Status of radioactivity monitoring in French Polynesia in 2012. Synthesis of IRSN's monitoring network results

Exercised in Polynesia since 1962, the radiological monitoring of the French environment, which takes place on seven islands (Tahiti, Maupiti, Hao, Rangiroa, Hiva Oa, Mangareva and Tubuai) representing the five archipelagos, and consists of taking regular samples of various kinds from the different environmental compartments (air, water, soil, food...) with which the population may be in contact. Regarding food, the samples analyzed are representative of the diet of Polynesians living in the five archipelagos of that territory, and from the marine environment of the open sea, from the lagoon environment and from the terrestrial environment. Almost all the samples are measured at the Laboratory for the Study and Monitoring of the Environment (LESE) IRSN, based in Vairao on the island of Tahiti. During the year 2012, were stable and typical of the regular reduction of the levels of radioactivity since the stop, in 1974, of the French atmospheric tests. This residual radioactivity relates primarily to the 137Cs. In term of additional dose, this artificial and residual radioactivity is lower than 5 μSv.y-1 (5 micro-sieverts per year). This value corresponds to less than 0,5 % of exposure due to natural radioactivity in Polynesia (approximately 1 000 μSv.y-1). Enhanced radiological monitoring of the environment set up in the wake of the Fukushima disaster, continued in 2012 in the marine field. The measurements carried out throughout the year confirm the lack of impact of the contamination of Japanese marine area in Polynesian waters. Samples of pelagic fish (tuna, swordfish, dolphin fish, wahoo...) were made in the vicinity of five Polynesian archipelagos: no increase of 137Cs compared to previous years was observed and 134Cs was never detected. (authors)