A decontaminant storage leak at the Tricastin nuclear site near Avignon in southern France has led to uranium oxide in solution entering local rivers, and residents over a wide area being told not to drink water or eat fish from the rivers Gaffière and Lauzon, which are tributaries of the Rhône. Radiation levels have since been measured, and radiation protection authorities now say that the effects of the leak should be negligible, but the ban remains in force for the time being.

The incident occurred at about 11pm on 7 July at a decontamination facility operated by Areva subsidiary Socatri. The company specialises in maintaining, dismantling and cleaning nuclear equipment and recovering the uranium contained in the cleaning solution.

About 30 cubic metres of stored decontamination solution containing 12 grams of uranium per litre – 75 kg of uranium compounds in all – escaped. The fluid overflowed from one tank into another one designed for this purpose but the secondary tank was not watertight and the fluid leaked out of the plant and into the ground.

Once this was discovered Socatri workers reacted by notifying the Nuclear Safety Authority (Autorité De Sûreté Nucléaire, ASN) and drilling a borehole in the immediate vicinity of the spill to begin to assess potential environmental impacts. As the solution would travel through storm drains and reach the Gaffière and Lauzon rivers, then the Rhône, a precautionary measure taken immediately by the ASN was to advise authorities in the Drôme and Vaucluse regions, both as it happens popular holiday areas, to restrict fishing and the use of river water by the public. The ASN said it did this without waiting for the outcome of tests, adding that eating fish from the rivers would anyway have a very limited effects on health.

The Institute for Radiological Protection and Nuclear Safety (IRSN) have since taken environmental measurements. Seven surface tests and nine groundwater tests showed contamination levels to be receding rapidly, although Socatri’s initial test showed radiation in groundwater to be 1000 times higher than the World Health Organization’s 15 µg of uranium per litre guideline for water intended for human consumption. IRSN said it “believes the radiological consequences for people should be neglibile.” Monitoring of the area by IRSN continues.

Areva, owner of Socatri, said that it had proposed to ASN that the incident be rated at Level 1 on the International Nuclear Event Scale, ie, an ‘anomaly’.

Tricastin is a very large nuclear site, with four power reactors, the Comhurex uranium conversion facility, the Eurodif enrichment plant and the Pierrelatte weapons facility.