Abstract:
In pursuing carbon emission free technologies in the energy industry, interest in nuclear energy has grown.
However, technology for handling radioactive waste containing organic materials are lacking. Methods are
required for biodegradation of often recalcitrant irradiated organic compounds which are persistent in radioactive
waste from the nuclear industry. In this study, a bioseparation process for extraction of 14C and de-radiation of
nuclear graphite was investigated in a continuous flow sequencing-batch/biofilm reactor. Dehalogenation and
mineralisation of aromatic halogenated compounds in the waste stream of a pebble bed manufacturing process
was simulated by the photocatalytic/biological hybrid system in the 50 to 1,000 4-CP mg.L-1. The efficiency of
degradation of the irradiated compounds was compared to conventional degradation using PAH degrading
microorganisms. The Pathway of degradation was established for both systems by evaluating the intermediates
of degradation of radiolabelled phenolic compounds with ortho-13C-ortho and para-13C phenol. Phenol
degradation under photocatalytic conditions was shown to follow the catechol hydroquinone
hydroxyhydroquinone benzene-1,2,3-triol pathway, whereas the degradation in the biological stage followed
the meta-cleavage pathway via catechol 2-hydromuconic semialdehyde pyruvate under aerobic conditions.
This study demonstrates the potential of efficiently managing the organic component of nuclear waste using a
cleaner, environmentally friendly biological process.
