Could such an accident happen in France?
Nuclear accidents - Kyshtym (USSR)

The chemical treatment process is different in France. It is the PUREX process, based on the separation and purification of uranium and plutonium by liquid-liquid extraction, the solvent used being a 30% by volume mixture of tributyl phosphate diluted in a long-chain alkane.

One might wonder about an "analogous risk" to that of Mayak, in operations involving a mixture of organic products and concentrated nitric solutions.

To eliminate this risk, the concentration of fission product solutions prior to vitrification is carried out at boiling point in an evaporator...