Automatic or Manual Safe Shutdown of Industrial Facilities on Earthquake Signal, Guidelines to Meet the New French Regulation: Seismological and Instrumental Aspects

The French regulation has been updated in 2010, and now explicitly requires that equipment of high hazard industrial facilities (outside nuclear field) do not lead to unacceptable consequences under the highest earthquake of the seismic zone where the facility is located. As well the seismic zones have been re-evaluated, considering four levels for the French metropolitan territory. To meet this new requirement AFPS has been asked to draft a guide that defines a strategy to stop the facility on detection of the earthquake. This specific guide is part of a set of documents that will support operators in the different design requirements that could be implemented to demonstrate compliance with the regulation. The guide explains how automatic or manual actuators could isolate the dangerous inventory inside the facility to prevent or limit the impact. As well mitigation of indirect effects is considered. Earthquake phenomenology, threshold to trigger the safe shutdown, principle to demonstrate compliance with the regulation, logic, hardware & software requirements, qualification and in service inspection are described together with real case study. The present paper focuses on earthquake phenomenology, detection strategies and threshold to trigger the safe shutdown. As far as the threshold level is concerned a possible -very low- default threshold that would prevent long diagnostic analysis of the weaknesses of the equipment will be discussed.