Spanish contribution to the development and application of best estimate plus uncertainty methodologies: Past, present and future

Best-Estimate Plus Uncertainty (BEPU) nuclear safety analysis is an approach widely used in the field of nuclear engineering and reactor safety assessment. It aims to provide a more realistic assessment of reactor safety by considering a combination of best-estimate models and the quantification of the uncertainty of the input and code data.The Spanish research community in collaboration with the regulatory body and the industry has substan-tially contributed to the development and application of BEPU methodologies by taking an active role in the international joint efforts. The present article provides an overview of the key contributions performed by Spanish institutions. Many of the activities performed in BEPU are dedicated to the thermal-hydraulics field where Spanish researchers have contributed to both the development of forward and inverse uncertainty propagation methods. On the other hand, BEPU related works have also been performed in several other disciplines such as neutron-kinetics, fuel thermo-mechanics, computational fluid dynamics, containment, severe accident and in coupled multi-physics applications. All these contributions are first summarized to set the framework for a final section that provides the future challenges that lay ahead in the upcoming years in relation to the implementation of BEPU methods.