Role of ENSI in PEGASOS and PRP

What is the role of ENSI?

The Swiss Federal Nuclear Safety Inspectorate (ENSI) is the federal regulatory authority responsible for the nuclear safety and security of the Swiss nuclear installations. Swiss legislation specifies that these installations should not present a hazard to humans and the environment. ENSI’s task is to ensure safety within the framework of the legislation and to ensure, through its supervisory role, that the operators observe their responsibility for the safe operation of their installations at all times. ENSI relies on the state of the art in science and technology in performing its work, as well as on worldwide experience in the field of nuclear energy.

New review of seismic hazard assessment

In 1999, and based on its legal mandate, the regulatory authority requested the power plant operators to reassess the seismic hazard of their facilities using the methods available at the time. The operators then commissioned the PEGASOS project and the refinement project PRP.

ENSI monitored all the phases of the PEGASOS and PRP projects with its own group of experts, the ENSI Review Team. A particular responsibility was checking whether the guidelines relating to the independence of the international experts had been followed. The ENSI experts participated in all the workshops of the two projects, but were not permitted to influence the judgment of the independent experts by expressing their own opinions. Their comments were recorded in written form after the workshops. This close involvement of ENSI in the two seismic hazard studies allows it to better review and evaluate the quality of the results.

Following completion of the projects, ENSI decrees the new seismic hazard curves at plant site. Thereupon the power plant operators have to demonstrate the earthquake safety of the power plants based on the current status of science and technology.