Fangataufa atoll

More sophisticated devices use less plutonium it is assumed that the French bombs tested at Mururoa and Fangataufa Atolls used a plutonium pit of about 3.7 kg, 3.4 kg of which was Pu and 0.3 kg of which was Pu. 

Mumroa and Fangataufa atolls are situated at 21°50 S, 138°54 W and 22°14 S, 138°45 W, respectively, in French Polynesia in the South Pacific Ocean, about halfway between Australia and South America (Fig. 10.17). The two atolls belong to the Pitcaim-Gambier island chain at the south-eastern extremity of the Tuamotu Archipelago which consists of 76 atolls. Polynesia ranges from New Zealand, 4800 km from Mururoa, to Hawaii. The two atolls lie towards the eastern boundary of French Polynesia which comprises five archipelagos of about 130 atolls and reef islands in all. 

In all, 193 experiences nucleaires (nuclear tests and safety trials) were conducted at the French nuclear weapon test site at Mururoa and Fangataufa atolls. Of these, 178 were nuclear tests , in which a nuclear device was exploded with a large release of fission and, in some cases, fusion energy and 15 were safety trials in which more or less fully developed nuclear devices were subjected to simulated accident conditions and the nuclear weapon cores were destroyed by means of conventional explosives, with no or—on a few occasions—very small releases of fission energy. 

A total of 41 atmospheric nuclear tests were conducted in the open air between July 1966 and September 1974, 37 at Mururoa Atoll and four at Fangataufa Atoll, and 137 underground nuclear tests took place deep below the surface of the atolls between June 1975 and January 1996, 127 at Mururoa Atoll and ten at Fangataufa Atoll. 

French atmospheric nuclear tests and safety trials at Mururoa and Fangataufa Atolls ... 

All tests were performed at Mururoa Atoll except for these four tests which were carried out at Fangataufa Atoll. 

Fig. 10.19. Locations and yields of underground test at Fangataufa Atoll.

Safety trials were conducted to investigate the behaviour of the core of a nuclear device under simulated faulty detonation conditions. The core is destroyed by the conventional explosive detonation of such a device, with the production of finely divided plutonium and plutonium oxide which are widely dispersed if the test is not confined. Usually no fission takes place, though there was a very small fission energy release in three of the French underground safety trials. (Since there was some explosive yield, these three trials are sometimes counted as nuclear tests which would put the total number of underground nuclear tests at Mururoa and Fangataufa atolls at 140 rather than 137.) All of the 15 safety trials were carried out at Mururoa. 

There are thus three main sources of the man-made residual radioactive material that is at present found at very low levels in the terrestrial and aquatic environments of Mururoa and Fangataufa atolls ... 

In August 1995, following the announcement in June 1995 of a final series of eight underground nuclear tests at the South Pacific site, the French Government submitted a written request to the IAEA to assess independently the radiological consequences of the nuclear tests at Mururoa and Fangataufa atolls, and undertook to provide information needed for the assessment. 

The Basic Safety Standards were mainly used to establish the criteria for use in assessing whether the radiological conditions at Mururoa and Fangataufa atolls represent any hazard to people presently in the region or who may reside on the atolls, and in making recommendations on any monitoring or remedial action that might be required. 

The terrestrial sampling and surveillance campaign was focused on Mururoa and Fangataufa atolls but at the time of the atmospheric nuclear testing, there was also some deposition of radionuclides on neighbouring islands, most notably at Tureia Atoll. Levels of activity were therefore measured at Tureia Atoll in order to calculate present dose rates for the inhabitants. 

A separate underground water sampling campaign was carried out at Mururoa and Fangataufa atolls in May-June 1997. Samples were taken from two test cavities on Mururoa and from nine monitoring wells in the carbonate rock. This is discussed later in the section on the solution source term . 

Elevated levels of Cs were found over small areas totalling several hectares on the Kilo-Empereur rim of Fangataufa Atoll. 

The Study concluded that there will be no radiation health effects which could be either medically diagnosed in an individual or epidemiologically discerned in a group of people and which would be attributable to the estimated radiation doses that are now being received or that would be received in the future by people as a result of the residual radioactive material at Mururoa and Fangataufa atolls. 

Given the measured and predicted radionuclide activity levels, and the low dose levels estimated for the present and for the future, and with account taken of international guidance, the Study concluded that no remedial action at Mururoa and Fangataufa atolls is needed on radiological protection grounds, either now or in the future. 

Bourlat, Y., Millies-Lacroix, J.-C. and Rancher, J., u, Cs, Sr contents in seawater in the vicinity of Mururoa and Fangataufa atolls and in French Polynesia, Int. Symp. on Radionuclides in the Study of Marine Processes, 9-14 September 1991, Norwich, U.K. 

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