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| élément radioactif primordial (natural, of half-life sufficiently long to exist since the formation of earth's crust); élément radioactif primitif (natural, of half-life sufficiently long to exist since the formation of earth's crust); radioélément primordial (natural, of half-life sufficiently long to exist since the formation of earth's crust); radioélément primitif (natural, of half-life sufficiently long to exist since the formation of earth's crust) | |||
