RHONE-ALPES TRICASTIN/PIERRELATTE VIII. PROBLEMS IN REGARD TO THE TRICASTIN SITE IN GENERAL VIII.A. The terrain The installations are located on marshy land that necessitated important changes, including removing a layer of soil to an average depth of 25 cm to eliminate the layer of vegetable earth and silt, and also construction of a platform of about 200 ha. An alluvial layer under the site is mainly fed by the Donzère-Mondragon canal and by precipitation and is drained by the Rhône and the Gaffière, a stream that crosses the site. Like the natural precipitation, leaks of liquids and contaminated water can reach the alluvial layer and then the Gaffière and the Rhône. The Donzère-Mondragon canal receives at least a part of the liquid releases. VIII.B. Deposits of atmospheric origin According to the Work Group, straight underneath and in the area immediately around Tricastin, the principal contamination observed consists of solid deposits related to gaseous uranium and fluoride discharges, from Cogema, Eurodif, and Comurhex. Typical on-site measurements are on the order of a hundred micrograms per square meter and per year in uranium (in 1995, the highest measurements were 3000 micrograms/m2 southeast of Comurhex) and a hundred milligrams per square meter and per year in fluorides (in 1995, the highest measurements were 650 mg/m2 south of Plant W). Rain quickly leaches these deposits. The uranium and the fluorides enter the surface or sub-surface waters where they are undetectable because of the heavy flows. Sensitive points regarding external radiation were found in 1995: -- inside the site, at the edge of the Comurhex plant, 29 mGy; -- on a site south of the Eurodif plant on the public road, at the edge of
the VIII.C. Ground water Because of some indications of ground water pollution (by uranium and by fluorides downstream from Comurhex, by chromium at Socrati, by tetrachlorethylene at Comurhex and at Eurodif), the operators decided to launch a hydrogeological study of the total site, complemented by a study of the radioactive and chemical pollutants and their movement [HC 98]. In 1999, DSIN asked the operators to carry out a study of the ground (activities carried out on the site and samples). The first results were submitted to DSIN in 2000. The study made possible improvements in the monitoring of the groundwater by the addition of new piezometers. No problems were found in surface waters or in soils. Anomalies were noted in the ground water, but the levels of pollutants were "generally below the limits for potability" . . . The main anomalies concerned 1) contamination by nickel and hexavalent chrome of the ground underneath the site of Socatri; 2) "the presence of fluorine and uranium, limited to the north of the site" ; 3) "the presence of borium and of ammonia under the perimeter of the Eurodif plant." Investigations continued in 2000 [DSIN 00].
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