| dc.description.abstract | For several decades, nuclear power has been of interest as an energy source. Advantages
include reliability and zero carbon emissions, however there are disadvantages in waste
management and the risk of proliferation. Current research aims to address these by developing
proliferation resistant methods to reprocesses the spent fuel and close the fuel cycle.
Whilst aqueous liquid-extraction reprocessing techniques are in use, these are confined to
specific fuel types and produce significant additional low-level radioactive waste. Separation
of spent fuel in molten salts has been proposed as an alternative to such aqueous methods.
These systems include using liquid metals as electrodes at which selective metal deposition
takes place. There are several technical and materials hurdles to overcome, these include:
characterisation and optimisation of the processes taking place at the liquid electrode/ molten
salt interface; and the development of the necessary on-line analysis techniques for process
monitoring.
This thesis takes a step-by-step approach to: characterise the behaviour of liquid metal
electrodes; explore how molten salts interact with materials to inform the development of
microelectrodes for on-line monitoring, and; develop methods to prepare molten salts for
rigorous study.
First the fundamental response of liquid cathodes is demonstrated through comparative studies
in aqueous systems. By comparing electrochemical studies of mercury cathodes at ambient
temperatures and liquid cathodes in molten salts, characteristic responses for deposition,
alloying and dendritic growth are observed. In ambient conditions, the bounded Cottrell
equation is applied to a liquid cathode for, what is believed to be, the first time to explain alloy
formation in the upper layers of a liquid cathode.
The contact angles of lithium chloride - potassium chloride eutectic (LKE) on materials used
in microelectrode fabrication have been measured. These wettability measurements confirm
silicon nitride and tungsten as suitable materials in design and fabrication of microelectrodes
for online process monitoring.
Ensuring the correct speciation is studied in the molten salt is of significant importance in
developing a pyroprocessing system. Characterisation must be performed in a high purity,
rigorously dry molten salt, and a new method for removing water from lithium chloride-potassium chloride eutectic melt (LKE) has been developed. | en |
