The presence of natural nuclear reactors 2 billion years ago beneath Africa sounds like a hoax, but it actually happened – they are the only known natural nuclear reactors to have existed. By studying the behavior of the elements produced, scientists are learning lessons for the storage of waste from modern reactors. The remains of the Gabon reactor in Oklo were first discovered in 1972, and since then 17 reactor sites have been found nearby. Scientists examining the site as a potential uranium mine realized the metal’s isotope ratio was different from anywhere else on Earth, indicating induced fission of uranium-235. The deposit also contained the products of induced radioactive decay such as neodymium-143 and ruthenium-99. A study in Proceedings of the National Academy of Sciences describes an examination of these products. Although the radioactive decay chain initiated during fission is well studied, we know less about how the resulting isotopes behave if released into the environment. With so many sites, and different conditions at each, the Oklo reactors provided Dr Evan Groopman of the US Naval Research Laboratory and co-authors with a rich natural laboratory.
IFL Science 13th Aug 2018 read more »