Experimental study of the APR+ reactor core flow and pressure distributions under 4-pump running conditions

•Experimental facility with a 1/5 scale was designed to perform various hydraulic tests of an APR+ reactor.•Two kinds of experiments, balanced and unbalanced flows under 4-pump running conditions were carried out.•The core inlet flow rates and exit pressure distributions were measured and analyzed at 257 discrete points.•The coolant mixing characteristics were investigated with the sectional pressure loss coefficients. The core inlet flow rates and exit pressure distributions of an APR+ (Advanced Power Reactor Plus) reactor were evaluated experimentally with the ACOP (APR+ Core Flow & Pressure) test facility. The ACOP test facility was constructed with a linear reduced scale of 1/5 referring to the APR+ reactor. The major flow path from the clod leg to hot leg was preserved with a principle of similarity. The core region was simulated using 257 core simulators, which are representative of the real HIPER fuel assemblies that APR+ reactor adopted. The core inlet flow rates and pressure distributions along the main flow path, which are significant information as an input data to evaluate the core thermal margin and reactor safety, were obtained by differential pressures measured at core simulators representing 257 fuel assemblies, and the static or differential pressures at 584 points, respectively. Two kinds of experiments, 4-pump balanced and unbalanced flow conditions, were conducted to examine the hydraulic characteristics of the reactor coolant flow. The mass balance and overall pressure drop were carefully examined to check the reliability of the obtained values. The inlet flow rates of the two test results showed similar distributions, which met the hydraulic performance requirement. The details of these experiments, the facility, and a data analysis are also described in this paper.