Experiments have shown the need for three sequential and separate cleaning steps to achieve a decontamination factor of 100 million that is required for the gases exhausted from ITER.
According to the TLK concept deuterium and tritium are separated in a front-end permeator in the first step. Afterwards, tritium is extracted in a chemical process from the impurities so that it can be returned into the inner loop.
In the third and last step, the exhaust gases are decontaminated further. The residual tritium attached to hydrocarbons is removed from it by isotopic exchange. All three steps are combined in the so-called CAPER process. The decontamination factor of the CAPER process even exceeds the requirement of ITER.
The CAPER facility fulfills as central part of the TLK infrastructure the part of the tritium recovery.