Particle Image Velocimetry (PIV) is a state-of-the-art non-intrusive optical flow measurement method based on the recording images of the movement of flow-following particles added to the liquid in the investigated flow domain. PIV is in use at BME Institute of Nuclear Techniques (NTI) since 2007, and has been applied for such investigations as coolant mixing, heat transfer of the fuel rod of the training Reactor or thermal-hydraulics characteristics of the MSFR molten salt reactor concept core. With the application of Matched Index of Refraction (MIR) method it is possible to investigate the flow field in complex geometries. By matching the refractive indices of the model material and the working fluid the flow domain behind a solid model part becomes visible for the optical method, thus allowing the measurement in geometries such as rod bundles.
Most of the publications in the international literature focus on rectangular lattice geometries as these are common for fuel rod bundles applied in western pressurized water reactors (PWRs). However in case of VVER reactors and some Generation IV reactor types, for example the Allegro gas-cooled demonstrator fast reactor hexagonal lattice is applied. So far only a limited number of publications presented PIV measurement results on hexagonal lattice rod bundle PIV measurements. Main purpose of the work proposed here is to develop an appropriate experimental model of hexagonal fuel rod bundles that can be applied with PIV. The measurement data would lead to a deeper understanding of flow behaviour in such geometries, and would be invaluable for validating computational models and simulation results like CFD or subchannel code calculations. Such an experimental model would be a new, state-of-the-art and unique facility even in terms of international comparison. One of the objectives of the PhD research is to deliver new CFD-grade experimental data, which would be applicable for the validation of CFD codes and models. The research work could contribute to the development and optimization of spacer girds with mixing vanes for nuclear reactors.
The PhD candidate would perform the following tasks:
- Study the latest findings of the international literature on Particle Image Velocimetry, Matched Index of Refraction and their application in nuclear thermal-hydraulics.
- Select the applicable model and liquid materials for a such experimental model.
- Design a hexagonal fuel rod bundle experimental model that will be used for extensive series of PIV measurements.
- Perform measurements on the experimental model, analyze the measurement results and discuss the flow characteristics of different rod bundle types.
- Discuss different options of geometry modifications and their effects on rod bundle thermal-hydraulics, including the effects of different spacer grids on flow behavior.
- Documentation of measurement results on a level which is applicable for validation of numerical models and codes.
Adequate knowledge of nuclear reactor thermal hydraulics and Computational Fluid Dynamics
Basic knowledge of measurement techniques applied in thermal-hydraulics
Affinity for using computational modelling tools, applying experimental methods
Good level of English