Ground deposition of radionuclides in French Polynesia resulting from atmospheric nuclear weapons tests at Mururoa and Fangataufa atolls

This paper presents the results of the first comprehensive estimation of the ground deposition density of radionuclides in French Polynesia resulting from the 41 atmospheric nuclear weapons tests that were conducted between 1966 and 1974 at Mururoa and Fangataufa. For each test, the deposition density at the time of arrival of fallout was estimated for 33 radionuclides either from measurements of total ground deposition or from measurements of total beta-concentration in filtered air and exposure rate at different locations in French Polynesia. The results of the measurements were mainly taken from reports that were recently de-classified by the French Ministry of Defense. The highest total deposition densities in inhabited islands and atolls occurred in Gambier: 6.1 × 10⁷ Bq m⁻² after test Aldébaran conducted on 2 July 1966 and 9.2 × 10⁶ Bq m⁻² after test Phoebé conducted on 8 August 1971. Next was Tureia with deposition densities of 1.6 × 10⁷ Bq m⁻² after test Arcturus of 2 July 1967 and 1.2 × 10⁷ Bq m⁻² after test Encelade of 12 June 1971. In Tahiti, the most populated island in French Polynesia, major fallout occurred after tests Centaure of 17 July 1974 (3.4 × 10⁶ Bq m⁻²), Sirius of 4 October 1966 (4.4 × 10⁵ Bq m⁻²) and Arcturus of 2 July 1967 (1.1 × 10⁵ Bq m⁻²); these three tests contributed about 94% to the total deposition density of radioactive fallout in Tahiti from all 41 tests and around 85% of the ¹³¹I deposition density. The results of this study are being used to reconstruct the radiation dose to the thyroid gland for the 950 subjects of a case-control study of thyroid cancer among French Polynesians exposed as children and adolescents to fallout from the atmospheric nuclear weapons tests conducted in 1966–1974.