French nuclear testing at Moruroa

Since 1966, France has used the atoll of Moruroa as the place of 178 nuclear testings, both in the atmosphere and under sea level. Moruroa is located roughly in the middle of the South Pacific and consists of a coral atoll perched on the submerged tip of a 6000 meter-high underwater volcano which has been extinct for millions of years. In 1960, France conducted its first test in the atmosphere in Algeria. France's nuclear testing program was shifted to …

…barge in a specific sequence. Within the next tenth of a second the explosion creates a spherical cavity about 50 meters in diameter containing several thousand tones of a certain type of lava. This lava traps 95% of the radioactivity produced. The system then cools down and stabilises only minutes later. The last underground nuclear test conducted at Moruroa was in 1991. In 1995, testing was again resumed in the area and was yet again stopped the next year.