BEPU-FSAR: A new paradigm in Nuclear Reactor Safety

Nuclear safety has become a technology following extraordinary industrial investments since the 50’s. Events in the last decades occurring in the Three Mile Island Unit-2, Chernobyl Unit-4 and Fukushima Units 1-3 have challenged the sustainability of nuclear technology and undermined the trust of the public, of the decision makers and even of the scientific community toward nuclear safety. Innovative ideas and proposals are possibly needed to restore the confidence and escape the irreversible loss of competence which also feeds the further degradation of sustainability for the technology. Efforts have been completed by the technological community following each of the disasters and ended-up in reinforcements of the Engineered Safety Features (ESF) and of Safety Barriers. The FSAR shall be seen as the compendium of information concerned with the safety of the specific NPP and includes the demonstration of acceptability of the NPP against the rules and related criteria established for the Country. The Safety Analysis is part of the licensing process and is documented in the FSAR. The role of safety analysis as a key part of Nuclear Reactor Safety Technology (NRST) is discussed first and the innovation connected with the words ‘independent’ and ‘systematic Best Estimate Plus Uncertainty’ is presented, as well as the propose of a BEPU-FSAR. To perform an entire FSAR based on BEPU, a homogenization of the analysis is proposed. The first step towards BEPU-FSAR requires identification and characterization of the parts where numerical analyses are needed (so-called BEPU topics). The next step is to create a list of key technological areas, so-called key disciplines and their related key topics and then an overview of the currently computational activities in each technological area. Based on the finalized BEPU applications one can conclude that this methodology is feasible, which encourage to extended its range of use to the other technological areas of FSAR, and therefore to demonstrate the industrial worth and interest. The future step of this work will mainly be focused on the propagation of this expertise into the remaining technical areas of FSAR, adding new knowledge and therefore creating coherent and rigorous background of the BEPU-FSAR methodology. The purpose of the present paper is to provide the background and the framework for the proposed approach.