High-Resolution Flow Measurement Techniques for the Generation of Validation Data in Nuclear Thermal Hydraulics Experiments

The past years have seen a tremendous increase in computational power and hence a trend to employ more and more advanced numerical tools for the analysis of nuclear thermal hydraulics. Primary applications are accident analyses as well as safety assessment for new reactor systems and prominent directions are 3D computational multiphase fluid dynamics, coupled codes, and advanced BEPU analyses. While years ago it was believed that one day such tools may be able to replace experiments fully or in part, it is meanwhile commonly accepted, that a focus must be given on validation experiments for single effect problems and that such validation experiments should be preferably at original system t/h conditions to account for difficult upscaling conditions, and that such experiments need new instrumentation in order to get CFD grade data. The latter means field quantities of phase fraction, velocity and temperature at high spatial and temporal resolution.
The lecture gives an in-depth overview over novel field measuring techniques for nuclear thermal hydraulics experiments. We will briefly touch the field of distributed sensors for phase fraction, temperature and velocity and then dive into the field of advanced imaging techniques. We will discuss the application of well-known imaging techniques, such as high speed videometry, PIV and IR thermography and then come to computed tomography techniques, which are very useful to study multiphase problems. The methodological description of the basic physics and technology will be accompanied by application examples in nuclear safety research being pursued at the TOPFLOW facility at Helmholtz-Zentrum Dresden-Rossendorf.