OECD/NEA/CSNI/WGEV Benchmark: External Events Hazard Frequency and Magnitude Statistical Modelling-IRSN approach
Résumé
A general feature of external hazards is that they produce off-normal conditions that can impact nuclear installations. Scenarios- and frequencies-based risk analysis allows a more reliable practice by allowing key stakeholders to make risk informed choices rather than simply relying on traditional deterministic estimates of risk, with a brief description of uncertainty. This benchmark is conducted to facilitate an exercise on the estimation of extreme external events. The aim of the benchmark is to better understand the technical aspects and processes used for the characterization of natural hazards. Data and overall objectives for the benchmarking exercise are presented for a hypothetical external event (e.g., precipitation, extreme temperatures, high winds). Our analysis steps, assumptions and modelling results were summarized. Uncertainties are generated by the fact that the provided synthetic data (SD) is relatively uninformative. The use of this SD-based approach allows to evaluate the proposed statistical model and add known uncertainty to the data. Two cases are provided: (i) with a given generating model, (ii) a “blind-test case” where only the data is provided. To make the exercise as useful as possible and to present the work in the most comprehensible way, some theoretical and technical background for the selected approaches and the assumptions are provided. After recalling the data provided in the exercise, the underlying theory and assumptions are presented. The results of the proposed statistical models are then presented for each test case together with the associated uncertainties as well as the model adequacy assessment. This work is concluded with a summary of the most essential results.