Study On Improving Properties Of Alkali-Activated Slag Cement Based Simulated High-Level Waste Forms And Mechanism Of Cs～+ Solidified

Research on the solidification of High-Lever Radioactive Waste (HLRW) by cement-based materials has recently become an important worldwide subject. That Alkali-Activated Slag Cement (AASC) based solidification process of simulated HLRW in room temperature compared to glass solidification, cement solidification has a variety of advantages, such as easy process and cheap cost et al. Therefore, this method has a promising prospect.In view of the characters of the liquid and the demands of its relevant solidification form properties, the radioactive element Cs ions` leach rates are above all researched, so the investigative way of changing the pretreatment of simulated HLRW that the influence compose of simulated HLRW to the solidified form is lowering and quantity of Cs ions in the liquid is reduced; Adjusting the solidified method and the containing quantity of Zeolite in its cementitious material increase the compressive strength of the solidified form. Establish a new process on the pretreatment of simulated HLRW and the solidified molding in room temperature so as to realize AASC based solidification of HLRW in room temperature.Experimental results show that simulated HLRW have been pretreated by NiSO₄ and K₄[Fe(CN)₆] , been neutralized by Ca(OH)₂ and been concentrated, while solidified waste form had a WOx loading of 16%, by pressing, the constituent of AASC matrix is slag : zeolite: activator(by Na₂O )=100:15:5(5%Na₂O provided 2% by NaOH and 3% by Na₂SiO₃), the solidified form have excellent properties as follows:At 25℃,cured in sealing, compress strength of solidification form have 80.6 Mpa. In deionized water, the leach rates of Cs⁺ in 42nd day only 1.0×10^{-7}cm·d^{-1}(GB7023-86, 25℃),the relevancies in 28 days reached 9.1×10^{-6}g·cm^{-2}·d^{-1}(MCC-IP,90℃),and solidification form have fine thermal stability property.Based on study leaching property by the modern analysis methods of XRD,SEM-EDS,AAS,DTA-TG, the behavior of Cs+ in solidification form have been not only deduced, but also the solidification mechanism of Cs+ is be explained.1.Reactant of NiSO₄ ,K₄[Fe(CN)₆] and Cs⁺ is infusibility Cs₂Ni[Fe(CN)₆] and Cs4Ni4[Fe(CN)₆]₃ solid solution .These solid solutions are retained by mechanical sealing of solidification form.2.Cs⁺ is adsorbed and retained by Zeolite ,hydration products and solidification form pore .3.Cs⁺ can enter crystal lattices of hydrate products of AASC and be retained.The physical model of Cs⁺ solidified founded on the above and give a reasonable explain on the solidification mechanism of Cs+.