads in puzzlement and trying to solve the dilemma - “Either someone stole almost 200 kilograms of uranium-235 from here, or this is a natural nuclear reactor who had already burned it completely." The correct answer is after the second "or" if someone did not follow the thread of the presentation.

Why is the Gabon reactor so important to science?

Nevertheless, it is a very important object for science. For the reason that it worked without harm to the environment for about a million years. Not a single gram of waste has leaked into nature, nothing in it has been affected! This is extremely unusual, because the by-products of uranium fission are extremely dangerous. We still don't know what to do with them. One of them is cesium. There are other elements that can directly harm human health, but it is because of cesium that the ruins of Chernobyl and Fukushima will pose a danger for a long time to come.

Gabonese natural nuclear reactor

Scientists who recently surveyed the mines in Oklo found that cesium in this natural reactor was absorbed and bound by another element - ruthenium. It is very rare in nature, and we cannot use it on an industrial scale to neutralize nuclear waste. But understanding how the reactor works can give us hope that we can find something similar and get rid of this long-standing problem for humanity.

One of the hypotheses about the alien origin of man says that in ancient times the solar system was visited by an expedition of a race from the central region of the galaxy, where the stars and planets are much older, and therefore life originated there much earlier.

First, space travelers settled on Phaethon, once located between Mars and Jupiter, but unleashed a nuclear war there, and the planet died. The remnants of this civilization settled on Mars, but even there atomic energy killed most of the population. Then the remaining colonists arrived on Earth, becoming our distant ancestors.

This theory may be confirmed by an amazing discovery made 45 years ago in Africa. In 1972, a French corporation was mining uranium ore from the Oklo mine in the Gabonese Republic. Then, during the standard analysis of ore samples, specialists discovered a relatively large shortage of uranium-235 - more than 200 kilograms of this isotope were missing. The French immediately sounded the alarm, because the missing radioactive substance would be enough to make more than one atomic bomb.

However, further investigation showed that the concentration of uranium-235 in the Gabon mine is as low as in the spent fuel from a nuclear power plant reactor. Is this some kind of nuclear reactor? Analysis of ore bodies in an unusual uranium deposit showed that nuclear fission took place in them as early as 1.8 billion years ago. But how is this possible without human intervention?

Natural nuclear reactor?

Three years later, a scientific conference dedicated to the Oklo phenomenon was held in the Gabonese capital of Libreville. The most daring scientists then considered that the mysterious nuclear reactor is the result of the activities of an ancient race, which was subject to nuclear energy. However, most of those present agreed that the mine is the only "natural nuclear reactor" on the planet. Like, it started many millions of years by itself due to natural conditions.

People of official science suggest that a layer of sandstone rich in radioactive ore was deposited on a solid basalt bed in the river delta. Due to tectonic activity in this region, the basalt basement with uranium-bearing sandstone was sunk several kilometers into the ground. The sandstone allegedly cracked, and groundwater penetrated the cracks. Nuclear fuel was located in the mine in compact deposits inside the moderator, which served as water. In clay "lenses" of ore, the concentration of uranium increased from 0.5 percent to 40 percent. The thickness and mass of the layers at a certain moment reached a critical point, a chain reaction took place, and the "natural reactor" started working.

Water, being a natural regulator, entered the core and started a chain reaction of fission of uranium nuclei. Emissions of energy led to the evaporation of water, and the reaction stopped. However, a few hours later, when the core of the reactor created by nature cooled down, the cycle was repeated. Subsequently, presumably, a new natural disaster occurred, which raised this “installation” to its original level, or the uranium-235 simply burned out. And the operation of the reactor stopped.

Scientists have calculated that although energy was generated underground, its power was small - no more than 100 kilowatts, which would be enough to operate several dozen toasters. However, the very fact that the generation of atomic energy spontaneously occurred in nature is impressive.

Or is it a nuclear repository?

However, many experts do not believe in such fantastic coincidences. The discoverers of atomic energy proved long ago that a nuclear reaction can only be obtained artificially. The natural environment is too unstable and chaotic to support such a process for millions and millions of years.

Therefore, many experts are convinced that this is not a nuclear reactor in Oklo, but a nuclear repository. This place really looks more like a spent uranium fuel dump, and the dump is perfectly equipped. Immured in a basalt “sarcophagus”, uranium was stored underground for hundreds of millions of years, and only human intervention caused it to appear on the surface.

But since there is a burial ground, it means that there was also a reactor that produced nuclear energy! That is, someone who inhabited our planet 1.8 billion years ago already had the technology of nuclear energy. Where did all this go?

According to alternative historians, our technocratic civilization is by no means the first on Earth. There is every reason to believe that in the past there were highly developed civilizations that used the nuclear reaction to produce energy. However, like humanity today, our distant ancestors turned this technology into a weapon, and then killed themselves with it. It is possible that our future is also predetermined, and after a couple of billion years, the descendants of the current civilization will come across the nuclear waste dumps left by us and wonder: where did they come from? ..

Much that nature offers us is in itself more perfect and simpler than what a person plans to make, so researchers are studying, first of all, what nature offers us.

But in what will be discussed in this article, everything happened exactly the opposite.

On December 2, 1942, a team of scientists at the University of Chicago, led by Nobel laureate Enrico Fermi, created the first man-made nuclear reactor. This achievement was kept secret during World War II, as part of the so-called "Manhattan Project" to build the atomic bomb.

Fifteen years after the fission reactor was created by man, scientists began to think about the possibility of the existence of a nuclear reactor created by nature itself. The first official publication on the subject was by the Japanese professor Paul Kuroda (1956), who laid down detailed requirements for any plausible natural reactors, if any, in nature.

The scientist described this phenomenon in detail, and its description is still considered the best (classical) in nuclear physics:

1. Approximate age range for natural reactor formation
2. The required concentration of uranium in it
3. The required ratio of uranium isotopes in it is 235 U / 238 U

Despite careful research, Paul Kuroda was unable to find an example of a natural reactor for his model among the uranium ore deposits on the planet.

A small but critical detail that the scientist overlooked is the possibility of water participating as a chain reaction moderator. He also didn't realize that certain ores could be so porous that they could hold enough water to slow down the neutrons and keep the reaction going.

Scientists argued that only man is capable of creating a nuclear reactor, but nature turned out to be more sophisticated.

A natural nuclear reactor was discovered on June 2, 1972 by the French analyst Boujigues in southeastern Gabon, West Africa, right in the body of a uranium deposit.

And this is how the discovery happened.

During routine spectrometric studies of the 235U/238U isotope ratio in Oklo ore in the laboratory of the French uranium enrichment plant Pierrelatt, a chemist found a slight deviation (0.00717, compared to the norm of 0.00720).

Nature is characterized by the stability of the isotopic composition of various elements. It is the same all over the planet. In nature, of course, isotope decay processes take place, but this is not characteristic of heavy elements, because the difference in their masses is insufficient for these isotopes to fission during any geochemical processes. But in the Oklo deposit, the isotopic composition of uranium was uncharacteristic. This small difference was enough to keep scientists interested.

Immediately there were various hypotheses about the causes of the strange phenomenon. Some argued that the deposit was contaminated with spent fuel from alien spacecraft, others considered it a burial place for nuclear waste, which we inherited from ancient highly developed civilizations. However, detailed studies have shown that such an unusual ratio of uranium isotopes was formed naturally.

Here is the simulated history of this "wonder of nature".

The reactor was put into operation about two billion years ago during the Proterozoic. The Proterozoic is generous with discoveries. It was in the Proterozoic that the basic principles for the existence of living matter and the development of life on Earth were developed. The first multicellular organisms appeared and began to develop coastal waters, the amount of free oxygen in the Earth's atmosphere reached 1%, and prerequisites for the rapid flourishing of life appeared, there was a transition from simple division to sexual reproduction.

And now, at such an important time for the Earth, our "nuclear natural phenomenon" appears.

Still, it is surprising that no other similar reactor has been found in the world. True, according to some reports, traces of a similar reactor were found in Australia. This can only be explained by the fact that in the distant Cambrian period, Africa and Australia were a single whole. Another fossilized reactor zone has also been discovered in Gabon, but in a different uranium deposit at Bangombe, 35 kilometers southeast of Oklo.

On Earth, uranium deposits of the same age are known, in which, however, nothing similar happened. Here are just the most famous of them: Devil's Hole and Rainier Mays in Nevada, Pena Blanca in Mexico, Box Canyon in Idaho, Kaimakli in Turkey, Chauvet Cave in France, Cigar Lake in Canada and Owens Lake in California.

Apparently, in the Proterozoic in Africa, a number of unique conditions arose that were necessary to start a natural reactor.

What is the mechanism of such an amazing process?

Probably, first in a certain depression, perhaps in the delta of an ancient river, a layer of sandstone rich in uranium ore was formed, which rested on a strong basalt bed. After another earthquake, common in that era, the basalt foundation of the future reactor sank several kilometers, pulling the uranium vein with it. The vein cracked, groundwater penetrated into the cracks. In this case, uranium readily migrates with water containing a large amount of oxygen, that is, in an oxidizing environment.

Oxygen-saturated water makes its way through the rock mass, leaches uranium out of it, drags it along with it, and gradually consumes the oxygen contained in it for the oxidation of organics and ferrous iron. When the supply of oxygen is exhausted, the chemical situation in the earth's depths changes from an oxidizing one into a reducing one. The "wandering" of uranium then ends: it is deposited in rocks, accumulating over many millennia. Then another cataclysm raised the foundation to the modern level. This scheme is followed by many scientists, including those who proposed it.

As soon as the mass and thickness of the layers enriched with uranium reached critical dimensions, a chain reaction arose in them, and the "unit" started working.

A few words should be said about the chain reaction itself, which is the result of complex chemical processes taking place in a "natural reactor". The 235 U nuclei are the easiest to split, which, absorbing a neutron, are divided into two fragments of splitting and emit two or three neutrons. The ejected neutrons can, in turn, be absorbed by other uranium nuclei, causing decay to escalate.

Such a self-sustaining reaction is controllable, which is what the people who created the nuclear fission reactor took advantage of. In it, control is carried out by means of control rods (made from materials that absorb neutrons well, such as cadmium), which are lowered into the "hot zone". In his reactor, Enrico Fermi used just such cadmium plates to regulate the nuclear reaction. The reactor in Oklo was not operated by anyone in the usual sense of the term.

The chain reaction is accompanied by the release of a large amount of heat, so it was still unclear why the natural reactors in Gabon did not explode, but the reactions self-regulated.

Now scientists are sure they know the answer. Researchers from the University of Washington believe that the explosions did not happen due to the presence of mountain water sources. In various man-made reactors, graphite is used as a moderator, necessary to absorb emitted neutrons and maintain a chain reaction, and in Oklo, water played the role of moderator of the reaction. When water entered the natural reactor, it boiled and evaporated, as a result of which the chain reaction stopped for a while. It took about two and a half hours to cool the reactor and accumulate water, and the duration of the active period was about 30 minutes, according to Nature.

When the rock cooled, water seeped through again and started a nuclear reaction. And so, flaring up, then fading away, the reactor, whose power was about 25 kW (which is 200 times less than that of the very first nuclear power plant), worked for approximately 500 thousand years.

In Oklo, as well as throughout the rest of the Earth and in the solar system as a whole, two billion years ago, the relative content of the isotope 235 U in uranium ore was 3,000 per million atoms. At present, the formation of a nuclear reactor on Earth in a natural way is no longer possible, since there is a shortage of 235 U in natural uranium.

There are a number of other conditions that must be met in order to start a natural fission reaction:

1. High total uranium concentration
2. Low concentration of neutron absorbers
3. High retarder concentration
4. Minimum or critical mass to start a fission reaction

In addition to the fact that nature launched the very mechanism of a natural reactor, one cannot but worry about the next, perhaps the most "urgent" question for the world ecology: what happened to the waste of a natural nuclear "power plant"?

As a result of the operation of the natural reactor, about six tons of fission products and 2.5 tons of plutonium were formed. The bulk of the radioactive waste is "buried" within the crystalline structure of the uranite mineral found in the Oklo ore body.

Unsuitable ionic radius elements that cannot penetrate the uranite lattice either interpenetrate or leach out.

The Oaklin reactor "told" mankind about how to bury nuclear waste in such a way that this burial site was harmless to the environment. There is evidence that at a depth of more than a hundred meters, in the absence of free oxygen, almost all products of nuclear burials did not go beyond the boundaries of ore bodies. Movements of only elements such as iodine or cesium have been recorded. This makes it possible to draw an analogy between natural processes and technological ones.

The problem of plutonium migration is attracting the closest attention of environmentalists. It is known that plutonium decays almost completely to 235 U, so its constant amount may indicate that there is no excess uranium not only outside the reactor, but also outside the uranite granules, where plutonium was formed during the reactor activity.

Plutonium is a rather alien element for the biosphere, and it occurs in scanty concentrations. Along with some uranium deposits in the ore, where it subsequently decays, some plutonium is formed from uranium by interaction with neutrons of cosmic origin. In small quantities, uranium can occur in nature in various concentrations in completely different natural environments - in granites, phosphorites, apatites, sea water, soil, etc.

Oklo is currently an active uranium deposit. Those ore bodies that are located near the surface are mined by a quarry method, and those that are at a depth, by mine workings.

Of the seventeen known fossil reactors, nine are completely buried (inaccessible).
Reactor Zone 15 is the only reactor that is accessible through a tunnel in the reactor shaft. The remains of Fossil Reactor 15 are clearly visible as a light gray-yellow colorful rock, which is composed mainly of uranium oxide.

The light colored streaks in the rocks above the reactor are quartz that crystallized from hot underground water sources that circulated during the period of reactor activity and after its extinction.

However, as an alternative assessment of the events of that distant time, one can also mention the following opinion related to the consequences of the operation of a natural reactor. It is assumed that a natural nuclear reactor could lead to numerous mutations of living organisms in that region, the vast majority of which died out as unviable. Some paleoanthropologists believe that it was high radiation that caused unexpected mutations in African human ancestors roaming just nearby and made them people (!).