Nuclear data target accuracy requirements for advanced reactors: The ALFRED case

Uncertainties estimation is essential for a sound assessment and a clear definition of safety margins, which in turn are crucial for licensing approval of new nuclear reactors by safety authorities. Moreover, uncertainties are also matter for target accuracy requirements (TARs), whose achievement could disclose new or enhanced opportunities. The concept of target accuracy requirements has been over the years one of the returning focuses of Massimo Salvatores, who just recently relaunched an update exercise within the OECD/NEA Working Party on International Nuclear Data Evaluation Co-operation (WPEC) aiming at providing new estimates having as reference the advanced systems meant for tomorrow. This work presents an evaluation of the current accuracies on the main core integral parameters of the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED), as a starting point to discuss which would be the target values that might introduce beneficial improvements in the design. Despite the use of one of the most recent nuclear data libraries (ENDF/B-VIII.0), and the broad margins set in the design of ALFRED according to its mission as demonstrator, room for improvement is found on the multiplication factor. Then, moving from the target accuracies on the integral parameters, an inverse uncertainty problem is solved to derive the corresponding target accuracies on nuclear data, meeting which would guarantee the achievement for the former ones. The inverse problem is solved introducing three different sets of cost parameters, reflecting possible challenges related to the execution of the differential experiments requested to achieve the aimed reductions of the accuracies. By this, the resulting target accuracies on nuclear data here presented are deemed useful to obtain information for the high-priority lists driving the selection of isotopes and reactions for future refinement experiments.