Applying the PIRT Approach to the Meteorological Hazards Wind and Rainfall in Relation to Industrial Needs: Benefits and Lessons Learned

As an integrated nuclear engineer and operator, EDF has a strong background in studying extreme natural hazards for its Nuclear Power Plants (NPPs) fleet safety demonstration. The state-of-the art evolution and the development of natural hazards Probabilistic Safety Analysis provide an opportunity to go more in depth in our studies. To reinforce or, if need be, to adjust our hypotheses regarding the detailed characterization of natural hazards, we decided to investigate the detailed phenomenology associated with strong winds and rainfall in France. The PIRT process (Phenomena Identification and Ranking Table) allows a physics-oriented approach to complex phenomena by systematically analyzing relevant parameters and their influence on a scenario of interest. This approach appears like a legitimate way to go more in depth in the phenomenology associated with strong winds and rainfall. This approach, used in the nuclear energy field, for example, as support for complex transients numerical modelling, is here tested on complex natural phenomena. Strong winds, rainfall and other associated phenomena are very complex if one wishes to consider a high detail level. It was decided during the exercise to limit the technical complexity to a level relevant to industrial concerns. Even with this simplification, the lessons learned will allow EDF to be more precise in future studies, such as those regarding strong winds directions and some phenomena specific to certain geographical locations. This article describes the PIRT approach and modifications that were made to the classical PIRT steps both for strong winds and rainfall. We also outline the main lessons we learned, from the PIRT application and regarding the analysis we were able to gain regarding specific needs for our studies. We found that the PIRT approach can be used to study meteorological phenomenology with the following adaptations: - An adapted detail level — some very complex aspects, coming under Research & Development (R&D) or advanced meteorological expertise have not been taken into account in the present exercise - Use the PIRT as a way to present and organize advanced knowledge on a subject. The aim is to shed more light on an end user issue, like to better comprehend the underlying physical processes for strong winds safety demonstration studies: speed, direction, duration ... The exercise was possible thanks to the strong collaboration with Météo France, the national French Meteorological Agency, who was the referent expert bringing the technical and scientific knowledge on meteorology.