Assessment of the Recovery of Maltenes from Bituminised Waste Simulates

Bitumen has been used as a matrix for inorganic radioactive waste salts. In an earlier paper we presented some lab-scale experiments on the recovery of the maltenes from a non-radioactive waste simulate mixture containing blown bitumen (Shell type R85/25) and waste salts. Our maltene recovery method is based on (1) dissolving the bitumen and (2) settling of asphaltenes and salts from this solution. In order to minimise the amount of inorganic (possibly radioactive) impurities in the maltenes we aim at optimising the separation method. Chemical and gravimetrical analyses were applied, but for the best-recovered maltene fractions their detection limits were not low enough. Therefore, we started using NAA (neutron activation analysis) and gamma spectrometry. This paper also proposes a direct method to measure the settling kinetics of radionuclides by gamma spectrometry.