Thermal-Hydraulic Behavior in Containment as Influenced by Steam Injection Location: Insights from the OECD-ATLAS3 C5.2 Separate Effect Tests

Abstract

This study presents the C5.2 test series, a part of the OECD/NEA ATLAS phase 3 project, conducted at the CUBE (Containment Utility for Best-Estimate Evaluation) facility. The focus was on analyzing thermal-hydraulic behaviors during constant-rate steam injection, emphasizing heat transfer between fluid and structure. The research included two steam injection scenarios: RUN1, via the reactor coolant pump discharge position, and RUN2, through the main steam line position. Extensive measurements of containment pressures, fluid and wall temperatures, and relative humidity were undertaken to provide comprehensive insights on the thermal-hydraulic phenomena. The highlight of the present study was the observation of thermal stratification variations according to steam injection location and the changing role of the compartments as passive heat sinks, influenced by the formation of distinct thermal boundary layer. The test results demonstrate how the role of compartments as passive heat sinks varies with thermal stratification, influenced by the location of the break within a containment. These findings offer a valuable database for validating containment safety analysis codes. Additionally, the study reveals that the lumped model code, commonly used in containment safety analysis, may produce non-conservative calculations depending on the patterns of thermal stratification.