Bsc & MSc
Parallel flow microfluidic solvent extraction could be used for extracting radioactive isotopes. For the success of the extraction, a stable interface between the immiscible aqueous and organic should be established inside the micro-channel. However, the interface is sometimes not stable, forming slug flow. In addition, due to the wettability of the channel, one phase tends to leak to the other one at the end of the channel. Both of the above mentioned problems will lead to the failure of extraction. In this project, the student is expected to study the flow problem by using the lattice-Boltzmann method.
The most innovative aspects of the Molten Salt Fast Reactor (MSFR), one of the six Generation IV nuclear reactors, are that the fuel is dissolved in a liquid salt, and that it can be passively drained in an Emergency Safety Tank placed underneath the core, via the melting of plugs made of frozen salt. Modeling solidification/melting phenomena is numerically challenging due to the presence of a moving solid-liquid interface. The enthalpy-porosity method is often employed, because of its versatility and convenience: it is easy to adapt to complex geometries, and, in it, the solid-liquid interface is implicitly tracked, by smearing the phase-change region over several grid cells and implicitly accounting for the latent heat. With this project, we want to continue the investigation of phase-change processes inside the MSFR. The student will do so by first implementing an enthalpy-porosity method in an existent CFD code (written in Fortran), based on the Discontinuous Galerkin Finite Element Method for the spatial discretization of the governing equations. The second goal will be to investigate the possibility of extending the model to simulate the contact-melting mechanism.
Despite the high pressure requirements, supercritical fluids are commonly used in pharmaceutical and chemical extraction processes. This is because of their unique fluid properties, where small changes in pressure and temperature result in a large change of e.g. the density. Supercritical fluids are also able to transfer larger amounts of heat than subcritical fluids because of their sharp increase in specific heat capacity. As such, these fluids are being used in modern power plants. But also on smaller power scale, supercritical fluids are attracting attention, as supercritical CO2 is seen as a future natural refrigerant for automotive applications. Flow measurements with Laser Doppler Anemometry in loops with supercritical fluids are still rare, difficult to perform, because of density differences in the fluid at supercritical conditions. Although recently we performed several measurements in a small test loop with supercritical Freon.
The goal of the project is to model this loop (with forced and natural circulation) and compare these results with LDA-measurements in the loop. The work is partly numerical (model) and experimental (measurements).
Bsc & MSc
This project is part of our goal to measure the viscosity of molten fuel salts at high temperature with the help of an ultrasonic guide. These properties are needed to predict turbulence and local melting and solidification of the salt. Ultrasonic waves propagating in a metal waveguide are possibly influenced by the temperature. The shear and longitudinal velocity and attenuation of these waves will be evaluated at different temperatures up to 1500 degree Celsius with a finite element software (COMSOL).
Bsc & MSc
SMR's (Small Modular Reactors) are interesting for remote areas and/or offers a more controled way to invest in nuclear power. One may start with one small reactor (e.g. 200 MWe) and build additional ones if required. Another feature is that small reactors are easier to cool in the case of a station blackout (no power to extract decay heat from the core), as the coolant inventory is smaller.
The design of this reactor is based on the NUSCALE reactor. The difference is that this reactor is cooled by supercritical water, which enhances efficiency and is better for natural circulation of the coolant through the primary circuit. The vessel is entirely submerged into a large pool of water, which is used to cool the reactor if a station-blackout occurs.
The project focuses on an emergency cooling system. The idea is to add an additional vessel around the reactor, which is filled with gas. During nominal conditions, this gas filled tank causes a heat transfer barrier to the cooling pool. Under emergency conditions, however, the tank needs to be filled with water. There are two ways of doing this: by using a syphon system or by using a freeze plug. The aim of this project is to develop such a system and investigate its applicability.
Martin Rohde (2020)