Béryl incident

The "Béryl incident" was a French nuclear test, conducted on May 1, 1962, during which nine soldiers of the 621st Groupe d'Armes Spéciales unit were heavily contaminated by radioactivity. The test took place at In Eker, Algeria, then a French department, and was designed as an underground shaft test. Due to improper sealing of the shaft, radioactive rock and dust were released into the atmosphere. The soldiers were exposed to as much as 600 mSv. As many as 100 additional personnel were exposed to lower levels of radiation, estimated at about 50 mSv, when the radioactive cloud produced by the blast passed over the command post, due to an unexpected change in wind direction. Among those exposed were several French government officials, including French Defense Minister Pierre Messmer and Gaston Palewski.

The site chosen for the test was In Eker (Algerian Sahara), around 150 km north of Tamnarasset. The Taourirt Tan Afella mountain, one of the granite Hoggar Mountains (south of Algeria), after having been the object of geotechnical surveys (erroneously shown as a gold or uranium mine), was kept as a test site. The site was laid out from 1961 onward (on an airfield built northeast of In Amguel and base camp between the Tuareg village of In Amugel and the well in In Eker of which the border was controlled and occupied by gendarmes). A base called DAM Oasis 1, then Oasis 2, was then built to not be visible from the road a few miles east of Tan Affela.

France, having had to abandon aerial tests and replace them with less-polluting underground tests, opted for underground testing in marine (atoll) or desert zones. The Saharan test sites were produced “in galleries”, those having been horizontally excavated in the Tan Afella on the site In Eker.

This type of “shooting gallery” was dug to end in a spiral shape. On the one hand, this shape of tunnel seriously weakened the ground at this point, and on the other hand, it dampened the expulsion of gases, of dust, and of lava produced by the vitrification of the soil. According to calculations by engineers, due to these two factors, the gallery went to the point of collapse and sealing. It was also closed by a concrete plug. Actually, four highly resistant steel doors closed the gallery at different covered levels in order to seal the shaft with polyurethane foam. These measures were used to ensure the greatest possible containment of radioactivity, which justified inviting so many “officials” to attend the test.

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Wikipedia