Sustainable mix design for liquid radioactive waste with an extremely high boron concentration using alkali-activated Portland-limestone cement

Abstract The radioactive waste cementation plant at Paks Nuclear Power Plant in Hungary solidifies liquid radioactive waste using Portland cement blends. Under the European Green Deal, Portland-limestone cements are expected to become increasingly important due to their lower carbon footprint. However, these cements are generally unsuitable for solidification of radioactive waste with high borate concentration. This work investigates the applicability of alkali-activation for the solidification of evaporator residues with extremely high borate concentrations using Portland-limestone cement. Surface cracking was reduced using polypropylene microfibres and zeolite, resulting in stable and readily available mix designs fulfilling all technological and waste acceptance criteria.