Research ArticleSPACE SCIENCES

Origin of uranium isotope variations in early solar nebula condensates

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Science Advances  04 Mar 2016:
Vol. 2, no. 3, e1501400
DOI: 10.1126/sciadv.1501400

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  • Explaining U235 excesses in meteorites

    The increases in 235U vs. 238U in meteorites [1] [2] find an explanation in cross-section trends of 238U and 235U. The issue is the isotopic ratio which is more favorable to 235U than usual ; bolides (fireballs) present typically the same 238U/235U ratio found in the raw matter expelled by black holes (likewise they are abundant in 247Cm but there is no “247Cm excess” relative to 250Cm) (see [3] and [4]).
    The neutron cross-section for fission of fissile materials at slow neutron speeds such as 235U and 239Pu fall down at extremely rapid neutron speeds (in the direction of relativistic neutrons). They behave the opposite of 238U, 232Th which cannot fission with slow neutrons but can fission very easily by extremely fast neutrons, there is a symmetry. This explains why in stars in end of life, with the extremely rapid neutron speeds in the hot plasma through all the life of the star, where 238U and 232Th and their parents have been progressively "eaten" (through fission), there is an inner layer, it is made of 235U, 237Np and their parents (they were naturally isolated by the naturally very high speeds of neutrons in the hot star plasma) ; so it is that inner layer that then receives the decelerating neutrons, because as the 238U / 232Th content of the plasma almost disappeared (through fission) the plasma cools downs strongly. The impact of these slowed down neutrons will then trigger a chain reaction in that inner layer of 235U, 237Np and parents, hence the...

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    Competing Interests: None declared.

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