An historian by training, J.K. Obatala is one of the world’s best known Black Amateur Astronomers. In this article, he commemorates the 52nd Anniversary of Gabon’s famous natural reactor—and reminds Africans in Nigeria and abroad, of a missed opportunity.

In 1972, French scientists announced a startling discovery: 1,800 million years ago, they said, a natural nuclear fission reactor—similar, in principle, to the modern, manmade devices that generate electricity—had switched on, at Oklo, in the Central West African country of Gabon.

The “Oklo Phenomenon,” as it became known, is the only documented instance, on Earth, of a natural nuclear pile igniting, without human intervention, and releasing energy. There were, in fact, no modern humans at the time. Our evolution, lie 1.5 billion years in the future!

Intellectually and politically, Black people – especially Nigerians and African Americans – ought to have taken an interest in the Oklo Complex. It holds out the promise of enhanced knowledge and understanding, not only of Africa’s place in the world but also the universe.

Pragmatically, this includes an environmental analogue, that will provide useful clues concerning the long term stability of irradiated fuel in a nuclear waste disposal site and the migration patterns of uranium and fission products.

Then again, Black people must learn to think about abstract issues—which have genetic implications. This is pertinent to intellectuals, for whom the Oklo Complex provides fresh approaches to issues like the fine structure constant, the origin of life and the content galaxies.

“Oklo,” is the name given to 17 deposits of depleted uranium, in the rich ore fields of Franceville district, Gabon. The depletion came to notice, radioactivity.eu.com says, when Soviet Union buyers “complained about an ore delivery with a low uranium-235 content”.

There are three isotopes (types) of uranium, found in nature—U-234, U-235 and U-238 (the heaviest and most abundant). Uranium-235 is rare and highly valued, because it is fissile. This means it can be fissioned in a reactor, to generate energy or produce nuclear weapons.

Normally, U-235 – whether it is from the Moon, Earth or found in meteorites – has a uranium concentration 0.7202%. But samples taken from the Oklo Complex (which actually consists of Oklo, Okelobondo, Mounana, Boyindzi, Mikouloungou and Bangombé) showed only 0.7171%.

After an involved process of elimination, investigators concluded that the deficit could only have resulted from a chain reaction, that induced criticality—and “burned” the U-235! This became possible, when concentrations of high grade ore, built up through geological processes.

“The high grade ore is restricted to areas associated with tectonic structures,” notes the International Atomic Energy Agency, “and is located in bodies about 5 to 20m in length, 5 to 10m wide and 0.3 to 2m thick…” This, it explains, is where the “fission reactions” began.

“Fission reactions,” are all about “neutrons”—uncharged subatomic particles, used to bombard uranium nuclei. The bombardment fractures (or fissions) the target nucleus, causing it to release, on average, 2.5 additional neutrons. One of these, will hit another uranium nucleus.

“Critical mass,” is the minimum amount of uranium required, for this process to become self-sustaining. In nuclear power plants, criticality is controlled, either by inserting graphite rods into the reactor core, or injecting water, as a moderator. (In bombs, criticality is uncontrolled).

Three factors, brought Oklo to life. First, was lens-shaped geological structures, with masses of 20% to 60% uranium. “The chain reaction took place in these lenses,” allowed Yu. V. Petrov et. al. “After the end of the chain reaction the deposit was raised to the surface…”

Secondly, the geological “moderators” kicked in –slowing down fast neutrons. Neutrons must “lose energy to become thermal neutrons,” writes Toshikazu Ebisuzaki and Shigenori Maruyama, “through collisions with protons (hydrogen nucleus).”

Water is rich in hydrogen atoms and, hence, a very effective moderator. This explains why most modern reactors use either graphite or water, as moderators. It also offers insight into the operation of the Oklo Complex.

The Oklo process was cyclic. It generated energy for 30 minutes, then went dormant for 2.5 hours. Sustaining this pattern, for more than 100,000 years, was the porosity of sandstone in the Franceville basin, which Richard T. Ibekwe, of M.I.T. says, ranges between 20% and 40%.

Steam was created, as water seeped through the pores and cracks of minerals, and made contact with hot uranium cores. This would, as A. P. Meshik et.al. explain, “reduce the neutron thermalization and shut down the chain reaction”. Operation resumed, when the cores cooled.

Finally, the natural reactors did not have to contend with exceptionally high levels of “neutron poison” – elements, such as lithium, gadolinium, samarium and other rare earth nuclides. These tend to absorb neutrons, thus subverting their role as moderators.

By modern standards, the output of the natural reactors was modest. It was equivalent to roughly 100kw which, Steenkamp estimates, in, “Gabon’s Natural Fission Sites,” would power “about 1000 lightbulbs.”

The power of the reactors, is not the point. Anytime you look in the sky, day or night, examples of nuclear fusion abound (the Sun during the day, stars at night). Why did nature lay such heavy emphasis on fusion – to the neglect of fission, which is exceedingly rare on Earth?

Originally, the bias was less than is apparent, today. True, there were always fewer visible examples of fission, than fusion. But there were some. In fact, many scholars believe natural reactors, like the Oklo Complex, may have been fairly widespread, on early Earth.

Laurence A. Coogan and Jay T. Cullen, for instance, posit that, during the Archean, U-235 deposits formed in isolated marine and fresh water basins, creating “oxygen oases”. Oxygen converted UIV to the water soluble UVI, facilitating its transport and isotopic concentration.

Such oxygenated “oasis,” they say, were sparse, yet distinctly present on Earth, 2.5 billion years ago. “Because of the high abundance of 235U at this time,” they surmise, “these uranium deposits could have formed widespread, near-surface, critical natural fission reactors.”

Yet most scientists link Oklo, in particular, to “the Great Oxidation Event”. It occurred 2.4 billion years ago, when photosynthetic cyanobacteria flooded Earth’s atmosphere with oxygen—killing off species, which couldn’t breathe oxygen, but making higher lifeforms possible.

“The reason uranium only became concentrated enough around two billion years ago to initiate natural fission,” notes Steenkamp, “has been linked to the ‘Great Oxidation Event’…. At that time, the levels of oxygen in the atmosphere rose significantly, from 1% to 15%”.

The question, you might ask, is “Why have investigators found only one surviving natural reactor complex—when there were, in all likelihood, others?” The short answer, is that, while scientists have little hope of finding another reactor, they have not given up, entirely.

According to E.D. Davis, et.al., for instance, in 1953, investigators found evidence that natural fission had taken place in the Congo. They stated, it was reported, that “the deposit was twenty-five percent of the way to becoming a pile”. (“Pile,” is the former name for a reactor.)

In 1956, Paul Kuroda, a Japanese American, used xenon/plutonium analysis, to predict that a natural reactor, should exist somewhere on Earth. Unfortunately, he had not seen mining samples from Oklo. So, he couldn’t pinpoint the location.

But the long answer lies in physics. Heavy elements are unstable and ever changing. These spontaneous changes, are expressed as “half-life”. This is the time it takes for one half of a given quantity of, say, uranium, to evolve through its 14 intermediate “daughter” products, and stabilize as lead!

Differences in the half-lives of uranium isotopes, impinge on the probability of finding another natural reactor, on Earth. A reactor uses the fissile U-235, for instance, at concentrations of 3% to 5%. (U-238, is non-fissile; but can be enriched, for use in a reactor).

Hence, as Davis et.al. explain, the likelihood of a natural reactor existing increases, going backward in geological time, but greatly diminishes in the present. U-235, for instance, has a half-life of 710 million years, compared with the half-life of U-238, which is 4.51 billion years.

Naturally, prospects for U-235 would diminish more rapidly, than for U-238. The authors show, for example, that the enrichment of U-235 was 1.3% 700 million years ago, 2.3% 1.40 billion years ago, 4.0% 2.10 billion years ago and up to 17% when the solar system was created.

This, of course, does not in any way reduce the value of the Oklo Complex, either to Africans or to humanity. The number of papers published (nearly 200) and international research groups set up to investigate the “Oklo Phenomenon,” attests to its importance.

I note only a few of these groups here, starting with the International Atomic Energy Agency’s International Working Group On Natural Reactors. The U.S Department of Energy also sent a team of investigators, which issued a report.

But Laurent Trotignon, in Oklo (Gabon), says the main impetus came from the European Community (EU). He cites three major Projects: The Franceville Project (1972-1978; The EC funded Oklo Phase I project (1991-1995); and The EC funded Oklo Phase II project (1996-1999).

A key interest of Europe and the U.S.A., was to see what they could learn, about the storage of nuclear material. François Gauthier-Lafaye, the chief geologist, stated explicitly that he considers the Oklo complex, to be “a good natural analogue for nuclear waste disposal.”

He believes that the survival of the site, over 1,800 million years, is due mainly to geological stability, the occurrence of clays surrounding and shielding the reactors and the existence of organic matter “that maintained the environment in reducing conditions.”

The “fine structure” (in fine structure constant) refers to spectral lines, that reflect specific detail about the electron, such as its spin, quantum fluctuation and speed. The study of Oklo data, has triggered a debate, of sorts, about alpha—a constant which encompasses these details.

This is highfalutin stuff, for us. I know! Yet we are part-and-parcel of the universe. We need to extend our interest, beyond conventional issues. Some physicists, for example, are using Gabon data, to argue that the speed of light has varied, since the Oklo cores became active.

Meanwhile, Clara Moskowitz reported on studies, indicating that natural reactors may be implicated in the origin of life. The scientists she interviewed on the Space.com, think radiation from reactors may have provided the energy that sparked life and also influenced its evolution.

Ebisuzaki and Maruyama share this hypothesis. Oko-type reactors, they argue, were numerous, two billion years ago. They believe the nuclear geyser system, with its ionizing radiation and cyclic energy regime, tops hydrothermal vents, interstellar space or other models.

Let’s end this short review segment, on a novelty note. A dosimetry expert (they use radiation to treat disease) named Robert B. Hayes extrapolates, from Oklo, the possibility of natural reactors beyond the solar system.

I could only access the abstract. But he raised the prospect that Oklo reactors, are operating galaxy-wide and may even be connected with gamma ray bursts!

“With one verified natural criticality event,” he writes, “more…are postulated both on earth and throughout our galaxy”.

Mining operations ceased, at the Oklo Complex, in 2000. Generally, nothing of archaeological or historical value was preserved. Commemorative structures ought to have been erected—with Nigeria’s participation—in each reactor zone and tours conducted, from a safe distance.

Experts from the National Space Research and Development Agency, in conjunction with the Nigerian Atomic Energy Commission and the Nigerian Geological Survey Agency can still put together a team to conduct research at Bangombe and prevail on white scientists for data.

Judging from what I’ve read, Bangombe—30 km from Oklo—has been made available to scientists. This decision followed a letter, published in the influential science magazine, Nature. It was signed by “F. Gauthier-Lafaye” and nine of his European colleagues.

In his letter, Gauthier-Lafaye advised that “This deposit is no less unique, and certainly more irreplaceable, than the most valued specimens from the Moon and Mars…. Prudence and responsibility require that careful consideration be given to the preservation of this last natural reactor.”