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Zeolite, as a common adsorption material, should be safely treated after adsorbing different nuclear wastes. In this study, different types of simulated zeolite wastes were successfully immobilized based on the exploring result of suitable experiment conditions. Firstly, sintering temperature was selected based on TG‐DSC and phase results, which represented mainly as glassy phase. Then, the holding time was chosen through density and Vickers hardness results. For the sintering of zeolite, the suitable temperature is 1500℃ and the holding time is 1 h. Through the fitting process, FT‐IR results demonstrate that the main microstructures compose of sheet silicates. Three types of simulated zeolite wastes can successfully transform into matrix and all the waste contents were uniformly immobilized. Finally, SEM‐EDS results prove that the matrix is glass‐ceramic which can well immobilize the considered nuclear wastes. This work proposes the idea of treatment of zeolite adsorbed material as a potential nuclear waste glass‐ceramic matrix and the suitable conditions were also investigated.

A new glass solidification process aims at radioactive iodine waste was explored in order to reduce the possible harm to environment. Samples with different iodine content in silver-coated silica gel were pretreated by hydration device at 300 °C and then sintered at relatively low temperatures (500, 550 and 600 °C). XRD results show that AgI is mainly chemically fixed in the glass network with some AgI particles being physically wrapped by the glass. Moreover, as the sintering temperature reached to 550 °C, B element crystallized. SEM-EDS results show that Ag and I elements are enriched, while the other elements are evenly distributed. AFM results showed that the sample surface becomes rougher as the iodine content increases in the silver coated silica gel. The FT-IR results show that the structure of the sintered sample is mainly composed of [BiO3], [BiO6] and [BO3]. This study provides a new sintering method by hydration device for the treatment of radioactive iodine waste.

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As a rapid sintering method, spark plasma sintering (SPS) process has been widely applied to immobilize nuclear waste. In this work, trialkyl phosphine oxides (TRPO) were immobilized by the mixture of Gd 2 O 3 and ZrO 2 with SPS proceedings at 1650 C in 3 minutes. X-ray diffraction results present that the solid solubility is 10 to 20 wt% and all the sintered samples show a fluorite structure. Raman spectroscopy results show that the order degree of structure decreases as waste content increases. The lattice parameters decrease with the increasing doped waste content indicating the success of waste immobilization. Densities decrease for the sample with higher waste content which mainly caused by the existence of pores. Scanning electron microscope-energy dispersive X-ray spectroscopy and backscattered electron results perform the microstructure of the sintered sample. Furthermore, the leaching test shows that the sample has a considerable chemical stability. This study confirmed the possibility of rapid consolidation of Gd 2 Zr 2 O 7 bulk, dense ceramic with up to 10~20 wt% of immobilized TRPO waste. Highlights• Multi-nuclides waste was rapidly immobilized by Gd 2 Zr 2 O 7 via SPS process.• Phase transition happened with enhanced doping content.• Density results decreased with the higher waste content.• The order degree of structure decreased as waste content increased.• The sintered matrix represented considerable chemical stability. K E Y W O R D S ceramic, Gd 2 Zr 2 O 7 , immobilization, SPS, TRPO waste Ningning He and Guilin Wei contributed equally to this work.

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