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ARCHEAN URANIUM DEPOSITS AND THE ORIGIN OF LIFE
by
León Garzón

THE AGGREGATES AS NUCLEAR REACTORS

An aggregate is a volume of mineral constituted of:


Uraninite
(UO2)	C%
Gangue	G""
Water	W""

Nuclear characteristics:


Uraninite was the fuel
The enrichment was ~11.3% 3.5 Ga years ago

The gangue was the moderator
Constituted mainly by O, Al, Si, etc. with low absorption cross sections for thermal neutrons and with good slowing down properties

Water is a good moderator, cooland and control agent

The Model:
By using one group of thermal neutrons we have obtained the critical mass, M_c, of the aggregates (assuming that its composition is unifrorm) as a function of C, W and age (t). Our results show that M_c values decrease when t and C increase. So, the formation of aggregates, with masses equal or greater than M_c, could be a relatively frequent phenomenom !