The Paul Scherrer Institute PSI is the largest research institute for natural and engineering sciences in Switzerland. It develops, builds, and operates large-scale research facilities, and conducts research into future technologies, energy and climate, health innovation, and the fundamentals of nature. In addition, the PSI runs the Federal Collection Centre. It receives the radioactive waste from medicine, industry and research throughout Switzerland that is subject to mandatory delivery and takes care of its conditioning and interim storage.

The hot laboratory, the research reactors Saphir, Diorit and Proteus (currently undergoing decommissioning), the experimental incineration plant and the radioactive waste management facilities are all nuclear installations and as such are supervised by ENSI.