French Nuclear Testing at Mururoa

The explosive impulse is also sent through these cables. The shaft is then filled with both cement and basalt sand, the sand acting as a shock absorber during detonation so that cracks and therefore leaks cannot occur. After the device is triggered, in the millionth of a second before the canister is destroyed by the explosion, electronic senses send to the surface 80 000 items of data which reach the 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.
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