Thermal-hydraulic safety research for LWR safety upgrading; Validation of thermal-hydraulic analysis methodology through ROSA/LSTF experiments

Takeda, Takeshi 

In this thermo-hydraulic research group, studies for upgrading of phenomena predictability of thermal-hydraulic safety analysis methodology are being conducted through the clarification of phenomena and the validation of analysis codes using LSTF facility in the first and second programs of OECD/NEA ROSA Project. Best-estimate (BE) code predicted break flow rate reasonably well through combination of appropriate models in post-test analysis of pressure vessel top break LOCA based on recent incident. Computational fluid dynamics code reproduced fluid temperature distribution by three-dimensional thermal-fluid analysis of temperature stratification experiment with ECCS injection. In addition, it was confirmed that BE code has remaining problems on predictability through blind analysis of intermediate-size break LOCA experiment based on risk-information.