Thermal-hydraulic research on future reactor systems in the ROSA program at JAERI

Yonomoto, Taisuke ; Otsu, Iwao ; Svetlov, S.*

A research project is being conducted at the Japan Atomic Energy Research Institute on thermal hydraulics for the future reactor systems. The present paper provides the belief description of the project, followed by two recent topics: the natural circulation in the PWR loop and the condensation heat transfer for a passive cooling system. For the first topic, we discuss the importance of the modeling of the nonuniform flow behavior among SG U-tubes for the assessment of the long-term decay heat removal systems relying on the SG secondary side cooling. Such a system is planned to be used in APWR+, a Japanese next-generation PWR. The condensation heat transfer was investigated using the data obtained at the SPOT test facility in Russia. The results have shown that the measured heat transfer rates on the inner surface of the tube consisting of several bends and short straight sections can be predicted using the existing correlations with the accuracy of several percentage, although the correlations are based typically on the data taken using relatively long straight tube.