PREMIUM, a benchmark on the quantification of the uncertainty of the physical models in the system thermal-hydraulic codes: methodologies and data review

The objective of the Post-BEMUSE Reflood Model Input Uncertainty Methods (PREMIUM) benchmark is to progress on the issue of the quantification of the uncertainty of the physical models in system thermalhydraulic codes by considering a concrete case: the physical models involved in the prediction of core reflooding. The present document was initially conceived as a final report for the Phase I “Introduction and Methodology Review” of the PREMIUM benchmark. The objective of Phase I is to refine the definition of the benchmark and publish the available methodologies of model input uncertainty quantification relevant to the objectives of the benchmark. In this initial version the document was approved by WGAMA and has shown its usefulness during the subsequent phases of the project. Once Phase IV was completed, and following the suggestion of WGAMA members, the document was updated adding a few new sections, particularly the description of four new methodologies that were developed during this activity. Such developments were performed by some participants while contributing to PREMIUM progress (which is why this report arrives after those of other phases). After this revision the document title was changed to “PREMIUM methodologies and data review”. The introduction includes first a chapter devoted to contextualization of the benchmark in nuclear safety research and licensing, followed by a description of the PREMIUM objectives. Next, a description of the Phases in which the benchmark is divided and its organization is explained. Chapter two consists of a review of the involvement of the different participants, making a brief explanation of the input uncertainty quantification methodologies used in the activity. The document ends with some conclusions on the development of Phase I, some more general remarks and some statements on the benefits of the benchmark, which can be briefly summarized as it follows: - Contribution to development of tools and experience related to uncertainty calculation and promotion of the use of BEPU approaches for licensing and safety assessment purposes; - Contribution to prioritization of improvements to thermal-hydraulic system codes; - Contribution to a fluent and close interaction between the scientific community and regulatory organizations. Appendices include the complete description of the experimental data FEBA/SEFLEX used in the benchmark and the methodologies CIRCÉ and FFTBM and the general requirements and description specification used for Phase I. Due to the revision of the document, four extra appendixes have been added related to the methods developed during the activity, MCDA DIPE, Tractebel IUQ and PSI methods.