Assessment of physical properties developed and leaching capability by binary and ternary cementitious mixtures containing spent ion-exchange resins
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Ion-exchange resins (IERs) are used for the decontamination of effluents from chemical impurities and radioisotopes in the primary and secondary cooling circuits of pressured water reactors. Cementation in OPC matrices (CA, cement and fly ash) has been the preferred alternative for the conditioning of spent IERs (SIERs). Due to the progressive supply shortage of ash in the international market, the technical feasibility of other alternative cementitious formulations (CAS, cement, ash and slag, and CS, cement and slag) to confine this waste has been assessed. In this study, aspects such as the maximum waste loading, physic-chemical characteristics of the wasteforms, or their radionuclide retention capacity were evaluated. The maximum SIERs surrogates admitted for each formulation was 7.5 % wt./wt. resin/binder (12 % volume). For all wasteforms, boron released from SIERs surrogates seemed to interact with calcium compounds of the raw materials, retarding the reaction kinetics and setting, especially in the CS sample, and delaying the formation of the gel and the portlandite. No formation of boron compound but substitution of silicon tetrahedral by boron tetrahedral in the gel structure. CAS wasteforms sample with immobilised resin, independently of the SIERs surrogates content, exhibited an improved performance compared to the CA formulation currently in use.
Abstract
Ion-exchange resins (IERs) are used for the decontamination of effluents from chemical impurities and radioisotopes in the primary and secondary cooling circuits of pressured water reactors. Cementation in OPC matrices (CA, cement and fly ash) has been the preferred alternative for the conditioning of spent IERs (SIERs). Due to the progressive supply shortage of ash in the international market, the technical feasibility of other alternative cementitious formulations (CAS, cement, ash and slag, and CS, cement and slag) to confine this waste has been assessed. In this study, aspects such as the maximum waste loading, physic-chemical characteristics of the wasteforms, or their radionuclide retention capacity were evaluated. The maximum SIERs surrogates admitted for each formulation was 7.5 % wt./wt. resin/binder (12 % volume). For all wasteforms, boron released from SIERs surrogates seemed to interact with calcium compounds of the raw materials, retarding the reaction kinetics and setting, especially in the CS sample, and delaying the formation of the gel and the portlandite. No formation of boron compound but substitution of silicon tetrahedral by boron tetrahedral in the gel structure. CAS wasteforms sample with immobilised resin, independently of the SIERs surrogates content, exhibited an improved performance compared to the CA formulation currently in use.