Scaling analysis in BEPU licensing of LWR

Scaling plays an important role for safety analyses in the licensing of water cooled nuclear power reactors. Accident analyses, a sub set of safety analyses, is mostly based on nuclear reactor system thermal hydraulics, and therefore based on an adequate experimental data base, and in recent licensing applications, on best estimate computer code calculations. In the field of nuclear reactor technology, only a small set of the needed experiments can be executed at a nuclear power plant; the major part of experiments, either because of economics or because of safety concerns, has to be executed at reduced scale facilities. How to address the scaling issue has been the subject of numerous investigations in the past few decades (a lot of work has been performed in the 80thies and 90thies of the last century), and is still the focus of many scientific studies. The present paper proposes a “roadmap” to scaling. Key elements are the “scaling-pyramid”, related “scaling bridges” and a logical path across scaling achievements (which constitute the “scaling puzzle”). The objective is addressing the scaling issue when demonstrating the applicability of the system codes, the “key-to-scaling”, in the licensing process of a nuclear power plant. The proposed “road map to scaling” aims at solving the “scaling puzzle”, by introducing a unified approach to the problem