Conditioning of a Na-bearing waste stream from Na-cooled fast reactors

The remnants of the sodium-cooled fast reactor test campaigns performed at SCK CEN are to be treated in a joint decommissioning effort between SCK CEN and Belgoprocess. In an established chemical passivation process, the contaminated sodium and eutectic sodium-potassium are converted into stable carbonate form. In this process minor tweaks in set up can strongly influence the concentration of the contamination in the carbonate. However, there is no established waste management and disposal route for this formed carbonate.

Thus, further investigation into suitable conditioning methods aims to evaluate the feasibility of both cementation and vitrification as potential conditioning strategies. A comparative analysis will be performed between the technical properties and maximum loading of the studied matrixes. The vitrification assessment will focus on the theoretical evaluation of matrix stability when sodium oxide originating from the waste replaces part of the oxide from the glass mixture. For the cementation route, both surface and geological disposal options will be considered in light of technical characteristics, the maximum achievable waste loading within the cement matrices and existing acceptance criteria. The theoretical study of cement matrices will be complemented by a cold testing campaign to experimentally validate findings from literature and confirm the validity of the mixtures’ conditioning capability.

Ultimately, the research will provide a recommendation for the optimal conditioning strategy for chemically passivated sodium and potassium waste, allowing for the finalisation of the chemical process in light of the targeted concentration of the formed carbonate.