Fission product retention in the Oklo natural fission reactors

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

“…Yet, there has been several localities in which "natural reactors" were known to exist, the most studied of which were the deposits at Oklo, in the central West African country of Gabon (e.g., Brookins 1990;Curtis 1986;Curtis et al 1989;Gauthier-Lafaye et al 1996;Janeczek 1999). In all, 15 natural reactors are known to have operated for various durations in the nearly 2 billion-year-old (2.0 Ga) uranium deposits.…”

Petrographic relationships between mineral phases and bitumen in the Oklo Proterozoic natural fission reactors, Gabon

“…others have migrated but are retained at the reactor boundaries (Brookins, 1983(Brookins, , 1984Curtis et al, 1989;De Laeter et al, 1980;Hemond et al, 1992;Loss et al, 1984). Uraninite in particular is known to retain many elements in the reactors (Ruffenach et al, 1980).…”

“…Uraninite in particular is known to retain many elements in the reactors (Ruffenach et al, 1980). In the peripheral rocks, elements are probably fixed by a variety of authigenic minerals including clays, carbonates and sulphates (Brookins, 1983(Brookins, , 1984(Brookins, , 1990De Laeter, 1985;Loss et al, 1989). The clays in the reactors are considered to be analogues for artificial barrier clays around nuclear waste repositories (Brookins, 1990).…”

Reconstruction of cumulative fission yield curve and geochemical behaviors of fissiogenic nuclides in the Oklo natural reactors.

“…Moreover, the fission yields of nuclides in the valley between two fission peaks, are sensitive to neutron energy (e.g., Crouch, 1977), and will give a clue to the average neutron energy. Especially these three mass regions, (two max (i) It has been previously reported that the reten tion of Te is excellent, and that of Pd is also con siderably good (Curtis et al, 1989). (ii) In our previous paper (Hidaka and Masuda, 1988), Gd isotopes were found to be reliable for the estima tion of nuclear parameters because of their good retentivity.…”

“…In general, most of these data are in agreement with the observations at the Oklo site. Many studies on the isotopic compositions of various elements in Oklo samples have been performed, and the behaviors of fissiogenic nuclides have been dis cussed (The Oklo Phenomenon, 1975;Roth, 1977;The Natural Fission Reactors, 1978;De Laeter et al, 1980;Holliger and Devillers, 1981;228 H. Hidaka et al Loss et al, 1984;Curtis et al, 1989). These works as a whole cover nearly all aspects of isotopic abundances, but in general have been rather fragmentary individually, although they had focal points of their own in order to unders tand the features of the Oklo reactors.…”