The 'fossil' nuclear reactors in Gabon

The Oklo phenomenon is described and discussed. It is shown how the study of the fission products indicates that the effect level seems to have been about 15 kW over a period of about 600,000 years. The control mechanism is said to have been by thermal regulation of the water moderator proportion in the short term, while lanthanides in the mineral have acted as burnable poison for long term control. Study of the migration of the fission products is of interest for radioactive waste disposal, and it appears that, amongst others, Sr and Cs have migrated considerably. The possible existence of other phenomena of a similar nature is discussed, and, while it cannot be excluded, the possibility appears to be remote. (JIW)