Transport Phenomena in Nuclear Applications

Student projects

Numerical and experimental work in a test loop with a super critical fluid

MSc

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).

Available!
Contact Martin Rohde 

Temperature dependency of metal ultrasonic guides 

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).

Thermo-physical properties of molten fuel salts determined by longitudinal waves propagating in a tapered buffer rod

Bsc & MSc

Thermo-physical properties such as density and viscosity of molten fuel salts (for the molten salt fast reactor) can be measured with longitudinal waves propagating in a tapered buffer rod and reflected by the fluid surface. The student will simulate these waves with a finite element software (COMSOL) to measure these properties.

Study the interaction of molten salt fast reactor's fuel salt with water

Bsc & MSc

Study the interaction of molten salt fast reactor's fuel salt with water to understand its behaviour in case of leakage of salt in water or vice versa. The interaction will be studied in normal condition at room temperature and also under irradiation condition (Co-source). The concentration of the salt in water will be studied along the course of 3 months with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES) coupled with Energy Dispersive X-ray spectroscopy (EDX). X-ray Diffraction (XRD) will clarify which species are formed in such interaction and Scanning Electron Microscopy (SEM) will show the possible changes on the surface of the salt.

Modeling melting/solidification processes in the Molten Salt Fast Reactor (MEP)

Msc

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.

Available!
Contact Marco Tiberga  

Investigating flow patterns inside a microchannel

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 experimentally check the formation of slug flow or parallel flow inside the channel,  to explore the mechanism of the flow patterns and to propose conditions that can keep the interface stable and avoid leakage.

Occupied

An emergency cooling system for SLIMR, the supercritical-water Small, Modular Reactor

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.

Occupied

Theoretical description of 177LuDOTATATE synthesis in a microchannel

Bsc & MSc

To analyse and understand the reaction taking place in the microchannel and to optimize the reactor geometry, the radiolabelling setup is being modelled using Comsol Multiphysics. Currently, a bachelor student has looked at the mixing of the reactants before the reaction is started. A start was also made on modelling the reaction. However, the current model is not accurate enough. Therefore, the model should be improved using the Finite Element Method or another method, e.g. the Langrangian-based particle method. The final model should be compared to experimental results achieved in the lab for mixing and reactions.

Currently unavailable

Theoretical and experimental analysis of room temperature reactions in a microchannel

Bsc & MSc

The synthesis of 68GaDOTATATE, which is used as diagnostic agent in combination with 177LuDOTATATE, happens already at room temperature. To study this reaction in a microchannel and especially to obtain reaction rate constants for this reaction, a theoretical model is needed that describes mixing and reaction at the same time. Further, the results from this model should be compared with reaction yields obtained experimentally. The goal would be to obtain reaction rates for the synthesis of 68GaDOTATATE.

Currently unavailable

Theoretical study of radiolysis in microchannels

Bsc & MSc

Experiments done for 18F radiopharmaceuticals have shown that autoradiolysis (degradation of the radioactively labeled compound due to the activity of the labeled compound itself) can be reduced when the synthesis of the radiopharmaceutical is done in microchannels (Rensch, 2012). The aim of this project is to evaluate theoretically how big this effect would be for radiopharmaceuticals containing other radioactive isotopes (positron, beta or alpha emitters) considering different micro reactor geometries.

Currently unavailable

Propagation of waves at the solid-fluid interface

Bsc & MSc

A constant improvement of nuclear technology has led to Molten Salt Fast Reactors. The use of liquid fuel creates the necessity of a database of physicochemical properties of the fuel salt. Accurate measurements of density and viscosity are necessary to predict the flow of the fuel through the reactor circuit. This characterization is very challenging for the corrosion and the radioactivity of these salts and for the high temperature in which the experiments will be performed. Within SAMOFAR (Safety Assessment of the Molten Salt Fast Reactor) TU Delft will develop new experimental techniques and measure the thermal properties of the liquid salts like viscosity at these extreme conditions. An ultrasonic technique will be used in our lab as a non-invasive and non-destructive device. Ultrasonic waves will be propagating in a buffer rod to perform measurements at high temperature using a very small amount of sample. The project will involve the simulation of the propagating waves for designing the material and the shape of the ultrasonic buffer rod for high temperature. The optimisation of the rod will be a crucial point for this experimental technique. Ultrasonic wave propagation can be modelled using Finite Element Method (FEM). A FEM model will be designed in COMSOL for simulating ultrasonic waves propagating in different material and at the solid fluid interface.

Currently unavailable

Design of the MSR safety plug

Bsc & MSc

Under emergency conditions, the molten salt needs to be drained as quickly as possible to underground storage tanks. The subject of this research project is to develop such a system. Questions that need to b addressed are: how would this system look like/ (diameter, length of piping system), how would crystallization at the walls of the drainage pipes influence the flow (and thus: drainage speed)? To what extent does the decay heat influence the entire proces?

Currently unavailable

Martin Rohde (2018)