Scaling analysis of an IBLOCA counterpart test between the ATLAS and LSTF facilities

Abstract

[EN] The experiments carried out in test facilities improve knowledge of the phenomena that would occur in a nuclear power plant during an accident, and support the validation of the thermal-hydraulic codes used in the nuclear safety analysis. Among them, counterpart tests between two facilities allow analyzing the different technology and scale effects, and the inherent distortion, in the evolution of a specific transient. Thus, counterparts contribute to address the scaling methodologies and enhance confidence in extrapolating results from the facilities to their reference power plants.

The objective of this study is to analyze an Intermediate Break Loss-Of-Coolant Accident (IBLOCA) counterpart test at the ATLAS and LSTF facilities. The experiment is based on a 13% break in a cold leg, followed by the actuation of the High Pressure Injection (HPI), accumulators and Low Pressure Injection (LPI) systems. The study is supported by the simulation of the experiment with the TRACE5 thermal-hydraulic code. The results are compared with the available data of the A5.2 and IB-CL-05 tests, in the OECD-ATLAS and OECD/NEA ROSA-2 projects, respectively, in order to evaluate the prediction capabilities of TRACE5 and clarify the causes of the important differences between the transients. The analysis is completed by calculating the dimensionless groups derived from the first approach in the top-down scaling. The comparison of the groups determines, since an analytic point of view, the relevant phenomenology during the transient and the scaling distortion between both facilities. The system scaling analysis assesses a great similarity in the evolution of the main thermal-hydraulic parameters and in the operation of the safety systems throughout this transient.