|
|
| Fig. 1: An aerial photo of Mururoa Atoll. (Source: Wikimedia Commons) |
On the 6th and 9th of August 1945, the United States detonated two atomic bombs in Hiroshima and Nagasaki, ending World War II, but starting a new race, a race for nuclear armament. While the cold war and race to nuclear arsenals is widely framed as one between the US and the Soviet Union, seven other countries, including France, also scrambled to protect themselves with these weapons of mass destruction. Between 1966 and 1996, France conducted 179 nuclear weapons tests on the French-occupied collection of atolls in the South Pacific. [1] We shall seek to describe the effects of these nuclear detonations that remain today.
France originally began pursuit of an independent French deterrent in the mid-1950s. While initial testing was conducted in the African Sahara, testing was moved to French Polynesia when French Algeria was granted independence. This had the added benefits of allowing atmospheric tests and minimizing political pressure because of the remoteness of the location. Mururoa and Fangataufa, two uninhabited atolls, were the selected test sites within French Polynesia (Fig. 1). Testing included both atmospheric and underground nuclear weapons testing. In addition to damage directly from the tests, radioactive waste was unintentionally released. A leaked secret report from 1981 revealed that 10-20 kg of plutonium had been washed out to sea onto the reef between 1966 and 1974 as a result of failing infrastructure that was not built to withstand typhoons. [2] The effects of nuclear testing include both physical damage to the atolls and radioactive leakage to the biosphere. [3]
The majority of persisting radioactive deposition in the local marine environments occurred from atmospheric testing. The lagoons of both atolls retain high levels of radioactivity. On Mururoa, radioactive hot spots are at the locations of barge tests, as measured in 1998. In sediments collected from a sandbank close to the Colette test area, the highest measured concentrations of Pu-239 + Pu-240 were 1 MBq/kg dry weight. Other radionuclides such as Am-241 and Pu-238 measured at 70 kBq/kg and 11 kBq/kg, respectively. Gamma-emitting radionuclide levels were also significantly elevated, with highest recorded measurements at 5 kBq/kg Cs-137, 4 kBq/kg Eu-155, and 2 kBq/kg Co-60. [4]
For reference, while there is no data to obtain a baseline level in French Polynesia, radionuclide activity in sediments measured in Fiji, another Polynesian island formed by similar processes, are on the scale of a single digit Bq/kg dry weight. [5] Pu-239 and Pu-240 have half-lives of 24,110 and 6,560 years, respectively. As a result of these long timescales, these actinides are likely to persist locally for the forseeable future.
To put this number into context, let us consider a purely hypothetical example in which someone accidentally ingests one teaspoon (approximately 5 cl, or 8 g) of sand. These 8 g of sand containing 1 MBq/kg would yield 8,000 Bq, multiplied by an ingestion effective dose coefficient of 2.5 × 10-7 Sv/Bq (Pu-239 and Pu-240), or approximately 2 mSv. This is a relatively low dose, and the equivalent to the background annual effective dose in some high-elevation towns in the Colorado Plateau. [6,7]
Radionuclide activity in the lagoon water is significantly lower than that of sediment, but still elevated relative to other environments. Pu-239 + Pu-240 were measured to be 0.3 Bq/m3. Tritium measurements, however, peaked at 800 Bq/m3.
It is worth noting however that these are local phenomena. While there is some mixing of these sediments and waters into the surrrounding ocean, they become so diluted as to become irrelevant in the stock of radioactive actinides already present in the ocean. [4] Any risk from these sediments are to organisms in the immediate vicinity.
The health fallout of French nuclear testing, with the exception of direct interaction with contaminated areas of Mururoa or Fangataufa, is primarily limited to the nuclear fallout at the time of nuclear testing. French regulations set a limit of 1 mSv per year maximum admissible effective dose from human activities. A 2010 law known as Loi Morin awards compensation to people present in French Polynesia during the time of nuclear testing who develop certain cancers, if approved by the Comité d'Indemnisation des Victimes des Essais Nucléaires (CIVEN). Cumulative deposition from all 179 nuclear tests on the most populated island of French Polynesia, Tahiti, was measured to be 3.4 × 106 Bq/m2. Approximately 110,000 people, or 90% of the French Polynesian population at the time of testing, are estimated to have been exposed to levels up to 7 mSv through inhalation of radioactive aerosols, external irradiation by the plume or ground deposits, and ingestion of contaminated food. [8]
A study published in 2000 observed two- to three-fold more cases of thyroid cancer in French Polynesia compared to native populations in Hawaii and New Zealand, who share a similar genetic history. This increase was observed regardless of whether residents were children during the period of nuclear testing. It is worth noting, however, that between 1981 and 2003 only 229 people were diagnosed with differentiated thyroid carcinoma, representing a relatively small sample size. [9]
The physical effects of nuclear testing in French Polynesia remaining to this day are largely limited to physical degradation of Mururoa and Fangataufa atolls and some concentrated areas of sedimentary contamination. Risks to residents are largely confined to nuclear fallout at the time of testing, rather than persisting radioactivity today. Although residents were exposed to significantly elevated levels of radioactivity, extreme population-level health effects have not been conclusively demonstrated, with the important caveat that limited long-term research has been conducted. Further research could help to better understand the remaining environmental and public health impacts of nuclear testing in French Polynesia.
© Max Shen. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] R. Prăvălie, "Nuclear Weapons Tests and Environmental Consequences: A Global Perspective," Ambio 43, 729 (2014).
[2] B. Danielsson, "Poisoned Pacific: The Legacy of French Nuclear Testing," Bull. Atom. Sci. 46, No. 2, 22 (1990).
[3] R. Thakur, "The Last Bang Before a Total Ban: French Nuclear Testing in the Pacific," International J. 51, 466 (1996).
[4] "The Radiological Situation at the Atolls of Mururoa and Fangataufa," International Atomic Energy Agency, 1998.
[5] A. Anderson et al., "Times of Sand: Sedimentary History and Archaeology at the Sigatoka Dunes, Fiji," Geoarchaeology 21, 131 (2006).
[6] K. Eckerman et al., "Compendium of Dose Coefficients Based on ICRP Publication 60," ICRP Publication 119, Ann. ICRP 41 (Suppl.) (2012).
[7] Leveraging Advances in Modern Science to Revitalize Low-Dose Radiation Research in the United States (National Academies Press, 2022), Ch. 2.
[8] S. Philippe, S. Schoenberger, and N. Ahmed, "Radiation Exposures and Compensation of Victims of French Atmospheric Nuclear Tests in Polynesia," Sci. Glob. Secur. 30, 62 (2022).
[9] F. de Vathaire, B. Le Vu, and C. Challeton-de Vathaire, "Thyroid Cancer in French Polynesia Between 1985 and 1995: Influence of Atmospheric Nuclear Bomb Tests Performed at Mururoa and Fangataufa between 1966 and 1974," Cancer Causes Control 11(1), 59 (2000).
