Mururoa atoll

Caroff, M., Maury, R. C., Leterrier, J., Joron, J.-L., Cotten, J. Guille, G. (1993). Trace element behavior in the alkali basalt-comenditic trachyte series from Mururoa Atoll, French Polynesia. Lithos, 30, 1-22. 

It seems likely that some atolls of the Tuamotu Archipelago may have been settled for more than 1000 years. However, habitation of the atolls of Polynesian archipelagos has been discontinuous and populations are generally sparse. Around 8000 people at present live within 1000 km of Mururoa Atoll. Tureia Atoll, 130 km distant, is the closest inhabited land, with a population of around 120 living a semi-subsistence lifestyle that is, depending of fish and seafood gathered from the ocean and the atoll s lagoon, produce harvested from a small area of cultivated land and some imported food. 

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. 

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

Fig. 10.18. Locations and yields of underground tests at Mururoa Atoll.

Of the 15 safety trials, five were carried out in the atmosphere and ten underground. The five atmospheric safety trials were conducted between 1966 and 1974 on the surface at the northern tip of the atoll on the three motus of Colette, Ariel and Vesta. The ten underground safety trials were performed in the north-eastern part of Mururoa Atoll, three in vertical drilled shafts that penetrated from the rim into the volcanic rock. 

The safety trials The safety trials conducted at the northern tip of Mururoa Atoll on the motus of Colette, Ariel and Vesta have left some particulate plutonium on the surface in that area, despite extensive cleanup operations carried out in 1982-1987 and in an adjacent sand bank in the lagoon. 

The above cleanup operations have led to the elimination of the main sources of plutonium activity on the ground. The extremely high sensitivity for the detection of atmospheric plutonium (of the order of 10 Bq/m ) has made it possible to measure the re-suspension of on the Mururoa Atoll, as a result of the cleanup work. This was... 

Nevertheless, the missions found that by the mid-1980s there had been some visible damage to Mururoa atoll, in the form of fissures, subsidence and submarine landslides off the side of the atoll. Moreover, the tests, which are conducted between 6(X) and 1200 m underground in volcanic rock, by their very nature result in localised fracturing of the rock around each test site. A substantial number of tests have been conducted since the most recent of the missions, which will have added to the structural changes observed in the atolls. 

Information from a number of sources, including the open scientific literature, was consulted in addition to that provided by the French authorities. Reports on three independent scientific missions to the atolls that are available in the public domain were consulted—the Scientific Mission of French Polynesia (Tazieff mission) of June 1982, the New Zealand, Australia and Papua New Guinea Scientific Mission of Mururoa Atoll (Atkinson mission) of October 1983, and the Scientific Mission of the Calypso to the Site of the Nuclear Experiments at Mururoa Atoll (Cousteau mission) of June 1987. 

Several kilograms of plutonium resulting from the atmospheric nuclear tests carried out at the atolls remain in sediments under the lagoon of each atoll. Some of the plutonium in the sediments of the Mururoa Atoll lagoon came from the atmospheric safety trials. 

Particles containing plutonium and small amounts of americium resulting from atmospheric safety trials remain in the area of the trial sites—the motus of Colette, Ariel and Vesta on Mururoa Atoll. The Study analysed these types of particles, found in samples of sand and coral collected from the surface of the motu of Colette and in sand taken from a sandbank adjacent to it. 

Atkinson, H.R., Davis, J.P., Davy, D.R., Hill, L. and McEwan, A.C., Report of New Zealand, Australian and Papua New Guinea Scientific Mission to Mururoa Atoll, 1983. 

Ballestra, S., Baxter, M.S., Gaustaud, J., Pettersson, H., Province, P.P. and Vas, D., Intercomparison report on radionuclide measurements on biological samples collected at Mururoa atoll. IAEA/AL/085, lAEA-MEL Report no. 60, August 1995. 

Ballestra, S. and Noshkin, V., Summary of radionuclide intercomparison results in seawater and plankton collected outside Mururoa atoll. IAEA/AL/044, lAEA-ILMR Report no. 48, July 1991. 

Polynesian atolls Obtained by J. Trichet (University of Orleans, France). These samples are from lagoons of the Mururoa and Hao atolls. They are described by Niaussat et al. (18) and were received as freeze-dried samples. Sample 33 is from the Mururoa atoll. Samples 34 and 35 are from the Hao atoll at depths of 0 cm (still living algae) and 1 cm, respectively. 

In underground tests performed below a water body, as in the case of the tests at the Mururoa Atoll, underwater rock slides creating anomalous waves and tsunamis. An event of this kind really happened at Mururoa (25 July 1975) when an underwater slide of about 10 m of coral rock was created leaving a cavity of about 140 m in diameter, accompanied by... 

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. 

To describe underground testing in some detail, we shall follow the report of Bouchez and Lecomte (1996) which describes the French nuclear testing in the Atolls of Mururoa and Fangataufa (French Polynesia). The measurements relating to the operation of the device were made in the immediate proximity of the explosion point. All the measuring instruments were housed in a container, the lower part of which contains the nuclear device. 

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. 

The Hao atoll initially served as a rear base where the nuclear test devices were assembled. The components were flown from France on planes that were refuelled in Martinique to avoid altogether the densely populated Tahiti Hao, a bigger atoll than Mururoa, which is located 450 km north-west of Mururoa and 900 km east of Tahiti. Built by the military, Hao has one of the longest runways in the South Pacific (3600 m) plus a large number of storehouses and workshops. Following the construction of a runway on Mururoa, the nuclear device assembly facility (Centre Technique CEA/DAM) at Hao was deactivated and transferred to Mururoa. 

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. 

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

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 ... 

Bourlat et al. (1995) have presented results on the plutonium radioactivity levels in Mururoa lagoon water during the 1985-1991 period. The low radioactivity levels recorded, from 0.01 to 1.5 Bq/m are due to the slow solubilization of plutonium deposited in lagoon sediments following atmospheric experiments which took place from 1966 to 1974. The average concentrations of the lagoon water decrease from one year to the next. Since the Mururoa lagoon is open to the ocean, plutonium radioactivity traces are also detectable in the immediate vicinity of the atoll. 

The atmospheric nuclear tests which took place at the Mururoa Lagoon between 1966 and 1974 did not produce significant fallout on the emerged part of the atoll. The tests (three carried out on a barge) only affected the sediments at the bottom of the lagoon, especially in the area directly under the barge. In contrast, a few safety air tests that took place between 1966 and 1974 in the northern part of the atoll (between the Colette Motu and the Denise area) resulted in localised plutonium deposition on the coral bedrock. 

The above activity levels measured at Mururoa are comparable to the levels observed world-wide in the early 1980s (with the exception of a few specific sites). These concentrations result from earlier safety tests made on the motus in the northern zone of the atoll from 1966 to 1974, and from the cleanup work undertaken in the years 1981-1987. This work resulted in a great reduction of radioactivity on the ground, but produced a slight temporary increase of plutonium in the air. 

Hence it was the Commission s view that a complete verification mission required access for verification purposes to the atolls of Mururoa and Fangataufa. Access was granted to Mururoa but the French authorities held the view that this invitation was solely for the purposes of information, not of verification. Access was denied to Fangataufa for reasons of defence security . Access was also denied to military premises at Faaa (Tahiti Airport) in which facilities for aerosol sampling and gamma monitoring are installed. While the last-mentioned facilities are of less importance because they duplicate similar facilities nearby, the denial of verification access at... 

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. 

---