Dosimetric assessment of the exposure due to natural accumulation of uranium and thorium in sands of some beaches of Camargue

In 2000, abnormally high ray fluxes have been detected on some beaches of Camargue. Then, sands of these beaches have been studied from a radiological point of view, showing on the one hand mean levels of uranium-238 and thorium-232 activity about some tens of Bq kg-1, and on the other hand some hot spots with more of 1000 Bq kg-1; and even more on two beaches: one to the east of the Beauduc lighthouse, the other to the east of Espiguette lighthouse. This radioactivity, of natural origin, is responsible of exposure of the public frequenting these two secluded beaches, but nevertheless open to everybody. The Institute for radiological protection and nuclear safety has carried out a dose assessment for people likely to frequent these beaches, taking into account local measurements and samples, in establishing the solubility of sands in the gastric and intestinal fluids, and with assumptions for site frequentation. The maximal annual effective dose is about 0.8 mSv for adults and about 0.5 mSv for children; very wise values, in which external exposure widely predominates. (authors)