A Pacific Proving Ground
Between 1966 and 1996, the French government conducted 193 nuclear tests at the remote atolls of Moruroa and Fangataufa in French Polynesia. After its testing site in Algeria became unavailable due to Algerian independence, France established the Centre d'Expérimentation du Pacifique (CEP) and shifted its program to the South Pacific. The program began with atmospheric tests, the first of which, codenamed Aldébaran, was a plutonium fission device detonated in Moruroa's lagoon on July 2, 1966. This initial phase included 46 atmospheric detonations.
The most powerful explosion was the Canopus test on August 24, 1968. Detonated from a balloon over Fangataufa, this thermonuclear device yielded 2.6 megatons—nearly 200 times the power of the Hiroshima bomb—and made France the world's fifth thermonuclear power. These atmospheric tests dispersed radioactive fallout over thousands of kilometers, with increased radioactivity recorded as far away as Peru and New Zealand. Facing intense international pressure, France moved its testing program underground in 1975. Over the next two decades, 147 underground tests were conducted, drilling shafts deep into the volcanic basalt beneath the coral atolls.
Geological and Radiological Scars
The underground detonations inflicted massive and permanent damage on the atolls' geology. Each explosion created a large cavity and extensively fractured the surrounding rock. This activity led to subsidence and triggered submarine landslides along the atoll's outer slopes. A significant event occurred on July 25, 1979, when a device detonated at half its intended depth after becoming stuck in the shaft. The blast caused a major underwater landslide, which in turn generated a tsunami that struck Moruroa, injuring workers. Following the explosion, a crack 2 kilometers long and 40 centimeters wide appeared on the atoll's surface.
These fractures are a primary concern for long-term radioactive containment. The underground test chambers hold large quantities of radioactive material, including plutonium-239, cesium-137, and strontium-90. While the tests were intended to be contained, evidence shows that fissures in the rock could allow radioactive isotopes to leak into the Pacific Ocean over time. Several kilograms of plutonium reside in the lagoon sediments from early atmospheric tests and safety trials. The final test occurred on January 27, 1996, but the atolls remain a restricted military zone under guard due to the lasting contamination.