Appliance of scaling methodologies for designing counterpart experiments dominated by natural circulation phenomena

Abstract

The utility of the Integral Test Facilities (ITF) for the study of thermohydraulic phenomena that can occur in nuclear power plants has been demonstrated. However, direct extrapolation of data between different scales is challenged due to the uncertainty and distortion that implies the application of scaling laws. In this sense, the analyses of counterpart experiments help to clarify the capabilities and limitations of scaling methodologies.This work focuses on the design and study of a counterpart experiment in the LSTF facility based on the ATLAS A1.1 test. The transient at issue reproduces a SBO-type scenario with the asymmetric and delayed supply of auxiliary feedwater. The scenario in ATLAS and LSTF facilities is simulated with the TRACE5 thermal-hydraulic code and the results are compared. Then, a global system scaling analysis is performed and the calculation of dimensionless groups reveals, through an analytical approach, the relevance of the transfer processes (mass, enthalpy and so on) in the evolution of the transient and the scaling distortion between both facilities.This study assesses a great similarity in the evolution of the main thermal-hydraulic phenomena throughout the experiment, despite a significant discrepancy is evidenced in the chronology. Likewise, the results support the novel procedure to design the counterpart test.