From routine sample measurements in CEA to the Oklo phenomenon.

In 1972, before shipping natural uranium to the USSR for enrichment operations in 235 U, the analysts at Pierrelatte plant noted a slight deficit in ²³⁵U: 0.7171 instead of 0.7202. The Direction des Productions of the CEA launched a vast campaign of analyses for the different mines exploited, at all stages of the elaboration of uranium; for this analysis campaign, the Direction des Productions relied on the analytical laboratory of the Pierrelatte plant and on the Central Analytical Laboratory of the CEA where I was in charge of analyses by mass spectrometry. [ABSTRACT FROM AUTHOR]