At 5:30 p.m., radioactivity was detected on a truck leaving waste treatment facility after collecting liquid waste. Firefighters carried out measurements to determine the source of the emission and estimate the exposure of the facility’s personnel to ionising radiation. The identified source was 600 kg of a mixture of water and activated carbon that had just been unloaded onto the site by the truck. The operator contacted the French Nuclear Safety Authority to find out what to do with the waste. The truck, and the water/activated-carbon slurry were left to decay for three weeks in a part of the site far away from the rest of its operations. The facility’s employees were monitored for radiation exposure; none was found. The firefighters went to the company that delivered the load to notify them of the presence of radioactivity in their materials and search for the source.
The mixture came from a company where groundwater is treated via adsorption on activated carbon following pollution by perchloroethylene (1,1,2,2-Tetrachloroethane) and trichloroethylene (1,1,2-Trichloroethane). This treatment process generates wet activated carbon, the source of the radiation detected at the waste treatment facility. The radioactivity identified came from radon, which is naturally present in the groundwater under the site and was adsorbed by the activated carbon. The operator treating the groundwater is now required to take precautions to avoid exposing its employees, particularly when they handle the activated carbon are replace it.