During reprocessing, the fuel elements were mechanically shredded and a chemical process was used to separate the recyclable nuclear fuel from the waste. Around 95% of this waste is of low- or intermediate-level radioactivity, and only a residual 5% is highly radioactive. However, the latter contains about 99% of the activity of the entire waste and generates heat.

The fission products, which arise during electricity generation in the nuclear power plant by converting the fuel uranium, are responsible for the largest proportion of radioactivity. During reprocessing, these fission products are separated from the reusable nuclear fuel. After reprocessing, approx. 98 to 99% of the highly radioactive substances previously contained in the spent fuel elements are contained in an acid solution, which is first dried for further treatment.