In order to maintain the necessary share of clean nuclear energy in the Hungarian electricity mix, new VVER-1200 pressurised water reactors are being built in Hungary. The thermal-hydraulic investigation of fuel assemblies of these nuclear reactors is a high priority task.
At the BME Institute of Nuclear Techniques (BME NTI), a Particle Image Velocimetry (PIV) measurement system (2D non-intrusive measurement technique) has been available since 2007 and has proven to be extremely useful for nuclear thermal-hydraulic research. The BME NTI’s PIV laboratory is able to provide measurements that directly map the flow conditions in the VVER-1200 rod bundles. In accordance with international best practice the combination of experiments and computer simulations delivers reliable results, which is accepted as validated.
The objective of this PhD research is to construct an adiabatic 19-rod bundle mock-up using transparent FEP tubes that models a section of a fuel assembly, the results of which can be used to validate Computational Fluid Dynamics (CFD) models that support full-scale nuclear power plant fuel assembly analyses. The measurements shall be using matching index of refraction in order to investigate the flow field between the simulated fuel rods.
BME NTI has decades of experience in numerical modelling of thermal-hydraulic problems of nuclear reactors. Simulations using 3D CFD models can investigate flow fields in high detail, but the results are always subject to uncertainties. In order to reduce these uncertainties, problem-specific benchmark models can be developed to reproduce the results of dedicated measurements as accurately as possible. The VVER-1200 rod bundle consisting of 19 rods and the PIV measurements performed on it, to be established in the this project, serve this purpose.
During the PhD research, the student will be required to carry out the following tasks:
- a detailed study of the VVER-1200 reactor fuel assembly, its geometrical and thermal-hydraulic characteristics,
- a critical review of the relevant scientific literature,
- in-depth understanding of the PIV measurement methodology, including measurement uncertainties and their possible reduction,
- design and construction of a PIV experiment consisting of 19 rods and at least 4 spacer grids of the VVER-1200 fuel assembly, possibly applying matching index of refraction ,
- perform measurements on the constructed experimental geometry, evaluate the results, quantify the uncertainties of the measurements and document the results,
- development of detailed CFD models to reproduce the results of the 19-rod VVER-1200 PIV measurements,
- in-depth CFD modelling of the investigated problem using ANSYS CFX, comparison of the CFD model results with the PIV measurements results,
- formulation of recommendations for models and modelling considerations to be used in CFD analyses of triangular rod bundles applied in power plants,
- extend the studies to different spacer grid geometries to create more efficient mixing under operational conditions, suggest methods to improve mixing,
- investigate, by CFD or PIV, the region of adjacent assemblies and the effect of the central instrumentation tube on flows field.
• Adequate knowledge of nuclear reactor thermal-hydraulics and Computational Fluid Dynamics • Capabilities and good manual skill in design, construction and operation of experimental setups and test rigs • Basic knowledge of measurement techniques applied in thermal-hydraulics • Good knowledge and experience in lasers, precision mechanics and optics • Affinity for using computational modelling tools, applying experimental methods • Knowledge and experience of CFD methods and codes is an advantage • Good level of English • Diligence, precision, commitment