Kv-scaling in thermal hydraulics: Background, applications and forthcoming uses

Addressing the scaling issue refers to a rather complex process of demonstrating the applicability of activities devoted to predict the behaviour of actual nuclear power plants using the knowledge acquired in scaled -down test facilities. Such activities involve, among others, the evaluation of the capability of Best Estimate codes to scale-up processes from reduced scale test facilities to full scale Nuclear Power Plants (NPP) and the quantification of the effects of scale distortions. In this context, a Kv scaled calculation is a system -code simulation in which, defined test conditions of an Integral Test Facility (ITF) are scaled-up to a NPP nodalization to reproduce the same scenario. The practical use of such kind of calculation is to permit a comparison of the behaviour of the plant and the ITF nodalizations under the same conditions. The comparison between the NPP Kv-scaled results and those of the experiment post-test calculation will show unavoidable differences or distortions. Explaining such distortions is the key process in methods devoted to qualify plant nodalizations. The aim of this paper is to show the effectiveness of Kv-scaled calculations and to outline the forthcoming use of hybrid nodalizations and scale-up nodalizations. The paper includes a thorough literature review of these type of approaches as well as the perspectives of future use of the Kv scaling analysis. Such future uses include the feedback to experimentation. Despite the fact that the hybrid calculations presented here are related to existing ITFs and NPPs, feedback to experimentation intents to show the essentials of a future practice to be mainly implemented in modular ITFs.