Hydraulic flow tests of APWR reactor internals for safety analysis

A concept of radial neutron reflector of APWR brings about safety problems relevant to the flow induced vibration and thermal deformation. The CFD code has been expected to solve them by calculating pressure fluctuations of turbulent flow in the downcomer and the flow distribution into the neutron reflector. A series of hydraulic flow tests was conducted by NUPEC from 1998 to 2002 to demonstrate the new design of the neutron reflector and to obtain test data for validating the CFD code. The measured pressure fluctuations in the downcomer and their statistics were utilized for validating the specific turbulent model to be able to calculate a spectrum of pressure fluctuation such as the LES model. The measured flow rates at inlet holes of the lower core plate were utilized for validating for the general turbulent model, for example, the k– turbulent model. The calculated results with the LES model agreed well with the measured pressure fluctuations and their spectrum, but did not agree with the correlation between adjacent pressure fluctuations. On the other hand, the calculation results with the k– turbulent model agreed well with the measured flow rates at inlet holes of the lower core plate.