The aim of this work was to determine the solubility of radionuclides in solutions of cellulose
degradation products (COP) and isosaccharinic acid (ISA) the main product of cellulose
degradation. Thorium was the main radionuclide investigated as the solubility of tetravalent
actinides in the near field of a nuclear waste repository at high pH and low Eh has been shown
to increase in the presence of such ligands. The measurement of thorium solubility was
achieved by using different methods e.g. liquid scintillation counting, gamma spectrometry,
ICP-MS and ICP-OES. ICP-OES was shown to be the most accurate method for this analysis.
Various methods have been used to obtain solubility values e.g:. undersaturation arid
oversaturation, and these have been investigated to determine whether the values obtained from
these methods differ. Solubility studies were carried out at different pHs (6, 8 and 12). The
kinetics of the complexation of thorium with ISA and with COP were investigated at these
pHs. The concentration of ISA in a solution of synthesised 10% COP was approximately·O.OI
In high pH solutions, the solubility of thorium was found to be 31 times greater in a
solution of COP compared to a solution of ISA at the same ISA concentration. No significant
differences in thorium solubilities were found in similar solutions at pH 6 and 8.....
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.